avr-libc - TuxGraphics.org

avr-libc - TuxGraphics.org
avr-libc
1.7.1
Generated by Doxygen 1.7.3
Thu May 19 2011 13:29:12
Contents
1
2
3
4
5
AVR Libc
1.1 Introduction . . . . . . . . . . . . . .
1.2 General information about this library
1.3 Supported Devices . . . . . . . . . .
1.4 avr-libc License . . . . . . . . . . . .
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1
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10
Toolchain Overview
2.1 Introduction . . . . . . . . . . .
2.2 FSF and GNU . . . . . . . . . .
2.3 GCC . . . . . . . . . . . . . . .
2.4 GNU Binutils . . . . . . . . . .
2.5 avr-libc . . . . . . . . . . . . .
2.6 Building Software . . . . . . . .
2.7 AVRDUDE . . . . . . . . . . .
2.8 GDB / Insight / DDD . . . . . .
2.9 AVaRICE . . . . . . . . . . . .
2.10 SimulAVR . . . . . . . . . . . .
2.11 Utilities . . . . . . . . . . . . .
2.12 Toolchain Distributions (Distros)
2.13 Open Source . . . . . . . . . . .
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11
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Memory Areas and Using malloc()
3.1 Introduction . . . . . . . . . .
3.2 Internal vs. external RAM . .
3.3 Tunables for malloc() . . . . .
3.4 Implementation details . . . .
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17
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20
Memory Sections
4.1 The .text Section . . . . . . . . .
4.2 The .data Section . . . . . . . . .
4.3 The .bss Section . . . . . . . . . .
4.4 The .eeprom Section . . . . . . .
4.5 The .noinit Section . . . . . . . .
4.6 The .initN Sections . . . . . . . .
4.7 The .finiN Sections . . . . . . . .
4.8 Using Sections in Assembler Code
4.9 Using Sections in C Code . . . . .
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21
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Data in Program Space
5.1 Introduction . . . . . . . . . . . . . . . . . . . . . .
5.2 A Note On const . . . . . . . . . . . . . . . . . . .
5.3 Storing and Retrieving Data in the Program Space . .
5.4 Storing and Retrieving Strings in the Program Space
5.5 Caveats . . . . . . . . . . . . . . . . . . . . . . . .
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26
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CONTENTS
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9
ii
avr-libc and assembler programs
6.1 Introduction . . . . . . . . .
6.2 Invoking the compiler . . . .
6.3 Example program . . . . . .
6.4 Pseudo-ops and operators . .
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31
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Inline Assembler Cookbook
7.1 GCC asm Statement . . . . . . . .
7.2 Assembler Code . . . . . . . . . .
7.3 Input and Output Operands . . . .
7.4 Clobbers . . . . . . . . . . . . . .
7.5 Assembler Macros . . . . . . . .
7.6 C Stub Functions . . . . . . . . .
7.7 C Names Used in Assembler Code
7.8 Links . . . . . . . . . . . . . . .
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37
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How to Build a Library
8.1 Introduction . . . . . . .
8.2 How the Linker Works .
8.3 How to Design a Library
8.4 Creating a Library . . . .
8.5 Using a Library . . . . .
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50
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Benchmarks
9.1 A few of libc functions. . . . . . . . . . . . . . . . . . . . . . . . . .
9.2 Math functions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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10 Porting From IAR to AVR GCC
10.1 Introduction . . . . . . . . . . . .
10.2 Registers . . . . . . . . . . . . .
10.3 Interrupt Service Routines (ISRs) .
10.4 Intrinsic Routines . . . . . . . . .
10.5 Flash Variables . . . . . . . . . .
10.6 Non-Returning main() . . . . . .
10.7 Locking Registers . . . . . . . . .
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11 Frequently Asked Questions
11.1 FAQ Index . . . . . . . . . . . . . . . . . . . . . . . . .
11.2 My program doesn’t recognize a variable updated within
routine . . . . . . . . . . . . . . . . . . . . . . . . . . .
11.3 I get "undefined reference to..." for functions like "sin()"
11.4 How to permanently bind a variable to a register? . . . .
11.5 How to modify MCUCR or WDTCR early? . . . . . . .
11.6 What is all this _BV() stuff about? . . . . . . . . . . . .
11.7 Can I use C++ on the AVR? . . . . . . . . . . . . . . .
11.8 Shouldn’t I initialize all my variables? . . . . . . . . . .
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
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an interrupt
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CONTENTS
iii
11.9 Why do some 16-bit timer registers sometimes get trashed? . . . . . .
11.10How do I use a #define’d constant in an asm statement? . . . . . . . .
11.11Why does the PC randomly jump around when single-stepping through
my program in avr-gdb? . . . . . . . . . . . . . . . . . . . . . . . .
11.12How do I trace an assembler file in avr-gdb? . . . . . . . . . . . . . .
11.13How do I pass an IO port as a parameter to a function? . . . . . . . .
11.14What registers are used by the C compiler? . . . . . . . . . . . . . .
11.15How do I put an array of strings completely in ROM? . . . . . . . . .
11.16How to use external RAM? . . . . . . . . . . . . . . . . . . . . . . .
11.17Which -O flag to use? . . . . . . . . . . . . . . . . . . . . . . . . . .
11.18How do I relocate code to a fixed address? . . . . . . . . . . . . . . .
11.19My UART is generating nonsense! My ATmega128 keeps crashing!
Port F is completely broken! . . . . . . . . . . . . . . . . . . . . . .
11.20Why do all my "foo...bar" strings eat up the SRAM? . . . . . . . . .
11.21Why does the compiler compile an 8-bit operation that uses bitwise
operators into a 16-bit operation in assembly? . . . . . . . . . . . . .
11.22How to detect RAM memory and variable overlap problems? . . . . .
11.23Is it really impossible to program the ATtinyXX in C? . . . . . . . . .
11.24What is this "clock skew detected" message? . . . . . . . . . . . . . .
11.25Why are (many) interrupt flags cleared by writing a logical 1? . . . .
11.26Why have "programmed" fuses the bit value 0? . . . . . . . . . . . .
11.27Which AVR-specific assembler operators are available? . . . . . . . .
11.28Why are interrupts re-enabled in the middle of writing the stack pointer?
11.29Why are there five different linker scripts? . . . . . . . . . . . . . . .
11.30How to add a raw binary image to linker output? . . . . . . . . . . . .
11.31How do I perform a software reset of the AVR? . . . . . . . . . . . .
11.32I am using floating point math. Why is the compiled code so big? Why
does my code not work? . . . . . . . . . . . . . . . . . . . . . . . .
11.33What pitfalls exist when writing reentrant code? . . . . . . . . . . . .
11.34Why are some addresses of the EEPROM corrupted (usually address
zero)? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
11.35Why is my baud rate wrong? . . . . . . . . . . . . . . . . . . . . . .
11.36On a device with more than 128 KiB of flash, how to make function
pointers work? . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12 Building and Installing the GNU Tool Chain
12.1 Building and Installing under Linux, FreeBSD, and Others
12.2 Required Tools . . . . . . . . . . . . . . . . . . . . . . .
12.3 Optional Tools . . . . . . . . . . . . . . . . . . . . . . . .
12.4 GNU Binutils for the AVR target . . . . . . . . . . . . . .
12.5 GCC for the AVR target . . . . . . . . . . . . . . . . . . .
12.6 AVR Libc . . . . . . . . . . . . . . . . . . . . . . . . . .
12.7 AVRDUDE . . . . . . . . . . . . . . . . . . . . . . . . .
12.8 GDB for the AVR target . . . . . . . . . . . . . . . . . .
12.9 SimulAVR . . . . . . . . . . . . . . . . . . . . . . . . . .
12.10AVaRICE . . . . . . . . . . . . . . . . . . . . . . . . . .
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
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CONTENTS
iv
12.11Building and Installing under Windows . . . . . . . . . . . . . . . .
12.12Tools Required for Building the Toolchain for Windows . . . . . . . .
12.13Building the Toolchain for Windows . . . . . . . . . . . . . . . . . .
96
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13 Using the GNU tools
13.1 Options for the C compiler avr-gcc . . . . . . . . . . . . . . . . . . .
13.1.1 Machine-specific options for the AVR . . . . . . . . . . . . .
13.1.2 Selected general compiler options . . . . . . . . . . . . . . .
13.2 Options for the assembler avr-as . . . . . . . . . . . . . . . . . . . .
13.2.1 Machine-specific assembler options . . . . . . . . . . . . . .
13.2.2 Examples for assembler options passed through the C compiler
13.3 Controlling the linker avr-ld . . . . . . . . . . . . . . . . . . . . . .
13.3.1 Selected linker options . . . . . . . . . . . . . . . . . . . . .
13.3.2 Passing linker options from the C compiler . . . . . . . . . .
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14 Using the avrdude program
120
15 Release Numbering and Methodology
15.1 Release Version Numbering Scheme
15.2 Releasing AVR Libc . . . . . . . .
15.2.1 Creating an SVN branch . .
15.2.2 Making a release . . . . . .
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122
. 122
. 122
. 122
. 123
16 Acknowledgments
125
17 Todo List
126
18 Deprecated List
126
19 Module Index
127
19.1 Modules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127
20 Data Structure Index
129
20.1 Data Structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129
21 File Index
129
21.1 File List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129
22 Module Documentation
22.1 <alloca.h>: Allocate space in the stack
22.1.1 Function Documentation . . . .
22.2 <assert.h>: Diagnostics . . . . . . . .
22.2.1 Detailed Description . . . . . .
22.2.2 Define Documentation . . . . .
22.3 <ctype.h>: Character Operations . . .
22.3.1 Detailed Description . . . . . .
22.3.2 Function Documentation . . . .
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
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134
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CONTENTS
22.4 <errno.h>: System Errors . . . . . . . . . . .
22.4.1 Detailed Description . . . . . . . . . .
22.4.2 Define Documentation . . . . . . . . .
22.5 <inttypes.h>: Integer Type conversions . . . .
22.5.1 Detailed Description . . . . . . . . . .
22.5.2 Define Documentation . . . . . . . . .
22.5.3 Typedef Documentation . . . . . . . .
22.6 <math.h>: Mathematics . . . . . . . . . . . .
22.6.1 Detailed Description . . . . . . . . . .
22.6.2 Define Documentation . . . . . . . . .
22.6.3 Function Documentation . . . . . . . .
22.7 <setjmp.h>: Non-local goto . . . . . . . . . .
22.7.1 Detailed Description . . . . . . . . . .
22.7.2 Function Documentation . . . . . . . .
22.8 <stdint.h>: Standard Integer Types . . . . . .
22.8.1 Detailed Description . . . . . . . . . .
22.8.2 Define Documentation . . . . . . . . .
22.8.3 Typedef Documentation . . . . . . . .
22.9 <stdio.h>: Standard IO facilities . . . . . . . .
22.9.1 Detailed Description . . . . . . . . . .
22.9.2 Define Documentation . . . . . . . . .
22.9.3 Function Documentation . . . . . . . .
22.10<stdlib.h>: General utilities . . . . . . . . . .
22.10.1 Detailed Description . . . . . . . . . .
22.10.2 Define Documentation . . . . . . . . .
22.10.3 Typedef Documentation . . . . . . . .
22.10.4 Function Documentation . . . . . . . .
22.10.5 Variable Documentation . . . . . . . .
22.11<string.h>: Strings . . . . . . . . . . . . . . .
22.11.1 Detailed Description . . . . . . . . . .
22.11.2 Define Documentation . . . . . . . . .
22.11.3 Function Documentation . . . . . . . .
22.12<avr/boot.h>: Bootloader Support Utilities . .
22.12.1 Detailed Description . . . . . . . . . .
22.12.2 Define Documentation . . . . . . . . .
22.13<avr/cpufunc.h>: Special AVR CPU functions
22.13.1 Detailed Description . . . . . . . . . .
22.13.2 Define Documentation . . . . . . . . .
22.14<avr/eeprom.h>: EEPROM handling . . . . .
22.14.1 Detailed Description . . . . . . . . . .
22.14.2 Define Documentation . . . . . . . . .
22.14.3 Function Documentation . . . . . . . .
22.15<avr/fuse.h>: Fuse Support . . . . . . . . . .
22.16<avr/interrupt.h>: Interrupts . . . . . . . . . .
22.16.1 Detailed Description . . . . . . . . . .
22.16.2 Define Documentation . . . . . . . . .
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
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CONTENTS
vi
22.17<avr/io.h>: AVR device-specific IO definitions . . . . . . . . . . . . 266
22.18<avr/lock.h>: Lockbit Support . . . . . . . . . . . . . . . . . . . . . 267
22.19<avr/pgmspace.h>: Program Space Utilities . . . . . . . . . . . . . 269
22.19.1 Detailed Description . . . . . . . . . . . . . . . . . . . . . . 271
22.19.2 Define Documentation . . . . . . . . . . . . . . . . . . . . . 272
22.19.3 Typedef Documentation . . . . . . . . . . . . . . . . . . . . 275
22.19.4 Function Documentation . . . . . . . . . . . . . . . . . . . . 276
22.20<avr/power.h>: Power Reduction Management . . . . . . . . . . . . 291
22.21Additional notes from <avr/sfr_defs.h> . . . . . . . . . . . . . . . . 293
22.22<avr/sfr_defs.h>: Special function registers . . . . . . . . . . . . . . 295
22.22.1 Detailed Description . . . . . . . . . . . . . . . . . . . . . . 295
22.22.2 Define Documentation . . . . . . . . . . . . . . . . . . . . . 296
22.23<avr/signature.h>: Signature Support . . . . . . . . . . . . . . . . . 297
22.24<avr/sleep.h>: Power Management and Sleep Modes . . . . . . . . . 298
22.24.1 Detailed Description . . . . . . . . . . . . . . . . . . . . . . 298
22.24.2 Function Documentation . . . . . . . . . . . . . . . . . . . . 300
22.25<avr/version.h>: avr-libc version macros . . . . . . . . . . . . . . . 300
22.25.1 Detailed Description . . . . . . . . . . . . . . . . . . . . . . 300
22.25.2 Define Documentation . . . . . . . . . . . . . . . . . . . . . 301
22.26<avr/wdt.h>: Watchdog timer handling . . . . . . . . . . . . . . . . 302
22.26.1 Detailed Description . . . . . . . . . . . . . . . . . . . . . . 302
22.26.2 Define Documentation . . . . . . . . . . . . . . . . . . . . . 303
22.27<util/atomic.h> Atomically and Non-Atomically Executed Code Blocks306
22.27.1 Detailed Description . . . . . . . . . . . . . . . . . . . . . . 306
22.27.2 Define Documentation . . . . . . . . . . . . . . . . . . . . . 308
22.28<util/crc16.h>: CRC Computations . . . . . . . . . . . . . . . . . . 309
22.28.1 Detailed Description . . . . . . . . . . . . . . . . . . . . . . 309
22.28.2 Function Documentation . . . . . . . . . . . . . . . . . . . . 310
22.29<util/delay_basic.h>: Basic busy-wait delay loops . . . . . . . . . . 313
22.29.1 Detailed Description . . . . . . . . . . . . . . . . . . . . . . 313
22.29.2 Function Documentation . . . . . . . . . . . . . . . . . . . . 313
22.30<util/parity.h>: Parity bit generation . . . . . . . . . . . . . . . . . . 314
22.30.1 Detailed Description . . . . . . . . . . . . . . . . . . . . . . 314
22.30.2 Define Documentation . . . . . . . . . . . . . . . . . . . . . 314
22.31<util/setbaud.h>: Helper macros for baud rate calculations . . . . . . 314
22.31.1 Detailed Description . . . . . . . . . . . . . . . . . . . . . . 315
22.31.2 Define Documentation . . . . . . . . . . . . . . . . . . . . . 316
22.32<util/twi.h>: TWI bit mask definitions . . . . . . . . . . . . . . . . 317
22.32.1 Detailed Description . . . . . . . . . . . . . . . . . . . . . . 318
22.32.2 Define Documentation . . . . . . . . . . . . . . . . . . . . . 318
22.33<compat/deprecated.h>: Deprecated items . . . . . . . . . . . . . . 321
22.33.1 Detailed Description . . . . . . . . . . . . . . . . . . . . . . 322
22.33.2 Define Documentation . . . . . . . . . . . . . . . . . . . . . 323
22.33.3 Function Documentation . . . . . . . . . . . . . . . . . . . . 325
22.34<compat/ina90.h>: Compatibility with IAR EWB 3.x . . . . . . . . 325
22.35Demo projects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 325
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
CONTENTS
vii
22.35.1 Detailed Description . . . . . . . .
22.36Combining C and assembly source files . .
22.36.1 Hardware setup . . . . . . . . . . .
22.36.2 A code walkthrough . . . . . . . .
22.36.3 The source code . . . . . . . . . .
22.37A simple project . . . . . . . . . . . . . . .
22.37.1 The Project . . . . . . . . . . . . .
22.37.2 The Source Code . . . . . . . . . .
22.37.3 Compiling and Linking . . . . . . .
22.37.4 Examining the Object File . . . . .
22.37.5 Linker Map Files . . . . . . . . . .
22.37.6 Generating Intel Hex Files . . . . .
22.37.7 Letting Make Build the Project . . .
22.37.8 Reference to the source code . . . .
22.38A more sophisticated project . . . . . . . .
22.38.1 Hardware setup . . . . . . . . . . .
22.38.2 Functional overview . . . . . . . .
22.38.3 A code walkthrough . . . . . . . .
22.38.4 The source code . . . . . . . . . .
22.39Using the standard IO facilities . . . . . . .
22.39.1 Hardware setup . . . . . . . . . . .
22.39.2 Functional overview . . . . . . . .
22.39.3 A code walkthrough . . . . . . . .
22.39.4 The source code . . . . . . . . . .
22.40Example using the two-wire interface (TWI)
22.40.1 Introduction into TWI . . . . . . .
22.40.2 The TWI example project . . . . .
22.40.3 The Source Code . . . . . . . . . .
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23 Data Structure Documentation
23.1 div_t Struct Reference . . .
23.1.1 Detailed Description
23.1.2 Field Documentation
23.2 ldiv_t Struct Reference . . .
23.2.1 Detailed Description
23.2.2 Field Documentation
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24 File Documentation
24.1 assert.h File Reference . . .
24.1.1 Detailed Description
24.2 atoi.S File Reference . . . .
24.2.1 Detailed Description
24.3 atol.S File Reference . . . .
24.3.1 Detailed Description
24.4 atomic.h File Reference . . .
24.4.1 Detailed Description
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Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
CONTENTS
24.5 boot.h File Reference . . . . .
24.5.1 Detailed Description .
24.5.2 Define Documentation
24.6 cpufunc.h File Reference . . .
24.6.1 Detailed Description .
24.7 crc16.h File Reference . . . .
24.7.1 Detailed Description .
24.8 ctype.h File Reference . . . .
24.8.1 Detailed Description .
24.9 delay_basic.h File Reference .
24.9.1 Detailed Description .
24.10errno.h File Reference . . . .
24.10.1 Detailed Description .
24.11fdevopen.c File Reference . .
24.11.1 Detailed Description .
24.12ffs.S File Reference . . . . . .
24.12.1 Detailed Description .
24.13ffsl.S File Reference . . . . .
24.13.1 Detailed Description .
24.14ffsll.S File Reference . . . . .
24.14.1 Detailed Description .
24.15fuse.h File Reference . . . . .
24.15.1 Detailed Description .
24.16interrupt.h File Reference . . .
24.16.1 Detailed Description .
24.17inttypes.h File Reference . . .
24.17.1 Detailed Description .
24.18io.h File Reference . . . . . .
24.18.1 Detailed Description .
24.19lock.h File Reference . . . . .
24.19.1 Detailed Description .
24.20math.h File Reference . . . . .
24.20.1 Detailed Description .
24.21memccpy.S File Reference . .
24.21.1 Detailed Description .
24.22memchr.S File Reference . . .
24.22.1 Detailed Description .
24.23memchr_P.S File Reference . .
24.23.1 Detailed Description .
24.24memcmp.S File Reference . .
24.24.1 Detailed Description .
24.25memcmp_P.S File Reference .
24.25.1 Detailed Description .
24.26memcmp_PF.S File Reference
24.26.1 Detailed Description .
24.27memcpy.S File Reference . . .
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CONTENTS
24.27.1 Detailed Description .
24.28memcpy_P.S File Reference .
24.28.1 Detailed Description .
24.29memmem.S File Reference . .
24.29.1 Detailed Description .
24.30memmove.S File Reference . .
24.30.1 Detailed Description .
24.31memrchr.S File Reference . .
24.31.1 Detailed Description .
24.32memrchr_P.S File Reference .
24.32.1 Detailed Description .
24.33memset.S File Reference . . .
24.33.1 Detailed Description .
24.34parity.h File Reference . . . .
24.34.1 Detailed Description .
24.35pgmspace.h File Reference . .
24.35.1 Detailed Description .
24.35.2 Define Documentation
24.36power.h File Reference . . . .
24.36.1 Detailed Description .
24.37setbaud.h File Reference . . .
24.37.1 Detailed Description .
24.38setjmp.h File Reference . . . .
24.38.1 Detailed Description .
24.39signature.h File Reference . .
24.39.1 Detailed Description .
24.40sleep.h File Reference . . . . .
24.40.1 Detailed Description .
24.41stdint.h File Reference . . . .
24.41.1 Detailed Description .
24.42stdio.h File Reference . . . . .
24.42.1 Detailed Description .
24.43stdlib.h File Reference . . . .
24.43.1 Detailed Description .
24.44strcasecmp.S File Reference .
24.44.1 Detailed Description .
24.45strcasecmp_P.S File Reference
24.45.1 Detailed Description .
24.46strcasestr.S File Reference . .
24.46.1 Detailed Description .
24.47strcat.S File Reference . . . .
24.47.1 Detailed Description .
24.48strcat_P.S File Reference . . .
24.48.1 Detailed Description .
24.49strchr.S File Reference . . . .
24.49.1 Detailed Description .
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Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
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CONTENTS
24.50strchr_P.S File Reference . . . .
24.50.1 Detailed Description . .
24.51strchrnul.S File Reference . . .
24.51.1 Detailed Description . .
24.52strchrnul_P.S File Reference . .
24.52.1 Detailed Description . .
24.53strcmp.S File Reference . . . . .
24.53.1 Detailed Description . .
24.54strcmp_P.S File Reference . . .
24.54.1 Detailed Description . .
24.55strcpy.S File Reference . . . . .
24.55.1 Detailed Description . .
24.56strcpy_P.S File Reference . . . .
24.56.1 Detailed Description . .
24.57strcspn.S File Reference . . . .
24.57.1 Detailed Description . .
24.58strcspn_P.S File Reference . . .
24.58.1 Detailed Description . .
24.59strdup.c File Reference . . . . .
24.59.1 Detailed Description . .
24.60string.h File Reference . . . . .
24.60.1 Detailed Description . .
24.61strlcat.S File Reference . . . . .
24.61.1 Detailed Description . .
24.62strlcat_P.S File Reference . . . .
24.62.1 Detailed Description . .
24.63strlcpy.S File Reference . . . . .
24.63.1 Detailed Description . .
24.64strlcpy_P.S File Reference . . .
24.64.1 Detailed Description . .
24.65strlen.S File Reference . . . . .
24.65.1 Detailed Description . .
24.66strlen_P.S File Reference . . . .
24.66.1 Detailed Description . .
24.67strlwr.S File Reference . . . . .
24.67.1 Detailed Description . .
24.68strncasecmp.S File Reference . .
24.68.1 Detailed Description . .
24.69strncasecmp_P.S File Reference
24.69.1 Detailed Description . .
24.70strncat.S File Reference . . . . .
24.70.1 Detailed Description . .
24.71strncat_P.S File Reference . . .
24.71.1 Detailed Description . .
24.72strncmp.S File Reference . . . .
24.72.1 Detailed Description . .
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CONTENTS
24.73strncmp_P.S File Reference .
24.73.1 Detailed Description
24.74strncpy.S File Reference . .
24.74.1 Detailed Description
24.75strncpy_P.S File Reference .
24.75.1 Detailed Description
24.76strnlen.S File Reference . . .
24.76.1 Detailed Description
24.77strnlen_P.S File Reference .
24.77.1 Detailed Description
24.78strpbrk.S File Reference . .
24.78.1 Detailed Description
24.79strpbrk_P.S File Reference .
24.79.1 Detailed Description
24.80strrchr.S File Reference . . .
24.80.1 Detailed Description
24.81strrchr_P.S File Reference .
24.81.1 Detailed Description
24.82strrev.S File Reference . . .
24.82.1 Detailed Description
24.83strsep.S File Reference . . .
24.83.1 Detailed Description
24.84strsep_P.S File Reference . .
24.84.1 Detailed Description
24.85strspn.S File Reference . . .
24.85.1 Detailed Description
24.86strspn_P.S File Reference . .
24.86.1 Detailed Description
24.87strstr.S File Reference . . . .
24.87.1 Detailed Description
24.88strstr_P.S File Reference . .
24.88.1 Detailed Description
24.89strtok.c File Reference . . .
24.89.1 Detailed Description
24.90strtok_P.c File Reference . .
24.90.1 Detailed Description
24.91strtok_r.S File Reference . .
24.91.1 Detailed Description
24.92strtok_rP.S File Reference .
24.92.1 Detailed Description
24.93strupr.S File Reference . . .
24.93.1 Detailed Description
24.94twi.h File Reference . . . . .
24.94.1 Detailed Description
24.95wdt.h File Reference . . . .
24.95.1 Detailed Description
1
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Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
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1 AVR Libc
1
2
AVR Libc
1.1
Introduction
The latest version of this document is always available from http://savannah.nongnu.org/projects/avr-l
The AVR Libc package provides a subset of the standard C library for Atmel AVR
8-bit RISC microcontrollers. In addition, the library provides the basic
startup code needed by most applications.
There is a wealth of information in this document which goes beyond simply describing the interfaces and routines provided by the library. We hope that this document
provides enough information to get a new AVR developer up to speed quickly using
the freely available development tools: binutils, gcc avr-libc and many others.
If you find yourself stuck on a problem which this document doesn’t quite address, you
may wish to post a message to the avr-gcc mailing list. Most of the developers of the
AVR binutils and gcc ports in addition to the devleopers of avr-libc subscribe to the
list, so you will usually be able to get your problem resolved. You can subscribe to the
list at http://lists.nongnu.org/mailman/listinfo/avr-gcc-list
. Before posting to the list, you might want to try reading the Frequently Asked Questions chapter of this document.
Note
If you think you’ve found a bug, or have a suggestion for an improvement, either in this documentation or in the library itself, please use the bug tracker at
https://savannah.nongnu.org/bugs/?group=avr-libc to ensure
the issue won’t be forgotten.
1.2
General information about this library
In general, it has been the goal to stick as best as possible to established standards
while implementing this library. Commonly, this refers to the C library as described by
the ANSI X3.159-1989 and ISO/IEC 9899:1990 ("ANSI-C") standard, as well as parts
of their successor ISO/IEC 9899:1999 ("C99"). Some additions have been inspired by
other standards like IEEE Std 1003.1-1988 ("POSIX.1"), while other extensions are
purely AVR-specific (like the entire program-space string interface).
Unless otherwise noted, functions of this library are not guaranteed to be reentrant. In
particular, any functions that store local state are known to be non-reentrant, as well
as functions that manipulate IO registers like the EEPROM access routines. If these
functions are used within both standard and interrupt contexts undefined behaviour will
result. See the FAQ for a more detailed discussion.
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
1.3
Supported Devices
1.3
Supported Devices
3
The following is a list of AVR devices currently supported by the library. Note that
actual support for some newer devices depends on the ability of the compiler/assembler
to support these devices at library compile-time.
megaAVR Devices:
• atmega103
• atmega128
• atmega1280
• atmega1281
• atmega1284p
• atmega16
• atmega161
• atmega162
• atmega163
• atmega164a
• atmega164p
• atmega165
• atmega165a
• atmega165p
• atmega168
• atmega168a
• atmega168p
• atmega16a
• atmega2560
• atmega2561
• atmega32
• atmega323
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
1.3
Supported Devices
• atmega324a
• atmega324p
• atmega324pa
• atmega325
• atmega325a
• atmega325p
• atmega325pa
• atmega3250
• atmega3250a
• atmega3250p
• atmega3250pa
• atmega328
• atmega328p
• atmega48
• atmega48a
• atmega48pa
• atmega48p
• atmega64
• atmega640
• atmega644
• atmega644a
• atmega644p
• atmega644pa
• atmega645
• atmega645a
• atmega645p
• atmega6450
• atmega6450a
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
4
1.3
Supported Devices
• atmega6450p
• atmega8
• atmega88
• atmega88a
• atmega88p
• atmega88pa
• atmega8515
• atmega8535
tinyAVR Devices:
• attiny4
• attiny5
• attiny10
• attiny11 [1]
• attiny12 [1]
• attiny13
• attiny13a
• attiny15 [1]
• attiny20
• attiny22
• attiny24
• attiny24a
• attiny25
• attiny26
• attiny261
• attiny261a
• attiny28 [1]
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
5
1.3
Supported Devices
• attiny2313
• attiny2313a
• attiny40
• attiny4313
• attiny43u
• attiny44
• attiny44a
• attiny45
• attiny461
• attiny461a
• attiny48
• attiny84
• attiny84a
• attiny85
• attiny861
• attiny861a
• attiny87
• attiny88
• attiny1634
Automotive AVR Devices:
• atmega16m1
• atmega32c1
• atmega32m1
• atmega64c1
• atmega64m1
• attiny167
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
6
1.3
Supported Devices
CAN AVR Devices:
• at90can32
• at90can64
• at90can128
LCD AVR Devices:
• atmega169
• atmega169a
• atmega169p
• atmega169pa
• atmega329
• atmega329a
• atmega329p
• atmega329pa
• atmega3290
• atmega3290a
• atmega3290p
• atmega3290pa
• atmega649
• atmega649a
• atmega6490
• atmega6490a
• atmega6490p
• atmega649p
Lighting AVR Devices:
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
7
1.3
Supported Devices
• at90pwm1
• at90pwm2
• at90pwm2b
• at90pwm216
• at90pwm3
• at90pwm3b
• at90pwm316
• at90pwm161
• at90pwm81
Smart Battery AVR Devices:
• atmega8hva
• atmega16hva
• atmega16hva2
• atmega16hvb
• atmega16hvbrevb
• atmega32hvb
• atmega32hvbrevb
• atmega64hve
• atmega406
USB AVR Devices:
• at90usb82
• at90usb162
• at90usb646
• at90usb647
• at90usb1286
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
8
1.3
Supported Devices
• at90usb1287
• atmega8u2
• atmega16u2
• atmega16u4
• atmega32u2
• atmega32u4
• atmega32u6
XMEGA Devices:
• atxmega16a4
• atxmega16d4
• atxmega32a4
• atxmega32d4
• atxmega64a1
• atxmega64a1u
• atxmega64a3
• atxmega64d3
• atxmega128a1
• atxmega128a1u
• atxmega128a3
• atxmega128b1
• atxmega128d3
• atxmega192a3
• atxmega192d3
• atxmega256a3
• atxmega256a3b
• atxmega256a3bu
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
9
1.3
Supported Devices
10
• atxmega256d3
Miscellaneous Devices:
• at94K [2]
• at76c711 [3]
• at43usb320
• at43usb355
• at86rf401
• at90scr100
• ata6289
• m3000 [4]
Classic AVR Devices:
• at90s1200 [1]
• at90s2313
• at90s2323
• at90s2333
• at90s2343
• at90s4414
• at90s4433
• at90s4434
• at90s8515
• at90c8534
• at90s8535
Note
[1] Assembly only. There is no direct support for these devices to be programmed
in C since they do not have a RAM based stack. Still, it could be possible to
program them in C, see the FAQ for an option.
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
1.4
avr-libc License
11
Note
[2] The at94K devices are a combination of FPGA and AVR microcontroller.
[TRoth-2002/11/12: Not sure of the level of support for these. More information
would be welcomed.]
Note
[3] The at76c711 is a USB to fast serial interface bridge chip using an AVR core.
Note
[4] The m3000 is a motor controller AVR ASIC from Intelligent Motion Systems
(IMS) / Schneider Electric.
1.4
avr-libc License
avr-libc can be freely used and redistributed, provided the following license conditions
are met.
Portions of avr-libc are Copyright (c) 1999-2010
Werner Boellmann,
Dean Camera,
Pieter Conradie,
Brian Dean,
Keith Gudger,
Wouter van Gulik,
Bjoern Haase,
Steinar Haugen,
Peter Jansen,
Reinhard Jessich,
Magnus Johansson,
Harald Kipp,
Carlos Lamas,
Cliff Lawson,
Artur Lipowski,
Marek Michalkiewicz,
Todd C. Miller,
Rich Neswold,
Colin O’Flynn,
Bob Paddock,
Andrey Pashchenko,
Reiner Patommel,
Florin-Viorel Petrov,
Alexander Popov,
Michael Rickman,
Theodore A. Roth,
Juergen Schilling,
Philip Soeberg,
Anatoly Sokolov,
Nils Kristian Strom,
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2 Toolchain Overview
12
Michael Stumpf,
Stefan Swanepoel,
Helmut Wallner,
Eric B. Weddington,
Joerg Wunsch,
Dmitry Xmelkov,
Atmel Corporation,
egnite Software GmbH,
The Regents of the University of California.
All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:
* Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
* Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in
the documentation and/or other materials provided with the
distribution.
* Neither the name of the copyright holders nor the names of
contributors may be used to endorse or promote products derived
from this software without specific prior written permission.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
POSSIBILITY OF SUCH DAMAGE.
2
2.1
Toolchain Overview
Introduction
Welcome to the open source software development toolset for the Atmel AVR!
There is not a single tool that provides everything needed to develop software for the
AVR. It takes many tools working together. Collectively, the group of tools are called a
toolset, or commonly a toolchain, as the tools are chained together to produce the final
executable application for the AVR microcontroller.
The following sections provide an overview of all of these tools. You may be used
to cross-compilers that provide everything with a GUI front-end, and not know what
goes on "underneath the hood". You may be coming from a desktop or server computer
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2.2
FSF and GNU
13
background and not used to embedded systems. Or you may be just learning about the
most common software development toolchain available on Unix and Linux systems.
Hopefully the following overview will be helpful in putting everything in perspective.
2.2
FSF and GNU
According to its website, "the Free Software Foundation (FSF), established in 1985, is
dedicated to promoting computer users’ rights to use, study, copy, modify, and redistribute computer programs. The FSF promotes the development and use of free software, particularly the GNU operating system, used widely in its GNU/Linux variant."
The FSF remains the primary sponsor of the GNU project.
The GNU Project was launched in 1984 to develop a complete Unix-like operating
system which is free software: the GNU system. GNU is a recursive acronym for
»GNU’s Not Unix«; it is pronounced guh-noo, approximately like canoe.
One of the main projects of the GNU system is the GNU Compiler Collection, or GCC,
and its sister project, GNU Binutils. These two open source projects provide a foundation for a software development toolchain. Note that these projects were designed to
originally run on Unix-like systems.
2.3
GCC
GCC stands for GNU Compiler Collection. GCC is highly flexible compiler system. It
has different compiler front-ends for different languages. It has many back-ends that
generate assembly code for many different processors and host operating systems. All
share a common "middle-end", containing the generic parts of the compiler, including
a lot of optimizations.
In GCC, a host system is the system (processor/OS) that the compiler runs on. A
target system is the system that the compiler compiles code for. And, a build system
is the system that the compiler is built (from source code) on. If a compiler has the
same system for host and for target, it is known as a native compiler. If a compiler
has different systems for host and target, it is known as a cross-compiler. (And if all
three, build, host, and target systems are different, it is known as a Canadian cross
compiler, but we won’t discuss that here.) When GCC is built to execute on a host
system such as FreeBSD, Linux, or Windows, and it is built to generate code for the
AVR microcontroller target, then it is a cross compiler, and this version of GCC is
commonly known as "AVR GCC". In documentation, or discussion, AVR GCC is
used when referring to GCC targeting specifically the AVR, or something that is AVR
specific about GCC. The term "GCC" is usually used to refer to something generic
about GCC, or about GCC as a whole.
GCC is different from most other compilers. GCC focuses on translating a high-level
language to the target assembly only. AVR GCC has three available compilers for the
AVR: C language, C++, and Ada. The compiler itself does not assemble or link the
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2.4
GNU Binutils
14
final code.
GCC is also known as a "driver" program, in that it knows about, and drives other
programs seamlessly to create the final output. The assembler, and the linker are part
of another open source project called GNU Binutils. GCC knows how to drive the
GNU assembler (gas) to assemble the output of the compiler. GCC knows how to drive
the GNU linker (ld) to link all of the object modules into a final executable.
The two projects, GCC and Binutils, are very much interrelated and many of the same
volunteers work on both open source projects.
When GCC is built for the AVR target, the actual program names are prefixed with
"avr-". So the actual executable name for AVR GCC is: avr-gcc. The name "avr-gcc"
is used in documentation and discussion when referring to the program itself and not
just the whole AVR GCC system.
See the GCC Web Site and GCC User Manual for more information about GCC.
2.4
GNU Binutils
The name GNU Binutils stands for "Binary Utilities". It contains the GNU assembler
(gas), and the GNU linker (ld), but also contains many other utilities that work with
binary files that are created as part of the software development toolchain.
Again, when these tools are built for the AVR target, the actual program names are
prefixed with "avr-". For example, the assembler program name, for a native assembler
is "as" (even though in documentation the GNU assembler is commonly referred to as
"gas"). But when built for an AVR target, it becomes "avr-as". Below is a list of the
programs that are included in Binutils:
avr-as
The Assembler.
avr-ld
The Linker.
avr-ar
Create, modify, and extract from libraries (archives).
avr-ranlib
Generate index to library (archive) contents.
avr-objcopy
Copy and translate object files to different formats.
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2.5
avr-libc
15
avr-objdump
Display information from object files including disassembly.
avr-size
List section sizes and total size.
avr-nm
List symbols from object files.
avr-strings
List printable strings from files.
avr-strip
Discard symbols from files.
avr-readelf
Display the contents of ELF format files.
avr-addr2line
Convert addresses to file and line.
avr-c++filt
Filter to demangle encoded C++ symbols.
2.5
avr-libc
GCC and Binutils provides a lot of the tools to develop software, but there is one critical
component that they do not provide: a Standard C Library.
There are different open source projects that provide a Standard C Library depending
upon your system time, whether for a native compiler (GNU Libc), for some other
embedded system (newlib), or for some versions of Linux (uCLibc). The open source
AVR toolchain has its own Standard C Library project: avr-libc.
AVR-Libc provides many of the same functions found in a regular Standard C Library
and many additional library functions that is specific to an AVR. Some of the Standard
C Library functions that are commonly used on a PC environment have limitations or
additional issues that a user needs to be aware of when used on an embedded system.
AVR-Libc also contains the most documentation about the whole AVR toolchain.
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2.6
Building Software
2.6
Building Software
16
Even though GCC, Binutils, and avr-libc are the core projects that are used to build
software for the AVR, there is another piece of software that ties it all together: Make.
GNU Make is a program that makes things, and mainly software. Make interprets and
executes a Makefile that is written for a project. A Makefile contains dependency rules,
showing which output files are dependent upon which input files, and instructions on
how to build output files from input files.
Some distributions of the toolchains, and other AVR tools such as MFile, contain a
Makefile template written for the AVR toolchain and AVR applications that you can
copy and modify for your application.
See the GNU Make User Manual for more information.
2.7
AVRDUDE
After creating your software, you’ll want to program your device. You can do this by
using the program AVRDUDE which can interface with various hardware devices to
program your processor.
AVRDUDE is a very flexible package. All the information about AVR processors
and various hardware programmers is stored in a text database. This database can be
modified by any user to add new hardware or to add an AVR processor if it is not
already listed.
2.8
GDB / Insight / DDD
The GNU Debugger (GDB) is a command-line debugger that can be used with the rest
of the AVR toolchain. Insight is GDB plus a GUI written in Tcl/Tk. Both GDB and
Insight are configured for the AVR and the main executables are prefixed with the target
name: avr-gdb, and avr-insight. There is also a "text mode" GUI for GDB: avr-gdbtui.
DDD (Data Display Debugger) is another popular GUI front end to GDB, available on
Unix and Linux systems.
2.9
AVaRICE
AVaRICE is a back-end program to AVR GDB and interfaces to the Atmel JTAG InCircuit Emulator (ICE), to provide emulation capabilities.
2.10
SimulAVR
SimulAVR is an AVR simulator used as a back-end with AVR GDB. Unfortunately,
this project is currently unmaintained and could use some help.
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2.11
Utilities
2.11
Utilities
17
There are also other optional utilities available that may be useful to add to your toolset.
SRecord is a collection of powerful tools for manipulating EPROM load files. It
reads and writes numerous EPROM file formats, and can perform many different manipulations.
MFile is a simple Makefile generator is meant as an aid to quickly customize a Makefile to use for your AVR application.
2.12
Toolchain Distributions (Distros)
All of the various open source projects that comprise the entire toolchain are normally
distributed as source code. It is left up to the user to build the tool application from its
source code. This can be a very daunting task to any potential user of these tools.
Luckily there are people who help out in this area. Volunteers take the time to build the
application from source code on particular host platforms and sometimes packaging
the tools for convenient installation by the end user. These packages contain the binary
executables of the tools, pre-made and ready to use. These packages are known as
"distributions" of the AVR toolchain, or by a more shortened name, "distros".
AVR toolchain distros are available on FreeBSD, Windows, Mac OS X, and certain
flavors of Linux.
2.13
Open Source
All of these tools, from the original source code in the multitude of projects, to the
various distros, are put together by many, many volunteers. All of these projects could
always use more help from other people who are willing to volunteer some of their time.
There are many different ways to help, for people with varying skill levels, abilities,
and available time.
You can help to answer questions in mailing lists such as the avr-gcc-list, or on forums
at the AVR Freaks website. This helps many people new to the open source AVR tools.
If you think you found a bug in any of the tools, it is always a big help to submit a good
bug report to the proper project. A good bug report always helps other volunteers to
analyze the problem and to get it fixed for future versions of the software.
You can also help to fix bugs in various software projects, or to add desirable new
features.
Volunteers are always welcome! :-)
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3 Memory Areas and Using malloc()
3
18
Memory Areas and Using malloc()
3.1
Introduction
Many of the devices that are possible targets of avr-libc have a minimal amount of
RAM. The smallest parts supported by the C environment come with 128 bytes of
RAM. This needs to be shared between initialized and uninitialized variables (sections
.data and .bss), the dynamic memory allocator, and the stack that is used for calling
subroutines and storing local (automatic) variables.
Also, unlike larger architectures, there is no hardware-supported memory management
which could help in separating the mentioned RAM regions from being overwritten by
each other.
The standard RAM layout is to place .data variables first, from the beginning of the
internal RAM, followed by .bss. The stack is started from the top of internal RAM,
growing downwards. The so-called "heap" available for the dynamic memory allocator
will be placed beyond the end of .bss. Thus, there’s no risk that dynamic memory will
ever collide with the RAM variables (unless there were bugs in the implementation of
the allocator). There is still a risk that the heap and stack could collide if there are large
requirements for either dynamic memory or stack space. The former can even happen
if the allocations aren’t all that large but dynamic memory allocations get fragmented
over time such that new requests don’t quite fit into the "holes" of previously freed
regions. Large stack space requirements can arise in a C function containing large
and/or numerous local variables or when recursively calling function.
Note
on−board RAM
.data
.bss
variables variables
heap
!
external RAM
0xFFFF
0x10FF
0x1100
0x0100
The pictures shown in this document represent typical situations where the RAM
locations refer to an ATmega128. The memory addresses used are not displayed
in a linear scale.
stack
SP
RAMEND
*(__brkval) (<= *SP − *(__malloc_margin))
*(__malloc_heap_start) == __heap_start
__bss_end
__data_end == __bss_start
__data_start
Figure 1: RAM map of a device with internal RAM
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3.2
Internal vs. external RAM
19
On a simple device like a microcontroller it is a challenge to implement a dynamic
memory allocator that is simple enough so the code size requirements will remain low,
yet powerful enough to avoid unnecessary memory fragmentation and to get it all done
with reasonably few CPU cycles. Microcontrollers are often low on space and also run
at much lower speeds than the typical PC these days.
The memory allocator implemented in avr-libc tries to cope with all of these constraints, and offers some tuning options that can be used if there are more resources
available than in the default configuration.
3.2
Internal vs. external RAM
Obviously, the constraints are much harder to satisfy in the default configuration where
only internal RAM is available. Extreme care must be taken to avoid a stack-heap
collision, both by making sure functions aren’t nesting too deeply, and don’t require
too much stack space for local variables, as well as by being cautious with allocating
too much dynamic memory.
If external RAM is available, it is strongly recommended to move the heap into the external RAM, regardless of whether or not the variables from the .data and .bss sections
are also going to be located there. The stack should always be kept in internal RAM.
Some devices even require this, and in general, internal RAM can be accessed faster
since no extra wait states are required. When using dynamic memory allocation and
stack and heap are separated in distinct memory areas, this is the safest way to avoid a
stack-heap collision.
3.3
Tunables for malloc()
There are a number of variables that can be tuned to adapt the behavior of malloc()
to the expected requirements and constraints of the application. Any changes to these
tunables should be made before the very first call to malloc(). Note that some library
functions might also use dynamic memory (notably those from the <stdio.h>: Standard IO facilities), so make sure the changes will be done early enough in the startup
sequence.
The variables __malloc_heap_start and __malloc_heap_end can be used
to restrict the malloc() function to a certain memory region. These variables are statically initialized to point to __heap_start and __heap_end, respectively, where
__heap_start is filled in by the linker to point just beyond .bss, and __heap_end
is set to 0 which makes malloc() assume the heap is below the stack.
If the heap is going to be moved to external RAM, __malloc_heap_end must be
adjusted accordingly. This can either be done at run-time, by writing directly to this
variable, or it can be done automatically at link-time, by adjusting the value of the
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3.3
Tunables for malloc()
20
symbol __heap_end.
The following example shows a linker command to relocate the entire .data and .bss
segments, and the heap to location 0x1100 in external RAM. The heap will extend up
to address 0xffff.
avr-gcc ... -Wl,--section-start,.data=0x801100,--defsym=__heap_end=0x80ffff ...
Note
on−board RAM
.data
stack
external RAM
0xFFFF
0x10FF
0x1100
0x0100
See explanation for offset 0x800000. See the chapter about using gcc for the -Wl
options.
The ld (linker) user manual states that using -Tdata=<x> is equivalent to using
--section-start,.data=<x>. However, you have to use --section-start as above because the GCC frontend also sets the -Tdata option for all MCU types where the
SRAM doesn’t start at 0x800060. Thus, the linker is being faced with two -Tdata
options. Sarting with binutils 2.16, the linker changed the preference, and picks
the "wrong" option in this situation.
.bss
variables variables
heap
SP
RAMEND
*(__malloc_heap_end) == __heap_end
*(__brkval)
*(__malloc_heap_start) == __heap_start
__bss_end
__data_end == __bss_start
__data_start
Figure 2: Internal RAM: stack only, external RAM: variables and heap
If dynamic memory should be placed in external RAM, while keeping the variables in
internal RAM, something like the following could be used. Note that for demonstration
purposes, the assignment of the various regions has not been made adjacent in this
example, so there are "holes" below and above the heap in external RAM that remain
completely unaccessible by regular variables or dynamic memory allocations (shown
in light bisque color in the picture below).
avr-gcc ... -Wl,--defsym=__heap_start=0x802000,--defsym=__heap_end=0x803fff ...
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3.4
Implementation details
21
.data
0xFFFF
0x3FFF
on−board RAM
0x2000
0x10FF
0x1100
0x0100
external RAM
.bss
stack
variables variables
heap
SP
RAMEND
__bss_end
*(__malloc_heap_end) == __heap_end
*(__brkval)
*(__malloc_heap_start) == __heap_start
__data_end == __bss_start
__data_start
Figure 3: Internal RAM: variables and stack, external RAM: heap
If __malloc_heap_end is 0, the allocator attempts to detect the bottom of stack
in order to prevent a stack-heap collision when extending the actual size of the heap
to gain more space for dynamic memory. It will not try to go beyond the current
stack limit, decreased by __malloc_margin bytes. Thus, all possible stack frames
of interrupt routines that could interrupt the current function, plus all further nested
function calls must not require more stack space, or they will risk colliding with the
data segment.
The default value of __malloc_margin is set to 32.
3.4
Implementation details
Dynamic memory allocation requests will be returned with a two-byte header prepended
that records the size of the allocation. This is later used by free(). The returned address
points just beyond that header. Thus, if the application accidentally writes before the
returned memory region, the internal consistency of the memory allocator is compromised.
The implementation maintains a simple freelist that accounts for memory blocks that
have been returned in previous calls to free(). Note that all of this memory is considered
to be successfully added to the heap already, so no further checks against stack-heap
collisions are done when recycling memory from the freelist.
The freelist itself is not maintained as a separate data structure, but rather by modifying
the contents of the freed memory to contain pointers chaining the pieces together. That
way, no additional memory is reqired to maintain this list except for a variable that
keeps track of the lowest memory segment available for reallocation. Since both, a
chain pointer and the size of the chunk need to be recorded in each chunk, the minimum
chunk size on the freelist is four bytes.
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4 Memory Sections
22
When allocating memory, first the freelist is walked to see if it could satisfy the request.
If there’s a chunk available on the freelist that will fit the request exactly, it will be
taken, disconnected from the freelist, and returned to the caller. If no exact match could
be found, the closest match that would just satisfy the request will be used. The chunk
will normally be split up into one to be returned to the caller, and another (smaller)
one that will remain on the freelist. In case this chunk was only up to two bytes larger
than the request, the request will simply be altered internally to also account for these
additional bytes since no separate freelist entry could be split off in that case.
If nothing could be found on the freelist, heap extension is attempted. This is where
__malloc_margin will be considered if the heap is operating below the stack, or
where __malloc_heap_end will be verified otherwise.
If the remaining memory is insufficient to satisfy the request, NULL will eventually be
returned to the caller.
When calling free(), a new freelist entry will be prepared. An attempt is then made to
aggregate the new entry with possible adjacent entries, yielding a single larger entry
available for further allocations. That way, the potential for heap fragmentation is
hopefully reduced. When deallocating the topmost chunk of memory, the size of the
heap is reduced.
A call to realloc() first determines whether the operation is about to grow or shrink the
current allocation. When shrinking, the case is easy: the existing chunk is split, and the
tail of the region that is no longer to be used is passed to the standard free() function for
insertion into the freelist. Checks are first made whether the tail chunk is large enough
to hold a chunk of its own at all, otherwise realloc() will simply do nothing, and return
the original region.
When growing the region, it is first checked whether the existing allocation can be extended in-place. If so, this is done, and the original pointer is returned without copying
any data contents. As a side-effect, this check will also record the size of the largest
chunk on the freelist.
If the region cannot be extended in-place, but the old chunk is at the top of heap, and
the above freelist walk did not reveal a large enough chunk on the freelist to satisfy
the new request, an attempt is made to quickly extend this topmost chunk (and thus
the heap), so no need arises to copy over the existing data. If there’s no more space
available in the heap (same check is done as in malloc()), the entire request will fail.
Otherwise, malloc() will be called with the new request size, the existing data will be
copied over, and free() will be called on the old region.
4
Memory Sections
Remarks
Need to list all the sections which are available to the avr.
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4.1
The .text Section
23
Weak Bindings
FIXME: need to discuss the .weak directive.
The following describes the various sections available.
4.1
The .text Section
The .text section contains the actual machine instructions which make up your program.
This section is further subdivided by the .initN and .finiN sections dicussed below.
Note
The avr-size program (part of binutils), coming from a Unix background,
doesn’t account for the .data initialization space added to the .text section, so in
order to know how much flash the final program will consume, one needs to add
the values for both, .text and .data (but not .bss), while the amount of pre-allocated
SRAM is the sum of .data and .bss.
4.2
The .data Section
This section contains static data which was defined in your code. Things like the following would end up in .data:
char err_str[] = "Your program has died a horrible death!";
struct point pt = { 1, 1 };
It is possible to tell the linker the SRAM address of the beginning of the .data section.
This is accomplished by adding -Wl,-Tdata,addr to the avr-gcc command
used to the link your program. Not that addr must be offset by adding 0x800000
the to real SRAM address so that the linker knows that the address is in the SRAM
memory space. Thus, if you want the .data section to start at 0x1100, pass 0x801100
at the address to the linker. [offset explained]
Note
When using malloc() in the application (which could even happen inside library
calls), additional adjustments are required.
4.3
The .bss Section
Uninitialized global or static variables end up in the .bss section.
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4.4
The .eeprom Section
4.4
The .eeprom Section
24
This is where eeprom variables are stored.
4.5
The .noinit Section
This sections is a part of the .bss section. What makes the .noinit section special is that
variables which are defined as such:
int foo __attribute__ ((section (".noinit")));
will not be initialized to zero during startup as would normal .bss data.
Only uninitialized variables can be placed in the .noinit section. Thus, the following
code will cause avr-gcc to issue an error:
int bar __attribute__ ((section (".noinit"))) = 0xaa;
It is possible to tell the linker explicitly where to place the .noinit section by adding
-Wl,--section-start=.noinit=0x802000 to the avr-gcc command line
at the linking stage. For example, suppose you wish to place the .noinit section at
SRAM address 0x2000:
$ avr-gcc ... -Wl,--section-start=.noinit=0x802000 ...
Note
Because of the Harvard architecture of the AVR devices, you must manually add
0x800000 to the address you pass to the linker as the start of the section. Otherwise, the linker thinks you want to put the .noinit section into the .text section
instead of .data/.bss and will complain.
Alternatively, you can write your own linker script to automate this. [FIXME: need an
example or ref to dox for writing linker scripts.]
4.6
The .initN Sections
These sections are used to define the startup code from reset up through the start of
main(). These all are subparts of the .text section.
The purpose of these sections is to allow for more specific placement of code within
your program.
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4.6
The .initN Sections
25
Note
Sometimes, it is convenient to think of the .initN and .finiN sections as functions,
but in reality they are just symbolic names which tell the linker where to stick a
chunk of code which is not a function. Notice that the examples for asm and C can
not be called as functions and should not be jumped into.
The .initN sections are executed in order from 0 to 9.
.init0:
Weakly bound to __init(). If user defines __init(), it will be jumped into immediately after a reset.
.init1:
Unused. User definable.
.init2:
In C programs, weakly bound to initialize the stack, and to clear __zero_reg__
(r1).
.init3:
Unused. User definable.
.init4:
For devices with > 64 KB of ROM, .init4 defines the code which takes care of copying
the contents of .data from the flash to SRAM. For all other devices, this code as well
as the code to zero out the .bss section is loaded from libgcc.a.
.init5:
Unused. User definable.
.init6:
Unused for C programs, but used for constructors in C++ programs.
.init7:
Unused. User definable.
.init8:
Unused. User definable.
.init9:
Jumps into main().
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4.7
The .finiN Sections
4.7
The .finiN Sections
26
These sections are used to define the exit code executed after return from main() or a
call to exit(). These all are subparts of the .text section.
The .finiN sections are executed in descending order from 9 to 0.
.finit9:
Unused. User definable. This is effectively where _exit() starts.
.fini8:
Unused. User definable.
.fini7:
Unused. User definable.
.fini6:
Unused for C programs, but used for destructors in C++ programs.
.fini5:
Unused. User definable.
.fini4:
Unused. User definable.
.fini3:
Unused. User definable.
.fini2:
Unused. User definable.
.fini1:
Unused. User definable.
.fini0:
Goes into an infinite loop after program termination and completion of any _exit()
code (execution of code in the .fini9 -> .fini1 sections).
4.8
Using Sections in Assembler Code
Example:
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4.9
Using Sections in C Code
27
#include <avr/io.h>
.section .init1,"ax",@progbits
ldi
r0, 0xff
out
_SFR_IO_ADDR(PORTB), r0
out
_SFR_IO_ADDR(DDRB), r0
Note
The ,"ax",@progbits tells the assembler that the section is allocatable ("a"),
executable ("x") and contains data ("@progbits"). For more detailed information
on the .section directive, see the gas user manual.
4.9
Using Sections in C Code
Example:
#include <avr/io.h>
void my_init_portb (void) __attribute__ ((naked)) \
__attribute__ ((section (".init3")));
void
my_init_portb (void)
{
PORTB = 0xff;
DDRB = 0xff;
}
Note
Section .init3 is used in this example, as this ensures the inernal __zero_reg__ has already been set up. The code generated by the compiler might blindly rely
on __zero_reg__ being really 0.
5
5.1
Data in Program Space
Introduction
So you have some constant data and you’re running out of room to store it? Many
AVRs have limited amount of RAM in which to store data, but may have more Flash
space available. The AVR is a Harvard architecture processor, where Flash is used for
the program, RAM is used for data, and they each have separate address spaces. It is
a challenge to get constant data to be stored in the Program Space, and to retrieve that
data to use it in the AVR application.
The problem is exacerbated by the fact that the C Language was not designed for
Harvard architectures, it was designed for Von Neumann architectures where code and
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5.2
A Note On const
28
data exist in the same address space. This means that any compiler for a Harvard
architecture processor, like the AVR, has to use other means to operate with separate
address spaces.
Some compilers use non-standard C language keywords, or they extend the standard
syntax in ways that are non-standard. The AVR toolset takes a different approach.
GCC has a special keyword, __attribute__ that is used to attach different attributes to things such as function declarations, variables, and types. This keyword is
followed by an attribute specification in double parentheses. In AVR GCC, there is a
special attribute called progmem. This attribute is use on data declarations, and tells
the compiler to place the data in the Program Memory (Flash).
AVR-Libc provides a simple macro PROGMEM that is defined as the attribute syntax of
GCC with the progmem attribute. This macro was created as a convenience to the end
user, as we will see below. The PROGMEM macro is defined in the <avr/pgmspace.h>
system header file.
It is difficult to modify GCC to create new extensions to the C language syntax, so
instead, avr-libc has created macros to retrieve the data from the Program Space. These
macros are also found in the <avr/pgmspace.h> system header file.
5.2
A Note On const
Many users bring up the idea of using C’s keyword const as a means of declaring
data to be in Program Space. Doing this would be an abuse of the intended meaning of
the const keyword.
const is used to tell the compiler that the data is to be "read-only". It is used to help
make it easier for the compiler to make certain transformations, or to help the compiler
check for incorrect usage of those variables.
For example, the const keyword is commonly used in many functions as a modifier on
the parameter type. This tells the compiler that the function will only use the parameter
as read-only and will not modify the contents of the parameter variable.
const was intended for uses such as this, not as a means to identify where the data
should be stored. If it were used as a means to define data storage, then it loses its
correct meaning (changes its semantics) in other situations such as in the function parameter example.
5.3
Storing and Retrieving Data in the Program Space
Let’s say you have some global data:
unsigned char mydata[11][10] =
{
{0x00,0x01,0x02,0x03,0x04,0x05,0x06,0x07,0x08,0x09},
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5.3
Storing and Retrieving Data in the Program Space
29
{0x0A,0x0B,0x0C,0x0D,0x0E,0x0F,0x10,0x11,0x12,0x13},
{0x14,0x15,0x16,0x17,0x18,0x19,0x1A,0x1B,0x1C,0x1D},
{0x1E,0x1F,0x20,0x21,0x22,0x23,0x24,0x25,0x26,0x27},
{0x28,0x29,0x2A,0x2B,0x2C,0x2D,0x2E,0x2F,0x30,0x31},
{0x32,0x33,0x34,0x35,0x36,0x37,0x38,0x39,0x3A,0x3B},
{0x3C,0x3D,0x3E,0x3F,0x40,0x41,0x42,0x43,0x44,0x45},
{0x46,0x47,0x48,0x49,0x4A,0x4B,0x4C,0x4D,0x4E,0x4F},
{0x50,0x51,0x52,0x53,0x54,0x55,0x56,0x57,0x58,0x59},
{0x5A,0x5B,0x5C,0x5D,0x5E,0x5F,0x60,0x61,0x62,0x63},
{0x64,0x65,0x66,0x67,0x68,0x69,0x6A,0x6B,0x6C,0x6D}
};
and later in your code you access this data in a function and store a single byte into a
variable like so:
byte = mydata[i][j];
Now you want to store your data in Program Memory. Use the PROGMEM macro found
in <avr/pgmspace.h> and put it after the declaration of the variable, but before
the initializer, like so:
#include <avr/pgmspace.h>
.
.
.
unsigned char mydata[11][10] PROGMEM =
{
{0x00,0x01,0x02,0x03,0x04,0x05,0x06,0x07,0x08,0x09},
{0x0A,0x0B,0x0C,0x0D,0x0E,0x0F,0x10,0x11,0x12,0x13},
{0x14,0x15,0x16,0x17,0x18,0x19,0x1A,0x1B,0x1C,0x1D},
{0x1E,0x1F,0x20,0x21,0x22,0x23,0x24,0x25,0x26,0x27},
{0x28,0x29,0x2A,0x2B,0x2C,0x2D,0x2E,0x2F,0x30,0x31},
{0x32,0x33,0x34,0x35,0x36,0x37,0x38,0x39,0x3A,0x3B},
{0x3C,0x3D,0x3E,0x3F,0x40,0x41,0x42,0x43,0x44,0x45},
{0x46,0x47,0x48,0x49,0x4A,0x4B,0x4C,0x4D,0x4E,0x4F},
{0x50,0x51,0x52,0x53,0x54,0x55,0x56,0x57,0x58,0x59},
{0x5A,0x5B,0x5C,0x5D,0x5E,0x5F,0x60,0x61,0x62,0x63},
{0x64,0x65,0x66,0x67,0x68,0x69,0x6A,0x6B,0x6C,0x6D}
};
That’s it! Now your data is in the Program Space. You can compile, link, and check
the map file to verify that mydata is placed in the correct section.
Now that your data resides in the Program Space, your code to access (read) the data
will no longer work. The code that gets generated will retrieve the data that is located
at the address of the mydata array, plus offsets indexed by the i and j variables.
However, the final address that is calculated where to the retrieve the data points to
the Data Space! Not the Program Space where the data is actually located. It is likely
that you will be retrieving some garbage. The problem is that AVR GCC does not
intrinsically know that the data resides in the Program Space.
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5.4
Storing and Retrieving Strings in the Program Space
30
The solution is fairly simple. The "rule of thumb" for accessing data stored in the
Program Space is to access the data as you normally would (as if the variable is stored
in Data Space), like so:
byte = mydata[i][j];
then take the address of the data:
byte = &(mydata[i][j]);
then use the appropriate pgm_read_∗ macro, and the address of your data becomes
the parameter to that macro:
byte = pgm_read_byte(&(mydata[i][j]));
The pgm_read_∗ macros take an address that points to the Program Space, and retrieves the data that is stored at that address. This is why you take the address of the
offset into the array. This address becomes the parameter to the macro so it can generate the correct code to retrieve the data from the Program Space. There are different
pgm_read_∗ macros to read different sizes of data at the address given.
5.4
Storing and Retrieving Strings in the Program Space
Now that you can successfully store and retrieve simple data from Program Space you
want to store and retrive strings from Program Space. And specifically you want to
store and array of strings to Program Space. So you start off with your array, like so:
char *string_table[] =
{
"String 1",
"String 2",
"String 3",
"String 4",
"String 5"
};
and then you add your PROGMEM macro to the end of the declaration:
char *string_table[] PROGMEM =
{
"String 1",
"String 2",
"String 3",
"String 4",
"String 5"
};
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5.4
Storing and Retrieving Strings in the Program Space
31
Right? WRONG!
Unfortunately, with GCC attributes, they affect only the declaration that they are attached to. So in this case, we successfully put the string_table variable, the array
itself, in the Program Space. This DOES NOT put the actual strings themselves into
Program Space. At this point, the strings are still in the Data Space, which is probably
not what you want.
In order to put the strings in Program Space, you have to have explicit declarations for
each string, and put each string in Program Space:
char
char
char
char
char
string_1[]
string_2[]
string_3[]
string_4[]
string_5[]
PROGMEM
PROGMEM
PROGMEM
PROGMEM
PROGMEM
=
=
=
=
=
"String
"String
"String
"String
"String
1";
2";
3";
4";
5";
Then use the new symbols in your table, like so:
PGM_P string_table[] PROGMEM =
{
string_1,
string_2,
string_3,
string_4,
string_5
};
Now this has the effect of putting string_table in Program Space, where string_table is an array of pointers to characters (strings), where each pointer is a pointer to
the Program Space, where each string is also stored.
The PGM_P type above is also a macro that defined as a pointer to a character in the
Program Space.
Retrieving the strings are a different matter. You probably don’t want to pull the string
out of Program Space, byte by byte, using the pgm_read_byte() macro. There are
other functions declared in the <avr/pgmspace.h> header file that work with strings
that are stored in the Program Space.
For example if you want to copy the string from Program Space to a buffer in RAM
(like an automatic variable inside a function, that is allocated on the stack), you can do
this:
void foo(void)
{
char buffer[10];
for (unsigned char i = 0; i < 5; i++)
{
strcpy_P(buffer, (PGM_P)pgm_read_word(&(string_table[i])));
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5.5
Caveats
32
// Display buffer on LCD.
}
return;
}
Here, the string_table array is stored in Program Space, so we access it normally,
as if were stored in Data Space, then take the address of the location we want to access,
and use the address as a parameter to pgm_read_word. We use the pgm_read_word macro to read the string pointer out of the string_table array. Remember
that a pointer is 16-bits, or word size. The pgm_read_word macro will return a 16bit unsigned integer. We then have to typecast it as a true pointer to program memory,
PGM_P. This pointer is an address in Program Space pointing to the string that we
want to copy. This pointer is then used as a parameter to the function strcpy_P. The
function strcpy_P is just like the regular strcpy function, except that it copies a
string from Program Space (the second parameter) to a buffer in the Data Space (the
first parameter).
There are many string functions available that work with strings located in Program
Space. All of these special string functions have a suffix of _P in the function name,
and are declared in the <avr/pgmspace.h> header file.
5.5
Caveats
The macros and functions used to retrieve data from the Program Space have to generate some extra code in order to actually load the data from the Program Space. This
incurs some extra overhead in terms of code space (extra opcodes) and execution time.
Usually, both the space and time overhead is minimal compared to the space savings
of putting data in Program Space. But you should be aware of this so you can minimize the number of calls within a single function that gets the same piece of data from
Program Space. It is always instructive to look at the resulting disassembly from the
compiler.
6
6.1
avr-libc and assembler programs
Introduction
There might be several reasons to write code for AVR microcontrollers using plain
assembler source code. Among them are:
• Code for devices that do not have RAM and are thus not supported by the C
compiler.
• Code for very time-critical applications.
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6.2
Invoking the compiler
33
• Special tweaks that cannot be done in C.
Usually, all but the first could probably be done easily using the inline assembler facility
of the compiler.
Although avr-libc is primarily targeted to support programming AVR microcontrollers
using the C (and C++) language, there’s limited support for direct assembler usage as
well. The benefits of it are:
• Use of the C preprocessor and thus the ability to use the same symbolic constants
that are available to C programs, as well as a flexible macro concept that can use
any valid C identifier as a macro (whereas the assembler’s macro concept is
basically targeted to use a macro in place of an assembler instruction).
• Use of the runtime framework like automatically assigning interrupt vectors. For
devices that have RAM, initializing the RAM variables can also be utilized.
6.2
Invoking the compiler
For the purpose described in this document, the assembler and linker are usually not
invoked manually, but rather using the C compiler frontend (avr-gcc) that in turn
will call the assembler and linker as required.
This approach has the following advantages:
• There is basically only one program to be called directly, avr-gcc, regardless
of the actual source language used.
• The invokation of the C preprocessor will be automatic, and will include the
appropriate options to locate required include files in the filesystem.
• The invokation of the linker will be automatic, and will include the appropriate options to locate additional libraries as well as the application start-up code
(crtXXX.o) and linker script.
Note that the invokation of the C preprocessor will be automatic when the filename
provided for the assembler file ends in .S (the capital letter "s"). This would even apply
to operating systems that use case-insensitive filesystems since the actual decision is
made based on the case of the filename suffix given on the command-line, not based on
the actual filename from the file system.
Alternatively, the language can explicitly be specified using the -x assembler-with-cpp
option.
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6.3
Example program
6.3
Example program
34
The following annotated example features a simple 100 kHz square wave generator
using an AT90S1200 clocked with a 10.7 MHz crystal. Pin PD6 will be used for the
square wave output.
#include <avr/io.h>
; Note [1]
work
tmp
=
=
16
17
; Note [2]
inttmp
=
19
intsav
=
0
SQUARE
=
PD6
tmconst= 10700000 / 200000
fuzz=
8
; Note [3]
; Note [4]:
; 100 kHz => 200000 edges/s
; # clocks in ISR until TCNT0 is set
.section .text
.global main
; Note [5]
main:
rcall
ioinit
rjmp
1b
1:
.global TIMER0_OVF_vect
TIMER0_OVF_vect:
ldi
inttmp, 256 - tmconst + fuzz
out
_SFR_IO_ADDR(TCNT0), inttmp
1:
2:
in
intsav, _SFR_IO_ADDR(SREG)
sbic
rjmp
sbi
rjmp
cbi
_SFR_IO_ADDR(PORTD), SQUARE
1f
_SFR_IO_ADDR(PORTD), SQUARE
2f
_SFR_IO_ADDR(PORTD), SQUARE
out
reti
_SFR_IO_ADDR(SREG), intsav
sbi
_SFR_IO_ADDR(DDRD), SQUARE
ldi
out
work, _BV(TOIE0)
_SFR_IO_ADDR(TIMSK), work
ldi
out
work, _BV(CS00)
; tmr0:
_SFR_IO_ADDR(TCCR0), work
ldi
work, 256 - tmconst
; Note [6]
; Note [7]
; Note [8]
; Note [9]
ioinit:
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CK/1
6.3
Example program
out
35
_SFR_IO_ADDR(TCNT0), work
sei
ret
.global __vector_default
__vector_default:
reti
; Note [10]
.end
Note [1]
As in C programs, this includes the central processor-specific file containing the IO port
definitions for the device. Note that not all include files can be included into assembler
sources.
Note [2]
Assignment of registers to symbolic names used locally. Another option would be to
use a C preprocessor macro instead:
#define work 16
Note [3]
Our bit number for the square wave output. Note that the right-hand side consists of a
CPP macro which will be substituted by its value (6 in this case) before actually being
passed to the assembler.
Note [4]
The assembler uses integer operations in the host-defined integer size (32 bits or longer)
when evaluating expressions. This is in contrast to the C compiler that uses the C type
int by default in order to calculate constant integer expressions.
In order to get a 100 kHz output, we need to toggle the PD6 line 200000 times per
second. Since we use timer 0 without any prescaling options in order to get the desired frequency and accuracy, we already run into serious timing considerations: while
accepting and processing the timer overflow interrupt, the timer already continues to
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6.3
Example program
36
count. When pre-loading the TCCNT0 register, we therefore have to account for the
number of clock cycles required for interrupt acknowledge and for the instructions to
reload TCCNT0 (4 clock cycles for interrupt acknowledge, 2 cycles for the jump from
the interrupt vector, 2 cycles for the 2 instructions that reload TCCNT0). This is what
the constant fuzz is for.
Note [5]
External functions need to be declared to be .global. main is the application entry
point that will be jumped to from the ininitalization routine in crts1200.o.
Note [6]
The main loop is just a single jump back to itself. Square wave generation itself is
completely handled by the timer 0 overflow interrupt service. A sleep instruction
(using idle mode) could be used as well, but probably would not conserve much energy
anyway since the interrupt service is executed quite frequently.
Note [7]
Interrupt functions can get the usual names that are also available to C programs. The
linker will then put them into the appropriate interrupt vector slots. Note that they must
be declared .global in order to be acceptable for this purpose. This will only work if
<avr/io.h> has been included. Note that the assembler or linker have no chance
to check the correct spelling of an interrupt function, so it should be double-checked.
(When analyzing the resulting object file using avr-objdump or avr-nm, a name
like __vector_N should appear, with N being a small integer number.)
Note [8]
As explained in the section about special function registers, the actual IO port address
should be obtained using the macro _SFR_IO_ADDR. (The AT90S1200 does not have
RAM thus the memory-mapped approach to access the IO registers is not available. It
would be slower than using in / out instructions anyway.)
Since the operation to reload TCCNT0 is time-critical, it is even performed before
saving SREG. Obviously, this requires that the instructions involved would not change
any of the flag bits in SREG.
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6.4
Pseudo-ops and operators
37
Note [9]
Interrupt routines must not clobber the global CPU state. Thus, it is usually necessary
to save at least the state of the flag bits in SREG. (Note that this serves as an example
here only since actually, all the following instructions would not modify SREG either,
but that’s not commonly the case.)
Also, it must be made sure that registers used inside the interrupt routine do not conflict
with those used outside. In the case of a RAM-less device like the AT90S1200, this can
only be done by agreeing on a set of registers to be used exclusively inside the interrupt
routine; there would not be any other chance to "save" a register anywhere.
If the interrupt routine is to be linked together with C modules, care must be taken
to follow the register usage guidelines imposed by the C compiler. Also, any register
modified inside the interrupt sevice needs to be saved, usually on the stack.
Note [10]
As explained in Interrupts, a global "catch-all" interrupt handler that gets all unassigned
interrupt vectors can be installed using the name __vector_default. This must
be .global, and obviously, should end in a reti instruction. (By default, a jump to
location 0 would be implied instead.)
6.4
Pseudo-ops and operators
The available pseudo-ops in the assembler are described in the GNU assembler (gas)
manual. The manual can be found online as part of the current binutils release under
http://sources.redhat.com/binutils/.
As gas comes from a Unix origin, its pseudo-op and overall assembler syntax is slightly
different than the one being used by other assemblers. Numeric constants follow the C
notation (prefix 0x for hexadecimal constants), expressions use a C-like syntax.
Some common pseudo-ops include:
• .byte allocates single byte constants
• .ascii allocates a non-terminated string of characters
• .asciz allocates a \0-terminated string of characters (C string)
• .data switches to the .data section (initialized RAM variables)
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7 Inline Assembler Cookbook
38
• .text switches to the .text section (code and ROM constants)
• .set declares a symbol as a constant expression (identical to .equ)
• .global (or .globl) declares a public symbol that is visible to the linker (e. g.
function entry point, global variable)
• .extern declares a symbol to be externally defined; this is effectively a comment
only, as gas treats all undefined symbols it encounters as globally undefined anyway
Note that .org is available in gas as well, but is a fairly pointless pseudo-op in an assembler environment that uses relocatable object files, as it is the linker that determines
the final position of some object in ROM or RAM.
Along with the architecture-independent standard operators, there are some AVR-specific
operators available which are unfortunately not yet described in the official documentation. The most notable operators are:
• lo8 Takes the least significant 8 bits of a 16-bit integer
• hi8 Takes the most significant 8 bits of a 16-bit integer
• pm Takes a program-memory (ROM) address, and converts it into a RAM address. This implies a division by 2 as the AVR handles ROM addresses as 16-bit
words (e.g. in an IJMP or ICALL instruction), and can also handle relocatable
symbols on the right-hand side.
Example:
ldi r24, lo8(pm(somefunc))
ldi r25, hi8(pm(somefunc))
call something
This passes the address of function somefunc as the first parameter to function
something.
7
Inline Assembler Cookbook
AVR-GCC
Inline Assembler Cookbook
About this Document
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7.1
GCC asm Statement
39
The GNU C compiler for Atmel AVR RISC processors offers, to embed assembly
language code into C programs. This cool feature may be used for manually optimizing
time critical parts of the software or to use specific processor instruction, which are not
available in the C language.
Because of a lack of documentation, especially for the AVR version of the compiler, it
may take some time to figure out the implementation details by studying the compiler
and assembler source code. There are also a few sample programs available in the net.
Hopefully this document will help to increase their number.
It’s assumed, that you are familiar with writing AVR assembler programs, because this
is not an AVR assembler programming tutorial. It’s not a C language tutorial either.
Note that this document does not cover file written completely in assembler language,
refer to avr-libc and assembler programs for this.
Copyright (C) 2001-2002 by egnite Software GmbH
Permission is granted to copy and distribute verbatim copies of this manual provided
that the copyright notice and this permission notice are preserved on all copies. Permission is granted to copy and distribute modified versions of this manual provided that
the entire resulting derived work is distributed under the terms of a permission notice
identical to this one.
This document describes version 3.3 of the compiler. There may be some parts, which
hadn’t been completely understood by the author himself and not all samples had been
tested so far. Because the author is German and not familiar with the English language,
there are definitely some typos and syntax errors in the text. As a programmer the
author knows, that a wrong documentation sometimes might be worse than none. Anyway, he decided to offer his little knowledge to the public, in the hope to get enough
response to improve this document. Feel free to contact the author via e-mail. For the
latest release check http://www.ethernut.de/.
Herne, 17th of May 2002 Harald Kipp harald.kipp-at-egnite.de
Note
As of 26th of July 2002, this document has been merged into the documentation for
avr-libc. The latest version is now available at http://savannah.nongnu.org/projects/avr-libc/.
7.1
GCC asm Statement
Let’s start with a simple example of reading a value from port D:
asm("in %0, %1" : "=r" (value) : "I" (_SFR_IO_ADDR(PORTD)) );
Each asm statement is devided by colons into (up to) four parts:
1. The assembler instructions, defined as a single string constant:
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7.1
GCC asm Statement
40
"in %0, %1"
2. A list of output operands, separated by commas. Our example uses just one:
"=r" (value)
3. A comma separated list of input operands. Again our example uses one operand
only:
"I" (_SFR_IO_ADDR(PORTD))
4. Clobbered registers, left empty in our example.
You can write assembler instructions in much the same way as you would write assembler programs. However, registers and constants are used in a different way if they refer
to expressions of your C program. The connection between registers and C operands is
specified in the second and third part of the asm instruction, the list of input and output
operands, respectively. The general form is
asm(code : output operand list : input operand list [: clobber list]);
In the code section, operands are referenced by a percent sign followed by a single digit.
0 refers to the first 1 to the second operand and so forth. From the above example:
0 refers to "=r" (value) and
1 refers to "I" (_SFR_IO_ADDR(PORTD)).
This may still look a little odd now, but the syntax of an operand list will be explained
soon. Let us first examine the part of a compiler listing which may have been generated
from our example:
lds r24,value
/* #APP */
in r24, 12
/* #NOAPP */
sts value,r24
The comments have been added by the compiler to inform the assembler that the included code was not generated by the compilation of C statements, but by inline assembler statements. The compiler selected register r24 for storage of the value read
from PORTD. The compiler could have selected any other register, though. It may not
explicitely load or store the value and it may even decide not to include your assembler
code at all. All these decisions are part of the compiler’s optimization strategy. For
example, if you never use the variable value in the remaining part of the C program,
the compiler will most likely remove your code unless you switched off optimization.
To avoid this, you can add the volatile attribute to the asm statement:
asm volatile("in %0, %1" : "=r" (value) : "I" (_SFR_IO_ADDR(PORTD)));
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7.2
Assembler Code
41
Alternatively, operands can be given names. The name is prepended in brackets to the
constraints in the operand list, and references to the named operand use the bracketed
name instead of a number after the % sign. Thus, the above example could also be
written as
asm("in %[retval], %[port]" :
[retval] "=r" (value) :
[port] "I" (_SFR_IO_ADDR(PORTD)) );
The last part of the asm instruction, the clobber list, is mainly used to tell the compiler
about modifications done by the assembler code. This part may be omitted, all other
parts are required, but may be left empty. If your assembler routine won’t use any
input or output operand, two colons must still follow the assembler code string. A
good example is a simple statement to disable interrupts:
asm volatile("cli"::);
7.2
Assembler Code
You can use the same assembler instruction mnemonics as you’d use with any other
AVR assembler. And you can write as many assembler statements into one code string
as you like and your flash memory is able to hold.
Note
The available assembler directives vary from one assembler to another.
To make it more readable, you should put each statement on a seperate line:
asm volatile("nop\n\t"
"nop\n\t"
"nop\n\t"
"nop\n\t"
::);
The linefeed and tab characters will make the assembler listing generated by the compiler more readable. It may look a bit odd for the first time, but that’s the way the
compiler creates it’s own assembler code.
You may also make use of some special registers.
Symbol
__SREG__
__SP_H__
__SP_L__
__tmp_reg__
__zero_reg__
Register
Status register at address 0x3F
Stack pointer high byte at address 0x3E
Stack pointer low byte at address 0x3D
Register r0, used for temporary storage
Register r1, always zero
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7.3
Input and Output Operands
42
Register r0 may be freely used by your assembler code and need not be restored at
the end of your code. It’s a good idea to use __tmp_reg__ and __zero_reg__
instead of r0 or r1, just in case a new compiler version changes the register usage
definitions.
7.3
Input and Output Operands
Each input and output operand is described by a constraint string followed by a C
expression in parantheses. AVR-GCC 3.3 knows the following constraint characters:
Note
The most up-to-date and detailed information on contraints for the avr can be found
in the gcc manual.
The x register is r27:r26, the y register is r29:r28, and the z register is
r31:r30
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7.3
Input and Output Operands
Constraint
a
b
d
e
q
r
t
w
x
y
z
G
I
J
K
L
l
M
N
O
P
Q
R
Used for
Simple upper registers
Base pointer registers
pairs
Upper register
Pointer register pairs
Stack pointer register
Any register
Temporary register
Special upper register
pairs
Pointer register pair X
Pointer register pair Y
Pointer register pair Z
Floating point constant
6-bit positive integer
constant
6-bit negative integer
constant
Integer constant
Integer constant
Lower registers
8-bit integer constant
Integer constant
Integer constant
Integer constant
(GCC >= 4.2.x) A
memory address based
on Y or Z pointer with
displacement.
(GCC >= 4.3.x) Integer
constant.
43
Range
r16 to r23
y, z
r16 to r31
x, y, z
SPH:SPL
r0 to r31
r0
r24, r26, r28, r30
x (r27:r26)
y (r29:r28)
z (r31:r30)
0.0
0 to 63
-63 to 0
2
0
r0 to r15
0 to 255
-1
8, 16, 24
1
-6 to 5
The selection of the proper contraint depends on the range of the constants or registers,
which must be acceptable to the AVR instruction they are used with. The C compiler
doesn’t check any line of your assembler code. But it is able to check the constraint
against your C expression. However, if you specify the wrong constraints, then the
compiler may silently pass wrong code to the assembler. And, of course, the assembler
will fail with some cryptic output or internal errors. For example, if you specify the
constraint "r" and you are using this register with an "ori" instruction in your assembler code, then the compiler may select any register. This will fail, if the compiler
chooses r2 to r15. (It will never choose r0 or r1, because these are uses for special
purposes.) That’s why the correct constraint in that case is "d". On the other hand, if
you use the constraint "M", the compiler will make sure that you don’t pass anything
else but an 8-bit value. Later on we will see how to pass multibyte expression results
to the assembler code.
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7.3
Input and Output Operands
44
The following table shows all AVR assembler mnemonics which require operands, and
the related contraints. Because of the improper constraint definitions in version 3.3,
they aren’t strict enough. There is, for example, no constraint, which restricts integer
constants to the range 0 to 7 for bit set and bit clear operations.
Mnemonic
adc
adiw
andi
bclr
brbc
bset
cbi
com
cpc
cpse
elpm
in
ld
ldi
lpm
lsr
movw
neg
ori
pop
rol
sbc
sbi
sbiw
sbrc
ser
std
sub
swap
Constraints
r,r
w,I
d,M
I
I,label
I
I,I
r
r,r
r,r
t,z
r,I
r,e
d,M
t,z
r
r,r
r
d,M
r
r
r,r
I,I
w,I
r,I
d
b,r
r,r
r
Mnemonic
add
and
asr
bld
brbs
bst
cbr
cp
cpi
dec
eor
inc
ldd
lds
lsl
mov
mul
or
out
push
ror
sbci
sbic
sbr
sbrs
st
sts
subi
Constraints
r,r
r,r
r
r,I
I,label
r,I
d,I
r,r
d,M
r
r,r
r
r,b
r,label
r
r,r
r,r
r,r
I,r
r
r
d,M
I,I
d,M
r,I
e,r
label,r
d,M
Constraint characters may be prepended by a single constraint modifier. Contraints
without a modifier specify read-only operands. Modifiers are:
Modifier
=
+
&
Specifies
Write-only operand, usually used for all
output operands.
Read-write operand
Register should be used for output only
Output operands must be write-only and the C expression result must be an lvalue,
which means that the operands must be valid on the left side of assignments. Note,
that the compiler will not check if the operands are of reasonable type for the kind of
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7.3
Input and Output Operands
45
operation used in the assembler instructions.
Input operands are, you guessed it, read-only. But what if you need the same operand
for input and output? As stated above, read-write operands are not supported in inline
assembler code. But there is another solution. For input operators it is possible to use
a single digit in the constraint string. Using digit n tells the compiler to use the same
register as for the n-th operand, starting with zero. Here is an example:
asm volatile("swap %0" : "=r" (value) : "0" (value));
This statement will swap the nibbles of an 8-bit variable named value. Constraint "0"
tells the compiler, to use the same input register as for the first operand. Note however,
that this doesn’t automatically imply the reverse case. The compiler may choose the
same registers for input and output, even if not told to do so. This is not a problem in
most cases, but may be fatal if the output operator is modified by the assembler code
before the input operator is used. In the situation where your code depends on different
registers used for input and output operands, you must add the & constraint modifier to
your output operand. The following example demonstrates this problem:
asm volatile("in %0,%1"
"\n\t"
"out %1, %2" "\n\t"
: "=&r" (input)
: "I" (_SFR_IO_ADDR(port)), "r" (output)
);
In this example an input value is read from a port and then an output value is written to
the same port. If the compiler would have choosen the same register for input and output, then the output value would have been destroyed on the first assembler instruction.
Fortunately, this example uses the & constraint modifier to instruct the compiler not to
select any register for the output value, which is used for any of the input operands.
Back to swapping. Here is the code to swap high and low byte of a 16-bit value:
asm volatile("mov __tmp_reg__, %A0" "\n\t"
"mov %A0, %B0"
"\n\t"
"mov %B0, __tmp_reg__" "\n\t"
: "=r" (value)
: "0" (value)
);
First you will notice the usage of register __tmp_reg__, which we listed among
other special registers in the Assembler Code section. You can use this register without
saving its contents. Completely new are those letters A and B in %A0 and %B0. In fact
they refer to two different 8-bit registers, both containing a part of value.
Another example to swap bytes of a 32-bit value:
asm volatile("mov __tmp_reg__, %A0" "\n\t"
"mov %A0, %D0"
"\n\t"
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7.3
Input and Output Operands
"mov %D0, __tmp_reg__"
"mov __tmp_reg__, %B0"
"mov %B0, %C0"
"mov %C0, __tmp_reg__"
: "=r" (value)
: "0" (value)
);
46
"\n\t"
"\n\t"
"\n\t"
"\n\t"
Instead of listing the same operand as both, input and output operand, it can also be
declared as a read-write operand. This must be applied to an output operand, and the
respective input operand list remains empty:
asm volatile("mov __tmp_reg__, %A0"
"mov %A0, %D0"
"mov %D0, __tmp_reg__"
"mov __tmp_reg__, %B0"
"mov %B0, %C0"
"mov %C0, __tmp_reg__"
: "+r" (value));
"\n\t"
"\n\t"
"\n\t"
"\n\t"
"\n\t"
"\n\t"
If operands do not fit into a single register, the compiler will automatically assign
enough registers to hold the entire operand. In the assembler code you use %A0 to refer
to the lowest byte of the first operand, %A1 to the lowest byte of the second operand
and so on. The next byte of the first operand will be %B0, the next byte %C0 and so on.
This also implies, that it is often neccessary to cast the type of an input operand to the
desired size.
A final problem may arise while using pointer register pairs. If you define an input
operand
"e" (ptr)
and the compiler selects register Z (r30:r31), then
%A0 refers to r30 and
%B0 refers to r31.
But both versions will fail during the assembly stage of the compiler, if you explicitely
need Z, like in
ld r24,Z
If you write
ld r24, %a0
with a lower case a following the percent sign, then the compiler will create the proper
assembler line.
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7.4
Clobbers
7.4
Clobbers
47
As stated previously, the last part of the asm statement, the list of clobbers, may be
omitted, including the colon seperator. However, if you are using registers, which
had not been passed as operands, you need to inform the compiler about this. The
following example will do an atomic increment. It increments an 8-bit value pointed
to by a pointer variable in one go, without being interrupted by an interrupt routine
or another thread in a multithreaded environment. Note, that we must use a pointer,
because the incremented value needs to be stored before interrupts are enabled.
asm volatile(
"cli"
"ld r24, %a0"
"inc r24"
"st %a0, r24"
"sei"
:
: "e" (ptr)
: "r24"
);
"\n\t"
"\n\t"
"\n\t"
"\n\t"
"\n\t"
The compiler might produce the following code:
cli
ld r24, Z
inc r24
st Z, r24
sei
One easy solution to avoid clobbering register r24 is, to make use of the special temporary register __tmp_reg__ defined by the compiler.
asm volatile(
"cli"
"ld __tmp_reg__, %a0"
"inc __tmp_reg__"
"st %a0, __tmp_reg__"
"sei"
:
: "e" (ptr)
);
"\n\t"
"\n\t"
"\n\t"
"\n\t"
"\n\t"
The compiler is prepared to reload this register next time it uses it. Another problem
with the above code is, that it should not be called in code sections, where interrupts
are disabled and should be kept disabled, because it will enable interrupts at the end.
We may store the current status, but then we need another register. Again we can solve
this without clobbering a fixed, but let the compiler select it. This could be done with
the help of a local C variable.
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7.4
Clobbers
48
{
uint8_t s;
asm volatile(
"in %0, __SREG__"
"cli"
"ld __tmp_reg__, %a1"
"inc __tmp_reg__"
"st %a1, __tmp_reg__"
"out __SREG__, %0"
: "=&r" (s)
: "e" (ptr)
);
"\n\t"
"\n\t"
"\n\t"
"\n\t"
"\n\t"
"\n\t"
}
Now every thing seems correct, but it isn’t really. The assembler code modifies the
variable, that ptr points to. The compiler will not recognize this and may keep its
value in any of the other registers. Not only does the compiler work with the wrong
value, but the assembler code does too. The C program may have modified the value
too, but the compiler didn’t update the memory location for optimization reasons. The
worst thing you can do in this case is:
{
uint8_t s;
asm volatile(
"in %0, __SREG__"
"cli"
"ld __tmp_reg__, %a1"
"inc __tmp_reg__"
"st %a1, __tmp_reg__"
"out __SREG__, %0"
: "=&r" (s)
: "e" (ptr)
: "memory"
);
"\n\t"
"\n\t"
"\n\t"
"\n\t"
"\n\t"
"\n\t"
}
The special clobber "memory" informs the compiler that the assembler code may modify any memory location. It forces the compiler to update all variables for which the
contents are currently held in a register before executing the assembler code. And of
course, everything has to be reloaded again after this code.
In most situations, a much better solution would be to declare the pointer destination
itself volatile:
volatile uint8_t *ptr;
This way, the compiler expects the value pointed to by ptr to be changed and will
load it whenever used and store it whenever modified.
Situations in which you need clobbers are very rare. In most cases there will be better
ways. Clobbered registers will force the compiler to store their values before and reload
them after your assembler code. Avoiding clobbers gives the compiler more freedom
while optimizing your code.
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7.5
Assembler Macros
7.5
Assembler Macros
49
In order to reuse your assembler language parts, it is useful to define them as macros
and put them into include files. AVR Libc comes with a bunch of them, which could be
found in the directory avr/include. Using such include files may produce compiler
warnings, if they are used in modules, which are compiled in strict ANSI mode. To
avoid that, you can write __asm__ instead of asm and __volatile__ instead of
volatile. These are equivalent aliases.
Another problem with reused macros arises if you are using labels. In such cases you
may make use of the special pattern =, which is replaced by a unique number on each
asm statement. The following code had been taken from avr/include/iomacros.h:
#define loop_until_bit_is_clear(port,bit) \
__asm__ __volatile__ (
\
"L_%=: " "sbic %0, %1" "\n\t"
\
"rjmp L_%="
\
: /* no outputs */
: "I" (_SFR_IO_ADDR(port)),
"I" (bit)
)
When used for the first time, L_= may be translated to L_1404, the next usage might
create L_1405 or whatever. In any case, the labels became unique too.
Another option is to use Unix-assembler style numeric labels. They are explained in
How do I trace an assembler file in avr-gdb?. The above example would then look like:
#define loop_until_bit_is_clear(port,bit)
__asm__ __volatile__ (
"1: " "sbic %0, %1" "\n\t"
"rjmp 1b"
: /* no outputs */
: "I" (_SFR_IO_ADDR(port)),
"I" (bit)
)
7.6
C Stub Functions
Macro definitions will include the same assembler code whenever they are referenced.
This may not be acceptable for larger routines. In this case you may define a C stub
function, containing nothing other than your assembler code.
void delay(uint8_t ms)
{
uint16_t cnt;
asm volatile (
"\n"
"L_dl1%=:" "\n\t"
"mov %A0, %A2" "\n\t"
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7.7
C Names Used in Assembler Code
50
"mov %B0, %B2" "\n"
"L_dl2%=:" "\n\t"
"sbiw %A0, 1" "\n\t"
"brne L_dl2%=" "\n\t"
"dec %1" "\n\t"
"brne L_dl1%=" "\n\t"
: "=&w" (cnt)
: "r" (ms), "r" (delay_count)
);
}
The purpose of this function is to delay the program execution by a specified number
of milliseconds using a counting loop. The global 16 bit variable delay_count must
contain the CPU clock frequency in Hertz divided by 4000 and must have been set
before calling this routine for the first time. As described in the clobber section, the
routine uses a local variable to hold a temporary value.
Another use for a local variable is a return value. The following function returns a 16
bit value read from two successive port addresses.
uint16_t inw(uint8_t port)
{
uint16_t result;
asm volatile (
"in %A0,%1" "\n\t"
"in %B0,(%1) + 1"
: "=r" (result)
: "I" (_SFR_IO_ADDR(port))
);
return result;
}
Note
inw() is supplied by avr-libc.
7.7
C Names Used in Assembler Code
By default AVR-GCC uses the same symbolic names of functions or variables in C and
assembler code. You can specify a different name for the assembler code by using a
special form of the asm statement:
unsigned long value asm("clock") = 3686400;
This statement instructs the compiler to use the symbol name clock rather than value.
This makes sense only for external or static variables, because local variables do not
have symbolic names in the assembler code. However, local variables may be held in
registers.
With AVR-GCC you can specify the use of a specific register:
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7.8
Links
51
void Count(void)
{
register unsigned char counter asm("r3");
... some code...
asm volatile("clr r3");
... more code...
}
The assembler instruction, "clr r3", will clear the variable counter. AVR-GCC will
not completely reserve the specified register. If the optimizer recognizes that the variable will not be referenced any longer, the register may be re-used. But the compiler
is not able to check wether this register usage conflicts with any predefined register. If
you reserve too many registers in this way, the compiler may even run out of registers
during code generation.
In order to change the name of a function, you need a prototype declaration, because
the compiler will not accept the asm keyword in the function definition:
extern long Calc(void) asm ("CALCULATE");
Calling the function Calc() will create assembler instructions to call the function
CALCULATE.
7.8
Links
For a more thorough discussion of inline assembly usage, see the gcc user manual. The
latest version of the gcc manual is always available here: http://gcc.gnu.org/onlinedocs/
8
8.1
How to Build a Library
Introduction
So you keep reusing the same functions that you created over and over? Tired of cut and
paste going from one project to the next? Would you like to reduce your maintenance
overhead? Then you’re ready to create your own library! Code reuse is a very laudable
goal. With some upfront investment, you can save time and energy on future projects
by having ready-to-go libraries. This chapter describes some background information,
design considerations, and practical knowledge that you will need to create and use
your own libraries.
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8.2
How the Linker Works
8.2
How the Linker Works
52
The compiler compiles a single high-level language file (C language, for example) into
a single object module file. The linker (ld) can only work with object modules to link
them together. Object modules are the smallest unit that the linker works with.
Typically, on the linker command line, you will specify a set of object modules (that
has been previously compiled) and then a list of libraries, including the Standard C
Library. The linker takes the set of object modules that you specify on the command
line and links them together. Afterwards there will probably be a set of "undefined
references". A reference is essentially a function call. An undefined reference is a
function call, with no defined function to match the call.
The linker will then go through the libraries, in order, to match the undefined references
with function definitions that are found in the libraries. If it finds the function that
matches the call, the linker will then link in the object module in which the function is
located. This part is important: the linker links in THE ENTIRE OBJECT MODULE in
which the function is located. Remember, the linker knows nothing about the functions
internal to an object module, other than symbol names (such as function names). The
smallest unit the linker works with is object modules.
When there are no more undefined references, the linker has linked everything and is
done and outputs the final application.
8.3
How to Design a Library
How the linker behaves is very important in designing a library. Ideally, you want to
design a library where only the functions that are called are the only functions to be
linked into the final application. This helps keep the code size to a minimum. In order
to do this, with the way the linker works, is to only write one function per code module.
This will compile to one function per object module. This is usually a very different
way of doing things than writing an application!
There are always exceptions to the rule. There are generally two cases where you
would want to have more than one function per object module.
The first is when you have very complementary functions that it doesn’t make much
sense to split them up. For example, malloc() and free(). If someone is going to use
malloc(), they will very likely be using free() (or at least should be using free()). In this
case, it makes more sense to aggregate those two functions in the same object module.
The second case is when you want to have an Interrupt Service Routine (ISR) in your
library that you want to link in. The problem in this case is that the linker looks for
unresolved references and tries to resolve them with code in libraries. A reference is
the same as a function call. But with ISRs, there is no function call to initiate the ISR.
The ISR is placed in the Interrupt Vector Table (IVT), hence no call, no reference,
and no linking in of the ISR. In order to do this, you have to trick the linker in a way.
Aggregate the ISR, with another function in the same object module, but have the other
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8.4
Creating a Library
53
function be something that is required for the user to call in order to use the ISR, like
perhaps an initialization function for the subsystem, or perhaps a function that enables
the ISR in the first place.
8.4
Creating a Library
The librarian program is called ar (for "archiver") and is found in the GNU Binutils
project. This program will have been built for the AVR target and will therefore be
named avr-ar.
The job of the librarian program is simple: aggregate a list of object modules into a
single library (archive) and create an index for the linker to use. The name that you
create for the library filename must follow a specific pattern: libname.a. The name part
is the unique part of the filename that you create. It makes it easier if the name part
relates to what the library is about. This name part must be prefixed by "lib", and it
must have a file extension of .a, for "archive". The reason for the special form of the
filename is for how the library gets used by the toolchain, as we will see later on.
Note
The filename is case-sensitive. Use a lowercase "lib" prefix, and a lowercase ".a"
as the file extension.
The command line is fairly simple:
avr-ar rcs <library name> <list of object modules>
The r command switch tells the program to insert the object modules into the archive
with replacement. The c command line switch tells the program to create the archive.
And the s command line switch tells the program to write an object-file index into the
archive, or update an existing one. This last switch is very important as it helps the
linker to find what it needs to do its job.
Note
The command line switches are case sensitive! There are uppercase switches that
have completely different actions.
MFile and the WinAVR distribution contain a Makefile Template that includes the
necessary command lines to build a library. You will have to manually modify the
template to switch it over to build a library instead of an application.
See the GNU Binutils manual for more information on the ar program.
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8.5
Using a Library
8.5
Using a Library
54
To use a library, use the -l switch on your linker command line. The string immediately following the -l is the unique part of the library filename that the linker will link
in. For example, if you use:
-lm
this will expand to the library filename:
libm.a
which happens to be the math library included in avr-libc.
If you use this on your linker command line:
-lprintf_flt
then the linker will look for a library called:
libprintf_flt.a
This is why naming your library is so important when you create it!
The linker will search libraries in the order that they appear on the command line.
Whichever function is found first that matches the undefined reference, it will be linked
in.
There are also command line switches that tell GCC which directory to look in (-L)
for the libraries that are specified to be linke in with -l.
See the GNU Binutils manual for more information on the GNU linker (ld) program.
9
Benchmarks
The results below can only give a rough estimate of the resources necessary for using
certain library functions. There is a number of factors which can both increase or
reduce the effort required:
• Expenses for preparation of operands and their stack are not considered.
• In the table, the size includes all additional functions (for example, function to
multiply two integers) but they are only linked from the library.
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9.1
A few of libc functions.
55
• Expenses of time of performance of some functions essentially depend on parameters of a call, for example, qsort() is recursive, and sprintf() receives parameters
in a stack.
• Different versions of the compiler can give a significant difference in code size
and execution time. For example, the dtostre() function, compiled with avr-gcc
3.4.6, requires 930 bytes. After transition to avr-gcc 4.2.3, the size become 1088
bytes.
9.1
A few of libc functions.
Avr-gcc version is 4.2.3
The size of function is given in view of all picked up functions. By default Avr-libc
is compiled with -mcall-prologues option. In brackets the size without taking
into account modules of a prologue and an epilogue is resulted. Both of the size can
coincide, if function does not cause a prologue/epilogue.
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9.1
A few of libc functions.
Function
atoi ("12345")
atol ("12345")
dtostre (1.2345,
s, 6, 0)
dtostrf (1.2345,
15, 6, s)
itoa (12345, s,
10)
ltoa (12345L, s,
10)
malloc (1)
realloc ((void
∗)0, 1)
qsort (s,
sizeof(s), 1, cmp)
sprintf_min (s,
"%d", 12345)
sprintf (s, "%d",
12345)
sprintf_flt (s,
"%e", 1.2345)
sscanf_min
("12345", "%d",
&i)
sscanf ("12345",
"%d", &i)
sscanf
("point,color",
"%[a-z]", s)
sscanf_flt
("1.2345", "%e",
&x)
strtod ("1.2345",
&p)
strtol ("12345",
&p, 0)
Units
Flash bytes
Stack bytes
MCU clocks
Flash bytes
Stack bytes
MCU clocks
Flash bytes
Stack bytes
MCU clocks
Flash bytes
Stack bytes
MCU clocks
Flash bytes
Stack bytes
MCU clocks
Flash bytes
Stack bytes
MCU clocks
Flash bytes
Stack bytes
MCU clocks
Flash bytes
Stack bytes
MCU clocks
Flash bytes
Stack bytes
MCU clocks
Flash bytes
Stack bytes
MCU clocks
Flash bytes
Stack bytes
MCU clocks
Flash bytes
Stack bytes
MCU clocks
Flash bytes
Stack bytes
MCU clocks
Flash bytes
Stack bytes
MCU clocks
Flash bytes
Stack bytes
MCU clocks
Flash bytes
Stack bytes
MCU clocks
Flash bytes
Stack bytes
MCU clocks
Flash bytes
Stack bytes
MCU clocks
56
Avr2
82 (82)
2
155
122 (122)
2
221
1184 (1072)
17
1313
1676 (1564)
36
1608
150 (150)
4
1172
220 (220)
9
3174
554 (554)
4
196
1152 (1040)
20
303
1242 (1130)
38
20914
1216 (1104)
59
1846
1674 (1562)
58
1610
3334 (3222)
66
2513
1540 (1428)
55
1339
1950 (1838)
53
1334
1950 (1838)
87
2878
3298 (3186)
63
2187
1570 (1458)
22
1237
942 (830)
29
1074
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Avr25
78 (78)
118 (118)
1088 (978)
1548 (1438)
134 (134)
200 (200)
506 (506)
1042 (932)
990 (880)
1090 (980)
1542 (1432)
3084 (2974)
1354 (1244)
1704 (1594)
1704 (1594)
2934 (2824)
1472 (1362)
874 (764)
Avr4
74 (74)
2
149
118 (118)
2
219
1088 (978)
17
1152
1548 (1438)
36
1443
134 (134)
4
1152
200 (200)
9
3136
506 (506)
4
178
1042 (932)
20
280
1008 (898)
38
16678
1086 (976)
59
1711
1498 (1388)
58
1528
3040 (2930)
66
2297
1354 (1244)
55
1240
1704 (1594)
53
1235
1704 (1594)
87
2718
2918 (2808)
63
1833
1456 (1346)
22
971
808 (698)
21
722
9.2
Math functions.
9.2
Math functions.
57
The table contains the number of MCU clocks to calculate a function with a given
argument(s). The main reason of a big difference between Avr2 and Avr4 is a hardware
multiplication.
Function
__addsf3 (1.234, 5.678)
__mulsf3 (1.234, 5.678)
__divsf3 (1.234, 5.678)
acos (0.54321)
asin (0.54321)
atan (0.54321)
atan2 (1.234, 5.678)
cbrt (1.2345)
ceil (1.2345)
cos (1.2345)
cosh (1.2345)
exp (1.2345)
fdim (5.678, 1.234)
floor (1.2345)
fmax (1.234, 5.678)
fmin (1.234, 5.678)
fmod (5.678, 1.234)
frexp (1.2345, 0)
hypot (1.234, 5.678)
ldexp (1.2345, 6)
log (1.2345)
log10 (1.2345)
modf (1.2345, 0)
pow (1.234, 5.678)
round (1.2345)
sin (1.2345)
sinh (1.2345)
sqrt (1.2345)
tan (1.2345)
tanh (1.2345)
trunc (1.2345)
10
10.1
Avr2
113
375
466
4411
4517
4710
5270
2684
177
3387
4922
4708
111
180
39
35
131
42
1341
42
4142
4498
433
9293
150
3353
4946
494
4381
5126
178
Avr4
108
138
465
2455
2556
2271
2857
2555
177
1671
2979
2765
111
180
37
35
131
41
866
42
2134
2260
429
5047
150
1653
3003
492
2426
3173
178
Porting From IAR to AVR GCC
Introduction
C language was designed to be a portable language. There two main types of porting activities: porting an application to a different platform (OS and/or processor),
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10.2
Registers
58
and porting to a different compiler. Porting to a different compiler can be exacerbated
when the application is an embedded system. For example, the C language Standard,
strangely, does not specify a standard for declaring and defining Interrupt Service Routines (ISRs). Different compilers have different ways of defining registers, some of
which use non-standard language constructs.
This chapter describes some methods and pointers on porting an AVR application built
with the IAR compiler to the GNU toolchain (AVR GCC). Note that this may not be
an exhaustive list.
10.2
Registers
IO header files contain identifiers for all the register names and bit names for a particular processor. IAR has individual header files for each processor and they must be
included when registers are being used in the code. For example:
#include <iom169.h>
Note
IAR does not always use the same register names or bit names that are used in the
AVR datasheet.
AVR GCC also has individual IO header files for each processor. However, the actual processor type is specified as a command line flag to the compiler. (Using the
-mmcu=processor flag.) This is usually done in the Makefile. This allows you to
specify only a single header file for any processor type:
#include <avr/io.h>
Note
The forward slash in the <avr/io.h> file name that is used to separate subdirectories can be used on Windows distributions of the toolchain and is the recommended
method of including this file.
The compiler knows the processor type and through the single header file above, it can
pull in and include the correct individual IO header file. This has the advantage that you
only have to specify one generic header file, and you can easily port your application
to another processor type without having to change every file to include the new IO
header file.
The AVR toolchain tries to adhere to the exact names of the registers and names of
the bits found in the AVR datasheet. There may be some descrepencies between the
register names found in the IAR IO header files and the AVR GCC IO header files.
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10.3
Interrupt Service Routines (ISRs)
10.3
Interrupt Service Routines (ISRs)
59
As mentioned above, the C language Standard, strangely, does not specify a standard
way of declaring and defining an ISR. Hence, every compiler seems to have their own
special way of doing so.
IAR declares an ISR like so:
#pragma vector=TIMER0_OVF_vect
__interrupt void MotorPWMBottom()
{
// code
}
In AVR GCC, you declare an ISR like so:
ISR(PCINT1_vect)
{
//code
}
AVR GCC uses the ISR macro to define an ISR. This macro requries the header file:
#include <avr/interrupt.h>
The names of the various interrupt vectors are found in the individual processor IO
header files that you must include with <avr/io.h>.
Note
The names of the interrupt vectors in AVR GCC has been changed to match the
names of the vectors in IAR. This significantly helps in porting applications from
IAR to AVR GCC.
10.4
Intrinsic Routines
IAR has a number of intrinsic routine such as
__enable_interrupts() __disable_interrupts() __watchdog_reset()
These intrinsic functions compile to specific AVR opcodes (SEI, CLI, WDR).
There are equivalent macros that are used in AVR GCC, however they are not located
in a single include file.
AVR GCC has sei() for __enable_interrupts(), and cli() for __disable_interrupts(). Both of these macros are located in <avr/interrupts.h>.
AVR GCC has the macro wdt_reset() in place of __watchdog_reset(). However, there is a whole Watchdog Timer API available in AVR GCC that can be found in
<avr/wdt.h>.
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10.5
Flash Variables
10.5
Flash Variables
60
The C language was not designed for Harvard architecture processors with separate
memory spaces. This means that there are various non-standard ways to define a variable whose data resides in the Program Memory (Flash).
IAR uses a non-standard keyword to declare a variable in Program Memory:
__flash int mydata[] = ....
AVR GCC uses Variable Attributes to achieve the same effect:
int mydata[] __attribute__((progmem))
Note
See the GCC User Manual for more information about Variable Attributes.
avr-libc provides a convenience macro for the Variable Attribute:
#include <avr/pgmspace.h>
.
.
.
int mydata[] PROGMEM = ....
Note
The PROGMEM macro expands to the Variable Attribute of progmem. This
macro requires that you include <avr/pgmspace.h>. This is the canonical
method for defining a variable in Program Space.
To read back flash data, use the pgm_read_∗() macros defined in <avr/pgmspace.h>.
All Program Memory handling macros are defined there.
There is also a way to create a method to define variables in Program Memory that is
common between the two compilers (IAR and AVR GCC). Create a header file that has
these definitions:
#if defined(__ICCAVR__) // IAR C Compiler
#define FLASH_DECLARE(x) __flash x
#endif
#if defined(__GNUC__) // GNU Compiler
#define FLASH_DECLARE(x) x __attribute__((__progmem__))
#endif
This code snippet checks for the IAR compiler or for the GCC compiler and defines a
macro FLASH_DECLARE(x) that will declare a variable in Program Memory using
the appropriate method based on the compiler that is being used. Then you would used
it like so:
FLASH_DECLARE(int mydata[] = ...);
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10.6
Non-Returning main()
10.6
Non-Returning main()
61
To declare main() to be a non-returning function in IAR, it is done like this:
__C_task void main(void)
{
// code
}
To do the equivalent in AVR GCC, do this:
void main(void) __attribute__((noreturn));
void main(void)
{
//...
}
Note
See the GCC User Manual for more information on Function Attributes.
In AVR GCC, a prototype for main() is required so you can declare the function attribute to specify that the main() function is of type "noreturn". Then, define main() as
normal. Note that the return type for main() is now void.
10.7
Locking Registers
The IAR compiler allows a user to lock general registers from r15 and down by using
compiler options and this keyword syntax:
__regvar __no_init volatile unsigned int filteredTimeSinceCommutation @14;
This line locks r14 for use only when explicitly referenced in your code thorugh the var
name "filteredTimeSinceCommutation". This means that the compiler cannot dispose
of it at its own will.
To do this in AVR GCC, do this:
register unsigned char counter asm("r3");
Typically, it should be possible to use r2 through r15 that way.
Note
Do not reserve r0 or r1 as these are used internally by the compiler for a temporary
register and for a zero value.
Locking registers is not recommended in AVR GCC as it removes this register
from the control of the compiler, which may make code generation worse. Use at
your own risk.
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11 Frequently Asked Questions
11
62
Frequently Asked Questions
11.1
FAQ Index
1. My program doesn’t recognize a variable updated within an interrupt routine
2. I get "undefined reference to..." for functions like "sin()"
3. How to permanently bind a variable to a register?
4. How to modify MCUCR or WDTCR early?
5. What is all this _BV() stuff about?
6. Can I use C++ on the AVR?
7. Shouldn’t I initialize all my variables?
8. Why do some 16-bit timer registers sometimes get trashed?
9. How do I use a #define’d constant in an asm statement?
10. Why does the PC randomly jump around when single-stepping through my program in avr-gdb?
11. How do I trace an assembler file in avr-gdb?
12. How do I pass an IO port as a parameter to a function?
13. What registers are used by the C compiler?
14. How do I put an array of strings completely in ROM?
15. How to use external RAM?
16. Which -O flag to use?
17. How do I relocate code to a fixed address?
18. My UART is generating nonsense! My ATmega128 keeps crashing! Port F is
completely broken!
19. Why do all my "foo...bar" strings eat up the SRAM?
20. Why does the compiler compile an 8-bit operation that uses bitwise operators
into a 16-bit operation in assembly?
21. How to detect RAM memory and variable overlap problems?
22. Is it really impossible to program the ATtinyXX in C?
23. What is this "clock skew detected" message?
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11.2 My program doesn’t recognize a variable updated within an interrupt
routine
63
24. Why are (many) interrupt flags cleared by writing a logical 1?
25. Why have "programmed" fuses the bit value 0?
26. Which AVR-specific assembler operators are available?
27. Why are interrupts re-enabled in the middle of writing the stack pointer?
28. Why are there five different linker scripts?
29. How to add a raw binary image to linker output?
30. How do I perform a software reset of the AVR?
31. I am using floating point math. Why is the compiled code so big? Why does my
code not work?
32. What pitfalls exist when writing reentrant code?
33. Why are some addresses of the EEPROM corrupted (usually address zero)?
34. Why is my baud rate wrong?
35. On a device with more than 128 KiB of flash, how to make function pointers
work?
11.2
My program doesn’t recognize a variable updated within an interrupt routine
When using the optimizer, in a loop like the following one:
uint8_t flag;
...
ISR(SOME_vect) {
flag = 1;
}
...
while (flag == 0) {
...
}
the compiler will typically access flag only once, and optimize further accesses completely away, since its code path analysis shows that nothing inside the loop could
change the value of flag anyway. To tell the compiler that this variable could be
changed outside the scope of its code path analysis (e. g. from within an interrupt
routine), the variable needs to be declared like:
volatile uint8_t flag;
Back to FAQ Index.
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11.3
I get "undefined reference to..." for functions like "sin()"
11.3
I get ”undefined reference to...” for functions like ”sin()”
64
In order to access the mathematical functions that are declared in <math.h>, the
linker needs to be told to also link the mathematical library, libm.a.
Typically, system libraries like libm.a are given to the final C compiler command
line that performs the linking step by adding a flag -lm at the end. (That is, the initial
lib and the filename suffix from the library are written immediately after a -l flag. So
for a libfoo.a library, -lfoo needs to be provided.) This will make the linker
search the library in a path known to the system.
An alternative would be to specify the full path to the libm.a file at the same place
on the command line, i. e. after all the object files (∗.o). However, since this requires knowledge of where the build system will exactly find those library files, this is
deprecated for system libraries.
Back to FAQ Index.
11.4
How to permanently bind a variable to a register?
This can be done with
register unsigned char counter asm("r3");
Typically, it should be safe to use r2 through r7 that way.
Registers r8 through r15 can be used for argument passing by the compiler in case
many or long arguments are being passed to callees. If this is not the case throughout
the entire application, these registers could be used for register variables as well.
Extreme care should be taken that the entire application is compiled with a consistent
set of register-allocated variables, including possibly used library functions.
See C Names Used in Assembler Code for more details.
Back to FAQ Index.
11.5
How to modify MCUCR or WDTCR early?
The method of early initialization (MCUCR, WDTCR or anything else) is different (and
more flexible) in the current version. Basically, write a small assembler file which
looks like this:
;; begin xram.S
#include <avr/io.h>
.section .init1,"ax",@progbits
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11.6
What is all this _BV() stuff about?
65
ldi r16,_BV(SRE) | _BV(SRW)
out _SFR_IO_ADDR(MCUCR),r16
;; end xram.S
Assemble it, link the resulting xram.o with other files in your program, and this piece
of code will be inserted in initialization code, which is run right after reset. See the
linker script for comments about the new .initN sections (which one to use, etc.).
The advantage of this method is that you can insert any initialization code you want
(just remember that this is very early startup -- no stack and no __zero_reg__ yet),
and no program memory space is wasted if this feature is not used.
There should be no need to modify linker scripts anymore, except for some very special cases. It is best to leave __stack at its default value (end of internal SRAM
-- faster, and required on some devices like ATmega161 because of errata), and add
-Wl,-Tdata,0x801100 to start the data section above the stack.
For more information on using sections, see Memory Sections. There is also an example for Using Sections in C Code. Note that in C code, any such function would
preferably be placed into section .init3 as the code in .init2 ensures the internal register
__zero_reg__ is already cleared.
Back to FAQ Index.
11.6
What is all this BV() stuff about?
When performing low-level output work, which is a very central point in microcontroller programming, it is quite common that a particular bit needs to be set or cleared
in some IO register. While the device documentation provides mnemonic names for
the various bits in the IO registers, and the AVR device-specific IO definitions reflect
these names in definitions for numerical constants, a way is needed to convert a bit
number (usually within a byte register) into a byte value that can be assigned directly
to the register. However, sometimes the direct bit numbers are needed as well (e. g. in
an SBI() instruction), so the definitions cannot usefully be made as byte values in the
first place.
So in order to access a particular bit number as a byte value, use the _BV() macro.
Of course, the implementation of this macro is just the usual bit shift (which is done
by the compiler anyway, thus doesn’t impose any run-time penalty), so the following
applies:
_BV(3) => 1 << 3 => 0x08
However, using the macro often makes the program better readable.
"BV" stands for "bit value", in case someone might ask you. :-)
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11.7
Can I use C++ on the AVR?
66
Example: clock timer 2 with full IO clock (CS2x = 0b001), toggle OC2 output on
compare match (COM2x = 0b01), and clear timer on compare match (CTC2 = 1). Make
OC2 (PD7) an output.
TCCR2 = _BV(COM20)|_BV(CTC2)|_BV(CS20);
DDRD = _BV(PD7);
Back to FAQ Index.
11.7
Can I use C++ on the AVR?
Basically yes, C++ is supported (assuming your compiler has been configured and
compiled to support it, of course). Source files ending in .cc, .cpp or .C will automatically cause the compiler frontend to invoke the C++ compiler. Alternatively, the C++
compiler could be explicitly called by the name avr-c++.
However, there’s currently no support for libstdc++, the standard support library
needed for a complete C++ implementation. This imposes a number of restrictions on
the C++ programs that can be compiled. Among them are:
• Obviously, none of the C++ related standard functions, classes, and template
classes are available.
• The operators new and delete are not implemented, attempting to use them
will cause the linker to complain about undefined external references. (This
could perhaps be fixed.)
• Some of the supplied include files are not C++ safe, i. e. they need to be wrapped
into
extern "C" { . . . }
(This could certainly be fixed, too.)
• Exceptions are not supported. Since exceptions are enabled by default in the
C++ frontend, they explicitly need to be turned off using -fno-exceptions
in the compiler options. Failing this, the linker will complain about an undefined
external reference to __gxx_personality_sj0.
Constructors and destructors are supported though, including global ones.
When programming C++ in space- and runtime-sensitive environments like microcontrollers, extra care should be taken to avoid unwanted side effects of the C++ calling
conventions like implied copy constructors that could be called upon function invocation etc. These things could easily add up into a considerable amount of time and
program memory wasted. Thus, casual inspection of the generated assembler code
(using the -S compiler option) seems to be warranted.
Back to FAQ Index.
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11.8
Shouldn’t I initialize all my variables?
11.8
Shouldn’t I initialize all my variables?
67
Global and static variables are guaranteed to be initialized to 0 by the C standard.
avr-gcc does this by placing the appropriate code into section .init4 (see The .initN
Sections). With respect to the standard, this sentence is somewhat simplified (because
the standard allows for machines where the actual bit pattern used differs from all bits
being 0), but for the AVR target, in general, all integer-type variables are set to 0, all
pointers to a NULL pointer, and all floating-point variables to 0.0.
As long as these variables are not initialized (i. e. they don’t have an equal sign and
an initialization expression to the right within the definition of the variable), they go
into the .bss section of the file. This section simply records the size of the variable,
but otherwise doesn’t consume space, neither within the object file nor within flash
memory. (Of course, being a variable, it will consume space in the target’s SRAM.)
In contrast, global and static variables that have an initializer go into the .data section
of the file. This will cause them to consume space in the object file (in order to record
the initializing value), and in the flash ROM of the target device. The latter is needed
since the flash ROM is the only way that the compiler can tell the target device the
value this variable is going to be initialized to.
Now if some programmer "wants to make doubly sure" their variables really get a 0
at program startup, and adds an initializer just containing 0 on the right-hand side,
they waste space. While this waste of space applies to virtually any platform C is
implemented on, it’s usually not noticeable on larger machines like PCs, while the
waste of flash ROM storage can be very painful on a small microcontroller like the
AVR.
So in general, variables should only be explicitly initialized if the initial value is nonzero.
Note
Recent versions of GCC are now smart enough to detect this situation, and revert
variables that are explicitly initialized to 0 to the .bss section. Still, other compilers
might not do that optimization, and as the C standard guarantees the initialization,
it is safe to rely on it.
Back to FAQ Index.
11.9
Why do some 16-bit timer registers sometimes get trashed?
Some of the timer-related 16-bit IO registers use a temporary register (called TEMP in
the Atmel datasheet) to guarantee an atomic access to the register despite the fact that
two separate 8-bit IO transfers are required to actually move the data. Typically, this
includes access to the current timer/counter value register (TCNTn), the input capture
register (ICRn), and write access to the output compare registers (OCRnM). Refer to
the actual datasheet for each device’s set of registers that involves the TEMP register.
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11.10
How do I use a #define’d constant in an asm statement?
68
When accessing one of the registers that use TEMP from the main application, and
possibly any other one from within an interrupt routine, care must be taken that no
access from within an interrupt context could clobber the TEMP register data of an
in-progress transaction that has just started elsewhere.
To protect interrupt routines against other interrupt routines, it’s usually best to use the
ISR() macro when declaring the interrupt function, and to ensure that interrupts are still
disabled when accessing those 16-bit timer registers.
Within the main program, access to those registers could be encapsulated in calls to the
cli() and sei() macros. If the status of the global interrupt flag before accessing one of
those registers is uncertain, something like the following example code can be used.
uint16_t
read_timer1(void)
{
uint8_t sreg;
uint16_t val;
sreg = SREG;
cli();
val = TCNT1;
SREG = sreg;
return val;
}
Back to FAQ Index.
11.10
How do I use a #define’d constant in an asm statement?
So you tried this:
asm volatile("sbi 0x18,0x07;");
Which works. When you do the same thing but replace the address of the port by its
macro name, like this:
asm volatile("sbi PORTB,0x07;");
you get a compilation error: "Error:
constant value required".
PORTB is a precompiler definition included in the processor specific file included in
avr/io.h. As you may know, the precompiler will not touch strings and PORTB,
instead of 0x18, gets passed to the assembler. One way to avoid this problem is:
asm volatile("sbi %0, 0x07" : "I" (_SFR_IO_ADDR(PORTB)):);
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11.11 Why does the PC randomly jump around when single-stepping through
my program in avr-gdb?
69
Note
For C programs, rather use the standard C bit operators instead, so the above would
be expressed as PORTB |= (1 << 7). The optimizer will take care to transform this into a single SBI instruction, assuming the operands allow for this.
Back to FAQ Index.
11.11
Why does the PC randomly jump around when single-stepping through my
program in avr-gdb?
When compiling a program with both optimization (-O) and debug information (-g)
which is fortunately possible in avr-gcc, the code watched in the debugger is optimized code. While it is not guaranteed, very often this code runs with the exact same
optimizations as it would run without the -g switch.
This can have unwanted side effects. Since the compiler is free to reorder code execution as long as the semantics do not change, code is often rearranged in order to
make it possible to use a single branch instruction for conditional operations. Branch
instructions can only cover a short range for the target PC (-63 through +64 words from
the current PC). If a branch instruction cannot be used directly, the compiler needs to
work around it by combining a skip instruction together with a relative jump (rjmp)
instruction, which will need one additional word of ROM.
Another side effect of optimization is that variable usage is restricted to the area of code
where it is actually used. So if a variable was placed in a register at the beginning of
some function, this same register can be re-used later on if the compiler notices that the
first variable is no longer used inside that function, even though the variable is still in
lexical scope. When trying to examine the variable in avr-gdb, the displayed result
will then look garbled.
So in order to avoid these side effects, optimization can be turned off while debugging.
However, some of these optimizations might also have the side effect of uncovering
bugs that would otherwise not be obvious, so it must be noted that turning off optimization can easily change the bug pattern. In most cases, you are better off leaving
optimizations enabled while debugging.
Back to FAQ Index.
11.12
How do I trace an assembler file in avr-gdb?
When using the -g compiler option, avr-gcc only generates line number and other
debug information for C (and C++) files that pass the compiler. Functions that don’t
have line number information will be completely skipped by a single step command
in gdb. This includes functions linked from a standard library, but by default also
functions defined in an assembler source file, since the -g compiler switch does not
apply to the assembler.
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11.12
How do I trace an assembler file in avr-gdb?
70
So in order to debug an assembler input file (possibly one that has to be passed through
the C preprocessor), it’s the assembler that needs to be told to include line-number
information into the output file. (Other debug information like data types and variable
allocation cannot be generated, since unlike a compiler, the assembler basically doesn’t
know about this.) This is done using the (GNU) assembler option --gstabs.
Example:
$ avr-as -mmcu=atmega128 --gstabs -o foo.o foo.s
When the assembler is not called directly but through the C compiler frontend (either
implicitly by passing a source file ending in .S, or explicitly using -x assembler-with-cpp),
the compiler frontend needs to be told to pass the --gstabs option down to the assembler. This is done using -Wa,--gstabs. Please take care to only pass this option
when compiling an assembler input file. Otherwise, the assembler code that results
from the C compilation stage will also get line number information, which confuses
the debugger.
Note
You can also use -Wa,-gstabs since the compiler will add the extra ’-’ for
you.
Example:
$ EXTRA_OPTS="-Wall -mmcu=atmega128 -x assembler-with-cpp"
$ avr-gcc -Wa,--gstabs ${EXTRA_OPTS} -c -o foo.o foo.S
Also note that the debugger might get confused when entering a piece of code that has
a non-local label before, since it then takes this label as the name of a new function that
appears to have been entered. Thus, the best practice to avoid this confusion is to only
use non-local labels when declaring a new function, and restrict anything else to local
labels. Local labels consist just of a number only. References to these labels consist
of the number, followed by the letter b for a backward reference, or f for a forward
reference. These local labels may be re-used within the source file, references will pick
the closest label with the same number and given direction.
Example:
myfunc: push
push
push
push
push
...
eor
ldi
ldi
r16
r17
r18
YL
YH
r16, r16
; start loop
YL, lo8(sometable)
YH, hi8(sometable)
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11.13
1:
2:
1:
How do I pass an IO port as a parameter to a function?
rjmp
ld
...
breq
...
inc
cmp
brlo
2f
r17, Y+
; jump to loop test at end
; loop continues here
1f
; return from myfunc prematurely
r16
r16, r18
1b
; jump back to top of loop
pop
pop
pop
pop
pop
ret
YH
YL
r18
r17
r16
71
Back to FAQ Index.
11.13
How do I pass an IO port as a parameter to a function?
Consider this example code:
#include <inttypes.h>
#include <avr/io.h>
void
set_bits_func_wrong (volatile uint8_t port, uint8_t mask)
{
port |= mask;
}
void
set_bits_func_correct (volatile uint8_t *port, uint8_t mask)
{
*port |= mask;
}
#define set_bits_macro(port,mask) ((port) |= (mask))
int main (void)
{
set_bits_func_wrong (PORTB, 0xaa);
set_bits_func_correct (&PORTB, 0x55);
set_bits_macro (PORTB, 0xf0);
return (0);
}
The first function will generate object code which is not even close to what is intended.
The major problem arises when the function is called. When the compiler sees this call,
it will actually pass the value of the PORTB register (using an IN instruction), instead
of passing the address of PORTB (e.g. memory mapped io addr of 0x38, io port 0x18
for the mega128). This is seen clearly when looking at the disassembly of the call:
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11.13
How do I pass an IO port as a parameter to a function?
set_bits_func_wrong
10a:
6a ea
10c:
88 b3
10e:
0e 94 65 00
(PORTB,
ldi
in
call
0xaa);
r22, 0xAA
r24, 0x18
0xca
72
; 170
; 24
So, the function, once called, only sees the value of the port register and knows nothing
about which port it came from. At this point, whatever object code is generated for
the function by the compiler is irrelevant. The interested reader can examine the full
disassembly to see that the function’s body is completely fubar.
The second function shows how to pass (by reference) the memory mapped address of
the io port to the function so that you can read and write to it in the function. Here’s
the object code generated for the function call:
set_bits_func_correct (&PORTB, 0x55);
112:
65 e5
ldi
r22, 0x55
114:
88 e3
ldi
r24, 0x38
116:
90 e0
ldi
r25, 0x00
118:
0e 94 7c 00
call
0xf8
; 85
; 56
; 0
You can clearly see that 0x0038 is correctly passed for the address of the io port.
Looking at the disassembled object code for the body of the function, we can see that
the function is indeed performing the operation we intended:
void
set_bits_func_correct (volatile uint8_t *port, uint8_t mask)
{
f8:
fc 01
movw
r30, r24
*port |= mask;
fa:
80 81
ld
r24, Z
fc:
86 2b
or
r24, r22
fe:
80 83
st
Z, r24
}
100:
08 95
ret
Notice that we are accessing the io port via the LD and ST instructions.
The port parameter must be volatile to avoid a compiler warning.
Note
Because of the nature of the IN and OUT assembly instructions, they can not be
used inside the function when passing the port in this way. Readers interested in
the details should consult the Instruction Set datasheet.
Finally we come to the macro version of the operation. In this contrived example, the
macro is the most efficient method with respect to both execution speed and code size:
set_bits_macro (PORTB, 0xf0);
11c:
88 b3
in
r24, 0x18
11e:
80 6f
ori
r24, 0xF0
120:
88 bb
out
0x18, r24
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; 24
; 240
; 24
11.14
What registers are used by the C compiler?
73
Of course, in a real application, you might be doing a lot more in your function which
uses a passed by reference io port address and thus the use of a function over a macro
could save you some code space, but still at a cost of execution speed.
Care should be taken when such an indirect port access is going to one of the 16-bit
IO registers where the order of write access is critical (like some timer registers). All
versions of avr-gcc up to 3.3 will generate instructions that use the wrong access order
in this situation (since with normal memory operands where the order doesn’t matter,
this sometimes yields shorter code).
See http://mail.nongnu.org/archive/html/avr-libc-dev/2003-01/msg00044.html
for a possible workaround.
avr-gcc versions after 3.3 have been fixed in a way where this optimization will be
disabled if the respective pointer variable is declared to be volatile, so the correct
behaviour for 16-bit IO ports can be forced that way.
Back to FAQ Index.
11.14
What registers are used by the C compiler?
• Data types:
char is 8 bits, int is 16 bits, long is 32 bits, long long is 64 bits, float and
double are 32 bits (this is the only supported floating point format), pointers
are 16 bits (function pointers are word addresses, to allow addressing up to 128K
program memory space). There is a -mint8 option (see Options for the C
compiler avr-gcc) to make int 8 bits, but that is not supported by avr-libc and
violates C standards (int must be at least 16 bits). It may be removed in a future
release.
• Call-used registers (r18-r27, r30-r31):
May be allocated by gcc for local data. You may use them freely in assembler
subroutines. Calling C subroutines can clobber any of them - the caller is responsible for saving and restoring.
• Call-saved registers (r2-r17, r28-r29):
May be allocated by gcc for local data. Calling C subroutines leaves them unchanged. Assembler subroutines are responsible for saving and restoring these
registers, if changed. r29:r28 (Y pointer) is used as a frame pointer (points to
local data on stack) if necessary. The requirement for the callee to save/preserve
the contents of these registers even applies in situations where the compiler assigns them for argument passing.
• Fixed registers (r0, r1):
Never allocated by gcc for local data, but often used for fixed purposes:
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11.15
How do I put an array of strings completely in ROM?
74
r0 - temporary register, can be clobbered by any C code (except interrupt handlers
which save it), may be used to remember something for a while within one piece of
assembler code
r1 - assumed to be always zero in any C code, may be used to remember something for
a while within one piece of assembler code, but must then be cleared after use (clr
r1). This includes any use of the [f]mul[s[u]] instructions, which return their
result in r1:r0. Interrupt handlers save and clear r1 on entry, and restore r1 on exit (in
case it was non-zero).
• Function call conventions:
Arguments - allocated left to right, r25 to r8. All arguments are aligned to start in
even-numbered registers (odd-sized arguments, including char, have one free
register above them). This allows making better use of the movw instruction on
the enhanced core.
If too many, those that don’t fit are passed on the stack.
Return values: 8-bit in r24 (not r25!), 16-bit in r25:r24, up to 32 bits in r22-r25, up to
64 bits in r18-r25. 8-bit return values are zero/sign-extended to 16 bits by the called
function (unsigned char is more efficient than signed char - just clr r25).
Arguments to functions with variable argument lists (printf etc.) are all passed on stack,
and char is extended to int.
Warning
There was no such alignment before 2000-07-01, including the old patches for
gcc-2.95.2. Check your old assembler subroutines, and adjust them accordingly.
Back to FAQ Index.
11.15
How do I put an array of strings completely in ROM?
There are times when you may need an array of strings which will never be modified.
In this case, you don’t want to waste ram storing the constant strings. The most obvious
(and incorrect) thing to do is this:
#include <avr/pgmspace.h>
PGM_P array[2] PROGMEM = {
"Foo",
"Bar"
};
int main (void)
{
char buf[32];
strcpy_P (buf, array[1]);
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11.15
How do I put an array of strings completely in ROM?
75
return 0;
}
The result is not what you want though. What you end up with is the array stored in
ROM, while the individual strings end up in RAM (in the .data section).
To work around this, you need to do something like this:
#include <avr/pgmspace.h>
const char foo[] PROGMEM = "Foo";
const char bar[] PROGMEM = "Bar";
PGM_P array[2] PROGMEM = {
foo,
bar
};
int main (void)
{
char buf[32];
PGM_P p;
int i;
memcpy_P(&p, &array[i], sizeof(PGM_P));
strcpy_P(buf, p);
return 0;
}
Looking at the disassembly of the resulting object file we see that array is in flash as
such:
00000026 <array>:
26:
2e 00
28:
2a 00
.word
.word
0x002e
0x002a
; ????
; ????
0000002a <bar>:
2a:
42 61 72 00
Bar.
0000002e <foo>:
2e:
46 6f 6f 00
Foo.
foo is at addr 0x002e.
bar is at addr 0x002a.
array is at addr 0x0026.
Then in main we see this:
memcpy_P(&p, &array[i], sizeof(PGM_P));
70:
66 0f
add
r22, r22
72:
77 1f
adc
r23, r23
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11.16
74:
76:
78:
7a:
7c:
7e:
80:
How to use external RAM?
6a
7f
42
50
ce
81
08
5d
4f
e0
e0
01
96
d0
subi
sbci
ldi
ldi
movw
adiw
rcall
76
r22,
r23,
r20,
r21,
r24,
r24,
.+16
0xDA
0xFF
0x02
0x00
r28
0x21
;
;
;
;
218
255
2
0
; 33
; 0x92
This code reads the pointer to the desired string from the ROM table array into a
register pair.
The value of i (in r22:r23) is doubled to accommodate for the word offset required to
access array[], then the address of array (0x26) is added, by subtracting the negated
address (0xffda). The address of variable p is computed by adding its offset within the
stack frame (33) to the Y pointer register, and memcpy_P is called.
strcpy_P(buf, p);
82:
69 a1
84:
7a a1
86:
ce 01
88:
01 96
8a:
0c d0
ldd
ldd
movw
adiw
rcall
r22,
r23,
r24,
r24,
.+24
Y+33
Y+34
r28
0x01
; 0x21
; 0x22
; 1
; 0xa4
This will finally copy the ROM string into the local buffer buf.
Variable p (located at Y+33) is read, and passed together with the address of buf (Y+1)
to strcpy_P. This will copy the string from ROM to buf.
Note that when using a compile-time constant index, omitting the first step (reading
the pointer from ROM via memcpy_P) usually remains unnoticed, since the compiler
would then optimize the code for accessing array at compile-time.
Back to FAQ Index.
11.16
How to use external RAM?
Well, there is no universal answer to this question; it depends on what the external
RAM is going to be used for.
Basically, the bit SRE (SRAM enable) in the MCUCR register needs to be set in order
to enable the external memory interface. Depending on the device to be used, and
the application details, further registers affecting the external memory operation like
XMCRA and XMCRB, and/or further bits in MCUCR might be configured. Refer to the
datasheet for details.
If the external RAM is going to be used to store the variables from the C program
(i. e., the .data and/or .bss segment) in that memory area, it is essential to set up the
external memory interface early during the device initialization so the initialization of
these variable will take place. Refer to How to modify MCUCR or WDTCR early? for
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11.17
Which -O flag to use?
77
a description how to do this using few lines of assembler code, or to the chapter about
memory sections for an example written in C.
The explanation of malloc() contains a discussion about the use of internal RAM vs.
external RAM in particular with respect to the various possible locations of the heap
(area reserved for malloc()). It also explains the linker command-line options that are
required to move the memory regions away from their respective standard locations in
internal RAM.
Finally, if the application simply wants to use the additional RAM for private data
storage kept outside the domain of the C compiler (e. g. through a char ∗ variable
initialized directly to a particular address), it would be sufficient to defer the initialization of the external RAM interface to the beginning of main(), so no tweaking of
the .init3 section is necessary. The same applies if only the heap is going to be located
there, since the application start-up code does not affect the heap.
It is not recommended to locate the stack in external RAM. In general, accessing external RAM is slower than internal RAM, and errata of some AVR devices even prevent
this configuration from working properly at all.
Back to FAQ Index.
11.17
Which -O flag to use?
There’s a common misconception that larger numbers behind the -O option might automatically cause "better" optimization. First, there’s no universal definition for "better",
with optimization often being a speed vs. code size trade off. See the detailed discussion for which option affects which part of the code generation.
A test case was run on an ATmega128 to judge the effect of compiling the library itself
using different optimization levels. The following table lists the results. The test case
consisted of around 2 KB of strings to sort. Test #1 used qsort() using the standard
library strcmp(), test #2 used a function that sorted the strings by their size (thus had
two calls to strlen() per invocation).
When comparing the resulting code size, it should be noted that a floating point version
of fvprintf() was linked into the binary (in order to print out the time elapsed) which
is entirely not affected by the different optimization levels, and added about 2.5 KB to
the code.
Optimization
flags
-O3
-O2
-Os
-Os
-mcall-prologues
Size of .text
Time for test #1
Time for test #2
6898
6666
6618
6474
903 µs
972 µs
955 µs
972 µs
19.7 ms
20.1 ms
20.1 ms
20.1 ms
(The difference between 955 µs and 972 µs was just a single timer-tick, so take this
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11.18
How do I relocate code to a fixed address?
78
with a grain of salt.)
So generally, it seems -Os -mcall-prologues is the most universal "best" optimization level. Only applications that need to get the last few percent of speed benefit
from using -O3.
Back to FAQ Index.
11.18
How do I relocate code to a fixed address?
First, the code should be put into a new named section. This is done with a section
attribute:
__attribute__ ((section (".bootloader")))
In this example, .bootloader is the name of the new section. This attribute needs to be
placed after the prototype of any function to force the function into the new section.
void boot(void) __attribute__ ((section (".bootloader")));
To relocate the section to a fixed address the linker flag --section-start is used.
This option can be passed to the linker using the -Wl compiler option:
-Wl,--section-start=.bootloader=0x1E000
The name after section-start is the name of the section to be relocated. The number
after the section name is the beginning address of the named section.
Back to FAQ Index.
11.19
My UART is generating nonsense! My ATmega128 keeps crashing! Port F
is completely broken!
Well, certain odd problems arise out of the situation that the AVR devices as shipped
by Atmel often come with a default fuse bit configuration that doesn’t match the user’s
expectations. Here is a list of things to care for:
• All devices that have an internal RC oscillator ship with the fuse enabled that
causes the device to run off this oscillator, instead of an external crystal. This
often remains unnoticed until the first attempt is made to use something critical
in timing, like UART communication.
• The ATmega128 ships with the fuse enabled that turns this device into ATmega103 compatibility mode. This means that some ports are not fully usable,
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11.20
Why do all my "foo...bar" strings eat up the SRAM?
79
and in particular that the internal SRAM is located at lower addresses. Since by
default, the stack is located at the top of internal SRAM, a program compiled for
an ATmega128 running on such a device will immediately crash upon the first
function call (or rather, upon the first function return).
• Devices with a JTAG interface have the JTAGEN fuse programmed by default.
This will make the respective port pins that are used for the JTAG interface unavailable for regular IO.
Back to FAQ Index.
11.20
Why do all my ”foo...bar” strings eat up the SRAM?
By default, all strings are handled as all other initialized variables: they occupy RAM
(even though the compiler might warn you when it detects write attempts to these RAM
locations), and occupy the same amount of flash ROM so they can be initialized to the
actual string by startup code. The compiler can optimize multiple identical strings into
a single one, but obviously only for one compilation unit (i. e., a single C source file).
That way, any string literal will be a valid argument to any C function that expects a
const char ∗ argument.
Of course, this is going to waste a lot of SRAM. In Program Space String Utilities, a
method is described how such constant data can be moved out to flash ROM. However, a constant string located in flash ROM is no longer a valid argument to pass to a
function that expects a const char ∗-type string, since the AVR processor needs
the special instruction LPM to access these strings. Thus, separate functions are needed
that take this into account. Many of the standard C library functions have equivalents
available where one of the string arguments can be located in flash ROM. Private functions in the applications need to handle this, too. For example, the following can be
used to implement simple debugging messages that will be sent through a UART:
#include <inttypes.h>
#include <avr/io.h>
#include <avr/pgmspace.h>
int
uart_putchar(char c)
{
if (c == ’\n’)
uart_putchar(’\r’);
loop_until_bit_is_set(USR, UDRE);
UDR = c;
return 0; /* so it could be used for fdevopen(), too */
}
void
debug_P(const char *addr)
{
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11.21 Why does the compiler compile an 8-bit operation that uses bitwise
operators into a 16-bit operation in assembly?
80
char c;
while ((c = pgm_read_byte(addr++)))
uart_putchar(c);
}
int
main(void)
{
ioinit(); /* initialize UART, ... */
debug_P(PSTR("foo was here\n"));
return 0;
}
Note
By convention, the suffix _P to the function name is used as an indication that
this function is going to accept a "program-space string". Note also the use of the
PSTR() macro.
Back to FAQ Index.
11.21
Why does the compiler compile an 8-bit operation that uses bitwise operators into a 16-bit operation in assembly?
Bitwise operations in Standard C will automatically promote their operands to an int,
which is (by default) 16 bits in avr-gcc.
To work around this use typecasts on the operands, including literals, to declare that
the values are to be 8 bit operands.
This may be especially important when clearing a bit:
var &= ~mask;
/* wrong way! */
The bitwise "not" operator (∼) will also promote the value in mask to an int. To keep
it an 8-bit value, typecast before the "not" operator:
var &= (unsigned char)~mask;
Back to FAQ Index.
11.22
How to detect RAM memory and variable overlap problems?
You can simply run avr-nm on your output (ELF) file. Run it with the -n option, and
it will sort the symbols numerically (by default, they are sorted alphabetically).
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11.23
Is it really impossible to program the ATtinyXX in C?
81
Look for the symbol _end, that’s the first address in RAM that is not allocated by
a variable. (avr-gcc internally adds 0x800000 to all data/bss variable addresses, so
please ignore this offset.) Then, the run-time initialization code initializes the stack
pointer (by default) to point to the last available address in (internal) SRAM. Thus, the
region between _end and the end of SRAM is what is available for stack. (If your
application uses malloc(), which e. g. also can happen inside printf(), the heap for
dynamic memory is also located there. See Memory Areas and Using malloc().)
The amount of stack required for your application cannot be determined that easily.
For example, if you recursively call a function and forget to break that recursion, the
amount of stack required is infinite. :-) You can look at the generated assembler code
(avr-gcc ... -S), there’s a comment in each generated assembler file that tells
you the frame size for each generated function. That’s the amount of stack required for
this function, you have to add up that for all functions where you know that the calls
could be nested.
Back to FAQ Index.
11.23
Is it really impossible to program the ATtinyXX in C?
While some small AVRs are not directly supported by the C compiler since they do not
have a RAM-based stack (and some do not even have RAM at all), it is possible anyway
to use the general-purpose registers as a RAM replacement since they are mapped into
the data memory region.
Bruce D. Lightner wrote an excellent description of how to do this, and offers this
together with a toolkit on his web page:
http://lightner.net/avr/ATtinyAvrGcc.html
Back to FAQ Index.
11.24
What is this ”clock skew detected” message?
It’s a known problem of the MS-DOS FAT file system. Since the FAT file system has
only a granularity of 2 seconds for maintaining a file’s timestamp, and it seems that
some MS-DOS derivative (Win9x) perhaps rounds up the current time to the next second when calculating the timestamp of an updated file in case the current time cannot
be represented in FAT’s terms, this causes a situation where make sees a "file coming
from the future".
Since all make decisions are based on file timestamps, and their dependencies, make
warns about this situation.
Solution: don’t use inferior file systems / operating systems. Neither Unix file systems
nor HPFS (aka NTFS) do experience that problem.
Workaround: after saving the file, wait a second before starting make. Or simply
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11.25
Why are (many) interrupt flags cleared by writing a logical 1?
82
ignore the warning. If you are paranoid, execute a make clean all to make sure
everything gets rebuilt.
In networked environments where the files are accessed from a file server, this message
can also happen if the file server’s clock differs too much from the network client’s
clock. In this case, the solution is to use a proper time keeping protocol on both systems, like NTP. As a workaround, synchronize the client’s clock frequently with the
server’s clock.
Back to FAQ Index.
11.25
Why are (many) interrupt flags cleared by writing a logical 1?
Usually, each interrupt has its own interrupt flag bit in some control register, indicating
the specified interrupt condition has been met by representing a logical 1 in the respective bit position. When working with interrupt handlers, this interrupt flag bit usually
gets cleared automatically in the course of processing the interrupt, sometimes by just
calling the handler at all, sometimes (e. g. for the U[S]ART) by reading a particular
hardware register that will normally happen anyway when processing the interrupt.
From the hardware’s point of view, an interrupt is asserted as long as the respective bit
is set, while global interrupts are enabled. Thus, it is essential to have the bit cleared
before interrupts get re-enabled again (which usually happens when returning from an
interrupt handler).
Only few subsystems require an explicit action to clear the interrupt request when using
interrupt handlers. (The notable exception is the TWI interface, where clearing the
interrupt indicates to proceed with the TWI bus hardware handshake, so it’s never done
automatically.)
However, if no normal interrupt handlers are to be used, or in order to make extra
sure any pending interrupt gets cleared before re-activating global interrupts (e. g.
an external edge-triggered one), it can be necessary to explicitly clear the respective
hardware interrupt bit by software. This is usually done by writing a logical 1 into this
bit position. This seems to be illogical at first, the bit position already carries a logical
1 when reading it, so why does writing a logical 1 to it clear the interrupt bit?
The solution is simple: writing a logical 1 to it requires only a single OUT instruction,
and it is clear that only this single interrupt request bit will be cleared. There is no need
to perform a read-modify-write cycle (like, an SBI instruction), since all bits in these
control registers are interrupt bits, and writing a logical 0 to the remaining bits (as it
is done by the simple OUT instruction) will not alter them, so there is no risk of any
race condition that might accidentally clear another interrupt request bit. So instead of
writing
TIFR |= _BV(TOV0); /* wrong! */
simply use
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11.26
Why have "programmed" fuses the bit value 0?
83
TIFR = _BV(TOV0);
Back to FAQ Index.
11.26
Why have ”programmed” fuses the bit value 0?
Basically, fuses are just a bit in a special EEPROM area. For technical reasons, erased
E[E]PROM cells have all bits set to the value 1, so unprogrammed fuses also have a
logical 1. Conversely, programmed fuse cells read out as bit value 0.
Back to FAQ Index.
11.27
Which AVR-specific assembler operators are available?
See Pseudo-ops and operators.
Back to FAQ Index.
11.28
Why are interrupts re-enabled in the middle of writing the stack pointer?
When setting up space for local variables on the stack, the compiler generates code like
this:
/* prologue: frame size=20 */
push r28
push r29
in r28,__SP_L__
in r29,__SP_H__
sbiw r28,20
in __tmp_reg__,__SREG__
cli
out __SP_H__,r29
out __SREG__,__tmp_reg__
out __SP_L__,r28
/* prologue end (size=10) */
It reads the current stack pointer value, decrements it by the required amount of bytes,
then disables interrupts, writes back the high part of the stack pointer, writes back
the saved SREG (which will eventually re-enable interrupts if they have been enabled
before), and finally writes the low part of the stack pointer.
At the first glance, there’s a race between restoring SREG, and writing SPL. However,
after enabling interrupts (either explicitly by setting the I flag, or by restoring it as part
of the entire SREG), the AVR hardware executes (at least) the next instruction still with
interrupts disabled, so the write to SPL is guaranteed to be executed with interrupts
disabled still. Thus, the emitted sequence ensures interrupts will be disabled only for
the minimum time required to guarantee the integrity of this operation.
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
11.29
Why are there five different linker scripts?
84
Back to FAQ Index.
11.29
Why are there five different linker scripts?
From a comment in the source code:
Which one of the five linker script files is actually used depends on command line
options given to ld.
A .x script file is the default script A .xr script is for linking without relocation (-r flag)
A .xu script is like .xr but ∗do∗ create constructors (-Ur flag) A .xn script is for linking
with -n flag (mix text and data on same page). A .xbn script is for linking with -N flag
(mix text and data on same page).
Back to FAQ Index.
11.30
How to add a raw binary image to linker output?
The GNU linker avr-ld cannot handle binary data directly. However, there’s a companion tool called avr-objcopy. This is already known from the output side: it’s
used to extract the contents of the linked ELF file into an Intel Hex load file.
avr-objcopy can create a relocatable object file from arbitrary binary input, like
avr-objcopy -I binary -O elf32-avr foo.bin foo.o
This will create a file named foo.o, with the contents of foo.bin. The contents
will default to section .data, and two symbols will be created named _binary_foo_bin_start and _binary_foo_bin_end. These symbols can be referred
to inside a C source to access these data.
If the goal is to have those data go to flash ROM (similar to having used the PROGMEM
attribute in C source code), the sections have to be renamed while copying, and it’s also
useful to set the section flags:
avr-objcopy --rename-section .data=.progmem.data,contents,alloc,load,readonly,dat
a -I binary -O elf32-avr foo.bin foo.o
Note that all this could be conveniently wired into a Makefile, so whenever foo.bin
changes, it will trigger the recreation of foo.o, and a subsequent relink of the final
ELF file.
Below are two Makefile fragments that provide rules to convert a .txt file to an object
file, and to convert a .bin file to an object file:
$(OBJDIR)/%.o : %.txt
@echo Converting $<
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11.31
How do I perform a software reset of the AVR?
85
@cp $(<) $(*).tmp
@echo -n 0 | tr 0 ’\000’ >> $(*).tmp
@$(OBJCOPY) -I binary -O elf32-avr \
--rename-section .data=.progmem.data,contents,alloc,load,readonly,data \
--redefine-sym _binary_$*_tmp_start=$* \
--redefine-sym _binary_$*_tmp_end=$*_end \
--redefine-sym _binary_$*_tmp_size=$*_size_sym \
$(*).tmp $(@)
@echo "extern const char" $(*)"[] PROGMEM;" > $(*).h
@echo "extern const char" $(*)_end"[] PROGMEM;" >> $(*).h
@echo "extern const char" $(*)_size_sym"[];" >> $(*).h
@echo "#define $(*)_size ((int)$(*)_size_sym)" >> $(*).h
@rm $(*).tmp
$(OBJDIR)/%.o : %.bin
@echo Converting $<
@$(OBJCOPY) -I binary -O elf32-avr \
--rename-section .data=.progmem.data,contents,alloc,load,readonly,data \
--redefine-sym _binary_$*_bin_start=$* \
--redefine-sym _binary_$*_bin_end=$*_end \
--redefine-sym _binary_$*_bin_size=$*_size_sym \
$(<) $(@)
@echo "extern const char" $(*)"[] PROGMEM;" > $(*).h
@echo "extern const char" $(*)_end"[] PROGMEM;" >> $(*).h
@echo "extern const char" $(*)_size_sym"[];" >> $(*).h
@echo "#define $(*)_size ((int)$(*)_size_sym)" >> $(*).h
Back to FAQ Index.
11.31
How do I perform a software reset of the AVR?
The canonical way to perform a software reset of non-XMega AVR’s is to use the
watchdog timer. Enable the watchdog timer to the shortest timeout setting, then go into
an infinite, do-nothing loop. The watchdog will then reset the processor.
XMega parts have a specific bit RST_SWRST_bm in the RST.CTRL register, that generates a hardware reset. RST_SWRST_bm is protected by the XMega Configuration
Change Protection system.
The reason why using the watchdog timer or RST_SWRST_bm is preferable over jumping to the reset vector, is that when the watchdog or RST_SWRST_bm resets the AVR,
the registers will be reset to their known, default settings. Whereas jumping to the reset
vector will leave the registers in their previous state, which is generally not a good idea.
CAUTION! Older AVRs will have the watchdog timer disabled on a reset. For these
older AVRs, doing a soft reset by enabling the watchdog is easy, as the watchdog will
then be disabled after the reset. On newer AVRs, once the watchdog is enabled, then it
stays enabled, even after a reset! For these newer AVRs a function needs to be added
to the .init3 section (i.e. during the startup code, before main()) to disable the watchdog
early enough so it does not continually reset the AVR.
Here is some example code that creates a macro that can be called to perform a soft
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11.32 I am using floating point math. Why is the compiled code so big? Why
does my code not work?
86
reset:
#include <avr/wdt.h>
...
#define soft_reset()
do
{
wdt_enable(WDTO_15MS);
for(;;)
{
}
} while(0)
\
\
\
\
\
\
\
For newer AVRs (such as the ATmega1281) also add this function to your code to then
disable the watchdog after a reset (e.g., after a soft reset):
#include <avr/wdt.h>
...
// Function Pototype
void wdt_init(void) __attribute__((naked)) __attribute__((section(".init3")));
...
// Function Implementation
void wdt_init(void)
{
MCUSR = 0;
wdt_disable();
return;
}
Back to FAQ Index.
11.32
I am using floating point math. Why is the compiled code so big? Why
does my code not work?
You are not linking in the math library from AVR-LibC. GCC has a library that is used
for floating point operations, but it is not optimized for the AVR, and so it generates big
code, or it could be incorrect. This can happen even when you are not using any floating
point math functions from the Standard C library, but you are just doing floating point
math operations.
When you link in the math library from AVR-LibC, those routines get replaced by
hand-optimized AVR assembly and it produces much smaller code.
See I get "undefined reference to..." for functions like "sin()" for more details on how
to link in the math library.
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11.33
What pitfalls exist when writing reentrant code?
87
Back to FAQ Index.
11.33
What pitfalls exist when writing reentrant code?
Reentrant code means the ability for a piece of code to be called simultaneously from
two or more threads. Attention to re-enterability is needed when using a multi-tasking
operating system, or when using interrupts since an interrupt is really a temporary
thread.
The code generated natively by gcc is reentrant. But, only some of the libraries in
avr-libc are explicitly reentrant, and some are known not to be reentrant. In general,
any library call that reads and writes global variables (including I/O registers) is not
reentrant. This is because more than one thread could read or write the same storage at
the same time, unaware that other threads are doing the same, and create inconsistent
and/or erroneous results.
A library call that is known not to be reentrant will work if it is used only within one
thread and no other thread makes use of a library call that shares common storage with
it.
Below is a table of library calls with known issues.
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11.33
What pitfalls exist when writing reentrant code?
Library call
Reentrant Issue
rand(), random()
Uses global variables to
keep state information.
strtod(), strtol(), strtoul()
Uses the global variable
errno to return
success/failure.
malloc(), realloc(),
calloc(), free()
Uses the stack pointer
and global variables to
allocate and free
memory.
fdevopen(), fclose()
Uses calloc() and free().
eeprom_∗(), boot_∗()
Accesses I/O registers.
pgm_∗_far()
Accesses I/O register
RAMPZ.
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printf(), printf_P(),
vprintf(), vprintf_P(),
puts(), puts_P()
Alters flags and character
count in global FILE
stdout.
88
Workaround/Alternative
Use special reentrant
versions: rand_r(),
random_r().
Ignore errno, or protect
calls with cli()/sei() or
ATOMIC_BLOCK() if
the application can
tolerate it. Or use
sccanf() or sccanf_P() if
possible.
Protect calls with
cli()/sei() or
ATOMIC_BLOCK() if
the application can
tolerate it. If using an
OS, use the OS provided
memory allocator since
the OS is likely
modifying the stack
pointer anyway.
Protect calls with
cli()/sei() or
ATOMIC_BLOCK() if
the application can
tolerate it. Or use
fdev_setup_stream() or
FDEV_SETUP_STREAM().
Note: fclose() will only
call free() if the stream
has been opened with
fdevopen().
Protect calls with
cli()/sei(),
ATOMIC_BLOCK(), or
use OS locking.
Starting with GCC 4.3,
RAMPZ is automatically
saved for ISRs, so
nothing further is needed
if only using interrupts.
Some OSes may
automatically preserve
RAMPZ during context
switching. Check the OS
documentation before
assuming it does.
Otherwise, protect calls
with cli()/sei(),
ATOMIC_BLOCK(), or
use explicit OS locking.
Use only in one thread.
Or if returned character
count is unimportant, do
11.34 Why are some addresses of the EEPROM corrupted (usually address
zero)?
89
Note
It’s not clear one would ever want to do character input simultaneously from more
than one thread anyway, but these entries are included for completeness.
An effort will be made to keep this table up to date if any new issues are discovered or
introduced.
Back to FAQ Index.
11.34
Why are some addresses of the EEPROM corrupted (usually address zero)?
The two most common reason for EEPROM corruption is either writing to the EEPROM beyond the datasheet endurance specification, or resetting the AVR while an
EEPROM write is in progress.
EEPROM writes can take up to tens of milliseconds to complete. So that the CPU
is not tied up for that long of time, an internal state-machine handles EEPROM write
requests. The EEPROM state-machine expects to have all of the EEPROM registers
setup, then an EEPROM write request to start the process. Once the EEPROM statemachine has started, changing EEPROM related registers during an EEPROM write
is guaranteed to corrupt the EEPROM write process. The datasheet always shows the
proper way to tell when a write is in progress, so that the registers are not changed by
the user’s program. The EEPROM state-machine will always complete the write in
progress unless power is removed from the device.
As with all EEPROM technology, if power fails during an EEPROM write the state of
the byte being written is undefined.
In older generation AVRs the EEPROM Address Register (EEAR) is initialized to zero
on reset, be it from Brown Out Detect, Watchdog or the Reset Pin. If an EEPROM
write has just started at the time of the reset, the write will be completed, but now
at address zero instead of the requested address. If the reset occurs later in the write
process both the requested address and address zero may be corrupted.
To distinguish which AVRs may exhibit the corrupt of address zero while a write is
in process during a reset, look at the "initial value" section for the EEPROM Address
Register. If EEAR shows the initial value as 0x00 or 0x0000, then address zero and
possibly the one being written will be corrupted. Newer parts show the initial value as
"undefined", these will not corrupt address zero during a reset (unless it was address
zero that was being written).
EEPROMs have limited write endurance. The datasheet specifies the number of EEPROM writes that are guaranteed to function across the full temperature specification of
the AVR, for a given byte. A read should always be performed before a write, to see
if the value in the EEPROM actually needs to be written, so not to cause unnecessary
EEPROM wear.
AVRs use a paging mechanism for doing EEPROM writes. This is almost entirely
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11.35
Why is my baud rate wrong?
90
transparent to the user with one exception: When a byte is written to the EEPROM,
the entire EEPROM page is also transparently erased and (re)written, which will cause
wear to bytes that the programmer did not explicitly write. If it is desired to extend
EEPROM write lifetimes, in an attempt not to exceed the datasheet EEPROM write
endurance specification for a given byte, then writes must be in multiples of the EEPROM page size, and not sequential bytes. The EEPROM write page size varies with
the device. The EEPROM page size is found in the datasheet section on Memory Programming, generally before the Electrical Specifications near the end of the datasheet.
The failure mechanism for an overwritten byte/page is generally one of "stuck" bits,
i. e. a bit will stay at a one or zero state regardless of the byte written. Also a write
followed by a read may return the correct data, but the data will change with the passage
of time, due the EEPROM’s inability to hold a charge from the excessive write wear.
Back to FAQ Index.
11.35
Why is my baud rate wrong?
Some AVR datasheets give the following formula for calculating baud rates:
(F_CPU/(UART_BAUD_RATE*16L)-1)
Unfortunately that formula does not work with all combinations of clock speeds and
baud rates due to integer truncation during the division operator.
When doing integer division it is usually better to round to the nearest integer, rather
than to the lowest. To do this add 0.5 (i. e. half the value of the denominator) to the
numerator before the division, resulting in the formula:
((F_CPU + UART_BAUD_RATE * 8L) / (UART_BAUD_RATE * 16L) - 1)
This is also the way it is implemented in <util/setbaud.h>: Helper macros for baud
rate calculations.
Back to FAQ Index.
11.36
On a device with more than 128 KiB of flash, how to make function pointers
work?
Function pointers beyond the "magical" 128 KiB barrier(s) on larger devices are supposed to be resolved through so-called trampolines by the linker, so the actual pointers
used in the code can remain 16 bits wide.
In order for this to work, the option -mrelax must be given on the compiler commandline that is used to link the final ELF file. (Older compilers did not implement this
option for the AVR, use -Wl,--relax instead.)
Back to FAQ Index.
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12 Building and Installing the GNU Tool Chain
12
91
Building and Installing the GNU Tool Chain
This chapter shows how to build and install, from source code, a complete development environment for the AVR processors using the GNU toolset. There are two main
sections, one for Linux, FreeBSD, and other Unix-like operating systems, and another
section for Windows.
12.1
Building and Installing under Linux, FreeBSD, and Others
The default behaviour for most of these tools is to install every thing under the /usr/local
directory. In order to keep the AVR tools separate from the base system, it is usually
better to install everything into /usr/local/avr. If the /usr/local/avr directory does not exist, you should create it before trying to install anything. You will
need root access to install there. If you don’t have root access to the system, you
can alternatively install in your home directory, for example, in $HOME/local/avr.
Where you install is a completely arbitrary decision, but should be consistent for all
the tools.
You specify the installation directory by using the --prefix=dir option with the
configure script. It is important to install all the AVR tools in the same directory
or some of the tools will not work correctly. To ensure consistency and simplify the
discussion, we will use $PREFIX to refer to whatever directory you wish to install in.
You can set this as an environment variable if you wish as such (using a Bourne-like
shell):
$ PREFIX=$HOME/local/avr
$ export PREFIX
Note
Be sure that you have your PATH environment variable set to search the directory you install everything in before you start installing anything. For example, if
you use --prefix=$PREFIX, you must have $PREFIX/bin in your exported
PATH. As such:
$ PATH=$PATH:$PREFIX/bin
$ export PATH
Warning
If you have CC set to anything other than avr-gcc in your environment, this will
cause the configure script to fail. It is best to not have CC set at all.
Note
It is usually the best to use the latest released version of each of the tools.
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12.2
Required Tools
12.2
Required Tools
92
• GNU Binutils
http://sources.redhat.com/binutils/
Installation
• GCC
http://gcc.gnu.org/
Installation
• AVR Libc
http://savannah.gnu.org/projects/avr-libc/
Installation
12.3
Optional Tools
You can develop programs for AVR devices without the following tools. They may or
may not be of use for you.
• AVRDUDE
http://savannah.nongnu.org/projects/avrdude/
Installation
Usage Notes
• GDB
http://sources.redhat.com/gdb/
Installation
• SimulAVR
http://savannah.gnu.org/projects/simulavr/
Installation
• AVaRICE
http://avarice.sourceforge.net/
Installation
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12.4
GNU Binutils for the AVR target
12.4
GNU Binutils for the AVR target
93
The binutils package provides all the low-level utilities needed in building and manipulating object files. Once installed, your environment will have an AVR assembler
(avr-as), linker (avr-ld), and librarian (avr-ar and avr-ranlib). In addition, you get tools which extract data from object files (avr-objcopy), dissassemble object file information (avr-objdump), and strip information from object files
(avr-strip). Before we can build the C compiler, these tools need to be in place.
Download and unpack the source files:
$ bunzip2 -c binutils-<version>.tar.bz2 | tar xf $ cd binutils-<version>
Note
Replace <version> with the version of the package you downloaded.
If you obtained a gzip compressed file (.gz), use gunzip instead of bunzip2.
It is usually a good idea to configure and build binutils in a subdirectory so as not
to pollute the source with the compiled files. This is recommended by the binutils
developers.
$ mkdir obj-avr
$ cd obj-avr
The next step is to configure and build the tools. This is done by supplying arguments
to the configure script that enable the AVR-specific options.
$ ../configure --prefix=$PREFIX --target=avr --disable-nls
If you don’t specify the --prefix option, the tools will get installed in the /usr/local
hierarchy (i.e. the binaries will get installed in /usr/local/bin, the info pages get
installed in /usr/local/info, etc.) Since these tools are changing frequently, It is
preferrable to put them in a location that is easily removed.
When configure is run, it generates a lot of messages while it determines what
is available on your operating system. When it finishes, it will have created several
Makefiles that are custom tailored to your platform. At this point, you can build the
project.
$ make
Note
BSD users should note that the project’s Makefile uses GNU make syntax.
This means FreeBSD users may need to build the tools by using gmake.
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12.5
GCC for the AVR target
94
If the tools compiled cleanly, you’re ready to install them. If you specified a destination
that isn’t owned by your account, you’ll need root access to install them. To install:
$ make install
You should now have the programs from binutils installed into $PREFIX/bin. Don’t
forget to set your PATH environment variable before going to build avr-gcc.
Note
The official version of binutils might lack support for recent AVR devices. A patch
that adds more AVR types can be found at http://www.freebsd.org/cgi/cvsweb.cgi/ports/devel/
12.5
GCC for the AVR target
Warning
You must install avr-binutils and make sure your path is set properly before installing avr-gcc.
The steps to build avr-gcc are essentially same as for binutils:
$
$
$
$
$
bunzip2 -c gcc-<version>.tar.bz2 | tar xf cd gcc-<version>
mkdir obj-avr
cd obj-avr
../configure --prefix=$PREFIX --target=avr --enable-languages=c,c++ \
--disable-nls --disable-libssp --with-dwarf2
$ make
$ make install
To save your self some download time, you can alternatively download only the gcc-core-<version>.tar.bz2
and gcc-c++-<version>.tar.bz2 parts of the gcc. Also, if you don’t need
C++ support, you only need the core part and should only enable the C language support.
Note
Early versions of these tools did not support C++.
The stdc++ libs are not included with C++ for AVR due to the size limitations of
the devices.
The official version of GCC might lack support for recent AVR devices. A patch
that adds more AVR types can be found at http://www.freebsd.org/cgi/cvsweb.cgi/ports/devel/
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12.6
AVR Libc
12.6
AVR Libc
95
Warning
You must install avr-binutils, avr-gcc and make sure your path is set properly before installing avr-libc.
Note
If you have obtained the latest avr-libc from cvs, you will have to run the bootstrap
script before using either of the build methods described below.
To build and install avr-libc:
$
$
$
$
$
gunzip -c avr-libc-<version>.tar.gz | tar xf cd avr-libc-<version>
./configure --prefix=$PREFIX --build=‘./config.guess‘ --host=avr
make
make install
12.7
AVRDUDE
Note
It has been ported to windows (via MinGW or cygwin), Linux and Solaris. Other
Unix systems should be trivial to port to.
avrdude is part of the FreeBSD ports system. To install it, simply do the following:
# cd /usr/ports/devel/avrdude
# make install
Note
Installation into the default location usually requires root permissions. However,
running the program only requires access permissions to the appropriate ppi(4)
device.
Building and installing on other systems should use the configure system, as such:
$
$
$
$
$
$
$
gunzip -c avrdude-<version>.tar.gz | tar xf cd avrdude-<version>
mkdir obj-avr
cd obj-avr
../configure --prefix=$PREFIX
make
make install
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12.8
GDB for the AVR target
12.8
GDB for the AVR target
96
GDB also uses the configure system, so to build and install:
$
$
$
$
$
$
$
bunzip2 -c gdb-<version>.tar.bz2 | tar xf cd gdb-<version>
mkdir obj-avr
cd obj-avr
../configure --prefix=$PREFIX --target=avr
make
make install
Note
If you are planning on using avr-gdb, you will probably want to install either
simulavr or avarice since avr-gdb needs one of these to run as a a remote target
backend.
12.9
SimulAVR
SimulAVR also uses the configure system, so to build and install:
$
$
$
$
$
$
$
gunzip -c simulavr-<version>.tar.gz | tar xf cd simulavr-<version>
mkdir obj-avr
cd obj-avr
../configure --prefix=$PREFIX
make
make install
Note
You might want to have already installed avr-binutils, avr-gcc and avr-libc if you
want to have the test programs built in the simulavr source.
12.10
AVaRICE
Note
These install notes are not applicable to avarice-1.5 or older. You probably don’t
want to use anything that old anyways since there have been many improvements
and bug fixes since the 1.5 release.
AVaRICE also uses the configure system, so to build and install:
$ gunzip -c avarice-<version>.tar.gz | tar xf $ cd avarice-<version>
$ mkdir obj-avr
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12.11
$
$
$
$
Building and Installing under Windows
97
cd obj-avr
../configure --prefix=$PREFIX
make
make install
Note
AVaRICE uses the BFD library for accessing various binary file formats. You
may need to tell the configure script where to find the lib and headers for the link
to work. This is usually done by invoking the configure script like this (Replace
<hdr_path> with the path to the bfd.h file on your system. Replace <lib_path> with the path to libbfd.a on your system.):
$ CPPFLAGS=-I<hdr_path> LDFLAGS=-L<lib_path> ../configure --prefix=$PREFIX
12.11
Building and Installing under Windows
Building and installing the toolchain under Windows requires more effort because all
of the tools required for building, and the programs themselves, are mainly designed
for running under a POSIX environment such as Unix and Linux. Windows does not
natively provide such an environment.
There are two projects available that provide such an environment, Cygwin and MinGW/MSYS. There are advantages and disadvantages to both. Cygwin provides a very
complete POSIX environment that allows one to build many Linux based tools from
source with very little or no source modifications. However, POSIX functionality is
provided in the form of a DLL that is linked to the application. This DLL has to be
redistributed with your application and there are issues if the Cygwin DLL already exists on the installation system and different versions of the DLL. On the other hand,
MinGW/MSYS can compile code as native Win32 applications. However, this means
that programs designed for Unix and Linux (i.e. that use POSIX functionality) will not
compile as MinGW/MSYS does not provide that POSIX layer for you. Therefore most
programs that compile on both types of host systems, usually must provide some sort
of abstraction layer to allow an application to be built cross-platform.
MinGW/MSYS does provide somewhat of a POSIX environment that allows you to
build Unix and Linux applications as they woud normally do, with a configure
step and a make step. Cygwin also provides such an environment. This means that
building the AVR toolchain is very similar to how it is built in Linux, described above.
The main differences are in what the PATH environment variable gets set to, pathname
differences, and the tools that are required to build the projects under Windows. We’ll
take a look at the tools next.
12.12
Tools Required for Building the Toolchain for Windows
These are the tools that are currently used to build WinAVR 20070525 (or later). This
list may change, either the version of the tools, or the tools themselves, as improveGenerated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
12.12
Tools Required for Building the Toolchain for Windows
98
ments are made.
• MinGW/MSYS
<http://downloads.sourceforge.net/mingw/MinGW-5.1.4.exe?use_mirror=superb-east>
– Put MinGW-5.1.4.exe in it’s own directory (for example: C:\MinGWSetup)
– Run MinGW-5.1.4.exe
– Select "Download and install"
– Select "Current" package.
– Select type of install: Full.
• Install MSYS-1.0.10.exe package.
<http://prdownloads.sf.net/mingw/MSYS-1.0.10.exe?download>
– Default selections
– Batch file will ask:
* "Do you wish to continue with the post install?" Press "y" and press
enter.
* "Do you have MinGW installed?" Press "y" and press enter.
* "Where is your MinGW installation?" Type in "c:/mingw" (without
quotes) and press enter
* "Do you wish for me to add mount bindings for c:/mingw to /mingw?"
Press "y" and press enter.
* It will display some messages on the screen, then it will display: "Press
any key to continue . . .". Press any key.
• Edit c:\msys\1.0\msys.bat
Change line (should be line 41):
if EXIST rxvt.exe goto startrxvt
to:
rem if EXIST rxvt.exe goto startrxvt
to remark out this line. Doing this will cause MSYS to always use the bash shell
and not the rxvt shell.
Note
The order of the next three is important. Install MSYS Developer toolkit before
the autotools.
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12.12
Tools Required for Building the Toolchain for Windows
99
• MSYS Developer Toolkit version 1.0.1
– This is needed to build avr-libc in MinGW.
– <http://downloads.sourceforge.net/mingw/msysDTK-1.0.1.exe?use_mirror=internap>
– Single file installer executable. Install.
• autoconf 2.59 from the "MSYS Developer Toolkit" release
– autoconf 2.59/2.60 is needed to build avr-libc in MinGW.
– <http://downloads.sourceforge.net/mingw/msys-autoconf-2.59.tar.bz2?use_mirror=internap>
– Extract to c:\msys\1.0
• automake 1.8.2
– automake 1.8/1.9 is needed to build avr-libc in MinGW.
– <http://downloads.sourceforge.net/mingw/msys-automake-1.8.2.tar.bz2?use_
mirror=internap>
– Extract to c:\msys\1.0
• Install Cygwin
– Install everything, all users, UNIX line endings. This will take a ∗long∗
time. A fat internet pipe is highly recommended. It is also recommended
that you download all to a directory first, and then install from that directory
to your machine.
Note
GMP is a prequisite for building MPFR. Build GMP first.
• Build GMP for MinGW
– Version 4.2.3
– <http://gmplib.org/>
– Build script:
./configure
make
make check
make install
2>&1
2>&1
2>&1
2>&1
|
|
|
|
tee
tee
tee
tee
gmp-configure.log
gmp-make.log
gmp-make-check.log
gmp-make-install.log
– GMP headers will be installed under /usr/local/include and library installed
under /usr/local/lib.
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12.12
Tools Required for Building the Toolchain for Windows
100
• Build MPFR for MinGW
– Version 2.3.2
– <http://www.mpfr.org/>
– Build script:
./configure --with-gmp=/usr/local 2>&1 | tee mpfr-configure.log
make
2>&1 | tee mpfr-make.log
make check
2>&1 | tee mpfr-make-check.log
make install 2>&1 | tee mpfr-make-install.log
– MPFR headers will be installed under /usr/local/include and library installed under /usr/local/lib.
• Install Doxygen
– Version 1.5.6
– <http://www.stack.nl/∼dimitri/doxygen/>
– Download and install.
• Install NetPBM
– Version 10.27.0
– From the GNUWin32 project: <http://gnuwin32.sourceforge.net/packages.html>
– Download and install.
• Install fig2dev
– Version 3.2 Patchlevel 5
– From WinFig 2.2: <http://www.schmidt-web-berlin.de/winfig/>
– Unzip the download file and install fig2dev.exe in a location of your choice.
• Install MiKTeX
– Version 2.7
– <http://miktex.org/>
– Download and install.
• Install Ghostscript
–
–
–
–
Version 8.63
<http://www.cs.wisc.edu/∼ghost/>
Download and install.
In the \bin subdirectory of the installaion, copy gswin32c.exe to gs.exe.
• Set the TEMP and TMP environment variables to c:\temp or to the short filename version. This helps to avoid NTVDM errors during building.
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12.13
Building the Toolchain for Windows
12.13
Building the Toolchain for Windows
101
All directories in the PATH enviornment variable should be specified using their short
filename (8.3) version. This will also help to avoid NTVDM errors during building.
These short filenames can be specific to each machine.
Build the tools below in MSYS.
• Binutils
– Open source code pacakge and patch as necessary.
– Configure and build in a directory outside of the source code tree.
– Set PATH, in order:
* <MikTex executables>
* /usr/local/bin
* /usr/bin
* /bin
* /mingw/bin
* c:/cygwin/bin
* <install directory>/bin
– Configure
CFLAGS=-D__USE_MINGW_ACCESS \
../$archivedir/configure \
--prefix=$installdir \
--target=avr \
--disable-nls \
--enable-doc \
--datadir=$installdir/doc/binutils \
--with-gmp=/usr/local \
--with-mpfr=/usr/local \
2>&1 | tee binutils-configure.log
– Make
make all html install install-html 2>&1 | tee binutils-make.log
– Manually change documentation location.
• GCC
– Open source code pacakge and patch as necessary.
– Configure and build in a directory outside of the source code tree.
– Set PATH, in order:
* <MikTex executables>
* /usr/local/bin
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12.13
Building the Toolchain for Windows
102
* /usr/bin
* /bin
* /mingw/bin
* c:/cygwin/bin
* <install directory>/bin
– Configure
CFLAGS=-D__USE_MINGW_ACCESS \
../gcc-$version/configure \
--prefix=$installdir \
--target=$target \
--enable-languages=c,c++ \
--with-dwarf2 \
--enable-win32-registry=WinAVR-$release \
--disable-nls \
--with-gmp=/usr/local \
--with-mpfr=/usr/local \
--enable-doc \
--disable-libssp \
2>&1 | tee $package-configure.log
– Make
make all html install 2>&1 | tee $package-make.log
– Manually copy the HTML documentation from the source code tree to the
installation tree.
• avr-libc
– Open source code package.
– Configure and build at the top of the source code tree.
– Set PATH, in order:
* /usr/local/bin
* /mingw/bin
* /bin
* <MikTex executables>
* <install directory>/bin
* <Doxygen executables>
* <NetPBM executables>
* <fig2dev executable>
* <Ghostscript executables>
* c:/cygwin/bin
– Configure
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12.13
Building the Toolchain for Windows
103
./configure \
--host=avr \
--prefix=$installdir \
--enable-doc \
--disable-versioned-doc \
--enable-html-doc \
--enable-pdf-doc \
--enable-man-doc \
--mandir=$installdir/man \
--datadir=$installdir \
2>&1 | tee $package-configure.log
– Make
make all install 2>&1 | tee $package-make.log
– Manually change location of man page documentation.
– Move the examples to the top level of the install tree.
– Convert line endings in examples to Windows line endings.
– Convert line endings in header files to Windows line endings.
• AVRDUDE
– Open source code package.
– Configure and build at the top of the source code tree.
– Set PATH, in order:
* <MikTex executables>
* /usr/local/bin
* /usr/bin
* /bin
* /mingw/bin
* c:/cygwin/bin
* <install directory>/bin
– Set location of LibUSB headers and libraries
export CPPFLAGS="-I../../libusb-win32-device-bin-$libusb_version/include"
export CFLAGS="-I../../libusb-win32-device-bin-$libusb_version/include"
export LDFLAGS="-L../../libusb-win32-device-bin-$libusb_version/lib/gcc"
– Configure
./configure \
--prefix=$installdir \
--datadir=$installdir \
--sysconfdir=$installdir/bin \
--enable-doc \
--disable-versioned-doc \
2>&1 | tee $package-configure.log
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12.13
Building the Toolchain for Windows
– Make
make -k all install 2>&1 | tee $package-make.log
– Convert line endings in avrdude config file to Windows line endings.
– Delete backup copy of avrdude config file in install directory if exists.
• Insight/GDB
– Open source code pacakge and patch as necessary.
– Configure and build in a directory outside of the source code tree.
– Set PATH, in order:
* <MikTex executables>
* /usr/local/bin
* /usr/bin
* /bin
* /mingw/bin
* c:/cygwin/bin
* <install directory>/bin
– Configure
CFLAGS=-D__USE_MINGW_ACCESS \
LDFLAGS=’-static’ \
../$archivedir/configure \
--prefix=$installdir \
--target=avr \
--with-gmp=/usr/local \
--with-mpfr=/usr/local \
--enable-doc \
2>&1 | tee insight-configure.log
– Make
make all install 2>&1 | tee $package-make.log
• SRecord
– Open source code package.
– Configure and build at the top of the source code tree.
– Set PATH, in order:
*
*
*
*
<MikTex executables>
/usr/local/bin
/usr/bin
/bin
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104
12.13
Building the Toolchain for Windows
105
* /mingw/bin
* c:/cygwin/bin
* <install directory>/bin
– Configure
./configure \
--prefix=$installdir \
--infodir=$installdir/info \
--mandir=$installdir/man \
2>&1 | tee $package-configure.log
– Make
make all install 2>&1 | tee $package-make.log
Build the tools below in Cygwin.
• AVaRICE
– Open source code package.
– Configure and build in a directory outside of the source code tree.
– Set PATH, in order:
* <MikTex executables>
* /usr/local/bin
* /usr/bin
* /bin
* <install directory>/bin
– Set location of LibUSB headers and libraries
export CPPFLAGS=-I$startdir/libusb-win32-device-bin-$libusb_version/include
export CFLAGS=-I$startdir/libusb-win32-device-bin-$libusb_version/include
export LDFLAGS="-static -L$startdir/libusb-win32-device-bin-$libusb_version/lib/gcc
– Configure
../$archivedir/configure \
--prefix=$installdir \
--datadir=$installdir/doc \
--mandir=$installdir/man \
--infodir=$installdir/info \
2>&1 | tee avarice-configure.log
– Make
make all install 2>&1 | tee avarice-make.log
• SimulAVR
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13 Using the GNU tools
106
– Open source code package.
– Configure and build in a directory outside of the source code tree.
– Set PATH, in order:
* <MikTex executables>
* /usr/local/bin
* /usr/bin
* /bin
* <install directory>/bin
– Configure
export LDFLAGS="-static"
../$archivedir/configure \
--prefix=$installdir \
--datadir=$installdir \
--disable-tests \
--disable-versioned-doc \
2>&1 | tee simulavr-configure.log
– Make
make -k all install 2>&1 | tee simulavr-make.log
make pdf install-pdf 2>&1 | tee simulavr-pdf-make.log
13
Using the GNU tools
This is a short summary of the AVR-specific aspects of using the GNU tools. Normally,
the generic documentation of these tools is fairly large and maintained in texinfo
files. Command-line options are explained in detail in the manual page.
13.1
Options for the C compiler avr-gcc
13.1.1
Machine-specific options for the AVR
The following machine-specific options are recognized by the C compiler frontend. In
addition to the preprocessor macros indicated in the tables below, the preprocessor will
define the macros __AVR and __AVR__ (to the value 1) when compiling for an AVR
target. The macro AVR will be defined as well when using the standard levels gnu89
(default) and gnu99 but not with c89 and c99.
• -mmcu=architecture
Compile code for architecture. Currently known architectures are
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
13.1
Options for the C compiler avr-gcc
Architecture
avr1
avr2
avr25 [1]
avr3
avr31
avr35 [3]
avr4
avr5
PBSMacros
PBS__AVR_ARCH__=1
__AVR_ASM_ONLY__
__AVR_2_BYTE_PC__ [2]
PBS__AVR_ARCH__=2
__AVR_2_BYTE_PC__ [2]
PBS__AVR_ARCH__=25
__AVR_HAVE_MOVW__ [1]
__AVR_HAVE_LPMX__ [1]
__AVR_2_BYTE_PC__ [2]
PBS__AVR_ARCH__=3
__AVR_MEGA__ [5]
__AVR_HAVE_JMP_CALL__ [4]
__AVR_2_BYTE_PC__ [2]
PBS__AVR_ARCH__=31
__AVR_MEGA__ [5]
__AVR_HAVE_JMP_CALL__ [4]
__AVR_HAVE_RAMPZ__ [4]
__AVR_HAVE_ELPM__ [4]
__AVR_2_BYTE_PC__ [2]
PBS__AVR_ARCH__=35
__AVR_MEGA__ [5]
__AVR_HAVE_JMP_CALL__ [4]
__AVR_HAVE_MOVW__ [1]
__AVR_HAVE_LPMX__ [1]
__AVR_2_BYTE_PC__ [2]
PBS__AVR_ARCH__=4
__AVR_ENHANCED__ [5]
__AVR_HAVE_MOVW__ [1]
__AVR_HAVE_LPMX__ [1]
__AVR_HAVE_MUL__ [1]
__AVR_2_BYTE_PC__ [2]
PBS__AVR_ARCH__=5
__AVR_MEGA__ [5]
__AVR_ENHANCED__ [5]
__AVR_HAVE_JMP_CALL__ [4]
__AVR_HAVE_MOVW__ [1]
__AVR_HAVE_LPMX__ [1]
__AVR_HAVE_MUL__ [1]
__AVR_2_BYTE_PC__ [2]
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107
PBSDescription
PBSSimple CPU core,
only assembler support
PBS"Classic" CPU core,
up to 8 KB of ROM
PBS"Classic"
CPU
core with ’MOVW’
and ’LPM Rx, Z[+]’
instruction, up to 8 KB
of ROM
PBS"Classic" CPU core,
16 KB to 64 KB of ROM
PBS"Classic" CPU core,
128 KB of ROM
PBS"Classic"
CPU
core with ’MOVW’
and ’LPM Rx, Z[+]’
instruction, 16 KB to 64
KB of ROM
PBS"Enhanced" CPU
core, up to 8 KB of
ROM
PBS"Enhanced" CPU
core, 16 KB to 64 KB of
ROM
13.1
Options for the C compiler avr-gcc
avr51
avr6 [2]
108
PBS__AVR_ARCH__=51
__AVR_MEGA__ [5]
__AVR_ENHANCED__ [5]
__AVR_HAVE_JMP_CALL__ [4]
__AVR_HAVE_MOVW__ [1]
__AVR_HAVE_LPMX__ [1]
__AVR_HAVE_MUL__ [1]
__AVR_HAVE_RAMPZ__ [4]
__AVR_HAVE_ELPM__ [4]
__AVR_HAVE_ELPMX__ [4]
__AVR_2_BYTE_PC__ [2]
PBS__AVR_ARCH__=6
__AVR_MEGA__ [5]
__AVR_ENHANCED__ [5]
__AVR_HAVE_JMP_CALL__ [4]
__AVR_HAVE_MOVW__ [1]
__AVR_HAVE_LPMX__ [1]
__AVR_HAVE_MUL__ [1]
__AVR_HAVE_RAMPZ__ [4]
__AVR_HAVE_ELPM__ [4]
__AVR_HAVE_ELPMX__ [4]
__AVR_3_BYTE_PC__ [2]
PBS"Enhanced" CPU
core, 128 KB of ROM
PBS"Enhanced" CPU
core, 256 KB of ROM
[1] New in GCC 4.2
[2] Unofficial patch for GCC 4.1
[3] New in GCC 4.2.3
[4] New in GCC 4.3
[5] Obsolete.
By default, code is generated for the avr2 architecture.
Note that when only using -mmcu=architecture but no -mmcu=MCU type, including
the file <avr/io.h> cannot work since it cannot decide which device’s definitions
to select.
• -mmcu=MCU type
The following MCU types are currently understood by avr-gcc. The table matches
them against the corresponding avr-gcc architecture name, and shows the preprocessor
symbol declared by the -mmcu option.
Architecture
avr1
avr1
MCU name
at90s1200
attiny11
Macro
__AVR_AT90S1200__
__AVR_ATtiny11__
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13.1
Options for the C compiler avr-gcc
avr1
avr1
avr1
avr2
avr2
avr2
avr2
avr2
avr2
avr2
avr2
avr2
avr2
avr2
avr2
avr2/avr25 [1]
avr2/avr25 [1]
avr2/avr25 [1]
avr2/avr25 [1]
avr2/avr25 [1]
avr2/avr25 [1]
avr2/avr25 [1]
avr2/avr25 [1]
avr2/avr25 [1]
avr2/avr25 [1]
avr2/avr25 [1]
avr2/avr25 [1]
avr2/avr25 [1]
avr2/avr25 [1]
avr2/avr25 [1]
avr2/avr25 [1]
avr2/avr25 [1]
avr2/avr25 [1]
avr2/avr25 [1]
avr2/avr25 [1]
avr2/avr25 [1]
avr2/avr25 [1]
avr2/avr25 [1]
avr2/avr25 [1]
avr2/avr25 [1]
avr2/avr25 [1]
avr3
avr3
avr3/avr31 [3]
avr3/avr31 [3]
attiny12
attiny15
attiny28
at90s2313
at90s2323
at90s2333
at90s2343
attiny22
attiny26
at90s4414
at90s4433
at90s4434
at90s8515
at90c8534
at90s8535
at86rf401
ata6289
attiny13
attiny13a
attiny2313
attiny2313a
attiny24
attiny24a
attiny25
attiny261
attiny261a
attiny4313
attiny43u
attiny44
attiny44a
attiny45
attiny461
attiny461a
attiny48
attiny84
attiny84a
attiny85
attiny861
attiny861a
attiny87
attiny88
atmega603
at43usb355
atmega103
at43usb320
109
__AVR_ATtiny12__
__AVR_ATtiny15__
__AVR_ATtiny28__
__AVR_AT90S2313__
__AVR_AT90S2323__
__AVR_AT90S2333__
__AVR_AT90S2343__
__AVR_ATtiny22__
__AVR_ATtiny26__
__AVR_AT90S4414__
__AVR_AT90S4433__
__AVR_AT90S4434__
__AVR_AT90S8515__
__AVR_AT90C8534__
__AVR_AT90S8535__
__AVR_AT86RF401__
__AVR_ATA6289__
__AVR_ATtiny13__
__AVR_ATtiny13A__
__AVR_ATtiny2313__
__AVR_ATtiny2313A__
__AVR_ATtiny24__
__AVR_ATtiny24A__
__AVR_ATtiny25__
__AVR_ATtiny261__
__AVR_ATtiny261A__
__AVR_ATtiny4313__
__AVR_ATtiny43U__
__AVR_ATtiny44__
__AVR_ATtiny44A__
__AVR_ATtiny45__
__AVR_ATtiny461__
__AVR_ATtiny461A__
__AVR_ATtiny48__
__AVR_ATtiny84__
__AVR_ATtiny84A__
__AVR_ATtiny85__
__AVR_ATtiny861__
__AVR_ATtiny861A__
__AVR_ATtiny87__
__AVR_ATtiny88__
__AVR_ATmega603__
__AVR_AT43USB355__
__AVR_ATmega103__
__AVR_AT43USB320__
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
13.1
Options for the C compiler avr-gcc
avr3/avr35 [2]
avr3/avr35 [2]
avr3/avr35 [2]
avr3/avr35 [2]
avr3/avr35 [2]
avr3/avr35 [2]
avr3/avr35 [2]
avr3
avr4
avr4
avr4
avr4
avr4
avr4
avr4
avr4
avr4
avr4
avr4
avr4
avr4
avr4
avr4
avr4
avr4
avr4
avr5
avr5
avr5
avr5
avr5
avr5
avr5
avr5
avr5
avr5
avr5
avr5
avr5
avr5
avr5
avr5
avr5
avr5
avr5
avr5
at90usb82
at90usb162
atmega8u2
atmega16u2
atmega32u2
attiny167
attiny1634
at76c711
atmega48
atmega48a
atmega48pa
atmega48p
atmega8
atmega8515
atmega8535
atmega88
atmega88a
atmega88p
atmega88pa
atmega8hva
at90pwm1
at90pwm2
at90pwm2b
at90pwm3
at90pwm3b
at90pwm81
at90can32
at90can64
at90pwm161
at90pwm216
at90pwm316
at90scr100
at90usb646
at90usb647
at94k
atmega16
atmega161
atmega162
atmega163
atmega164a
atmega164p
atmega165
atmega165a
atmega165p
atmega168
atmega168a
110
__AVR_AT90USB82__
__AVR_AT90USB162__
__AVR_ATmega8U2__
__AVR_ATmega16U2__
__AVR_ATmega32U2__
__AVR_ATtiny167__
__AVR_ATtiny1634__
__AVR_AT76C711__
__AVR_ATmega48__
__AVR_ATmega48A__
__AVR_ATmega48PA__
__AVR_ATmega48P__
__AVR_ATmega8__
__AVR_ATmega8515__
__AVR_ATmega8535__
__AVR_ATmega88__
__AVR_ATmega88A__
__AVR_ATmega88P__
__AVR_ATmega88PA__
__AVR_ATmega8HVA__
__AVR_AT90PWM1__
__AVR_AT90PWM2__
__AVR_AT90PWM2B__
__AVR_AT90PWM3__
__AVR_AT90PWM3B__
__AVR_AT90PWM81__
__AVR_AT90CAN32__
__AVR_AT90CAN64__
__AVR_AT90PWM161__
__AVR_AT90PWM216__
__AVR_AT90PWM316__
__AVR_AT90SCR100__
__AVR_AT90USB646__
__AVR_AT90USB647__
__AVR_AT94K__
__AVR_ATmega16__
__AVR_ATmega161__
__AVR_ATmega162__
__AVR_ATmega163__
__AVR_ATmega164A__
__AVR_ATmega164P__
__AVR_ATmega165__
__AVR_ATmega165A__
__AVR_ATmega165P__
__AVR_ATmega168__
__AVR_ATmega168A__
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
13.1
Options for the C compiler avr-gcc
avr5
avr5
avr5
avr5
avr5
avr5
avr5
avr5
avr5
avr5
avr5
avr5
avr5
avr5
avr5
avr5
avr5
avr5
avr5
avr5
avr5
avr5
avr5
avr5
avr5
avr5
avr5
avr5
avr5
avr5
avr5
avr5
avr5
avr5
avr5
avr5
avr5
avr5
avr5
avr5
avr5
avr5
avr5
avr5
avr5
atmega168p
atmega169
atmega169a
atmega169p
atmega169pa
atmega16a
atmega16hva
atmega16hva2
atmega16hvb
atmega16hvbrevb
atmega16m1
atmega16u4
atmega32
atmega323
atmega324a
atmega324p
atmega324pa
atmega325
atmega325a
atmega325p
atmega325pa
atmega3250
atmega3250a
atmega3250p
atmega3250pa
atmega328
atmega328p
atmega329
atmega329a
atmega329p
atmega329pa
atmega3290
atmega3290a
atmega3290p
atmega3290pa
atmega32c1
atmega32hvb
atmega32hvbrevb
atmega32m1
atmega32u4
atmega32u6
atmega406
atmega64
atmega640
atmega644
111
__AVR_ATmega168P__
__AVR_ATmega169__
__AVR_ATmega169A__
__AVR_ATmega169P__
__AVR_ATmega169PA__
__AVR_ATmega16A__
__AVR_ATmega16HVA__
__AVR_ATmega16HVA2__
__AVR_ATmega16HVB__
__AVR_ATmega16HVBREVB__
__AVR_ATmega16M1__
__AVR_ATmega16U4__
__AVR_ATmega32__
__AVR_ATmega323__
__AVR_ATmega324A__
__AVR_ATmega324P__
__AVR_ATmega324PA__
__AVR_ATmega325__
__AVR_ATmega325A__
__AVR_ATmega325P__
__AVR_ATmega325PA__
__AVR_ATmega3250__
__AVR_ATmega3250A__
__AVR_ATmega3250P__
__AVR_ATmega3250PA__
__AVR_ATmega328__
__AVR_ATmega328P__
__AVR_ATmega329__
__AVR_ATmega329A__
__AVR_ATmega329P__
__AVR_ATmega329PA__
__AVR_ATmega3290__
__AVR_ATmega3290A__
__AVR_ATmega3290P__
__AVR_ATmega3290PA__
__AVR_ATmega32C1__
__AVR_ATmega32HVB__
__AVR_ATmega32HVBREVB__
__AVR_ATmega32M1__
__AVR_ATmega32U4__
__AVR_ATmega32U6__
__AVR_ATmega406__
__AVR_ATmega64__
__AVR_ATmega640__
__AVR_ATmega644__
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13.1
Options for the C compiler avr-gcc
avr5
avr5
avr5
avr5
avr5
avr5
avr5
avr5
avr5
avr5
avr5
avr5
avr5
avr5
avr5
avr5
avr5
avr5
avr5
avr5/avr51 [3]
avr5/avr51 [3]
avr5/avr51 [3]
avr5/avr51 [3]
avr5/avr51 [3]
avr5/avr51 [3]
avr5/avr51 [3]
avr6
avr6
avrxmega2
avrxmega2
avrxmega2
avrxmega2
avrxmega4
avrxmega4
avrxmega5
avrxmega5
avrxmega6
avrxmega6
avrxmega6
avrxmega6
avrxmega6
avrxmega6
avrxmega6
avrxmega6
avrxmega6
avrxmega7
atmega644a
atmega644p
atmega644pa
atmega645
atmega645a
atmega645p
atmega6450
atmega6450a
atmega6450p
atmega649
atmega649a
atmega6490
atmega6490a
atmega6490p
atmega649p
atmega64c1
atmega64hve
atmega64m1
m3000
at90can128
at90usb1286
at90usb1287
atmega128
atmega1280
atmega1281
atmega1284p
atmega2560
atmega2561
atxmega16a4
atxmega16d4
atxmega32a4
atxmega32d4
atxmega64a3
atxmega64d3
atxmega64a1
atxmega64a1u
atxmega128a3
atxmega128b1
atxmega128d3
atxmega192a3
atxmega192d3
atxmega256a3
atxmega256a3b
atxmega256a3bu
atxmega256d3
atxmega128a1
112
__AVR_ATmega644A__
__AVR_ATmega644P__
__AVR_ATmega644PA__
__AVR_ATmega645__
__AVR_ATmega645A__
__AVR_ATmega645P__
__AVR_ATmega6450__
__AVR_ATmega6450A__
__AVR_ATmega6450P__
__AVR_ATmega649__
__AVR_ATmega649A__
__AVR_ATmega6490__
__AVR_ATmega6490A__
__AVR_ATmega6490P__
__AVR_ATmega649P__
__AVR_ATmega64C1__
__AVR_ATmega64HVE__
__AVR_ATmega64M1__
__AVR_M3000__
__AVR_AT90CAN128__
__AVR_AT90USB1286__
__AVR_AT90USB1287__
__AVR_ATmega128__
__AVR_ATmega1280__
__AVR_ATmega1281__
__AVR_ATmega1284P__
__AVR_ATmega2560__
__AVR_ATmega2561__
__AVR_ATxmega16A4__
__AVR_ATxmega16D4__
__AVR_ATxmega32A4__
__AVR_ATxmega32D4__
__AVR_ATxmega64A3__
__AVR_ATxmega64D3__
__AVR_ATxmega64A1__
__AVR_ATxmega64A1U__
__AVR_ATxmega128A3__
__AVR_ATxmega128B1__
__AVR_ATxmega128D3__
__AVR_ATxmega192A3__
__AVR_ATxmega192D3__
__AVR_ATxmega256A3__
__AVR_ATxmega256A3B__
__AVR_ATxmega256A3BU__
__AVR_ATxmega256D3__
__AVR_ATxmega128A1__
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13.1
Options for the C compiler avr-gcc
avrxmega7
avrtiny10
avrtiny10
avrtiny10
avrtiny10
avrtiny10
avrtiny10
atxmega128a1u
attiny4
attiny5
attiny9
attiny10
attiny20
attiny40
113
__AVR_ATxmega128A1U__
__AVR_ATtiny4__
__AVR_ATtiny5__
__AVR_ATtiny9__
__AVR_ATtiny10__
__AVR_ATtiny20__
__AVR_ATtiny40__
[1] ’avr25’ architecture is new in GCC 4.2
[2] ’avr35’ architecture is new in GCC 4.2.3
[3] ’avr31’ and ’avr51’ architectures is new in GCC 4.3
• -morder1
• -morder2
Change the order of register assignment. The default is
r24, r25, r18, r19, r20, r21, r22, r23, r30, r31, r26, r27, r28, r29, r17, r16, r15, r14, r13,
r12, r11, r10, r9, r8, r7, r6, r5, r4, r3, r2, r0, r1
Order 1 uses
r18, r19, r20, r21, r22, r23, r24, r25, r30, r31, r26, r27, r28, r29, r17, r16, r15, r14, r13,
r12, r11, r10, r9, r8, r7, r6, r5, r4, r3, r2, r0, r1
Order 2 uses
r25, r24, r23, r22, r21, r20, r19, r18, r30, r31, r26, r27, r28, r29, r17, r16, r15, r14, r13,
r12, r11, r10, r9, r8, r7, r6, r5, r4, r3, r2, r1, r0
• -mint8
Assume int to be an 8-bit integer. Note that this is not really supported by avr-libc,
so it should normally not be used. The default is to use 16-bit integers.
• -mno-interrupts
Generates code that changes the stack pointer without disabling interrupts. Normally,
the state of the status register SREG is saved in a temporary register, interrupts are
disabled while changing the stack pointer, and SREG is restored.
Specifying this option will define the preprocessor macro __NO_INTERRUPTS__ to
the value 1.
• -mcall-prologues
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13.1
Options for the C compiler avr-gcc
114
Use subroutines for function prologue/epilogue. For complex functions that use many
registers (that needs to be saved/restored on function entry/exit), this saves some space
at the cost of a slightly increased execution time.
• -mtiny-stack
Change only the low 8 bits of the stack pointer.
• -mno-tablejump
Deprecated, use -fno-jump-tables instead.
• -mshort-calls
Use rjmp/rcall (limited range) on >8K devices. On avr2 and avr4 architectures (less than 8 KB or flash memory), this is always the case. On avr3 and avr5
architectures, calls and jumps to targets outside the current function will by default use
jmp/call instructions that can cover the entire address range, but that require more
flash ROM and execution time.
• -mrtl
Dump the internal compilation result called "RTL" into comments in the generated
assembler code. Used for debugging avr-gcc.
• -msize
Dump the address, size, and relative cost of each statement into comments in the generated assembler code. Used for debugging avr-gcc.
• -mdeb
Generate lots of debugging information to stderr.
13.1.2
Selected general compiler options
The following general gcc options might be of some interest to AVR users.
• -On
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13.1
Options for the C compiler avr-gcc
115
Optimization level n. Increasing n is meant to optimize more, an optimization level of
0 means no optimization at all, which is the default if no -O option is present. The
special option -Os is meant to turn on all -O2 optimizations that are not expected to
increase code size.
Note that at -O3, gcc attempts to inline all "simple" functions. For the AVR target,
this will normally constitute a large pessimization due to the code increasement. The
only other optimization turned on with -O3 is -frename-registers, which could
rather be enabled manually instead.
A simple -O option is equivalent to -O1.
Note also that turning off all optimizations will prevent some warnings from being
issued since the generation of those warnings depends on code analysis steps that are
only performed when optimizing (unreachable code, unused variables).
See also the appropriate FAQ entry for issues regarding debugging optimized code.
• -Wa,assembler-options
• -Wl,linker-options
Pass the listed options to the assembler, or linker, respectively.
• -g
Generate debugging information that can be used by avr-gdb.
• -ffreestanding
Assume a "freestanding" environment as per the C standard. This turns off automatic
builtin functions (though they can still be reached by prepending __builtin_ to
the actual function name). It also makes the compiler not complain when main()
is declared with a void return type which makes some sense in a microcontroller
environment where the application cannot meaningfully provide a return value to its
environment (in most cases, main() won’t even return anyway). However, this also
turns off all optimizations normally done by the compiler which assume that functions
known by a certain name behave as described by the standard. E. g., applying the
function strlen() to a literal string will normally cause the compiler to immediately
replace that call by the actual length of the string, while with -ffreestanding, it
will always call strlen() at run-time.
• -funsigned-char
Make any unqualfied char type an unsigned char. Without this option, they default to
a signed char.
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13.2
Options for the assembler avr-as
116
• -funsigned-bitfields
Make any unqualified bitfield type unsigned. By default, they are signed.
• -fshort-enums
Allocate to an enum type only as many bytes as it needs for the declared range of
possible values. Specifically, the enum type will be equivalent to the smallest integer
type which has enough room.
• -fpack-struct
Pack all structure members together without holes.
• -fno-jump-tables
Do not generate tablejump instructions. By default, jump tables can be used to optimize switch statements. When turned off, sequences of compare statements are
used instead. Jump tables are usually faster to execute on average, but in particular for
switch statements, where most of the jumps would go to the default label, they might
waste a bit of flash memory.
NOTE: The tablejump instructions use the LPM assembler instruction for access to
jump tables. Always use -fno-jump-tables switch, if compiling a bootloader for
devices with more than 64 KB of code memory.
13.2
Options for the assembler avr-as
13.2.1
Machine-specific assembler options
• -mmcu=architecture
• -mmcu=MCU name
avr-as understands the same -mmcu= options as avr-gcc. By default, avr2 is assumed,
but this can be altered by using the appropriate .arch pseudo-instruction inside the
assembler source file.
• -mall-opcodes
Turns off opcode checking for the actual MCU type, and allows any possible AVR
opcode to be assembled.
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13.2
Options for the assembler avr-as
117
• -mno-skip-bug
Don’t emit a warning when trying to skip a 2-word instruction with a CPSE/SBIC/SBIS/SBRC/SBRS
instruction. Early AVR devices suffered from a hardware bug where these instructions
could not be properly skipped.
• -mno-wrap
For RJMP/RCALL instructions, don’t allow the target address to wrap around for devices that have more than 8 KB of memory.
• --gstabs
Generate .stabs debugging symbols for assembler source lines. This enables avr-gdb
to trace through assembler source files. This option must not be used when assembling
sources that have been generated by the C compiler; these files already contain the
appropriate line number information from the C source files.
• -a[cdhlmns=file]
Turn on the assembler listing. The sub-options are:
• c omit false conditionals
• d omit debugging directives
• h include high-level source
• l include assembly
• m include macro expansions
• n omit forms processing
• s include symbols
• =file set the name of the listing file
The various sub-options can be combined into a single -a option list; =file must be the
last one in that case.
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13.3
Controlling the linker avr-ld
13.2.2
Examples for assembler options passed through the C compiler
118
Remember that assembler options can be passed from the C compiler frontend using
-Wa (see above), so in order to include the C source code into the assembler listing in
file foo.lst, when compiling foo.c, the following compiler command-line can be
used:
$ avr-gcc -c -O foo.c -o foo.o -Wa,-ahls=foo.lst
In order to pass an assembler file through the C preprocessor first, and have the assembler generate line number debugging information for it, the following command can be
used:
$ avr-gcc -c -x assembler-with-cpp -o foo.o foo.S -Wa,--gstabs
Note that on Unix systems that have case-distinguishing file systems, specifying a file
name with the suffix .S (upper-case letter S) will make the compiler automatically
assume -x assembler-with-cpp, while using .s would pass the file directly to
the assembler (no preprocessing done).
13.3
Controlling the linker avr-ld
13.3.1
Selected linker options
While there are no machine-specific options for avr-ld, a number of the standard options might be of interest to AVR users.
• -lname
Locate the archive library named libname.a, and use it to resolve currently unresolved symbols from it. The library is searched along a path that consists of builtin
pathname entries that have been specified at compile time (e. g. /usr/local/avr/lib
on Unix systems), possibly extended by pathname entries as specified by -L options
(that must precede the -l options on the command-line).
• -Lpath
Additional location to look for archive libraries requested by -l options.
• --defsym symbol=expr
Define a global symbol symbol using expr as the value.
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13.3
Controlling the linker avr-ld
119
• -M
Print a linker map to stdout.
• -Map mapfile
Print a linker map to mapfile.
• --cref
Output a cross reference table to the map file (in case -Map is also present), or to
stdout.
• --section-start sectionname=org
Start section sectionname at absolute address org.
• -Tbss org
• -Tdata org
• -Ttext org
Start the bss, data, or text section at org, respectively.
• -T scriptfile
Use scriptfile as the linker script, replacing the default linker script. Default linker
scripts are stored in a system-specific location (e. g. under /usr/local/avr/lib/ldscripts
on Unix systems), and consist of the AVR architecture name (avr2 through avr5) with
the suffix .x appended. They describe how the various memory sections will be linked
together.
13.3.2
Passing linker options from the C compiler
By default, all unknown non-option arguments on the avr-gcc command-line (i. e.,
all filename arguments that don’t have a suffix that is handled by avr-gcc) are passed
straight to the linker. Thus, all files ending in .o (object files) and .a (object libraries)
are provided to the linker.
System libraries are usually not passed by their explicit filename but rather using the
-l option which uses an abbreviated form of the archive filename (see above). avrlibc ships two system libraries, libc.a, and libm.a. While the standard library
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13.3
Controlling the linker avr-ld
120
libc.a will always be searched for unresolved references when the linker is started
using the C compiler frontend (i. e., there’s always at least one implied -lc option),
the mathematics library libm.a needs to be explicitly requested using -lm. See also
the entry in the FAQ explaining this.
Conventionally, Makefiles use the make macro LDLIBS to keep track of -l (and
possibly -L) options that should only be appended to the C compiler command-line
when linking the final binary. In contrast, the macro LDFLAGS is used to store other
command-line options to the C compiler that should be passed as options during the
linking stage. The difference is that options are placed early on the command-line,
while libraries are put at the end since they are to be used to resolve global symbols
that are still unresolved at this point.
Specific linker flags can be passed from the C compiler command-line using the -Wl
compiler option, see above. This option requires that there be no spaces in the appended
linker option, while some of the linker options above (like -Map or --defsym) would
require a space. In these situations, the space can be replaced by an equal sign as
well. For example, the following command-line can be used to compile foo.c into an
executable, and also produce a link map that contains a cross-reference list in the file
foo.map:
$ avr-gcc -O -o foo.out -Wl,-Map=foo.map -Wl,--cref foo.c
Alternatively, a comma as a placeholder will be replaced by a space before passing the
option to the linker. So for a device with external SRAM, the following command-line
would cause the linker to place the data segment at address 0x2000 in the SRAM:
$ avr-gcc -mmcu=atmega128 -o foo.out -Wl,-Tdata,0x802000
See the explanation of the data section for why 0x800000 needs to be added to the
actual value. Note that the stack will still remain in internal RAM, through the symbol
__stack that is provided by the run-time startup code. This is probably a good idea
anyway (since internal RAM access is faster), and even required for some early devices
that had hardware bugs preventing them from using a stack in external RAM. Note
also that the heap for malloc() will still be placed after all the variables in the data
section, so in this situation, no stack/heap collision can occur.
In order to relocate the stack from its default location at the top of interns RAM, the
value of the symbol __stack can be changed on the linker command-line. As the
linker is typically called from the compiler frontend, this can be achieved using a compiler option like
-Wl,--defsym=__stack=0x8003ff
The above will make the code use stack space from RAM address 0x3ff downwards.
The amount of stack space available then depends on the bottom address of internal
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14 Using the avrdude program
121
RAM for a particular device. It is the responsibility of the application to ensure the
stack does not grow out of bounds, as well as to arrange for the stack to not collide
with variable allocations made by the compiler (sections .data and .bss).
14
Using the avrdude program
Note
This section was contributed by Brian Dean [ [email protected] ].
The avrdude program was previously called avrprog. The name was changed to
avoid confusion with the avrprog program that Atmel ships with AvrStudio.
avrdude is a program that is used to update or read the flash and EEPROM memories
of Atmel AVR microcontrollers on FreeBSD Unix. It supports the Atmel serial programming protocol using the PC’s parallel port and can upload either a raw binary file
or an Intel Hex format file. It can also be used in an interactive mode to individually
update EEPROM cells, fuse bits, and/or lock bits (if their access is supported by the
Atmel serial programming protocol.) The main flash instruction memory of the AVR
can also be programmed in interactive mode, however this is not very useful because
one can only turn bits off. The only way to turn flash bits on is to erase the entire
memory (using avrdude’s -e option).
avrdude is part of the FreeBSD ports system. To install it, simply do the following:
# cd /usr/ports/devel/avrdude
# make install
Once installed, avrdude can program processors using the contents of the .hex file
specified on the command line. In this example, the file main.hex is burned into the
flash memory:
# avrdude -p 2313 -e -m flash -i main.hex
avrdude: AVR device initialized and ready to accept instructions
avrdude: Device signature = 0x1e9101
avrdude:
avrdude:
avrdude:
avrdude:
erasing chip
done.
reading input file "main.hex"
input file main.hex auto detected as Intel Hex
avrdude: writing flash:
1749 0x00
avrdude: 1750 bytes of flash written
avrdude: verifying flash memory against main.hex:
avrdude: reading on-chip flash data:
1749 0x00
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14 Using the avrdude program
122
avrdude: verifying ...
avrdude: 1750 bytes of flash verified
avrdude done.
Thank you.
The -p 2313 option lets avrdude know that we are operating on an AT90S2313
chip. This option specifies the device id and is matched up with the device of the same
id in avrdude’s configuration file ( /usr/local/etc/avrdude.conf ). To list
valid parts, specify the -v option. The -e option instructs avrdude to perform a
chip-erase before programming; this is almost always necessary before programming
the flash. The -m flash option indicates that we want to upload data into the flash
memory, while -i main.hex specifies the name of the input file.
The EEPROM is uploaded in the same way, the only difference is that you would use
-m eeprom instead of -m flash.
To use interactive mode, use the -t option:
# avrdude -p 2313 -t
avrdude: AVR device initialized and ready to accept instructions
avrdude: Device signature = 0x1e9101
avrdude>
The ’?’ command displays a list of valid
commands:
avrdude> ?
>>> ?
Valid commands:
dump
read
write
erase
sig
part
send
help
?
quit
:
:
:
:
:
:
:
:
:
:
dump memory : dump <memtype> <addr> <N-Bytes>
alias for dump
write memory : write <memtype> <addr> <b1> <b2> ... <bN>
perform a chip erase
display device signature bytes
display the current part information
send a raw command : send <b1> <b2> <b3> <b4>
help
help
quit
Use the ’part’ command to display valid memory types for use with the
’dump’ and ’write’ commands.
avrdude>
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15 Release Numbering and Methodology
15
123
Release Numbering and Methodology
15.1
Release Version Numbering Scheme
Release numbers consist of three parts, a major number, a minor number, and a revision
number, each separated by a dot.
The major number is currently 1 (and has always been). It will only be bumped in case
a new version offers a major change in the API that is not backwards compatible.
In the past (up to 1.6.x), even minor numbers have been used to indicate "stable" releases, and odd minor numbers have been reserved for development branches/versions.
As the latter has never really been used, and maintaining a stable branch that eventually
became effectively the same as the development version has proven to be just a cumbersome and tedious job, this scheme has given up in early 2010, so starting with 1.7.0,
every minor number will be used. Minor numbers will be bumped upon judgement of
the development team, whenever it seems appropriate, but at least in cases where some
API was changed.
Starting with version 1.4.0, a file <avr/version.h> indicates the library version of an
installed library tree.
15.2
Releasing AVR Libc
The information in this section is only relevant to AVR Libc developers and can be
ignored by end users.
Note
In what follows, I assume you know how to use SVN and how to checkout multiple
source trees in a single directory without having them clobber each other. If you
don’t know how to do this, you probably shouldn’t be making releases or cutting
branches.
15.2.1
Creating an SVN branch
The following steps should be taken to cut a branch in SVN (assuming $username is
set to your savannah username):
1. Check out a fresh source tree from SVN trunk.
2. Update the NEWS file with pending release number and commit to SVN trunk:
Change Changes since avr-libc-<last_release>: to Changes in avr-libc-<this_relelase>.
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15.2
Releasing AVR Libc
124
3. Set the branch-point tag (setting <major> and <minor> accordingly):
svn copy svn+ssh://[email protected]/avr-libc/trunk
svn+ssh://[email protected]/avr-libc/tags/avr-libc-<major>_<minor>-branchpoint
4. Create the branch:
svn copy svn+ssh://[email protected]/avr-libc/trunk
svn+ssh://[email protected]/avr-libc/branches/avr-libc-<major
<minor>-branch
5. Update the package version in configure.ac and commit configure.ac to SVN
trunk:
Change minor number to next odd value.
6. Update the NEWS file and commit to SVN trunk:
Add Changes since avr-libc-<this_release>:
7. Check out a new tree for the branch:
svn co svn+ssh://[email protected]/avr-libc/branches/avr-lib
<minor>-branch
8. Update the package version in configure.ac and commit configure.ac to SVN
branch:
Change the patch number to 90 to denote that this now a branch leading up to a
release. Be sure to leave the <date> part of the version.
9. Bring the build system up to date by running bootstrap and configure.
10. Perform a ’make distcheck’ and make sure it succeeds. This will create the
snapshot source tarball. This should be considered the first release candidate.
11. Upload the snapshot tarball to savannah.
12. Update the bug tracker interface on Savannah: Bugs —> Edit field values —>
Release / Fixed Release
13. Announce the branch and the branch tag to the avr-libc-dev list so other developers can checkout the branch.
15.2.2
Making a release
A stable release will only be done on a branch, not from the SVN trunk.
The following steps should be taken when making a release:
1. Make sure the source tree you are working from is on the correct branch:
svn switch svn+ssh://[email protected]/avr-libc/branches/avr
<minor>-branch
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15.2
Releasing AVR Libc
125
2. Update the package version in configure.ac and commit it to SVN.
3. Update the gnu tool chain version requirements in the README and commit to
SVN.
4. Update the ChangeLog file to note the release and commit to SVN on the branch:
Add Released avr-libc-<this_release>.
5. Update the NEWS file with pending release number and commit to SVN:
Change Changes since avr-libc-<last_release>: to Changes in avr-libc-<this_relelase>:.
6. Bring the build system up to date by running bootstrap and configure.
7. Perform a ’make distcheck’ and make sure it succeeds. This will create the
source tarball.
8. Tag the release:
svn copy . svn+ssh://[email protected]/avr-libc/tags/avr-li
<minor>_<patch>-release
or
svn copy svn+ssh://[email protected]/avr-libc/branches/avr-l
<minor>-branch svn+ssh://[email protected]/avr-libc/tags/avr<minor>_<patch>-release
9. Upload the tarball to savannah.
10. Update the NEWS file, and commit to SVN:
Add Changes since avr-libc-<major>_<minor>_<patch>:
11. Update the bug tracker interface on Savannah: Bugs —> Edit field values —>
Release / Fixed Release
12. Generate the latest documentation and upload to savannah.
13. Announce the release.
The following hypothetical diagram should help clarify version and branch relationships.
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16 Acknowledgments
126
HEAD
1.0 Branch
1.2 Branch
cvs tag avr−libc−1_0−branchpoint
set version to 1.1.0.<date>
cvs tag −b avr−libc−1_0−branch
set version to 0.90.90.<date>
set version to 1.0
cvs tag avr−libc−1_0−release
set version to 1.0.0.<date>
set version to 1.0.1
cvs tag avr−libc−1_0_1−release
cvs tag avr−libc−1_2−branchpoint
set version to 1.3.0.<date>
cvs tag −b avr−libc−1_2−branch
set version to 1.1.90.<date>
set version to 1.2
cvs tag avr−libc−1_2−release
cvs tag avr−libc−2.0−branchpoint
set version to 2.1.0.<date>
Figure 4: Release tree
16
Acknowledgments
This document tries to tie together the labors of a large group of people. Without
these individuals’ efforts, we wouldn’t have a terrific, free set of tools to develop AVR
projects. We all owe thanks to:
• The GCC Team, which produced a very capable set of development tools for an
amazing number of platforms and processors.
• Denis Chertykov [ [email protected] ] for making the AVR-specific changes
to the GNU tools.
• Denis Chertykov and Marek Michalkiewicz [ [email protected] ] for
developing the standard libraries and startup code for AVR-GCC.
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17 Todo List
127
• Uros Platise for developing the AVR programmer tool, uisp.
• Joerg Wunsch [ [email protected] ] for adding all the AVR development
tools to the FreeBSD [ http://www.freebsd.org ] ports tree and for providing the basics for the demo project.
• Brian Dean [ [email protected] ] for developing avrdude (an alternative to
uisp) and for contributing documentation which describes how to use it. Avrdude was previously called avrprog.
• Eric Weddington [ [email protected] ] for maintaining the
WinAVR package and thus making the continued improvements to the open
source AVR toolchain available to many users.
• Rich Neswold for writing the original avr-tools document (which he graciously
allowed to be merged into this document) and his improvements to the demo
project.
• Theodore A. Roth for having been a long-time maintainer of many of the tools
(AVR-Libc, the AVR port of GDB, AVaRICE, uisp, avrdude).
• All the people who currently maintain the tools, and/or have submitted suggestions, patches and bug reports. (See the AUTHORS files of the various tools.)
• And lastly, all the users who use the software. If nobody used the software, we
would probably not be very motivated to continue to develop it. Keep those bug
reports coming. ;-)
17
Todo List
Group avr_boot From email with Marek: On smaller devices (all except ATmega64/128),
__SPM_REG is in the I/O space, accessible with the shorter "in" and "out" instructions - since the boot loader has a limited size, this could be an important
optimization.
18
Deprecated List
Global cbi(port, bit)
Global enable_external_int(mask)
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19 Module Index
128
Global inb(port)
Global inp(port)
Global INTERRUPT(signame)
Global ISR_ALIAS(vector, target_vector) For new code, the use of ISR(..., ISR_ALIASOF(...)) is recommended.
Global outb(port, val)
Global outp(val, port)
Global sbi(port, bit)
Global SIGNAL(vector) Do not use SIGNAL() in new code. Use ISR() instead.
Global timer_enable_int(unsigned char ints)
19
Module Index
19.1
Modules
Here is a list of all modules:
<alloca.h>: Allocate space in the stack
134
<assert.h>: Diagnostics
135
<ctype.h>: Character Operations
136
<errno.h>: System Errors
139
<inttypes.h>: Integer Type conversions
139
<math.h>: Mathematics
152
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19.1
Modules
129
<setjmp.h>: Non-local goto
166
<stdint.h>: Standard Integer Types
168
<stdio.h>: Standard IO facilities
181
<stdlib.h>: General utilities
201
<string.h>: Strings
213
<avr/boot.h>: Bootloader Support Utilities
227
<avr/cpufunc.h>: Special AVR CPU functions
234
<avr/eeprom.h>: EEPROM handling
234
<avr/fuse.h>: Fuse Support
239
<avr/interrupt.h>: Interrupts
242
<avr/io.h>: AVR device-specific IO definitions
266
<avr/lock.h>: Lockbit Support
267
<avr/pgmspace.h>: Program Space Utilities
269
<avr/power.h>: Power Reduction Management
291
<avr/sfr_defs.h>: Special function registers
295
Additional notes from <avr/sfr_defs.h>
293
<avr/signature.h>: Signature Support
297
<avr/sleep.h>: Power Management and Sleep Modes
298
<avr/version.h>: avr-libc version macros
300
<avr/wdt.h>: Watchdog timer handling
302
<util/atomic.h> Atomically and Non-Atomically Executed Code Blocks
306
<util/crc16.h>: CRC Computations
309
<util/delay_basic.h>: Basic busy-wait delay loops
313
<util/parity.h>: Parity bit generation
314
<util/setbaud.h>: Helper macros for baud rate calculations
314
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20 Data Structure Index
130
<util/twi.h>: TWI bit mask definitions
317
<compat/deprecated.h>: Deprecated items
321
<compat/ina90.h>: Compatibility with IAR EWB 3.x
325
Demo projects
325
20
Combining C and assembly source files
326
A simple project
330
A more sophisticated project
345
Using the standard IO facilities
353
Example using the two-wire interface (TWI)
361
Data Structure Index
20.1
Data Structures
Here are the data structures with brief descriptions:
div_t
366
ldiv_t
366
21
File Index
21.1
File List
Here is a list of all documented files with brief descriptions:
alloca.h
??
assert.h
367
atoi.S
367
atol.S
367
atomic.h
367
boot.h
368
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21.1
File List
131
cpufunc.h
374
crc16.h
374
ctype.h
375
defines.h
??
delay_basic.h
375
deprecated.h
??
dtoa_conv.h
??
eedef.h
??
eeprom.h
??
errno.h
376
fdevopen.c
376
ffs.S
376
ffsl.S
376
ffsll.S
376
fuse.h
376
hd44780.h
??
ina90.h
??
interrupt.h
377
inttypes.h
377
io.h
380
iocompat.h
??
lcd.h
??
lock.h
380
math.h
380
memccpy.S
384
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21.1
File List
132
memchr.S
384
memchr_P.S
384
memcmp.S
384
memcmp_P.S
384
memcmp_PF.S
384
memcpy.S
384
memcpy_P.S
384
memmem.S
384
memmove.S
384
memrchr.S
384
memrchr_P.S
384
memset.S
384
parity.h
384
pgmspace.h
385
portpins.h
??
power.h
396
project.h
??
setbaud.h
396
setjmp.h
397
sfr_defs.h
??
signal.h
??
signature.h
397
sleep.h
397
stdint.h
397
stdio.h
401
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21.1
File List
133
stdio_private.h
??
stdlib.h
stdlib_private.h
402
??
strcasecmp.S
406
strcasecmp_P.S
406
strcasestr.S
406
strcat.S
406
strcat_P.S
406
strchr.S
406
strchr_P.S
406
strchrnul.S
406
strchrnul_P.S
406
strcmp.S
406
strcmp_P.S
406
strcpy.S
406
strcpy_P.S
406
strcspn.S
406
strcspn_P.S
406
strdup.c
406
string.h
407
strlcat.S
410
strlcat_P.S
410
strlcpy.S
410
strlcpy_P.S
410
strlen.S
410
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21.1
File List
134
strlen_P.S
410
strlwr.S
410
strncasecmp.S
410
strncasecmp_P.S
410
strncat.S
410
strncat_P.S
410
strncmp.S
410
strncmp_P.S
410
strncpy.S
410
strncpy_P.S
410
strnlen.S
410
strnlen_P.S
410
strpbrk.S
410
strpbrk_P.S
410
strrchr.S
410
strrchr_P.S
410
strrev.S
410
strsep.S
410
strsep_P.S
410
strspn.S
410
strspn_P.S
410
strstr.S
410
strstr_P.S
410
strtok.c
410
strtok_P.c
411
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22 Module Documentation
135
strtok_r.S
411
strtok_rP.S
411
strupr.S
411
util/twi.h
411
compat/twi.h
??
uart.h
??
version.h
??
wdt.h
412
xtoa_fast.h
22
??
Module Documentation
<alloca.h>: Allocate space in the stack
22.1
Functions
• void ∗ alloca (size_t __size)
22.1.1
Function Documentation
22.1.1.1
void∗ alloca ( size_t __size )
Allocate __size bytes of space in the stack frame of the caller.
This temporary space is automatically freed when the function that called alloca() returns to its caller. Avr-libc defines the alloca() as a macro, which is translated into the
inlined __builtin_alloca() function. The fact that the code is inlined, means
that it is impossible to take the address of this function, or to change its behaviour by
linking with a different library.
Returns
alloca() returns a pointer to the beginning of the allocated space. If the allocation
causes stack overflow, program behaviour is undefined.
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<assert.h>: Diagnostics
22.2
136
Warning
Avoid use alloca() inside the list of arguments of a function call.
22.2
<assert.h>: Diagnostics
Defines
• #define assert(expression)
22.2.1
Detailed Description
#include <assert.h>
This header file defines a debugging aid.
As there is no standard error output stream available for many applications using this
library, the generation of a printable error message is not enabled by default. These
messages will only be generated if the application defines the macro
__ASSERT_USE_STDERR
before including the <assert.h> header file. By default, only abort() will be called
to halt the application.
22.2.2
Define Documentation
22.2.2.1
#define assert( expression )
Parameters
expression Expression to test for.
The assert() macro tests the given expression and if it is false, the calling process is
terminated. A diagnostic message is written to stderr and the function abort() is called,
effectively terminating the program.
If expression is true, the assert() macro does nothing.
The assert() macro may be removed at compile time by defining NDEBUG as a macro
(e.g., by using the compiler option -DNDEBUG).
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22.3
<ctype.h>: Character Operations
22.3
<ctype.h>: Character Operations
137
Character classification routines
These functions perform character classification. They return true or false status depending whether the character passed to the function falls into the function’s classification (i.e. isdigit() returns true if its argument is any value ’0’ though ’9’, inclusive).
If the input is not an unsigned char value, all of this function return false.
•
•
•
•
•
•
•
•
•
•
•
•
•
int isalnum (int __c)
int isalpha (int __c)
int isascii (int __c)
int isblank (int __c)
int iscntrl (int __c)
int isdigit (int __c)
int isgraph (int __c)
int islower (int __c)
int isprint (int __c)
int ispunct (int __c)
int isspace (int __c)
int isupper (int __c)
int isxdigit (int __c)
Character convertion routines
This realization permits all possible values of integer argument. The toascii() function
clears all highest bits. The tolower() and toupper() functions return an input argument
as is, if it is not an unsigned char value.
• int toascii (int __c)
• int tolower (int __c)
• int toupper (int __c)
22.3.1
Detailed Description
These functions perform various operations on characters.
#include <ctype.h>
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22.3
<ctype.h>: Character Operations
22.3.2
Function Documentation
22.3.2.1
138
int isalnum ( int __c )
Checks for an alphanumeric character. It is equivalent to (isalpha(c) ||
isdigit(c)).
22.3.2.2
int isalpha ( int __c )
Checks for an alphabetic character. It is equivalent to (isupper(c) ||
islower(c)).
22.3.2.3
int isascii ( int __c )
Checks whether c is a 7-bit unsigned char value that fits into the ASCII character set.
22.3.2.4
int isblank ( int __c )
Checks for a blank character, that is, a space or a tab.
22.3.2.5
int iscntrl ( int __c )
Checks for a control character.
22.3.2.6
int isdigit ( int __c )
Checks for a digit (0 through 9).
22.3.2.7
int isgraph ( int __c )
Checks for any printable character except space.
22.3.2.8
int islower ( int __c )
Checks for a lower-case character.
22.3.2.9
int isprint ( int __c )
Checks for any printable character including space.
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22.3
<ctype.h>: Character Operations
22.3.2.10
139
int ispunct ( int __c )
Checks for any printable character which is not a space or an alphanumeric character.
22.3.2.11
int isspace ( int __c )
Checks for white-space characters. For the avr-libc library, these are:
space, form-feed (’\f’), newline (’\n’), carriage return (’\r’), horizontal tab (’\t’), and
vertical tab (’\v’).
22.3.2.12
int isupper ( int __c )
Checks for an uppercase letter.
22.3.2.13
int isxdigit ( int __c )
Checks for a hexadecimal digits, i.e. one of 0 1 2 3 4 5 6 7 8 9 a b c d e f A B C D E
F.
22.3.2.14
int toascii ( int __c )
Converts c to a 7-bit unsigned char value that fits into the ASCII character set, by
clearing the high-order bits.
Warning
Many people will be unhappy if you use this function. This function will convert
accented letters into random characters.
22.3.2.15
int tolower ( int __c )
Converts the letter c to lower case, if possible.
22.3.2.16
int toupper ( int __c )
Converts the letter c to upper case, if possible.
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22.4
<errno.h>: System Errors
22.4
<errno.h>: System Errors
140
Defines
• #define EDOM 33
• #define ERANGE 34
22.4.1
Detailed Description
#include <errno.h>
Some functions in the library set the global variable errno when an error occurs. The
file, <errno.h>, provides symbolic names for various error codes.
Warning
The errno global variable is not safe to use in a threaded or multi-task system. A
race condition can occur if a task is interrupted between the call which sets error
and when the task examines errno. If another task changes errno during this
time, the result will be incorrect for the interrupted task.
22.4.2
Define Documentation
22.4.2.1
#define EDOM 33
Domain error.
22.4.2.2
#define ERANGE 34
Range error.
22.5
<inttypes.h>: Integer Type conversions
Far pointers for memory access >64K
• typedef int32_t int_farptr_t
• typedef uint32_t uint_farptr_t
macros for printf and scanf format specifiers
For C++, these are only included if __STDC_LIMIT_MACROS is defined before including <inttypes.h>.
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22.5
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
<inttypes.h>: Integer Type conversions
#define PRId8 "d"
#define PRIdLEAST8 "d"
#define PRIdFAST8 "d"
#define PRIi8 "i"
#define PRIiLEAST8 "i"
#define PRIiFAST8 "i"
#define PRId16 "d"
#define PRIdLEAST16 "d"
#define PRIdFAST16 "d"
#define PRIi16 "i"
#define PRIiLEAST16 "i"
#define PRIiFAST16 "i"
#define PRId32 "ld"
#define PRIdLEAST32 "ld"
#define PRIdFAST32 "ld"
#define PRIi32 "li"
#define PRIiLEAST32 "li"
#define PRIiFAST32 "li"
#define PRIdPTR PRId16
#define PRIiPTR PRIi16
#define PRIo8 "o"
#define PRIoLEAST8 "o"
#define PRIoFAST8 "o"
#define PRIu8 "u"
#define PRIuLEAST8 "u"
#define PRIuFAST8 "u"
#define PRIx8 "x"
#define PRIxLEAST8 "x"
#define PRIxFAST8 "x"
#define PRIX8 "X"
#define PRIXLEAST8 "X"
#define PRIXFAST8 "X"
#define PRIo16 "o"
#define PRIoLEAST16 "o"
#define PRIoFAST16 "o"
#define PRIu16 "u"
#define PRIuLEAST16 "u"
#define PRIuFAST16 "u"
#define PRIx16 "x"
#define PRIxLEAST16 "x"
#define PRIxFAST16 "x"
#define PRIX16 "X"
#define PRIXLEAST16 "X"
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141
22.5
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•
<inttypes.h>: Integer Type conversions
#define PRIXFAST16 "X"
#define PRIo32 "lo"
#define PRIoLEAST32 "lo"
#define PRIoFAST32 "lo"
#define PRIu32 "lu"
#define PRIuLEAST32 "lu"
#define PRIuFAST32 "lu"
#define PRIx32 "lx"
#define PRIxLEAST32 "lx"
#define PRIxFAST32 "lx"
#define PRIX32 "lX"
#define PRIXLEAST32 "lX"
#define PRIXFAST32 "lX"
#define PRIoPTR PRIo16
#define PRIuPTR PRIu16
#define PRIxPTR PRIx16
#define PRIXPTR PRIX16
#define SCNd16 "d"
#define SCNdLEAST16 "d"
#define SCNdFAST16 "d"
#define SCNi16 "i"
#define SCNiLEAST16 "i"
#define SCNiFAST16 "i"
#define SCNd32 "ld"
#define SCNdLEAST32 "ld"
#define SCNdFAST32 "ld"
#define SCNi32 "li"
#define SCNiLEAST32 "li"
#define SCNiFAST32 "li"
#define SCNdPTR SCNd16
#define SCNiPTR SCNi16
#define SCNo16 "o"
#define SCNoLEAST16 "o"
#define SCNoFAST16 "o"
#define SCNu16 "u"
#define SCNuLEAST16 "u"
#define SCNuFAST16 "u"
#define SCNx16 "x"
#define SCNxLEAST16 "x"
#define SCNxFAST16 "x"
#define SCNo32 "lo"
#define SCNoLEAST32 "lo"
#define SCNoFAST32 "lo"
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142
<inttypes.h>: Integer Type conversions
22.5
•
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•
22.5.1
143
#define SCNu32 "lu"
#define SCNuLEAST32 "lu"
#define SCNuFAST32 "lu"
#define SCNx32 "lx"
#define SCNxLEAST32 "lx"
#define SCNxFAST32 "lx"
#define SCNoPTR SCNo16
#define SCNuPTR SCNu16
#define SCNxPTR SCNx16
Detailed Description
#include <inttypes.h>
This header file includes the exact-width integer definitions from <stdint.h>, and
extends them with additional facilities provided by the implementation.
Currently, the extensions include two additional integer types that could hold a "far"
pointer (i.e. a code pointer that can address more than 64 KB), as well as standard
names for all printf and scanf formatting options that are supported by the <stdio.h>:
Standard IO facilities. As the library does not support the full range of conversion
specifiers from ISO 9899:1999, only those conversions that are actually implemented
will be listed here.
The idea behind these conversion macros is that, for each of the types defined by
<stdint.h>, a macro will be supplied that portably allows formatting an object of that
type in printf() or scanf() operations. Example:
#include <inttypes.h>
uint8_t smallval;
int32_t longval;
...
printf("The hexadecimal value of smallval is %" PRIx8
", the decimal value of longval is %" PRId32 ".\n",
smallval, longval);
22.5.2
Define Documentation
22.5.2.1
#define PRId16 "d"
decimal printf format for int16_t
22.5.2.2
#define PRId32 "ld"
decimal printf format for int32_t
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22.5
<inttypes.h>: Integer Type conversions
22.5.2.3
144
#define PRId8 "d"
decimal printf format for int8_t
22.5.2.4
#define PRIdFAST16 "d"
decimal printf format for int_fast16_t
22.5.2.5
#define PRIdFAST32 "ld"
decimal printf format for int_fast32_t
22.5.2.6
#define PRIdFAST8 "d"
decimal printf format for int_fast8_t
22.5.2.7
#define PRIdLEAST16 "d"
decimal printf format for int_least16_t
22.5.2.8
#define PRIdLEAST32 "ld"
decimal printf format for int_least32_t
22.5.2.9
#define PRIdLEAST8 "d"
decimal printf format for int_least8_t
22.5.2.10
#define PRIdPTR PRId16
decimal printf format for intptr_t
22.5.2.11
#define PRIi16 "i"
integer printf format for int16_t
22.5.2.12
#define PRIi32 "li"
integer printf format for int32_t
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22.5
<inttypes.h>: Integer Type conversions
22.5.2.13
145
#define PRIi8 "i"
integer printf format for int8_t
22.5.2.14
#define PRIiFAST16 "i"
integer printf format for int_fast16_t
22.5.2.15
#define PRIiFAST32 "li"
integer printf format for int_fast32_t
22.5.2.16
#define PRIiFAST8 "i"
integer printf format for int_fast8_t
22.5.2.17
#define PRIiLEAST16 "i"
integer printf format for int_least16_t
22.5.2.18
#define PRIiLEAST32 "li"
integer printf format for int_least32_t
22.5.2.19
#define PRIiLEAST8 "i"
integer printf format for int_least8_t
22.5.2.20
#define PRIiPTR PRIi16
integer printf format for intptr_t
22.5.2.21
#define PRIo16 "o"
octal printf format for uint16_t
22.5.2.22
#define PRIo32 "lo"
octal printf format for uint32_t
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22.5
<inttypes.h>: Integer Type conversions
22.5.2.23
146
#define PRIo8 "o"
octal printf format for uint8_t
22.5.2.24
#define PRIoFAST16 "o"
octal printf format for uint_fast16_t
22.5.2.25
#define PRIoFAST32 "lo"
octal printf format for uint_fast32_t
22.5.2.26
#define PRIoFAST8 "o"
octal printf format for uint_fast8_t
22.5.2.27
#define PRIoLEAST16 "o"
octal printf format for uint_least16_t
22.5.2.28
#define PRIoLEAST32 "lo"
octal printf format for uint_least32_t
22.5.2.29
#define PRIoLEAST8 "o"
octal printf format for uint_least8_t
22.5.2.30
#define PRIoPTR PRIo16
octal printf format for uintptr_t
22.5.2.31
#define PRIu16 "u"
decimal printf format for uint16_t
22.5.2.32
#define PRIu32 "lu"
decimal printf format for uint32_t
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22.5
<inttypes.h>: Integer Type conversions
22.5.2.33
147
#define PRIu8 "u"
decimal printf format for uint8_t
22.5.2.34
#define PRIuFAST16 "u"
decimal printf format for uint_fast16_t
22.5.2.35
#define PRIuFAST32 "lu"
decimal printf format for uint_fast32_t
22.5.2.36
#define PRIuFAST8 "u"
decimal printf format for uint_fast8_t
22.5.2.37
#define PRIuLEAST16 "u"
decimal printf format for uint_least16_t
22.5.2.38
#define PRIuLEAST32 "lu"
decimal printf format for uint_least32_t
22.5.2.39
#define PRIuLEAST8 "u"
decimal printf format for uint_least8_t
22.5.2.40
#define PRIuPTR PRIu16
decimal printf format for uintptr_t
22.5.2.41
#define PRIx16 "x"
hexadecimal printf format for uint16_t
22.5.2.42
#define PRIX16 "X"
uppercase hexadecimal printf format for uint16_t
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22.5
<inttypes.h>: Integer Type conversions
22.5.2.43
148
#define PRIx32 "lx"
hexadecimal printf format for uint32_t
22.5.2.44
#define PRIX32 "lX"
uppercase hexadecimal printf format for uint32_t
22.5.2.45
#define PRIx8 "x"
hexadecimal printf format for uint8_t
22.5.2.46
#define PRIX8 "X"
uppercase hexadecimal printf format for uint8_t
22.5.2.47
#define PRIxFAST16 "x"
hexadecimal printf format for uint_fast16_t
22.5.2.48
#define PRIXFAST16 "X"
uppercase hexadecimal printf format for uint_fast16_t
22.5.2.49
#define PRIxFAST32 "lx"
hexadecimal printf format for uint_fast32_t
22.5.2.50
#define PRIXFAST32 "lX"
uppercase hexadecimal printf format for uint_fast32_t
22.5.2.51
#define PRIXFAST8 "X"
uppercase hexadecimal printf format for uint_fast8_t
22.5.2.52
#define PRIxFAST8 "x"
hexadecimal printf format for uint_fast8_t
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22.5
<inttypes.h>: Integer Type conversions
22.5.2.53
149
#define PRIxLEAST16 "x"
hexadecimal printf format for uint_least16_t
22.5.2.54
#define PRIXLEAST16 "X"
uppercase hexadecimal printf format for uint_least16_t
22.5.2.55
#define PRIxLEAST32 "lx"
hexadecimal printf format for uint_least32_t
22.5.2.56
#define PRIXLEAST32 "lX"
uppercase hexadecimal printf format for uint_least32_t
22.5.2.57
#define PRIxLEAST8 "x"
hexadecimal printf format for uint_least8_t
22.5.2.58
#define PRIXLEAST8 "X"
uppercase hexadecimal printf format for uint_least8_t
22.5.2.59
#define PRIxPTR PRIx16
hexadecimal printf format for uintptr_t
22.5.2.60
#define PRIXPTR PRIX16
uppercase hexadecimal printf format for uintptr_t
22.5.2.61
#define SCNd16 "d"
decimal scanf format for int16_t
22.5.2.62
#define SCNd32 "ld"
decimal scanf format for int32_t
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22.5
<inttypes.h>: Integer Type conversions
22.5.2.63
150
#define SCNdFAST16 "d"
decimal scanf format for int_fast16_t
22.5.2.64
#define SCNdFAST32 "ld"
decimal scanf format for int_fast32_t
22.5.2.65
#define SCNdLEAST16 "d"
decimal scanf format for int_least16_t
22.5.2.66
#define SCNdLEAST32 "ld"
decimal scanf format for int_least32_t
22.5.2.67
#define SCNdPTR SCNd16
decimal scanf format for intptr_t
22.5.2.68
#define SCNi16 "i"
generic-integer scanf format for int16_t
22.5.2.69
#define SCNi32 "li"
generic-integer scanf format for int32_t
22.5.2.70
#define SCNiFAST16 "i"
generic-integer scanf format for int_fast16_t
22.5.2.71
#define SCNiFAST32 "li"
generic-integer scanf format for int_fast32_t
22.5.2.72
#define SCNiLEAST16 "i"
generic-integer scanf format for int_least16_t
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22.5
<inttypes.h>: Integer Type conversions
22.5.2.73
151
#define SCNiLEAST32 "li"
generic-integer scanf format for int_least32_t
22.5.2.74
#define SCNiPTR SCNi16
generic-integer scanf format for intptr_t
22.5.2.75
#define SCNo16 "o"
octal scanf format for uint16_t
22.5.2.76
#define SCNo32 "lo"
octal scanf format for uint32_t
22.5.2.77
#define SCNoFAST16 "o"
octal scanf format for uint_fast16_t
22.5.2.78
#define SCNoFAST32 "lo"
octal scanf format for uint_fast32_t
22.5.2.79
#define SCNoLEAST16 "o"
octal scanf format for uint_least16_t
22.5.2.80
#define SCNoLEAST32 "lo"
octal scanf format for uint_least32_t
22.5.2.81
#define SCNoPTR SCNo16
octal scanf format for uintptr_t
22.5.2.82
#define SCNu16 "u"
decimal scanf format for uint16_t
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22.5
<inttypes.h>: Integer Type conversions
22.5.2.83
152
#define SCNu32 "lu"
decimal scanf format for uint32_t
22.5.2.84
#define SCNuFAST16 "u"
decimal scanf format for uint_fast16_t
22.5.2.85
#define SCNuFAST32 "lu"
decimal scanf format for uint_fast32_t
22.5.2.86
#define SCNuLEAST16 "u"
decimal scanf format for uint_least16_t
22.5.2.87
#define SCNuLEAST32 "lu"
decimal scanf format for uint_least32_t
22.5.2.88
#define SCNuPTR SCNu16
decimal scanf format for uintptr_t
22.5.2.89
#define SCNx16 "x"
hexadecimal scanf format for uint16_t
22.5.2.90
#define SCNx32 "lx"
hexadecimal scanf format for uint32_t
22.5.2.91
#define SCNxFAST16 "x"
hexadecimal scanf format for uint_fast16_t
22.5.2.92
#define SCNxFAST32 "lx"
hexadecimal scanf format for uint_fast32_t
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<math.h>: Mathematics
22.6
22.5.2.93
153
#define SCNxLEAST16 "x"
hexadecimal scanf format for uint_least16_t
22.5.2.94
#define SCNxLEAST32 "lx"
hexadecimal scanf format for uint_least32_t
22.5.2.95
#define SCNxPTR SCNx16
hexadecimal scanf format for uintptr_t
22.5.3
Typedef Documentation
22.5.3.1
typedef int32_t int_farptr_t
signed integer type that can hold a pointer > 64 KB
22.5.3.2
typedef uint32_t uint_farptr_t
unsigned integer type that can hold a pointer > 64 KB
<math.h>: Mathematics
22.6
Defines
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#define M_E 2.7182818284590452354
#define M_LOG2E 1.4426950408889634074
#define M_LOG10E 0.43429448190325182765
#define M_LN2 0.69314718055994530942
#define M_LN10 2.30258509299404568402
#define M_PI 3.14159265358979323846
#define M_PI_2 1.57079632679489661923
#define M_PI_4 0.78539816339744830962
#define M_1_PI 0.31830988618379067154
#define M_2_PI 0.63661977236758134308
#define M_2_SQRTPI 1.12837916709551257390
#define M_SQRT2 1.41421356237309504880
#define M_SQRT1_2 0.70710678118654752440
#define NAN __builtin_nan("")
#define INFINITY __builtin_inf()
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22.6
<math.h>: Mathematics
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#define cosf cos
#define sinf sin
#define tanf tan
#define fabsf fabs
#define fmodf fmod
#define sqrtf sqrt
#define cbrtf cbrt
#define hypotf hypot
#define squaref square
#define floorf floor
#define ceilf ceil
#define frexpf frexp
#define ldexpf ldexp
#define expf exp
#define coshf cosh
#define sinhf sinh
#define tanhf tanh
#define acosf acos
#define asinf asin
#define atanf atan
#define atan2f atan2
#define logf log
#define log10f log10
#define powf pow
#define isnanf isnan
#define isinff isinf
#define isfinitef isfinite
#define copysignf copysign
#define signbitf signbit
#define fdimf fdim
#define fmaf fma
#define fmaxf fmax
#define fminf fmin
#define truncf trunc
#define roundf round
#define lroundf lround
#define lrintf lrint
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22.6
<math.h>: Mathematics
Functions
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double cos (double __x)
double sin (double __x)
double tan (double __x)
double fabs (double __x)
double fmod (double __x, double __y)
double modf (double __x, double ∗__iptr)
float modff (float __x, float ∗__iptr)
double sqrt (double __x)
double cbrt (double __x)
double hypot (double __x, double __y)
double square (double __x)
double floor (double __x)
double ceil (double __x)
double frexp (double __x, int ∗__pexp)
double ldexp (double __x, int __exp)
double exp (double __x)
double cosh (double __x)
double sinh (double __x)
double tanh (double __x)
double acos (double __x)
double asin (double __x)
double atan (double __x)
double atan2 (double __y, double __x)
double log (double __x)
double log10 (double __x)
double pow (double __x, double __y)
int isnan (double __x)
int isinf (double __x)
static int isfinite (double __x)
static double copysign (double __x, double __y)
int signbit (double __x)
double fdim (double __x, double __y)
double fma (double __x, double __y, double __z)
double fmax (double __x, double __y)
double fmin (double __x, double __y)
double trunc (double __x)
double round (double __x)
long lround (double __x)
long lrint (double __x)
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155
22.6
<math.h>: Mathematics
22.6.1
Detailed Description
156
#include <math.h>
This header file declares basic mathematics constants and functions.
Notes:
• In order to access the functions delcared herein, it is usually also required to
additionally link against the library libm.a. See also the related FAQ entry.
• Math functions do not raise exceptions and do not change the errno variable. Therefore the majority of them are declared with const attribute, for
better optimization by GCC.
22.6.2
Define Documentation
22.6.2.1
#define acosf acos
The alias for acos().
22.6.2.2
#define asinf asin
The alias for asin().
22.6.2.3
#define atan2f atan2
The alias for atan2().
22.6.2.4
#define atanf atan
The alias for atan().
22.6.2.5
#define cbrtf cbrt
The alias for cbrt().
22.6.2.6
#define ceilf ceil
The alias for ceil().
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22.6
<math.h>: Mathematics
22.6.2.7
157
#define copysignf copysign
The alias for copysign().
22.6.2.8
#define cosf cos
The alias for cos().
22.6.2.9
#define coshf cosh
The alias for cosh().
22.6.2.10
#define expf exp
The alias for exp().
22.6.2.11
#define fabsf fabs
The alias for fabs().
22.6.2.12
#define fdimf fdim
The alias for fdim().
22.6.2.13
#define floorf floor
The alias for floor().
22.6.2.14
#define fmaf fma
The alias for fma().
22.6.2.15
#define fmaxf fmax
The alias for fmax().
22.6.2.16
#define fminf fmin
The alias for fmin().
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22.6
<math.h>: Mathematics
22.6.2.17
158
#define fmodf fmod
The alias for fmod().
22.6.2.18
#define frexpf frexp
The alias for frexp().
22.6.2.19
#define hypotf hypot
The alias for hypot().
22.6.2.20
#define INFINITY __builtin_inf()
INFINITY constant.
22.6.2.21
#define isfinitef isfinite
The alias for isfinite().
22.6.2.22
#define isinff isinf
The alias for isinf().
22.6.2.23
#define isnanf isnan
The alias for isnan().
22.6.2.24
#define ldexpf ldexp
The alias for ldexp().
22.6.2.25
#define log10f log10
The alias for log10().
22.6.2.26
#define logf log
The alias for log().
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22.6
<math.h>: Mathematics
22.6.2.27
159
#define lrintf lrint
The alias for lrint().
22.6.2.28
#define lroundf lround
The alias for lround().
22.6.2.29
#define M_1_PI 0.31830988618379067154
The constant 1/pi.
22.6.2.30
#define M_2_PI 0.63661977236758134308
The constant 2/pi.
22.6.2.31
#define M_2_SQRTPI 1.12837916709551257390
The constant 2/sqrt(pi).
22.6.2.32
#define M_E 2.7182818284590452354
The constant e.
22.6.2.33
#define M_LN10 2.30258509299404568402
The natural logarithm of the 10.
22.6.2.34
#define M_LN2 0.69314718055994530942
The natural logarithm of the 2.
22.6.2.35
#define M_LOG10E 0.43429448190325182765
The logarithm of the e to base 10.
22.6.2.36
#define M_LOG2E 1.4426950408889634074
The logarithm of the e to base 2.
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22.6
<math.h>: Mathematics
22.6.2.37
160
#define M_PI 3.14159265358979323846
The constant pi.
22.6.2.38
#define M_PI_2 1.57079632679489661923
The constant pi/2.
22.6.2.39
#define M_PI_4 0.78539816339744830962
The constant pi/4.
22.6.2.40
#define M_SQRT1_2 0.70710678118654752440
The constant 1/sqrt(2).
22.6.2.41
#define M_SQRT2 1.41421356237309504880
The square root of 2.
22.6.2.42
#define NAN __builtin_nan("")
NAN constant.
22.6.2.43
#define powf pow
The alias for pow().
22.6.2.44
#define roundf round
The alias for round().
22.6.2.45
#define signbitf signbit
The alias for signbit().
22.6.2.46
#define sinf sin
The alias for sin().
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22.6
<math.h>: Mathematics
22.6.2.47
161
#define sinhf sinh
The alias for sinh().
22.6.2.48
#define sqrtf sqrt
The alias for sqrt().
22.6.2.49
#define squaref square
The alias for square().
22.6.2.50
#define tanf tan
The alias for tan().
22.6.2.51
#define tanhf tanh
The alias for tanh().
22.6.2.52
#define truncf trunc
The alias for trunc().
22.6.3
Function Documentation
22.6.3.1
double acos ( double __x )
The acos() function computes the principal value of the arc cosine of __x. The
returned value is in the range [0, pi] radians. A domain error occurs for arguments not
in the range [-1, +1].
22.6.3.2
double asin ( double __x )
The asin() function computes the principal value of the arc sine of
__x. The returned value is in the range [-pi/2, pi/2] radians. A domain error occurs for
arguments not in the range [-1, +1].
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22.6
<math.h>: Mathematics
22.6.3.3
162
double atan ( double __x )
The atan() function computes the principal value of the arc tangent of __x. The
returned value is in the range [-pi/2, pi/2] radians.
22.6.3.4
double atan2 ( double __y, double __x )
The atan2() function computes the principal value of the arc tangent of __y
/ __x, using the signs of both arguments to determine the quadrant of the return value.
The returned value is in the range [-pi, +pi] radians.
22.6.3.5
double cbrt ( double __x )
The cbrt() function returns the cube root of __x.
22.6.3.6
double ceil ( double __x )
The ceil() function returns the smallest integral value greater than or equal to __x,
expressed as a floating-point number.
22.6.3.7
static double copysign ( double __x, double __y ) [static]
The copysign() function returns __x but with the sign of __y. They work even if __x
or __y are NaN or zero.
22.6.3.8
double cos ( double __x )
The cos() function returns the cosine of __x, measured in radians.
22.6.3.9
double cosh ( double __x )
The cosh() function returns the hyperbolic cosine of __x.
22.6.3.10
double exp ( double __x )
The exp() function returns the exponential value of __x.
22.6.3.11
double fabs ( double __x )
The fabs() function computes the absolute value of a floating-point number __x.
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22.6
<math.h>: Mathematics
22.6.3.12
163
double fdim ( double __x, double __y )
The fdim() function returns max(__x - __y, 0). If __x or __y or both are NaN, NaN is
returned.
22.6.3.13
double floor ( double __x )
The floor() function returns the largest integral value less than or equal to __x,
expressed as a floating-point number.
22.6.3.14
double fma ( double __x, double __y, double __z )
The fma() function performs floating-point multiply-add. This is the operation (__x ∗
__y) + __z, but the intermediate result is not rounded to the destination type. This can
sometimes improve the precision of a calculation.
22.6.3.15
double fmax ( double __x, double __y )
The fmax() function returns the greater of the two values __x and __y. If an argument
is NaN, the other argument is returned. If both arguments are NaN, NaN is returned.
22.6.3.16
double fmin ( double __x, double __y )
The fmin() function returns the lesser of the two values __x and __y. If an argument
is NaN, the other argument is returned. If both arguments are NaN, NaN is returned.
22.6.3.17
double fmod ( double __x, double __y )
The function fmod() returns the floating-point remainder of __x / __y.
22.6.3.18
double frexp ( double __x, int ∗ __pexp )
The frexp() function breaks a floating-point number into a normalized fraction and an
integral power of 2. It stores the integer in the int object pointed to by __pexp.
If __x is a normal float point number, the frexp() function returns the value v, such that
v has a magnitude in the interval [1/2, 1) or zero, and __x equals v times 2 raised to
the power __pexp. If __x is zero, both parts of the result are zero. If __x is not a finite
number, the frexp() returns __x as is and stores 0 by __pexp.
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<math.h>: Mathematics
22.6
164
Note
This implementation permits a zero pointer as a directive to skip a storing the
exponent.
22.6.3.19
double hypot ( double __x, double __y )
The hypot() function returns sqrt(__x∗__x + __y∗__y). This
is the length of the hypotenuse of a right triangle with sides of length __x and __y, or
the distance of the point (__x, __y) from the origin. Using this function instead of the
direct formula is wise, since the error is much smaller. No underflow with small __x
and __y. No overflow if result is in range.
22.6.3.20
static int isfinite ( double __x ) [static]
The isfinite() function returns a nonzero value if __x is finite: not plus or minus
infinity, and not NaN.
22.6.3.21
int isinf ( double __x )
The function isinf() returns 1 if the argument __x is positive infinity, -1 if __x is
negative infinity, and 0 otherwise.
Note
The GCC 4.3 can replace this function with inline code that returns the 1 value for
both infinities (gcc bug #35509).
22.6.3.22
int isnan ( double __x )
The function isnan() returns 1 if the argument __x represents a "not-a-number" (NaN)
object, otherwise 0.
22.6.3.23
double ldexp ( double __x, int __exp )
The ldexp() function multiplies a floating-point number by an integral power of 2. It
returns the value of __x times 2 raised to the power __exp.
22.6.3.24
double log ( double __x )
The log() function returns the natural logarithm of argument __x.
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<math.h>: Mathematics
22.6
22.6.3.25
165
double log10 ( double __x )
The log10() function returns the logarithm of argument __x to base 10.
22.6.3.26
long lrint ( double __x )
The lrint() function rounds __x to the nearest
integer, rounding the halfway cases to the even integer direction. (That is both 1.5 and
2.5 values are rounded to 2). This function is similar to rint() function, but it differs in
type of return value and in that an overflow is possible.
Returns
The rounded long integer value. If __x is not a finite number or an overflow was,
this realization returns the LONG_MIN value (0x80000000).
22.6.3.27
long lround ( double __x )
The lround() function rounds __x to the nearest integer, but rounds
halfway cases away from zero (instead of to the nearest even integer). This function is
similar to round() function, but it differs in type of return value and in that an overflow
is possible.
Returns
The rounded long integer value. If __x is not a finite number or an overflow was,
this realization returns the LONG_MIN value (0x80000000).
22.6.3.28
double modf ( double __x, double ∗ __iptr )
The modf() function breaks the argument __x into integral and fractional parts,
each of which has the same sign as the argument. It stores the integral part as a double
in the object pointed to by __iptr.
The modf() function returns the signed fractional part of __x.
Note
This implementation skips writing by zero pointer. However, the GCC 4.3 can
replace this function with inline code that does not permit to use NULL address
for the avoiding of storing.
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22.6
<math.h>: Mathematics
22.6.3.29
166
float modff ( float __x, float ∗ __iptr )
The alias for modf().
22.6.3.30
double pow ( double __x, double __y )
The function pow() returns the value of __x to the exponent __y.
22.6.3.31
double round ( double __x )
The round() function rounds __x to the nearest integer, but rounds halfway cases
away from zero (instead of to the nearest even integer). Overflow is impossible.
Returns
The rounded value. If __x is an integral or infinite, __x itself is returned. If __x is
NaN, then NaN is returned.
22.6.3.32
int signbit ( double __x )
The signbit() function returns a nonzero value if the value of __x has its sign bit set.
This is not the same as ‘__x < 0.0’, because IEEE 754 floating point allows zero to be
signed. The comparison ‘-0.0 < 0.0’ is false, but ‘signbit (-0.0)’ will return a nonzero
value.
22.6.3.33
double sin ( double __x )
The sin() function returns the sine of __x, measured in radians.
22.6.3.34
double sinh ( double __x )
The sinh() function returns the hyperbolic sine of __x.
22.6.3.35
double sqrt ( double __x )
The sqrt() function returns the non-negative square root of __x.
22.6.3.36
double square ( double __x )
The function square() returns __x ∗ __x.
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22.7
167
Note
This function does not belong to the C standard definition.
22.6.3.37
double tan ( double __x )
The tan() function returns the tangent of __x, measured in radians.
22.6.3.38
double tanh ( double __x )
The tanh() function returns the hyperbolic tangent of __x.
22.6.3.39
double trunc ( double __x )
The trunc() function rounds __x to the nearest integer not larger in absolute value.
<setjmp.h>: Non-local goto
22.7
Functions
• int setjmp (jmp_buf __jmpb)
• void longjmp (jmp_buf __jmpb, int __ret) __ATTR_NORETURN__
22.7.1
Detailed Description
While the C language has the dreaded goto statement, it can only be used to jump to
a label in the same (local) function. In order to jump directly to another (non-local)
function, the C library provides the setjmp() and longjmp() functions. setjmp() and
longjmp() are useful for dealing with errors and interrupts encountered in a low-level
subroutine of a program.
Note
setjmp() and longjmp() make programs hard to understand and maintain. If possible, an alternative should be used.
longjmp() can destroy changes made to global register variables (see How to permanently bind a variable to a register?).
For a very detailed discussion of setjmp()/longjmp(), see Chapter 7 of Advanced Programming in the UNIX Environment, by W. Richard Stevens.
Example:
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<setjmp.h>: Non-local goto
22.7
168
#include <setjmp.h>
jmp_buf env;
int main (void)
{
if (setjmp (env))
{
... handle error ...
}
while (1)
{
... main processing loop which calls foo() some where ...
}
}
...
void foo (void)
{
... blah, blah, blah ...
if (err)
{
longjmp (env, 1);
}
}
22.7.2
Function Documentation
22.7.2.1
void longjmp ( jmp_buf __jmpb, int __ret )
Non-local jump to a saved stack context.
#include <setjmp.h>
longjmp() restores the environment saved by the last call of setjmp() with the corresponding __jmpb argument. After longjmp() is completed, program execution continues as if the corresponding call of setjmp() had just returned the value __ret.
Note
longjmp() cannot cause 0 to be returned. If longjmp() is invoked with a second
argument of 0, 1 will be returned instead.
Parameters
__jmpb Information saved by a previous call to setjmp().
__ret Value to return to the caller of setjmp().
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169
Returns
This function never returns.
22.7.2.2
int setjmp ( jmp_buf __jmpb )
Save stack context for non-local goto.
#include <setjmp.h>
setjmp() saves the stack context/environment in __jmpb for later use by longjmp(). The
stack context will be invalidated if the function which called setjmp() returns.
Parameters
__jmpb Variable of type jmp_buf which holds the stack information such that the
environment can be restored.
Returns
setjmp() returns 0 if returning directly, and non-zero when returning from longjmp()
using the saved context.
22.8
<stdint.h>: Standard Integer Types
Exact-width integer types
Integer types having exactly the specified width
•
•
•
•
•
•
•
•
typedef signed char int8_t
typedef unsigned char uint8_t
typedef signed int int16_t
typedef unsigned int uint16_t
typedef signed long int int32_t
typedef unsigned long int uint32_t
typedef signed long long int int64_t
typedef unsigned long long int uint64_t
Integer types capable of holding object pointers
These allow you to declare variables of the same size as a pointer.
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22.8
<stdint.h>: Standard Integer Types
170
• typedef int16_t intptr_t
• typedef uint16_t uintptr_t
Minimum-width integer types
Integer types having at least the specified width
•
•
•
•
•
•
•
•
typedef int8_t int_least8_t
typedef uint8_t uint_least8_t
typedef int16_t int_least16_t
typedef uint16_t uint_least16_t
typedef int32_t int_least32_t
typedef uint32_t uint_least32_t
typedef int64_t int_least64_t
typedef uint64_t uint_least64_t
Fastest minimum-width integer types
Integer types being usually fastest having at least the specified width
•
•
•
•
•
•
•
•
typedef int8_t int_fast8_t
typedef uint8_t uint_fast8_t
typedef int16_t int_fast16_t
typedef uint16_t uint_fast16_t
typedef int32_t int_fast32_t
typedef uint32_t uint_fast32_t
typedef int64_t int_fast64_t
typedef uint64_t uint_fast64_t
Greatest-width integer types
Types designating integer data capable of representing any value of any integer type in
the corresponding signed or unsigned category
• typedef int64_t intmax_t
• typedef uint64_t uintmax_t
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22.8
<stdint.h>: Standard Integer Types
171
Limits of specified-width integer types
C++ implementations should define these macros only when __STDC_LIMIT_MACROS
is defined before <stdint.h> is included
•
•
•
•
•
•
•
•
•
•
•
•
#define INT8_MAX 0x7f
#define INT8_MIN (-INT8_MAX - 1)
#define UINT8_MAX (__CONCAT(INT8_MAX, U) ∗ 2U + 1U)
#define INT16_MAX 0x7fff
#define INT16_MIN (-INT16_MAX - 1)
#define UINT16_MAX (__CONCAT(INT16_MAX, U) ∗ 2U + 1U)
#define INT32_MAX 0x7fffffffL
#define INT32_MIN (-INT32_MAX - 1L)
#define UINT32_MAX (__CONCAT(INT32_MAX, U) ∗ 2UL + 1UL)
#define INT64_MAX 0x7fffffffffffffffLL
#define INT64_MIN (-INT64_MAX - 1LL)
#define UINT64_MAX (__CONCAT(INT64_MAX, U) ∗ 2ULL + 1ULL)
Limits of minimum-width integer types
•
•
•
•
•
•
•
•
•
•
•
•
#define INT_LEAST8_MAX INT8_MAX
#define INT_LEAST8_MIN INT8_MIN
#define UINT_LEAST8_MAX UINT8_MAX
#define INT_LEAST16_MAX INT16_MAX
#define INT_LEAST16_MIN INT16_MIN
#define UINT_LEAST16_MAX UINT16_MAX
#define INT_LEAST32_MAX INT32_MAX
#define INT_LEAST32_MIN INT32_MIN
#define UINT_LEAST32_MAX UINT32_MAX
#define INT_LEAST64_MAX INT64_MAX
#define INT_LEAST64_MIN INT64_MIN
#define UINT_LEAST64_MAX UINT64_MAX
Limits of fastest minimum-width integer types
•
•
•
•
•
•
•
#define INT_FAST8_MAX INT8_MAX
#define INT_FAST8_MIN INT8_MIN
#define UINT_FAST8_MAX UINT8_MAX
#define INT_FAST16_MAX INT16_MAX
#define INT_FAST16_MIN INT16_MIN
#define UINT_FAST16_MAX UINT16_MAX
#define INT_FAST32_MAX INT32_MAX
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22.8
•
•
•
•
•
<stdint.h>: Standard Integer Types
172
#define INT_FAST32_MIN INT32_MIN
#define UINT_FAST32_MAX UINT32_MAX
#define INT_FAST64_MAX INT64_MAX
#define INT_FAST64_MIN INT64_MIN
#define UINT_FAST64_MAX UINT64_MAX
Limits of integer types capable of holding object pointers
• #define INTPTR_MAX INT16_MAX
• #define INTPTR_MIN INT16_MIN
• #define UINTPTR_MAX UINT16_MAX
Limits of greatest-width integer types
• #define INTMAX_MAX INT64_MAX
• #define INTMAX_MIN INT64_MIN
• #define UINTMAX_MAX UINT64_MAX
Limits of other integer types
C++ implementations should define these macros only when __STDC_LIMIT_MACROS
is defined before <stdint.h> is included
•
•
•
•
•
#define PTRDIFF_MAX INT16_MAX
#define PTRDIFF_MIN INT16_MIN
#define SIG_ATOMIC_MAX INT8_MAX
#define SIG_ATOMIC_MIN INT8_MIN
#define SIZE_MAX (__CONCAT(INT16_MAX, U))
Macros for integer constants
C++ implementations should define these macros only when __STDC_CONSTANT_MACROS is defined before <stdint.h> is included.
These definitions are valid for integer constants without suffix and for macros defined
as integer constant without suffix
•
•
•
•
•
#define INT8_C(value) ((int8_t) value)
#define UINT8_C(value) ((uint8_t) __CONCAT(value, U))
#define INT16_C(value) value
#define UINT16_C(value) __CONCAT(value, U)
#define INT32_C(value) __CONCAT(value, L)
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22.8
•
•
•
•
•
22.8.1
<stdint.h>: Standard Integer Types
173
#define UINT32_C(value) __CONCAT(value, UL)
#define INT64_C(value) __CONCAT(value, LL)
#define UINT64_C(value) __CONCAT(value, ULL)
#define INTMAX_C(value) __CONCAT(value, LL)
#define UINTMAX_C(value) __CONCAT(value, ULL)
Detailed Description
#include <stdint.h>
Use [u]intN_t if you need exactly N bits.
Since these typedefs are mandated by the C99 standard, they are preferred over rolling
your own typedefs.
22.8.2
Define Documentation
22.8.2.1
#define INT16_C( value ) value
define a constant of type int16_t
22.8.2.2
#define INT16_MAX 0x7fff
largest positive value an int16_t can hold.
22.8.2.3
#define INT16_MIN (-INT16_MAX - 1)
smallest negative value an int16_t can hold.
22.8.2.4
#define INT32_C( value ) __CONCAT(value, L)
define a constant of type int32_t
22.8.2.5
#define INT32_MAX 0x7fffffffL
largest positive value an int32_t can hold.
22.8.2.6
#define INT32_MIN (-INT32_MAX - 1L)
smallest negative value an int32_t can hold.
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22.8
<stdint.h>: Standard Integer Types
22.8.2.7
174
#define INT64_C( value ) __CONCAT(value, LL)
define a constant of type int64_t
22.8.2.8
#define INT64_MAX 0x7fffffffffffffffLL
largest positive value an int64_t can hold.
22.8.2.9
#define INT64_MIN (-INT64_MAX - 1LL)
smallest negative value an int64_t can hold.
22.8.2.10
#define INT8_C( value ) ((int8_t) value)
define a constant of type int8_t
22.8.2.11
#define INT8_MAX 0x7f
largest positive value an int8_t can hold.
22.8.2.12
#define INT8_MIN (-INT8_MAX - 1)
smallest negative value an int8_t can hold.
22.8.2.13
#define INT_FAST16_MAX INT16_MAX
largest positive value an int_fast16_t can hold.
22.8.2.14
#define INT_FAST16_MIN INT16_MIN
smallest negative value an int_fast16_t can hold.
22.8.2.15
#define INT_FAST32_MAX INT32_MAX
largest positive value an int_fast32_t can hold.
22.8.2.16
#define INT_FAST32_MIN INT32_MIN
smallest negative value an int_fast32_t can hold.
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22.8
<stdint.h>: Standard Integer Types
22.8.2.17
175
#define INT_FAST64_MAX INT64_MAX
largest positive value an int_fast64_t can hold.
22.8.2.18
#define INT_FAST64_MIN INT64_MIN
smallest negative value an int_fast64_t can hold.
22.8.2.19
#define INT_FAST8_MAX INT8_MAX
largest positive value an int_fast8_t can hold.
22.8.2.20
#define INT_FAST8_MIN INT8_MIN
smallest negative value an int_fast8_t can hold.
22.8.2.21
#define INT_LEAST16_MAX INT16_MAX
largest positive value an int_least16_t can hold.
22.8.2.22
#define INT_LEAST16_MIN INT16_MIN
smallest negative value an int_least16_t can hold.
22.8.2.23
#define INT_LEAST32_MAX INT32_MAX
largest positive value an int_least32_t can hold.
22.8.2.24
#define INT_LEAST32_MIN INT32_MIN
smallest negative value an int_least32_t can hold.
22.8.2.25
#define INT_LEAST64_MAX INT64_MAX
largest positive value an int_least64_t can hold.
22.8.2.26
#define INT_LEAST64_MIN INT64_MIN
smallest negative value an int_least64_t can hold.
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22.8
<stdint.h>: Standard Integer Types
22.8.2.27
176
#define INT_LEAST8_MAX INT8_MAX
largest positive value an int_least8_t can hold.
22.8.2.28
#define INT_LEAST8_MIN INT8_MIN
smallest negative value an int_least8_t can hold.
22.8.2.29
#define INTMAX_C( value ) __CONCAT(value, LL)
define a constant of type intmax_t
22.8.2.30
#define INTMAX_MAX INT64_MAX
largest positive value an intmax_t can hold.
22.8.2.31
#define INTMAX_MIN INT64_MIN
smallest negative value an intmax_t can hold.
22.8.2.32
#define INTPTR_MAX INT16_MAX
largest positive value an intptr_t can hold.
22.8.2.33
#define INTPTR_MIN INT16_MIN
smallest negative value an intptr_t can hold.
22.8.2.34
#define PTRDIFF_MAX INT16_MAX
largest positive value a ptrdiff_t can hold.
22.8.2.35
#define PTRDIFF_MIN INT16_MIN
smallest negative value a ptrdiff_t can hold.
22.8.2.36
#define SIG_ATOMIC_MAX INT8_MAX
largest positive value a sig_atomic_t can hold.
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22.8
<stdint.h>: Standard Integer Types
22.8.2.37
177
#define SIG_ATOMIC_MIN INT8_MIN
smallest negative value a sig_atomic_t can hold.
22.8.2.38
#define SIZE_MAX (__CONCAT(INT16_MAX, U))
largest value a size_t can hold.
22.8.2.39
#define UINT16_C( value ) __CONCAT(value, U)
define a constant of type uint16_t
22.8.2.40
#define UINT16_MAX (__CONCAT(INT16_MAX, U) ∗ 2U + 1U)
largest value an uint16_t can hold.
22.8.2.41
#define UINT32_C( value ) __CONCAT(value, UL)
define a constant of type uint32_t
22.8.2.42
#define UINT32_MAX (__CONCAT(INT32_MAX, U) ∗ 2UL + 1UL)
largest value an uint32_t can hold.
22.8.2.43
#define UINT64_C( value ) __CONCAT(value, ULL)
define a constant of type uint64_t
22.8.2.44
#define UINT64_MAX (__CONCAT(INT64_MAX, U) ∗ 2ULL +
1ULL)
largest value an uint64_t can hold.
22.8.2.45
#define UINT8_C( value ) ((uint8_t) __CONCAT(value, U))
define a constant of type uint8_t
22.8.2.46
#define UINT8_MAX (__CONCAT(INT8_MAX, U) ∗ 2U + 1U)
largest value an uint8_t can hold.
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22.8
<stdint.h>: Standard Integer Types
22.8.2.47
178
#define UINT_FAST16_MAX UINT16_MAX
largest value an uint_fast16_t can hold.
22.8.2.48
#define UINT_FAST32_MAX UINT32_MAX
largest value an uint_fast32_t can hold.
22.8.2.49
#define UINT_FAST64_MAX UINT64_MAX
largest value an uint_fast64_t can hold.
22.8.2.50
#define UINT_FAST8_MAX UINT8_MAX
largest value an uint_fast8_t can hold.
22.8.2.51
#define UINT_LEAST16_MAX UINT16_MAX
largest value an uint_least16_t can hold.
22.8.2.52
#define UINT_LEAST32_MAX UINT32_MAX
largest value an uint_least32_t can hold.
22.8.2.53
#define UINT_LEAST64_MAX UINT64_MAX
largest value an uint_least64_t can hold.
22.8.2.54
#define UINT_LEAST8_MAX UINT8_MAX
largest value an uint_least8_t can hold.
22.8.2.55
#define UINTMAX_C( value ) __CONCAT(value, ULL)
define a constant of type uintmax_t
22.8.2.56
#define UINTMAX_MAX UINT64_MAX
largest value an uintmax_t can hold.
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<stdint.h>: Standard Integer Types
22.8
22.8.2.57
179
#define UINTPTR_MAX UINT16_MAX
largest value an uintptr_t can hold.
22.8.3
Typedef Documentation
22.8.3.1
typedef signed int int16_t
16-bit signed type.
22.8.3.2
typedef signed long int int32_t
32-bit signed type.
22.8.3.3
typedef signed long long int int64_t
64-bit signed type.
Note
This type is not available when the compiler option -mint8 is in effect.
22.8.3.4
typedef signed char int8_t
8-bit signed type.
22.8.3.5
typedef int16_t int_fast16_t
fastest signed int with at least 16 bits.
22.8.3.6
typedef int32_t int_fast32_t
fastest signed int with at least 32 bits.
22.8.3.7
typedef int64_t int_fast64_t
fastest signed int with at least 64 bits.
Note
This type is not available when the compiler option -mint8 is in effect.
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<stdint.h>: Standard Integer Types
22.8
22.8.3.8
180
typedef int8_t int_fast8_t
fastest signed int with at least 8 bits.
22.8.3.9
typedef int16_t int_least16_t
signed int with at least 16 bits.
22.8.3.10
typedef int32_t int_least32_t
signed int with at least 32 bits.
22.8.3.11
typedef int64_t int_least64_t
signed int with at least 64 bits.
Note
This type is not available when the compiler option -mint8 is in effect.
22.8.3.12
typedef int8_t int_least8_t
signed int with at least 8 bits.
22.8.3.13
typedef int64_t intmax_t
largest signed int available.
22.8.3.14
typedef int16_t intptr_t
Signed pointer compatible type.
22.8.3.15
typedef unsigned int uint16_t
16-bit unsigned type.
22.8.3.16
typedef unsigned long int uint32_t
32-bit unsigned type.
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22.8
22.8.3.17
181
typedef unsigned long long int uint64_t
64-bit unsigned type.
Note
This type is not available when the compiler option -mint8 is in effect.
22.8.3.18
typedef unsigned char uint8_t
8-bit unsigned type.
22.8.3.19
typedef uint16_t uint_fast16_t
fastest unsigned int with at least 16 bits.
22.8.3.20
typedef uint32_t uint_fast32_t
fastest unsigned int with at least 32 bits.
22.8.3.21
typedef uint64_t uint_fast64_t
fastest unsigned int with at least 64 bits.
Note
This type is not available when the compiler option -mint8 is in effect.
22.8.3.22
typedef uint8_t uint_fast8_t
fastest unsigned int with at least 8 bits.
22.8.3.23
typedef uint16_t uint_least16_t
unsigned int with at least 16 bits.
22.8.3.24
typedef uint32_t uint_least32_t
unsigned int with at least 32 bits.
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<stdio.h>: Standard IO facilities
22.9
22.8.3.25
182
typedef uint64_t uint_least64_t
unsigned int with at least 64 bits.
Note
This type is not available when the compiler option -mint8 is in effect.
22.8.3.26
typedef uint8_t uint_least8_t
unsigned int with at least 8 bits.
22.8.3.27
typedef uint64_t uintmax_t
largest unsigned int available.
22.8.3.28
typedef uint16_t uintptr_t
Unsigned pointer compatible type.
<stdio.h>: Standard IO facilities
22.9
Defines
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#define FILE struct __file
#define stdin (__iob[0])
#define stdout (__iob[1])
#define stderr (__iob[2])
#define EOF (-1)
#define fdev_set_udata(stream, u) do { (stream)->udata = u; } while(0)
#define fdev_get_udata(stream) ((stream)->udata)
#define fdev_setup_stream(stream, put, get, rwflag)
#define _FDEV_SETUP_READ __SRD
#define _FDEV_SETUP_WRITE __SWR
#define _FDEV_SETUP_RW (__SRD|__SWR)
#define _FDEV_ERR (-1)
#define _FDEV_EOF (-2)
#define FDEV_SETUP_STREAM(put, get, rwflag)
#define fdev_close()
#define putc(__c, __stream) fputc(__c, __stream)
#define putchar(__c) fputc(__c, stdout)
#define getc(__stream) fgetc(__stream)
#define getchar() fgetc(stdin)
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Functions
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int fclose (FILE ∗__stream)
int vfprintf (FILE ∗__stream, const char ∗__fmt, va_list __ap)
int vfprintf_P (FILE ∗__stream, const char ∗__fmt, va_list __ap)
int fputc (int __c, FILE ∗__stream)
int printf (const char ∗__fmt,...)
int printf_P (const char ∗__fmt,...)
int vprintf (const char ∗__fmt, va_list __ap)
int sprintf (char ∗__s, const char ∗__fmt,...)
int sprintf_P (char ∗__s, const char ∗__fmt,...)
int snprintf (char ∗__s, size_t __n, const char ∗__fmt,...)
int snprintf_P (char ∗__s, size_t __n, const char ∗__fmt,...)
int vsprintf (char ∗__s, const char ∗__fmt, va_list ap)
int vsprintf_P (char ∗__s, const char ∗__fmt, va_list ap)
int vsnprintf (char ∗__s, size_t __n, const char ∗__fmt, va_list ap)
int vsnprintf_P (char ∗__s, size_t __n, const char ∗__fmt, va_list ap)
int fprintf (FILE ∗__stream, const char ∗__fmt,...)
int fprintf_P (FILE ∗__stream, const char ∗__fmt,...)
int fputs (const char ∗__str, FILE ∗__stream)
int fputs_P (const char ∗__str, FILE ∗__stream)
int puts (const char ∗__str)
int puts_P (const char ∗__str)
size_t fwrite (const void ∗__ptr, size_t __size, size_t __nmemb, FILE ∗__stream)
int fgetc (FILE ∗__stream)
int ungetc (int __c, FILE ∗__stream)
char ∗ fgets (char ∗__str, int __size, FILE ∗__stream)
char ∗ gets (char ∗__str)
size_t fread (void ∗__ptr, size_t __size, size_t __nmemb, FILE ∗__stream)
void clearerr (FILE ∗__stream)
int feof (FILE ∗__stream)
int ferror (FILE ∗__stream)
int vfscanf (FILE ∗__stream, const char ∗__fmt, va_list __ap)
int vfscanf_P (FILE ∗__stream, const char ∗__fmt, va_list __ap)
int fscanf (FILE ∗__stream, const char ∗__fmt,...)
int fscanf_P (FILE ∗__stream, const char ∗__fmt,...)
int scanf (const char ∗__fmt,...)
int scanf_P (const char ∗__fmt,...)
int vscanf (const char ∗__fmt, va_list __ap)
int sscanf (const char ∗__buf, const char ∗__fmt,...)
int sscanf_P (const char ∗__buf, const char ∗__fmt,...)
int fflush (FILE ∗stream)
FILE ∗ fdevopen (int(∗put)(char, FILE ∗), int(∗get)(FILE ∗))
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22.9
<stdio.h>: Standard IO facilities
22.9.1
Detailed Description
184
#include <stdio.h>
This file declares the standard IO facilities that
are implemented in avr-libc. Due to the nature of the underlying hardware, only a
limited subset of standard IO is implemented. There is no actual file implementation
available, so only device IO can be performed. Since there’s no operating system, the
application needs to provide enough details about their devices in order to make them
usable by the standard IO facilities.
Introduction to the Standard IO facilities
Due to space constraints, some functionality has not been implemented at all (like some
of the printf conversions that have been left out). Nevertheless, potential users of
this implementation should be warned: the printf and scanf families of functions,
although usually associated with presumably simple things like the famous "Hello,
world!" program, are actually fairly complex which causes their inclusion to eat up
a fair amount of code space. Also, they are not fast due to the nature of interpreting
the format string at run-time. Whenever possible, resorting to the (sometimes nonstandard) predetermined conversion facilities that are offered by avr-libc will usually
cost much less in terms of speed and code size.
In order to allow programmers a code size
vs. functionality tradeoff, the function vfprintf() which is the heart of the printf family
can be selected in different flavours using linker options. See the documentation of
vfprintf() for a detailed description. The same applies to vfscanf() and the scanf
family of functions.
Tunable options for code size vs. feature set
The standard streams stdin, stdout, and stderr are provided, but contrary to the C standard, since avr-libc has no knowledge about applicable
devices, these streams are not already pre-initialized at application startup. Also, since
there is no notion of "file" whatsoever to avr-libc, there is no function fopen() that
could be used to associate a stream to some device. (See note 1.) Instead, the function
fdevopen() is provided to associate a stream to a device, where the device needs to
provide a function to send a character, to receive a character, or both. There is no differentiation between "text" and "binary" streams inside avr-libc. Character \n is sent
literally down to the device’s put() function. If the device requires a carriage return
(\r) character to be sent before the linefeed, its put() routine must implement this
(see note 2).
Outline of the chosen API
As an alternative method to fdevopen(), the macro fdev_setup_stream() might be used
to setup a user-supplied FILE structure.
It should be noted that the automatic conversion of a newline character into a carriage
return - newline sequence breaks binary transfers. If binary transfers are desired, no
automatic conversion should be performed, but instead any string that aims to issue a
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185
CR-LF sequence must use "\r\n" explicitly.
For convenience, the first call to fdevopen() that opens a stream for reading will
cause the resulting stream to be aliased to stdin. Likewise, the first call to fdevopen()
that opens a stream for writing will cause the resulting stream to be aliased to both,
stdout, and stderr. Thus, if the open was done with both, read and write intent,
all three standard streams will be identical. Note that these aliases are indistinguishable
from each other, thus calling fclose() on such a stream will also effectively close
all of its aliases (note 3).
It is possible to tie additional user data to a stream, using fdev_set_udata(). The backend put and get functions can then extract this user data using fdev_get_udata(), and act
appropriately. For example, a single put function could be used to talk to two different
UARTs that way, or the put and get functions could keep internal state between calls
there.
Format strings in flash ROM All the printf and scanf family functions come in two
flavours: the standard name, where the format string is expected to be in SRAM, as
well as a version with the suffix "_P" where the format string is expected to reside in
the flash ROM. The macro PSTR (explained in <avr/pgmspace.h>: Program Space
Utilities) becomes very handy for declaring these format strings.
By default, fdevopen() requires malloc(). As this is often
not desired in the limited environment of a microcontroller, an alternative option is
provided to run completely without malloc().
Running stdio without malloc()
The macro fdev_setup_stream() is provided to prepare a user-supplied FILE buffer for
operation with stdio.
Example
#include <stdio.h>
static int uart_putchar(char c, FILE *stream);
static FILE mystdout = FDEV_SETUP_STREAM(uart_putchar, NULL,
_FDEV_SETUP_WRITE);
static int
uart_putchar(char c, FILE *stream)
{
if (c == ’\n’)
uart_putchar(’\r’, stream);
loop_until_bit_is_set(UCSRA, UDRE);
UDR = c;
return 0;
}
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186
int
main(void)
{
init_uart();
stdout = &mystdout;
printf("Hello, world!\n");
return 0;
}
This example uses the initializer form FDEV_SETUP_STREAM() rather than the functionlike fdev_setup_stream(), so all data initialization happens during C start-up.
If streams initialized that way are no longer needed, they can be destroyed by first
calling the macro fdev_close(), and then destroying the object itself. No call to fclose()
should be issued for these streams. While calling fclose() itself is harmless, it will cause
an undefined reference to free() and thus cause the linker to link the malloc module into
the application.
Notes
Note 1:
It might have been possible to implement a device abstraction that is compatible
with fopen() but since this would have required to parse a string, and to take all
the information needed either out of this string, or out of an additional table that
would need to be provided by the application, this approach was not taken.
Note 2:
This basically follows the Unix approach: if a device such as a terminal needs
special handling, it is in the domain of the terminal device driver to provide this
functionality. Thus, a simple function suitable as put() for fdevopen() that
talks to a UART interface might look like this:
int
uart_putchar(char c, FILE *stream)
{
if (c == ’\n’)
uart_putchar(’\r’);
loop_until_bit_is_set(UCSRA, UDRE);
UDR = c;
return 0;
}
Note 3:
This implementation has been chosen because the cost of maintaining an alias is
considerably smaller than the cost of maintaining full copies of each stream. Yet,
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providing an implementation that offers the complete set of standard streams was
deemed to be useful. Not only that writing printf() instead of fprintf(mystream,
...) saves typing work, but since avr-gcc needs to resort to pass all arguments of
variadic functions on the stack (as opposed to passing them in registers for functions that take a fixed number of parameters), the ability to pass one parameter less
by implying stdin or stdout will also save some execution time.
22.9.2
Define Documentation
22.9.2.1
#define _FDEV_EOF (-2)
Return code for an end-of-file condition during device read.
To be used in the get function of fdevopen().
22.9.2.2
#define _FDEV_ERR (-1)
Return code for an error condition during device read.
To be used in the get function of fdevopen().
22.9.2.3
#define _FDEV_SETUP_READ __SRD
fdev_setup_stream() with read intent
22.9.2.4
#define _FDEV_SETUP_RW (__SRD|__SWR)
fdev_setup_stream() with read/write intent
22.9.2.5
#define _FDEV_SETUP_WRITE __SWR
fdev_setup_stream() with write intent
22.9.2.6
#define EOF (-1)
EOF declares the value that is returned by various standard IO functions in
case of an error. Since the AVR platform (currently) doesn’t contain an abstraction for
actual files, its origin as "end of file" is somewhat meaningless here.
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<stdio.h>: Standard IO facilities
22.9
22.9.2.7
#define fdev_close(
188
)
This macro frees up any library resources that might
be associated with stream. It should be called if stream is no longer needed, right
before the application is going to destroy the stream object itself.
(Currently, this macro evaluates to nothing, but this might change in future versions of
the library.)
22.9.2.8
#define fdev_get_udata( stream ) ((stream)->udata)
This macro retrieves a pointer to user defined data from a FILE stream object.
22.9.2.9
#define fdev_set_udata( stream, u ) do { (stream)->udata = u; }
while(0)
This macro inserts a pointer to user defined data into a FILE stream object.
The user data can be useful for tracking state in the put and get functions supplied to
the fdevopen() function.
22.9.2.10
#define fdev_setup_stream( stream, put, get, rwflag )
Setup a user-supplied buffer as an stdio stream.
This macro takes a user-supplied buffer stream, and sets it up as a stream that is valid
for stdio operations, similar to one that has been obtained dynamically from fdevopen().
The buffer to setup must be of type FILE.
The arguments put and get are identical to those that need to be passed to fdevopen().
The rwflag argument can take one of the values _FDEV_SETUP_READ, _FDEV_SETUP_WRITE, or _FDEV_SETUP_RW, for read, write, or read/write intent, respectively.
Note
No assignments to the standard streams will be performed by fdev_setup_stream().
If standard streams are to be used, these need to be assigned by the user. See also
under Running stdio without malloc().
22.9.2.11
#define FDEV_SETUP_STREAM( put, get, rwflag )
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Initializer for a user-supplied stdio stream.
This macro acts similar to fdev_setup_stream(), but it is to be used as the initializer of
a variable of type FILE.
The remaining arguments are to be used as explained in fdev_setup_stream().
22.9.2.12
#define FILE struct __file
FILE is the opaque structure that is passed around between the various standard IO
functions.
22.9.2.13
#define getc( __stream ) fgetc(__stream)
The macro getc used to be a "fast" macro implementation with a functionality
identical to fgetc(). For space constraints, in avr-libc, it is just an alias for fgetc.
22.9.2.14
#define getchar( void ) fgetc(stdin)
The macro getchar reads a character from stdin. Return values and error
handling is identical to fgetc().
22.9.2.15
#define putc( __c, __stream ) fputc(__c, __stream)
The macro putc used to be a "fast" macro implementation with a functionality
identical to fputc(). For space constraints, in avr-libc, it is just an alias for fputc.
22.9.2.16
#define putchar( __c ) fputc(__c, stdout)
The macro putchar sends character c to stdout.
22.9.2.17
#define stderr (__iob[2])
Stream destined for error output. Unless specifically assigned, identical to stdout.
If stderr should point to another stream, the result of another fdevopen() must
be explicitly assigned to it without closing the previous stderr (since this would also
close stdout).
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22.9
<stdio.h>: Standard IO facilities
22.9.2.18
190
#define stdin (__iob[0])
Stream that will be used as an input stream by the simplified functions that don’t take
a stream argument.
The first stream opened with read intent using fdevopen() will be assigned to
stdin.
22.9.2.19
#define stdout (__iob[1])
Stream that will be used as an output stream by the simplified functions that don’t
take a stream argument.
The first stream opened with write intent using fdevopen() will be assigned to both,
stdin, and stderr.
22.9.3
Function Documentation
22.9.3.1
void clearerr ( FILE ∗ __stream )
Clear the error and end-of-file flags of stream.
22.9.3.2
int fclose ( FILE ∗ __stream )
This function closes stream, and disallows and further IO to and from it.
When using fdevopen() to setup the stream, a call to fclose() is needed in order to free
the internal resources allocated.
If the stream has been set up using fdev_setup_stream() or FDEV_SETUP_STREAM(),
use fdev_close() instead.
It currently always returns 0 (for success).
22.9.3.3
FILE∗ fdevopen ( int(∗)(char, FILE ∗) put, int(∗)(FILE ∗) get )
This function is a replacement for fopen().
It opens a stream for a device where the actual device implementation needs to be
provided by the application. If successful, a pointer to the structure for the opened
stream is returned. Reasons for a possible failure currently include that neither the
put nor the get argument have been provided, thus attempting to open a stream with
no IO intent at all, or that insufficient dynamic memory is available to establish a new
stream.
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If the put function pointer is provided, the stream is opened with write intent. The
function passed as put shall take two arguments, the first a character to write to the
device, and the second a pointer to FILE, and shall return 0 if the output was successful,
and a nonzero value if the character could not be sent to the device.
If the get function pointer is provided, the stream is opened with read intent. The
function passed as get shall take a pointer to FILE as its single argument, and return
one character from the device, passed as an int type. If an error occurs when trying
to read from the device, it shall return _FDEV_ERR. If an end-of-file condition was
reached while reading from the device, _FDEV_EOF shall be returned.
If both functions are provided, the stream is opened with read and write intent.
The first stream opened with read intent is assigned to stdin, and the first one opened
with write intent is assigned to both, stdout and stderr.
fdevopen() uses calloc() (und thus malloc()) in order to allocate the storage for the new
stream.
Note
If the macro __STDIO_FDEVOPEN_COMPAT_12 is declared before including
<stdio.h>, a function prototype for fdevopen() will be chosen that is backwards
compatible with avr-libc version 1.2 and before. This is solely intented for providing a simple migration path without the need to immediately change all source
code. Do not use for new code.
22.9.3.4
int feof ( FILE ∗ __stream )
Test the end-of-file flag of stream. This flag can only be cleared by a call to
clearerr().
22.9.3.5
int ferror ( FILE ∗ __stream )
Test the error flag of stream. This flag can only be cleared by a call to clearerr().
22.9.3.6
int fflush ( FILE ∗ stream )
Flush stream.
This is a null operation provided for source-code compatibility only, as the standard IO
implementation currently does not perform any buffering.
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<stdio.h>: Standard IO facilities
22.9.3.7
192
int fgetc ( FILE ∗ __stream )
The function fgetc reads a character from stream. It
returns the character, or EOF in case end-of-file was encountered or an error occurred.
The routines feof() or ferror() must be used to distinguish between both situations.
22.9.3.8
char∗ fgets ( char ∗ __str, int __size, FILE ∗ __stream )
Read at most
size - 1 bytes from stream, until a newline character was encountered, and store
the characters in the buffer pointed to by str. Unless an error was encountered while
reading, the string will then be terminated with a NUL character.
If an error was encountered, the function returns NULL and sets the error flag of
stream, which can be tested using ferror(). Otherwise, a pointer to the string will
be returned.
22.9.3.9
int fprintf ( FILE ∗ __stream, const char ∗ __fmt, ... )
The function fprintf performs formatted output to stream. See vfprintf()
for details.
22.9.3.10
int fprintf_P ( FILE ∗ __stream, const char ∗ __fmt, ... )
Variant of fprintf() that uses a fmt string that resides in program memory.
22.9.3.11
int fputc ( int __c, FILE ∗ __stream )
The function fputc sends the character c (though given as type int) to stream. It
returns the character, or EOF in case an error occurred.
22.9.3.12
int fputs ( const char ∗ __str, FILE ∗ __stream )
Write the string pointed to by str to stream stream.
Returns 0 on success and EOF on error.
22.9.3.13
int fputs_P ( const char ∗ __str, FILE ∗ __stream )
Variant of fputs() where str resides in program memory.
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22.9.3.14
193
size_t fread ( void ∗ __ptr, size_t __size, size_t __nmemb, FILE ∗
__stream )
Read nmemb objects, size bytes each, from stream, to the buffer pointed to by
ptr.
Returns the number of objects successfully read, i. e. nmemb unless an input error
occured or end-of-file was encountered. feof() and ferror() must be used to distinguish
between these two conditions.
22.9.3.15
int fscanf ( FILE ∗ __stream, const char ∗ __fmt, ... )
The function fscanf performs formatted input, reading the input data from
stream.
See vfscanf() for details.
22.9.3.16
int fscanf_P ( FILE ∗ __stream, const char ∗ __fmt, ... )
Variant of fscanf() using a fmt string in program memory.
22.9.3.17
size_t fwrite ( const void ∗ __ptr, size_t __size, size_t __nmemb,
FILE ∗ __stream )
Write nmemb objects, size bytes each, to stream. The first byte of the first object
is referenced by ptr.
Returns the number of objects successfully written, i. e. nmemb unless an output error
occured.
22.9.3.18
char∗ gets ( char ∗ __str )
Similar to fgets() except that it will operate on stream stdin, and the
trailing newline (if any) will not be stored in the string. It is the caller’s responsibility
to provide enough storage to hold the characters read.
22.9.3.19
int printf ( const char ∗ __fmt, ... )
The function printf performs formatted output to stream stdout. See
vfprintf() for details.
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22.9.3.20
194
int printf_P ( const char ∗ __fmt, ... )
Variant of printf() that uses a fmt string that resides in program memory.
22.9.3.21
int puts ( const char ∗ __str )
Write the string pointed to by str, and a trailing newline character, to stdout.
22.9.3.22
int puts_P ( const char ∗ __str )
Variant of puts() where str resides in program memory.
22.9.3.23
int scanf ( const char ∗ __fmt, ... )
The function scanf performs formatted input from stream stdin.
See vfscanf() for details.
22.9.3.24
int scanf_P ( const char ∗ __fmt, ... )
Variant of scanf() where fmt resides in program memory.
22.9.3.25
int snprintf ( char ∗ __s, size_t __n, const char ∗ __fmt, ... )
Like sprintf(), but instead of assuming s to be of infinite size, no more than n
characters (including the trailing NUL character) will be converted to s.
Returns the number of characters that would have been written to s if there were
enough space.
22.9.3.26
int snprintf_P ( char ∗ __s, size_t __n, const char ∗ __fmt, ... )
Variant of snprintf() that uses a fmt string that resides in program memory.
22.9.3.27
int sprintf ( char ∗ __s, const char ∗ __fmt, ... )
Variant of printf() that sends the formatted characters to string s.
22.9.3.28
int sprintf_P ( char ∗ __s, const char ∗ __fmt, ... )
Variant of sprintf() that uses a fmt string that resides in program memory.
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22.9.3.29
195
int sscanf ( const char ∗ __buf, const char ∗ __fmt, ... )
The function sscanf performs formatted input, reading the input data from the
buffer pointed to by buf.
See vfscanf() for details.
22.9.3.30
int sscanf_P ( const char ∗ __buf, const char ∗ __fmt, ... )
Variant of sscanf() using a fmt string in program memory.
22.9.3.31
int ungetc ( int __c, FILE ∗ __stream )
The ungetc() function pushes the character c (converted to an unsigned char)
back onto the input stream pointed to by stream. The pushed-back character will be
returned by a subsequent read on the stream.
Currently, only a single character can be pushed back onto the stream.
The ungetc() function returns the character pushed back after the conversion, or EOF if
the operation fails. If the value of the argument c character equals EOF, the operation
will fail and the stream will remain unchanged.
22.9.3.32
int vfprintf ( FILE ∗ __stream, const char ∗ __fmt, va_list __ap )
vfprintf is the central facility of the printf family of functions. It
outputs values to stream under control of a format string passed in fmt. The actual
values to print are passed as a variable argument list ap.
vfprintf returns the number of characters written to stream, or EOF in case of
an error. Currently, this will only happen if stream has not been opened with write
intent.
The format string is composed of zero or more directives: ordinary characters (not
%), which are copied unchanged to the output stream; and conversion specifications,
each of which results in fetching zero or more subsequent arguments. Each conversion
specification is introduced by the % character. The arguments must properly correspond
(after type promotion) with the conversion specifier. After the %, the following appear
in sequence:
• Zero or more of the following flags:
– # The value should be converted to an "alternate form". For c, d, i, s, and
u conversions, this option has no effect. For o conversions, the precision of
the number is increased to force the first character of the output string to
a zero (except if a zero value is printed with an explicit precision of zero).
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For x and X conversions, a non-zero result has the string ‘0x’ (or ‘0X’ for
X conversions) prepended to it.
– 0 (zero) Zero padding. For all conversions, the converted value is padded
on the left with zeros rather than blanks. If a precision is given with a
numeric conversion (d, i, o, u, i, x, and X), the 0 flag is ignored.
– - A negative field width flag; the converted value is to be left adjusted on
the field boundary. The converted value is padded on the right with blanks,
rather than on the left with blanks or zeros. A - overrides a 0 if both are
given.
– ’ ’ (space) A blank should be left before a positive number produced by a
signed conversion (d, or i).
– + A sign must always be placed before a number produced by a signed
conversion. A + overrides a space if both are used.
• An optional decimal digit string specifying a minimum field width. If the converted value has fewer characters than the field width, it will be padded with
spaces on the left (or right, if the left-adjustment flag has been given) to fill out
the field width.
• An optional precision, in the form of a period . followed by an optional digit
string. If the digit string is omitted, the precision is taken as zero. This gives the
minimum number of digits to appear for d, i, o, u, x, and X conversions, or the
maximum number of characters to be printed from a string for s conversions.
• An optional l or h length modifier, that specifies that the argument for the d, i,
o, u, x, or X conversion is a "long int" rather than int. The h is ignored,
as "short int" is equivalent to int.
• A character that specifies the type of conversion to be applied.
The conversion specifiers and their meanings are:
• diouxX The int (or appropriate variant) argument is converted to signed decimal
(d and i), unsigned octal (o), unsigned decimal (u), or unsigned hexadecimal
(x and X) notation. The letters "abcdef" are used for x conversions; the letters
"ABCDEF" are used for X conversions. The precision, if any, gives the minimum
number of digits that must appear; if the converted value requires fewer digits, it
is padded on the left with zeros.
• p The void ∗ argument is taken as an unsigned integer, and converted similarly
as a %#x command would do.
• c The int argument is converted to an "unsigned char", and the resulting
character is written.
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• s The "char ∗" argument is expected to be a pointer to an array of character
type (pointer to a string). Characters from the array are written up to (but not
including) a terminating NUL character; if a precision is specified, no more than
the number specified are written. If a precision is given, no null character need
be present; if the precision is not specified, or is greater than the size of the array,
the array must contain a terminating NUL character.
• % A % is written. No argument is converted. The complete conversion specification is "%%".
• eE The double argument is rounded and converted in the format "[-]d.ddde±dd"
where there is one digit before the decimal-point character and the number of
digits after it is equal to the precision; if the precision is missing, it is taken as
6; if the precision is zero, no decimal-point character appears. An E conversion
uses the letter ’E’ (rather than ’e’) to introduce the exponent. The exponent
always contains two digits; if the value is zero, the exponent is 00.
• fF The double argument is rounded and converted to decimal notation in the
format "[-]ddd.ddd", where the number of digits after the decimal-point
character is equal to the precision specification. If the precision is missing, it is
taken as 6; if the precision is explicitly zero, no decimal-point character appears.
If a decimal point appears, at least one digit appears before it.
• gG The double argument is converted in style f or e (or F or E for G conversions). The precision specifies the number of significant digits. If the precision
is missing, 6 digits are given; if the precision is zero, it is treated as 1. Style e is
used if the exponent from its conversion is less than -4 or greater than or equal to
the precision. Trailing zeros are removed from the fractional part of the result; a
decimal point appears only if it is followed by at least one digit.
• S Similar to the s format, except the pointer is expected to point to a programmemory (ROM) string instead of a RAM string.
In no case does a non-existent or small field width cause truncation of a numeric field;
if the result of a conversion is wider than the field width, the field is expanded to contain
the conversion result.
Since the full implementation of all the mentioned features becomes fairly large, three
different flavours of vfprintf() can be selected using linker options. The default vfprintf() implements all the mentioned functionality except floating point conversions.
A minimized version of vfprintf() is available that only implements the very basic integer and string conversion facilities, but only the # additional option can be specified
using conversion flags (these flags are parsed correctly from the format specification,
but then simply ignored). This version can be requested using the following compiler
options:
-Wl,-u,vfprintf -lprintf_min
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If the full functionality including the floating point conversions is required, the following options should be used:
-Wl,-u,vfprintf -lprintf_flt -lm
Limitations:
• The specified width and precision can be at most 255.
Notes:
• For floating-point conversions, if you link default or minimized version of
vfprintf(), the symbol ? will be output and double argument will be skiped.
So you output below will not be crashed. For default version the width field
and the "pad to left" ( symbol minus ) option will work in this case.
• The hh length modifier is ignored (char argument is promouted to int).
More exactly, this realization does not check the number of h symbols.
• But the ll length modifier will to abort the output, as this realization does
not operate long long arguments.
• The variable width or precision field (an asterisk ∗ symbol) is not realized
and will to abort the output.
22.9.3.33
int vfprintf_P ( FILE ∗ __stream, const char ∗ __fmt, va_list __ap )
Variant of vfprintf() that uses a fmt string that resides in program memory.
22.9.3.34
int vfscanf ( FILE ∗ stream, const char ∗ fmt, va_list ap )
Formatted input. This function is the heart of the scanf family of functions.
Characters are read from stream and processed in a way described by fmt. Conversion
results will be assigned to the parameters passed via ap.
The format string fmt is scanned for conversion specifications. Anything that doesn’t
comprise a conversion specification is taken as text that is matched literally against
the input. White space in the format string will match any white space in the data
(including none), all other characters match only itself. Processing is aborted as soon as
the data and format string no longer match, or there is an error or end-of-file condition
on stream.
Most conversions skip leading white space before starting the actual conversion.
Conversions are introduced with the character %. Possible options can follow the %:
• a ∗ indicating that the conversion should be performed but the conversion result
is to be discarded; no parameters will be processed from ap,
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• the character h indicating that the argument is a pointer to short int (rather
than int),
• the 2 characters hh indicating that the argument is a pointer to char (rather than
int).
• the character l indicating that the argument is a pointer to long int (rather
than int, for integer type conversions), or a pointer to double (for floating
point conversions),
In addition, a maximal field width may be specified as a nonzero positive decimal
integer, which will restrict the conversion to at most this many characters from the
input stream. This field width is limited to at most 255 characters which is also the
default value (except for the c conversion that defaults to 1).
The following conversion flags are supported:
• % Matches a literal % character. This is not a conversion.
• d Matches an optionally signed decimal integer; the next pointer must be a
pointer to int.
• i Matches an optionally signed integer; the next pointer must be a pointer to
int. The integer is read in base 16 if it begins with 0x or 0X, in base 8 if it
begins with 0, and in base 10 otherwise. Only characters that correspond to the
base are used.
• o Matches an octal integer; the next pointer must be a pointer to unsigned
int.
• u Matches an optionally signed decimal integer; the next pointer must be a
pointer to unsigned int.
• x Matches an optionally signed hexadecimal integer; the next pointer must be a
pointer to unsigned int.
• f Matches an optionally signed floating-point number; the next pointer must be
a pointer to float.
• e, g, F, E, G Equivalent to f.
• s Matches a sequence of non-white-space characters; the next pointer must be a
pointer to char, and the array must be large enough to accept all the sequence
and the terminating NUL character. The input string stops at white space or at the
maximum field width, whichever occurs first.
• c Matches a sequence of width count characters (default 1); the next pointer must
be a pointer to char, and there must be enough room for all the characters (no
terminating NUL is added). The usual skip of leading white space is suppressed.
To skip white space first, use an explicit space in the format.
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• [ Matches a nonempty sequence of characters from the specified set of accepted
characters; the next pointer must be a pointer to char, and there must be enough
room for all the characters in the string, plus a terminating NUL character. The
usual skip of leading white space is suppressed. The string is to be made up
of characters in (or not in) a particular set; the set is defined by the characters
between the open bracket [ character and a close bracket ] character. The set
excludes those characters if the first character after the open bracket is a circumflex ∧ . To include a close bracket in the set, make it the first character after the
open bracket or the circumflex; any other position will end the set. The hyphen
character - is also special; when placed between two other characters, it adds all
intervening characters to the set. To include a hyphen, make it the last character
before the final close bracket. For instance, [∧ ]0-9-] means the set of everything except close bracket, zero through nine, and hyphen. The string ends with
the appearance of a character not in the (or, with a circumflex, in) set or when
the field width runs out. Note that usage of this conversion enlarges the stack
expense.
• p Matches a pointer value (as printed by p in printf()); the next pointer must be
a pointer to void.
• n Nothing is expected; instead, the number of characters consumed thus far from
the input is stored through the next pointer, which must be a pointer to int. This
is not a conversion, although it can be suppressed with the ∗ flag.
These functions return the number of input items assigned, which can be fewer than
provided for, or even zero, in the event of a matching failure. Zero indicates that, while
there was input available, no conversions were assigned; typically this is due to an
invalid input character, such as an alphabetic character for a d conversion. The value
EOF is returned if an input failure occurs before any conversion such as an end-of-file
occurs. If an error or end-of-file occurs after conversion has begun, the number of
conversions which were successfully completed is returned.
By default, all the conversions described above are available except the floating-point
conversions and the width is limited to 255 characters. The float-point conversion will
be available in the extended version provided by the library libscanf_flt.a. Also
in this case the width is not limited (exactly, it is limited to 65535 characters). To link
a program against the extended version, use the following compiler flags in the link
stage:
-Wl,-u,vfscanf -lscanf_flt -lm
A third version is available for environments that are tight on space. In addition to
the restrictions of the standard one, this version implements no %[ specification. This
version is provided in the library libscanf_min.a, and can be requested using the
following options in the link stage:
-Wl,-u,vfscanf -lscanf_min -lm
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201
int vfscanf_P ( FILE ∗ __stream, const char ∗ __fmt, va_list __ap )
Variant of vfscanf() using a fmt string in program memory.
22.9.3.36
int vprintf ( const char ∗ __fmt, va_list __ap )
The function vprintf performs formatted output to stream stdout, taking a
variable argument list as in vfprintf().
See vfprintf() for details.
22.9.3.37
int vscanf ( const char ∗ __fmt, va_list __ap )
The function vscanf performs formatted input from stream stdin, taking a
variable argument list as in vfscanf().
See vfscanf() for details.
22.9.3.38
int vsnprintf ( char ∗ __s, size_t __n, const char ∗ __fmt, va_list ap )
Like vsprintf(), but instead of assuming s to be of infinite size, no more than n
characters (including the trailing NUL character) will be converted to s.
Returns the number of characters that would have been written to s if there were
enough space.
22.9.3.39
int vsnprintf_P ( char ∗ __s, size_t __n, const char ∗ __fmt, va_list
ap )
Variant of vsnprintf() that uses a fmt string that resides in program memory.
22.9.3.40
int vsprintf ( char ∗ __s, const char ∗ __fmt, va_list ap )
Like sprintf() but takes a variable argument list for the arguments.
22.9.3.41
int vsprintf_P ( char ∗ __s, const char ∗ __fmt, va_list ap )
Variant of vsprintf() that uses a fmt string that resides in program memory.
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202
22.10 <stdlib.h>: General utilities
Data Structures
• struct div_t
• struct ldiv_t
Defines
• #define RAND_MAX 0x7FFF
Typedefs
• typedef int(∗ __compar_fn_t )(const void ∗, const void ∗)
Functions
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
void abort (void) __ATTR_NORETURN__
int abs (int __i)
long labs (long __i)
void ∗ bsearch (const void ∗__key, const void ∗__base, size_t __nmemb, size_t
__size, int(∗__compar)(const void ∗, const void ∗))
div_t div (int __num, int __denom) __asm__("__divmodhi4")
ldiv_t ldiv (long __num, long __denom) __asm__("__divmodsi4")
void qsort (void ∗__base, size_t __nmemb, size_t __size, __compar_fn_t __compar)
long strtol (const char ∗__nptr, char ∗∗__endptr, int __base)
unsigned long strtoul (const char ∗__nptr, char ∗∗__endptr, int __base)
long atol (const char ∗__s) __ATTR_PURE__
int atoi (const char ∗__s) __ATTR_PURE__
void exit (int __status) __ATTR_NORETURN__
void ∗ malloc (size_t __size) __ATTR_MALLOC__
void free (void ∗__ptr)
void ∗ calloc (size_t __nele, size_t __size) __ATTR_MALLOC__
void ∗ realloc (void ∗__ptr, size_t __size) __ATTR_MALLOC__
double strtod (const char ∗__nptr, char ∗∗__endptr)
double atof (const char ∗__nptr)
int rand (void)
void srand (unsigned int __seed)
int rand_r (unsigned long ∗__ctx)
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203
Variables
• size_t __malloc_margin
• char ∗ __malloc_heap_start
• char ∗ __malloc_heap_end
Non-standard (i.e. non-ISO C) functions.
•
•
•
•
•
•
•
•
char ∗ ltoa (long int __val, char ∗__s, int __radix)
char ∗ utoa (unsigned int __val, char ∗__s, int __radix)
char ∗ ultoa (unsigned long int __val, char ∗__s, int __radix)
long random (void)
void srandom (unsigned long __seed)
long random_r (unsigned long ∗__ctx)
char ∗ itoa (int __val, char ∗__s, int __radix)
#define RANDOM_MAX 0x7FFFFFFF
Conversion functions for double arguments.
Note that these functions are not located in the default library, libc.a, but in the
mathematical library, libm.a. So when linking the application, the -lm option needs
to be specified.
• char ∗ dtostre (double __val, char ∗__s, unsigned char __prec, unsigned char
__flags)
• char ∗ dtostrf (double __val, signed char __width, unsigned char __prec, char
∗__s)
• #define DTOSTR_ALWAYS_SIGN 0x01
• #define DTOSTR_PLUS_SIGN 0x02
• #define DTOSTR_UPPERCASE 0x04
22.10.1
Detailed Description
#include <stdlib.h>
This file declares some basic C macros and functions as defined by the ISO standard,
plus some AVR-specific extensions.
22.10.2
Define Documentation
22.10.2.1
#define DTOSTR_ALWAYS_SIGN 0x01
Bit value that can be passed in flags to dtostre().
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204
#define DTOSTR_PLUS_SIGN 0x02
Bit value that can be passed in flags to dtostre().
22.10.2.3
#define DTOSTR_UPPERCASE 0x04
Bit value that can be passed in flags to dtostre().
22.10.2.4
#define RAND_MAX 0x7FFF
Highest number that can be generated by rand().
22.10.2.5
#define RANDOM_MAX 0x7FFFFFFF
Highest number that can be generated by random().
22.10.3
Typedef Documentation
22.10.3.1
typedef int(∗ __compar_fn_t)(const void ∗, const void ∗)
Comparision function type for qsort(), just for convenience.
22.10.4
Function Documentation
22.10.4.1
void abort ( void )
The abort() function causes abnormal program termination to
occur. This realization disables interrupts and jumps to _exit() function with argument
equal to 1. In the limited AVR environment, execution is effectively halted by entering
an infinite loop.
22.10.4.2
int abs ( int __i )
The abs() function computes the absolute value of the integer i.
Note
The abs() and labs() functions are builtins of gcc.
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205
double atof ( const char ∗ nptr )
The atof() function converts the initial portion of the string pointed to by nptr to
double representation.
It is equivalent to calling
strtod(nptr, (char **)0);
22.10.4.4
int atoi ( const char ∗ s )
Convert a string to an integer.
The atoi() function converts the initial portion of the string pointed to by s to integer
representation. In contrast to
(int)strtol(s, (char **)NULL, 10);
this function does not detect overflow (errno is not changed and the result value is
not predictable), uses smaller memory (flash and stack) and works more quickly.
22.10.4.5
long atol ( const char ∗ s )
Convert a string to a long integer.
The atol() function converts the initial portion of the string pointed to by s to long
integer representation. In contrast to
strtol(s, (char **)NULL, 10);
this function does not detect overflow (errno is not changed and the result value is
not predictable), uses smaller memory (flash and stack) and works more quickly.
22.10.4.6
void∗ bsearch ( const void ∗ __key, const void ∗ __base, size_t
__nmemb, size_t __size, int(∗)(const void ∗, const void ∗) __compar )
The bsearch() function searches an array of nmemb objects, the initial member of
which is pointed to by base, for a member that matches the object pointed to by key.
The size of each member of the array is specified by size.
The contents of the array should be in ascending sorted order according to the comparison function referenced by compar. The compar routine is expected to have two
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arguments which point to the key object and to an array member, in that order, and
should return an integer less than, equal to, or greater than zero if the key object is
found, respectively, to be less than, to match, or be greater than the array member.
The bsearch() function returns a pointer to a matching member of the array, or a null
pointer if no match is found. If two members compare as equal, which member is
matched is unspecified.
22.10.4.7
void∗ calloc ( size_t __nele, size_t __size )
Allocate nele elements of size each. Identical to calling malloc() using nele
∗ size as argument, except the allocated memory will be cleared to zero.
22.10.4.8
div_t div ( int __num, int __denom )
The div() function computes the value num/denom
and returns the quotient and remainder in a structure named div_t that contains two
int members named quot and rem.
22.10.4.9
char∗ dtostre ( double __val, char ∗ __s, unsigned char __prec,
unsigned char __flags )
The dtostre() function converts
the double value passed in val into an ASCII representation that will be stored under
s. The caller is responsible for providing sufficient storage in s.
Conversion is done in the format "[-]d.ddde±dd" where there is one digit before
the decimal-point character and the number of digits after it is equal to the precision
prec; if the precision is zero, no decimal-point character appears. If flags has the
DTOSTRE_UPPERCASE bit set, the letter ’E’ (rather than ’e’ ) will be used to
introduce the exponent. The exponent always contains two digits; if the value is zero,
the exponent is "00".
If flags has the DTOSTRE_ALWAYS_SIGN bit set, a space character will be placed
into the leading position for positive numbers.
If flags has the DTOSTRE_PLUS_SIGN bit set, a plus sign will be used instead of
a space character in this case.
The dtostre() function returns the pointer to the converted string s.
22.10.4.10
char∗ dtostrf ( double __val, signed char __width, unsigned char
__prec, char ∗ __s )
The dtostrf() function converts the double value passed in
val into an ASCII representationthat will be stored under s. The caller is responsible
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for providing sufficient storage in s.
Conversion is done in the format "[-]d.ddd". The minimum field width of the
output string (including the ’.’ and the possible sign for negative values) is given in
width, and prec determines the number of digits after the decimal sign. width is
signed value, negative for left adjustment.
The dtostrf() function returns the pointer to the converted string s.
22.10.4.11
void exit ( int __status )
The exit() function terminates the application. Since there
is no environment to return to, status is ignored, and code execution will eventually
reach an infinite loop, thereby effectively halting all code processing. Before entering
the infinite loop, interrupts are globally disabled.
In a C++ context, global destructors will be called before halting execution.
22.10.4.12
void free ( void ∗ __ptr )
The free() function causes the allocated memory referenced by ptr to be made
available for future allocations. If ptr is NULL, no action occurs.
22.10.4.13
char∗ itoa ( int __val, char ∗ __s, int __radix )
Convert an integer to a string.
The function itoa() converts the integer value from val into an ASCII representation
that will be stored under s. The caller is responsible for providing sufficient storage in
s.
Note
The minimal size of the buffer s depends on the choice of radix. For example, if
the radix is 2 (binary), you need to supply a buffer with a minimal length of 8 ∗
sizeof (int) + 1 characters, i.e. one character for each bit plus one for the string
terminator. Using a larger radix will require a smaller minimal buffer size.
Warning
If the buffer is too small, you risk a buffer overflow.
Conversion is done using the radix as base, which may be a number between 2
(binary conversion) and up to 36. If radix is greater than 10, the next digit after
’9’ will be the letter ’a’.
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If radix is 10 and val is negative, a minus sign will be prepended.
The itoa() function returns the pointer passed as s.
22.10.4.14
long labs ( long __i )
The labs() function computes the absolute value of the long integer i.
Note
The abs() and labs() functions are builtins of gcc.
22.10.4.15
ldiv_t ldiv ( long __num, long __denom )
The ldiv() function
computes the value num/denom and returns the quotient and remainder in a structure
named ldiv_t that contains two long integer members named quot and rem.
22.10.4.16
char∗ ltoa ( long int __val, char ∗ __s, int __radix )
Convert a long integer to a string.
The function ltoa() converts the long integer value from val into an ASCII representation that will be stored under s. The caller is responsible for providing sufficient
storage in s.
Note
The minimal size of the buffer s depends on the choice of radix. For example,
if the radix is 2 (binary), you need to supply a buffer with a minimal length of 8
∗ sizeof (long int) + 1 characters, i.e. one character for each bit plus one for the
string terminator. Using a larger radix will require a smaller minimal buffer size.
Warning
If the buffer is too small, you risk a buffer overflow.
Conversion is done using the radix as base, which may be a number between 2
(binary conversion) and up to 36. If radix is greater than 10, the next digit after
’9’ will be the letter ’a’.
If radix is 10 and val is negative, a minus sign will be prepended.
The ltoa() function returns the pointer passed as s.
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22.10.4.17
209
void∗ malloc ( size_t __size )
The malloc() function allocates size bytes of memory. If malloc() fails, a NULL
pointer is returned.
Note that malloc() does not initialize the returned memory to zero bytes.
See the chapter about malloc() usage for implementation details.
22.10.4.18
void qsort ( void ∗ __base, size_t __nmemb, size_t __size,
__compar_fn_t __compar )
The qsort() function is a modified partition-exchange sort, or quicksort.
The qsort() function sorts an array of nmemb objects, the initial member of which is
pointed to by base. The size of each object is specified by size. The contents of the
array base are sorted in ascending order according to a comparison function pointed to
by compar, which requires two arguments pointing to the objects being compared.
The comparison function must return an integer less than, equal to, or greater than zero
if the first argument is considered to be respectively less than, equal to, or greater than
the second.
22.10.4.19
int rand ( void )
The rand() function computes a sequence of pseudo-random integers in the range of 0
to RAND_MAX (as defined by the header file <stdlib.h>).
The srand() function sets its argument seed as the seed for a new sequence of pseudorandom numbers to be returned by rand(). These sequences are repeatable by calling
srand() with the same seed value.
If no seed value is provided, the functions are automatically seeded with a value of 1.
In compliance with the C standard, these functions operate on int arguments. Since
the underlying algorithm already uses 32-bit calculations, this causes a loss of precision. See random() for an alternate set of functions that retains full 32-bit precision.
22.10.4.20
int rand_r ( unsigned long ∗ __ctx )
Variant of rand() that stores the context in the user-supplied variable located at ctx
instead of a static library variable so the function becomes re-entrant.
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22.10.4.21
210
long random ( void )
The random() function computes a sequence of pseudo-random integers in the range
of 0 to RANDOM_MAX (as defined by the header file <stdlib.h>).
The srandom() function sets its argument seed as the seed for a new sequence of
pseudo-random numbers to be returned by rand(). These sequences are repeatable by
calling srandom() with the same seed value.
If no seed value is provided, the functions are automatically seeded with a value of 1.
22.10.4.22
long random_r ( unsigned long ∗ __ctx )
Variant of random() that stores the context in the user-supplied variable located at
ctx instead of a static library variable so the function becomes re-entrant.
22.10.4.23
void∗ realloc ( void ∗ __ptr, size_t __size )
The realloc() function tries to change the size of the region allocated at ptr to the
new size value. It returns a pointer to the new region. The returned pointer might be
the same as the old pointer, or a pointer to a completely different region.
The contents of the returned region up to either the old or the new size value (whatever
is less) will be identical to the contents of the old region, even in case a new region had
to be allocated.
It is acceptable to pass ptr as NULL, in which case realloc() will behave identical to
malloc().
If the new memory cannot be allocated, realloc() returns NULL, and the region at ptr
will not be changed.
22.10.4.24
void srand ( unsigned int __seed )
Pseudo-random number generator seeding; see rand().
22.10.4.25
void srandom ( unsigned long __seed )
Pseudo-random number generator seeding; see random().
22.10.4.26
double strtod ( const char ∗ nptr, char ∗∗ endptr )
The strtod() function converts the initial portion of the string pointed to by nptr to
double representation.
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211
The expected form of the string is an optional plus ( ’+’ ) or minus sign ( ’-’ )
followed by a sequence of digits optionally containing a decimal-point character, optionally followed by an exponent. An exponent consists of an ’E’ or ’e’, followed
by an optional plus or minus sign, followed by a sequence of digits.
Leading white-space characters in the string are skipped.
The strtod() function returns the converted value, if any.
If endptr is not NULL, a pointer to the character after the last character used in the
conversion is stored in the location referenced by endptr.
If no conversion is performed, zero is returned and the value of nptr is stored in the
location referenced by endptr.
If the correct value would cause overflow, plus or minus INFINITY is returned (according to the sign of the value), and ERANGE is stored in errno. If the correct value
would cause underflow, zero is returned and ERANGE is stored in errno.
22.10.4.27
long strtol ( const char ∗ __nptr, char ∗∗ __endptr, int __base )
The strtol() function converts the string in nptr to a long value. The conversion is
done according to the given base, which must be between 2 and 36 inclusive, or be the
special value 0.
The string may begin with an arbitrary amount of white space (as determined by isspace()) followed by a single optional ’+’ or ’-’ sign. If base is zero or 16, the string
may then include a "0x" prefix, and the number will be read in base 16; otherwise, a
zero base is taken as 10 (decimal) unless the next character is ’0’, in which case it is
taken as 8 (octal).
The remainder of the string is converted to a long value in the obvious manner, stopping
at the first character which is not a valid digit in the given base. (In bases above 10, the
letter ’A’ in either upper or lower case represents 10, ’B’ represents 11, and so forth,
with ’Z’ representing 35.)
If endptr is not NULL, strtol() stores the address of the first invalid character in
∗endptr. If there were no digits at all, however, strtol() stores the original value of
nptr in endptr. (Thus, if ∗nptr is not ’\0’ but ∗∗endptr is ’\0’ on return, the
entire string was valid.)
The strtol() function returns the result of the conversion, unless the value would underflow or overflow. If no conversion could be performed, 0 is returned. If an overflow or
underflow occurs, errno is set to ERANGE and the function return value is clamped
to LONG_MIN or LONG_MAX, respectively.
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22.10
<stdlib.h>: General utilities
22.10.4.28
212
unsigned long strtoul ( const char ∗ __nptr, char ∗∗ __endptr, int
__base )
The strtoul() function converts the string in nptr to an
unsigned long value. The conversion is done according to the given base, which must
be between 2 and 36 inclusive, or be the special value 0.
The string may begin with an arbitrary amount of white space (as determined by isspace()) followed by a single optional ’+’ or ’-’ sign. If base is zero or 16, the string
may then include a "0x" prefix, and the number will be read in base 16; otherwise, a
zero base is taken as 10 (decimal) unless the next character is ’0’, in which case it is
taken as 8 (octal).
The remainder of the string is converted to an unsigned long value in the obvious
manner, stopping at the first character which is not a valid digit in the given base.
(In bases above 10, the letter ’A’ in either upper or lower case represents 10, ’B’
represents 11, and so forth, with ’Z’ representing 35.)
If endptr is not NULL, strtoul() stores the address of the first invalid character in
∗endptr. If there were no digits at all, however, strtoul() stores the original value of
nptr in endptr. (Thus, if ∗nptr is not ’\0’ but ∗∗endptr is ’\0’ on return, the
entire string was valid.)
The strtoul() function return either the result of the conversion or, if there was a leading minus sign, the negation of the result of the conversion, unless the original (nonnegated) value would overflow; in the latter case, strtoul() returns ULONG_MAX, and
errno is set to ERANGE. If no conversion could be performed, 0 is returned.
22.10.4.29
char∗ ultoa ( unsigned long int __val, char ∗ __s, int __radix )
Convert an unsigned long integer to a string.
The function ultoa() converts the unsigned long integer value from val into an ASCII
representation that will be stored under s. The caller is responsible for providing sufficient storage in s.
Note
The minimal size of the buffer s depends on the choice of radix. For example, if
the radix is 2 (binary), you need to supply a buffer with a minimal length of 8 ∗
sizeof (unsigned long int) + 1 characters, i.e. one character for each bit plus one
for the string terminator. Using a larger radix will require a smaller minimal buffer
size.
Warning
If the buffer is too small, you risk a buffer overflow.
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Conversion is done using the radix as base, which may be a number between 2
(binary conversion) and up to 36. If radix is greater than 10, the next digit after
’9’ will be the letter ’a’.
The ultoa() function returns the pointer passed as s.
22.10.4.30
char∗ utoa ( unsigned int __val, char ∗ __s, int __radix )
Convert an unsigned integer to a string.
The function utoa() converts the unsigned integer value from val into an ASCII representation that will be stored under s. The caller is responsible for providing sufficient
storage in s.
Note
The minimal size of the buffer s depends on the choice of radix. For example, if
the radix is 2 (binary), you need to supply a buffer with a minimal length of 8 ∗
sizeof (unsigned int) + 1 characters, i.e. one character for each bit plus one for the
string terminator. Using a larger radix will require a smaller minimal buffer size.
Warning
If the buffer is too small, you risk a buffer overflow.
Conversion is done using the radix as base, which may be a number between 2
(binary conversion) and up to 36. If radix is greater than 10, the next digit after
’9’ will be the letter ’a’.
The utoa() function returns the pointer passed as s.
22.10.5
Variable Documentation
22.10.5.1
char∗ __malloc_heap_end
malloc() tunable.
22.10.5.2
char∗ __malloc_heap_start
malloc() tunable.
22.10.5.3
size_t __malloc_margin
malloc() tunable.
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<string.h>: Strings
22.11
214
22.11 <string.h>: Strings
Defines
• #define _FFS(x)
Functions
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int ffs (int __val)
int ffsl (long __val)
int ffsll (long long __val)
void ∗ memccpy (void ∗, const void ∗, int, size_t)
void ∗ memchr (const void ∗, int, size_t) __ATTR_PURE__
int memcmp (const void ∗, const void ∗, size_t) __ATTR_PURE__
void ∗ memcpy (void ∗, const void ∗, size_t)
void ∗ memmem (const void ∗, size_t, const void ∗, size_t) __ATTR_PURE__
void ∗ memmove (void ∗, const void ∗, size_t)
void ∗ memrchr (const void ∗, int, size_t) __ATTR_PURE__
void ∗ memset (void ∗, int, size_t)
int strcasecmp (const char ∗, const char ∗) __ATTR_PURE__
char ∗ strcasestr (const char ∗, const char ∗) __ATTR_PURE__
char ∗ strcat (char ∗, const char ∗)
char ∗ strchr (const char ∗, int) __ATTR_PURE__
char ∗ strchrnul (const char ∗, int) __ATTR_PURE__
int strcmp (const char ∗, const char ∗) __ATTR_PURE__
char ∗ strcpy (char ∗, const char ∗)
size_t strcspn (const char ∗__s, const char ∗__reject) __ATTR_PURE__
char ∗ strdup (const char ∗s1)
size_t strlcat (char ∗, const char ∗, size_t)
size_t strlcpy (char ∗, const char ∗, size_t)
size_t strlen (const char ∗) __ATTR_PURE__
char ∗ strlwr (char ∗)
int strncasecmp (const char ∗, const char ∗, size_t) __ATTR_PURE__
char ∗ strncat (char ∗, const char ∗, size_t)
int strncmp (const char ∗, const char ∗, size_t) __ATTR_PURE__
char ∗ strncpy (char ∗, const char ∗, size_t)
size_t strnlen (const char ∗, size_t) __ATTR_PURE__
char ∗ strpbrk (const char ∗__s, const char ∗__accept) __ATTR_PURE__
char ∗ strrchr (const char ∗, int) __ATTR_PURE__
char ∗ strrev (char ∗)
char ∗ strsep (char ∗∗, const char ∗)
size_t strspn (const char ∗__s, const char ∗__accept) __ATTR_PURE__
char ∗ strstr (const char ∗, const char ∗) __ATTR_PURE__
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<string.h>: Strings
215
• char ∗ strtok (char ∗, const char ∗)
• char ∗ strtok_r (char ∗, const char ∗, char ∗∗)
• char ∗ strupr (char ∗)
22.11.1
Detailed Description
#include <string.h>
The string functions perform string operations on NULL terminated strings.
Note
If the strings you are working on resident in program space (flash), you will need to
use the string functions described in <avr/pgmspace.h>: Program Space Utilities.
22.11.2
Define Documentation
22.11.2.1
#define _FFS( x )
This macro finds the first (least significant) bit set in the input value.
This macro is very similar to the function ffs() except that it evaluates its argument at
compile-time, so it should only be applied to compile-time constant expressions where
it will reduce to a constant itself. Application of this macro to expressions that are not
constant at compile-time is not recommended, and might result in a huge amount of
code generated.
Returns
The _FFS() macro returns the position of the first (least significant) bit set in the
word val, or 0 if no bits are set. The least significant bit is position 1. Only 16 bits
of argument are evaluted.
22.11.3
Function Documentation
22.11.3.1
int ffs ( int val )
This function finds the first (least significant) bit set in the input value.
Returns
The ffs() function returns the position of the first (least significant) bit set in the
word val, or 0 if no bits are set. The least significant bit is position 1.
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Note
For expressions that are constant at compile time, consider using the _FFS macro
instead.
22.11.3.2
int ffsl ( long __val )
Same as ffs(), for an argument of type long.
22.11.3.3
int ffsll ( long long __val )
Same as ffs(), for an argument of type long long.
22.11.3.4
void ∗ memccpy ( void ∗ dest, const void ∗ src, int val, size_t len )
Copy memory area.
The memccpy() function copies no more than len bytes from memory area src to
memory area dest, stopping when the character val is found.
Returns
The memccpy() function returns a pointer to the next character in dest after val,
or NULL if val was not found in the first len characters of src.
22.11.3.5
void ∗ memchr ( const void ∗ src, int val, size_t len )
Scan memory for a character.
The memchr() function scans the first len bytes of the memory area pointed to by src
for the character val. The first byte to match val (interpreted as an unsigned character)
stops the operation.
Returns
The memchr() function returns a pointer to the matching byte or NULL if the
character does not occur in the given memory area.
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<string.h>: Strings
22.11.3.6
217
int memcmp ( const void ∗ s1, const void ∗ s2, size_t len )
Compare memory areas.
The memcmp() function compares the first len bytes of the memory areas s1 and s2.
The comparision is performed using unsigned char operations.
Returns
The memcmp() function returns an integer less than, equal to, or greater than zero
if the first len bytes of s1 is found, respectively, to be less than, to match, or be
greater than the first len bytes of s2.
Note
Be sure to store the result in a 16 bit variable since you may get incorrect results if
you use an unsigned char or char due to truncation.
Warning
This function is not -mint8 compatible, although if you only care about testing for
equality, this function should be safe to use.
22.11.3.7
void ∗ memcpy ( void ∗ dest, const void ∗ src, size_t len )
Copy a memory area.
The memcpy() function copies len bytes from memory area src to memory area dest.
The memory areas may not overlap. Use memmove() if the memory areas do overlap.
Returns
The memcpy() function returns a pointer to dest.
22.11.3.8
void ∗ memmem ( const void ∗ s1, size_t len1, const void ∗ s2, size_t
len2 )
The memmem() function finds the start of the first occurrence of the substring s2 of
length len2 in the memory area s1 of length len1.
Returns
The memmem() function returns a pointer to the beginning of the substring, or
NULL if the substring is not found. If len2 is zero, the function returns s1.
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22.11.3.9
218
void ∗ memmove ( void ∗ dest, const void ∗ src, size_t len )
Copy memory area.
The memmove() function copies len bytes from memory area src to memory area dest.
The memory areas may overlap.
Returns
The memmove() function returns a pointer to dest.
22.11.3.10
void ∗ memrchr ( const void ∗ src, int val, size_t len )
The memrchr() function is like the memchr() function, except that it searches
backwards from the end of the len bytes pointed to by src instead of forwards from
the front. (Glibc, GNU extension.)
Returns
The memrchr() function returns a pointer to the matching byte or NULL if the
character does not occur in the given memory area.
22.11.3.11
void ∗ memset ( void ∗ dest, int val, size_t len )
Fill memory with a constant byte.
The memset() function fills the first len bytes of the memory area pointed to by dest
with the constant byte val.
Returns
The memset() function returns a pointer to the memory area dest.
22.11.3.12
int strcasecmp ( const char ∗ s1, const char ∗ s2 )
Compare two strings ignoring case.
The strcasecmp() function compares the two strings s1 and s2, ignoring the case of
the characters.
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Returns
The strcasecmp() function returns an integer less than, equal to, or greater than
zero if s1 is found, respectively, to be less than, to match, or be greater than
s2. A consequence of the ordering used by strcasecmp() is that if s1 is an initial
substring of s2, then s1 is considered to be "less than" s2.
22.11.3.13
char ∗ strcasestr ( const char ∗ s1, const char ∗ s2 )
The strcasestr() function finds the first occurrence of the substring s2 in the string
s1. This is like strstr(), except that it ignores case of alphabetic symbols in searching
for the substring. (Glibc, GNU extension.)
Returns
The strcasestr() function returns a pointer to the beginning of the substring, or
NULL if the substring is not found. If s2 points to a string of zero length, the
function returns s1.
22.11.3.14
char ∗ strcat ( char ∗ dest, const char ∗ src )
Concatenate two strings.
The strcat() function appends the src string to the dest string overwriting the ’\0’ character at the end of dest, and then adds a terminating ’\0’ character. The strings may not
overlap, and the dest string must have enough space for the result.
Returns
The strcat() function returns a pointer to the resulting string dest.
22.11.3.15
char ∗ strchr ( const char ∗ src, int val )
Locate character in string.
The strchr() function returns a pointer to the first occurrence of the character val in
the string src.
Here "character" means "byte" - these functions do not work with wide or multi-byte
characters.
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Returns
The strchr() function returns a pointer to the matched character or NULL if the
character is not found.
22.11.3.16
char ∗ strchrnul ( const char ∗ s, int c )
The strchrnul() function is like strchr() except that if c is not found
in s, then it returns a pointer to the null byte at the end of s, rather than NULL. (Glibc,
GNU extension.)
Returns
The strchrnul() function returns a pointer to the matched character, or a pointer to
the null byte at the end of s (i.e., s+strlen(s)) if the character is not found.
22.11.3.17
int strcmp ( const char ∗ s1, const char ∗ s2 )
Compare two strings.
The strcmp() function compares the two strings s1 and s2.
Returns
The strcmp() function returns an integer less than, equal to, or greater than zero
if s1 is found, respectively, to be less than, to match, or be greater than s2. A
consequence of the ordering used by strcmp() is that if s1 is an initial substring of
s2, then s1 is considered to be "less than" s2.
22.11.3.18
char ∗ strcpy ( char ∗ dest, const char ∗ src )
Copy a string.
The strcpy() function copies the string pointed to by src (including the terminating
’\0’ character) to the array pointed to by dest. The strings may not overlap, and the
destination string dest must be large enough to receive the copy.
Returns
The strcpy() function returns a pointer to the destination string dest.
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221
Note
If the destination string of a strcpy() is not large enough (that is, if the programmer
was stupid/lazy, and failed to check the size before copying) then anything might
happen. Overflowing fixed length strings is a favourite cracker technique.
22.11.3.19
size_t strcspn ( const char ∗ s, const char ∗ reject )
The strcspn() function calculates the length of the initial segment of s which consists
entirely of characters not in reject.
Returns
The strcspn() function returns the number of characters in the initial segment of s
which are not in the string reject. The terminating zero is not considered as a
part of string.
22.11.3.20
char ∗ strdup ( const char ∗ s1 )
Duplicate a string.
The strdup() function allocates memory and copies into it the string addressed by s1,
including the terminating null character.
Warning
The strdup() function calls malloc() to allocate the memory for the duplicated
string! The user is responsible for freeing the memory by calling free().
Returns
The strdup() function returns a pointer to the resulting string dest. If malloc()
cannot allocate enough storage for the string, strdup() will return NULL.
Warning
Be sure to check the return value of the strdup() function to make sure that the
function has succeeded in allocating the memory!
22.11.3.21
size_t strlcat ( char ∗ dst, const char ∗ src, size_t siz )
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Concatenate two strings.
Appends src to string dst of size siz (unlike strncat(), siz is the full size of dst, not space
left). At most siz-1 characters will be copied. Always NULL terminates (unless siz <=
strlen(dst)).
Returns
The strlcat() function returns strlen(src) + MIN(siz, strlen(initial dst)). If retval >=
siz, truncation occurred.
Appends src to string dst of size siz (unlike strncat(), siz is the full size of dst,
not space left). At most siz-1 characters will be copied. Always NULL terminates
(unless siz <= strlen(dst)).
Returns
The strlcat() function returns strlen(src) + MIN(siz, strlen(initial dst)). If retval >=
siz, truncation occurred.
22.11.3.22
size_t strlcpy ( char ∗ dst, const char ∗ src, size_t siz )
Copy a string.
Copy src to string dst of size siz. At most siz-1 characters will be copied. Always
NULL terminates (unless siz == 0).
Returns
The strlcpy() function returns strlen(src). If retval >= siz, truncation occurred.
Copy src to string dst of size siz. At most siz-1 characters will be copied.
Always NULL terminates (unless siz == 0).
Returns
The strlcpy() function returns strlen(src). If retval >= siz, truncation occurred.
22.11.3.23
size_t strlen ( const char ∗ src )
Calculate the length of a string.
The strlen() function calculates the length of the string src, not including the terminating ’\0’ character.
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Returns
The strlen() function returns the number of characters in src.
22.11.3.24
char ∗ strlwr ( char ∗ s )
Convert a string to lower case.
The strlwr() function will convert a string to lower case. Only the upper case alphabetic
characters [A .. Z] are converted. Non-alphabetic characters will not be changed.
Returns
The strlwr() function returns a pointer to the converted string.
22.11.3.25
int strncasecmp ( const char ∗ s1, const char ∗ s2, size_t len )
Compare two strings ignoring case.
The strncasecmp() function is similar to strcasecmp(), except it only compares the first
len characters of s1.
Returns
The strncasecmp() function returns an integer less than, equal to, or greater than
zero if s1 (or the first len bytes thereof) is found, respectively, to be less than, to
match, or be greater than s2. A consequence of the ordering used by strncasecmp()
is that if s1 is an initial substring of s2, then s1 is considered to be "less than"
s2.
22.11.3.26
char ∗ strncat ( char ∗ dest, const char ∗ src, size_t len )
Concatenate two strings.
The strncat() function is similar to strcat(), except that only the first n characters of src
are appended to dest.
Returns
The strncat() function returns a pointer to the resulting string dest.
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22.11
<string.h>: Strings
22.11.3.27
224
int strncmp ( const char ∗ s1, const char ∗ s2, size_t len )
Compare two strings.
The strncmp() function is similar to strcmp(), except it only compares the first (at most)
n characters of s1 and s2.
Returns
The strncmp() function returns an integer less than, equal to, or greater than zero
if s1 (or the first n bytes thereof) is found, respectively, to be less than, to match,
or be greater than s2.
22.11.3.28
char ∗ strncpy ( char ∗ dest, const char ∗ src, size_t len )
Copy a string.
The strncpy() function is similar to strcpy(), except that not more than n bytes of src
are copied. Thus, if there is no null byte among the first n bytes of src, the result will
not be null-terminated.
In the case where the length of src is less than that of n, the remainder of dest will be
padded with nulls.
Returns
The strncpy() function returns a pointer to the destination string dest.
22.11.3.29
size_t strnlen ( const char ∗ src, size_t len )
Determine the length of a fixed-size string.
The strnlen function returns the number of characters in the string pointed to by src, not
including the terminating ’\0’ character, but at most len. In doing this, strnlen looks
only at the first len characters at src and never beyond src+len.
Returns
The strnlen function returns strlen(src), if that is less than len, or len if there is no
’\0’ character among the first len characters pointed to by src.
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22.11
<string.h>: Strings
22.11.3.30
225
char ∗ strpbrk ( const char ∗ s, const char ∗ accept )
The strpbrk() function locates the first occurrence in the string s of any of the
characters in the string accept.
Returns
The strpbrk() function returns a pointer to the character in s that matches one of
the characters in accept, or NULL if no such character is found. The terminating
zero is not considered as a part of string: if one or both args are empty, the result
will NULL.
22.11.3.31
char ∗ strrchr ( const char ∗ src, int val )
Locate character in string.
The strrchr() function returns a pointer to the last occurrence of the character val in the
string src.
Here "character" means "byte" - these functions do not work with wide or multi-byte
characters.
Returns
The strrchr() function returns a pointer to the matched character or NULL if the
character is not found.
22.11.3.32
char ∗ strrev ( char ∗ s )
Reverse a string.
The strrev() function reverses the order of the string.
Returns
The strrev() function returns a pointer to the beginning of the reversed string.
22.11.3.33
char ∗ strsep ( char ∗∗ sp, const char ∗ delim )
Parse a string into tokens.
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The strsep() function locates, in the string referenced by ∗sp, the first occurrence of
any character in the string delim (or the terminating ’\0’ character) and replaces it
with a ’\0’. The location of the next character after the delimiter character (or NULL,
if the end of the string was reached) is stored in ∗sp. An “empty” field, i.e. one
caused by two adjacent delimiter characters, can be detected by comparing the location
referenced by the pointer returned in ∗sp to ’\0’.
Returns
The strsep() function returns a pointer to the original value of ∗sp. If ∗sp is
initially NULL, strsep() returns NULL.
22.11.3.34
size_t strspn ( const char ∗ s, const char ∗ accept )
The strspn() function calculates the length of the initial segment of s which consists
entirely of characters in accept.
Returns
The strspn() function returns the number of characters in the initial segment of
s which consist only of characters from accept. The terminating zero is not
considered as a part of string.
22.11.3.35
char ∗ strstr ( const char ∗ s1, const char ∗ s2 )
Locate a substring.
The strstr() function finds the first occurrence of the substring s2 in the string s1. The
terminating ’\0’ characters are not compared.
Returns
The strstr() function returns a pointer to the beginning of the substring, or NULL
if the substring is not found. If s2 points to a string of zero length, the function
returns s1.
22.11.3.36
char ∗ strtok ( char ∗ s, const char ∗ delim )
Parses the string s into tokens.
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strtok parses the string s into tokens. The first call to strtok should have s as its first
argument. Subsequent calls should have the first argument set to NULL. If a token
ends with a delimiter, this delimiting character is overwritten with a ’\0’ and a pointer
to the next character is saved for the next call to strtok. The delimiter string delim may
be different for each call.
Returns
The strtok() function returns a pointer to the next token or NULL when no more
tokens are found.
Note
strtok() is NOT reentrant. For a reentrant version of this function see strtok_r().
22.11.3.37
char ∗ strtok_r ( char ∗ string, const char ∗ delim, char ∗∗ last )
Parses string into tokens.
strtok_r parses string into tokens. The first call to strtok_r should have string as its
first argument. Subsequent calls should have the first argument set to NULL. If a token
ends with a delimiter, this delimiting character is overwritten with a ’\0’ and a pointer
to the next character is saved for the next call to strtok_r. The delimiter string delim
may be different for each call. last is a user allocated char∗ pointer. It must be the
same while parsing the same string. strtok_r is a reentrant version of strtok().
Returns
The strtok_r() function returns a pointer to the next token or NULL when no more
tokens are found.
22.11.3.38
char ∗ strupr ( char ∗ s )
Convert a string to upper case.
The strupr() function will convert a string to upper case. Only the lower case alphabetic
characters [a .. z] are converted. Non-alphabetic characters will not be changed.
Returns
The strupr() function returns a pointer to the converted string. The pointer is the
same as that passed in since the operation is perform in place.
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<avr/boot.h>: Bootloader Support Utilities
22.12
228
22.12 <avr/boot.h>: Bootloader Support Utilities
Defines
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
22.12.1
#define BOOTLOADER_SECTION __attribute__ ((section (".bootloader")))
#define boot_spm_interrupt_enable() (__SPM_REG |= (uint8_t)_BV(SPMIE))
#define boot_spm_interrupt_disable() (__SPM_REG &= (uint8_t)∼_BV(SPMIE))
#define boot_is_spm_interrupt() (__SPM_REG & (uint8_t)_BV(SPMIE))
#define boot_rww_busy() (__SPM_REG & (uint8_t)_BV(__COMMON_ASB))
#define boot_spm_busy() (__SPM_REG & (uint8_t)_BV(__SPM_ENABLE))
#define boot_spm_busy_wait() do{}while(boot_spm_busy())
#define GET_LOW_FUSE_BITS (0x0000)
#define GET_LOCK_BITS (0x0001)
#define GET_EXTENDED_FUSE_BITS (0x0002)
#define GET_HIGH_FUSE_BITS (0x0003)
#define boot_lock_fuse_bits_get(address)
#define boot_signature_byte_get(addr)
#define boot_page_fill(address, data) __boot_page_fill_normal(address, data)
#define boot_page_erase(address) __boot_page_erase_normal(address)
#define boot_page_write(address) __boot_page_write_normal(address)
#define boot_rww_enable() __boot_rww_enable()
#define boot_lock_bits_set(lock_bits) __boot_lock_bits_set(lock_bits)
#define boot_page_fill_safe(address, data)
#define boot_page_erase_safe(address)
#define boot_page_write_safe(address)
#define boot_rww_enable_safe()
#define boot_lock_bits_set_safe(lock_bits)
Detailed Description
#include <avr/io.h>
#include <avr/boot.h>
The macros in this module provide a C language interface to the bootloader support
functionality of certain AVR processors. These macros are designed to work with all
sizes of flash memory.
Global interrupts are not automatically disabled for these macros. It is left up to the
programmer to do this. See the code example below. Also see the processor datasheet
for caveats on having global interrupts enabled during writing of the Flash.
Note
Not all AVR processors provide bootloader support. See your processor datasheet
to see if it provides bootloader support.
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22.12
<avr/boot.h>: Bootloader Support Utilities
229
Todo
From email with Marek: On smaller devices (all except ATmega64/128), __SPM_REG is in the I/O space, accessible with the shorter "in" and "out" instructions since the boot loader has a limited size, this could be an important optimization.
API Usage Example
The following code shows typical usage of the boot API.
#include <inttypes.h>
#include <avr/interrupt.h>
#include <avr/pgmspace.h>
void boot_program_page (uint32_t page, uint8_t *buf)
{
uint16_t i;
uint8_t sreg;
// Disable interrupts.
sreg = SREG;
cli();
eeprom_busy_wait ();
boot_page_erase (page);
boot_spm_busy_wait ();
// Wait until the memory is erased.
for (i=0; i<SPM_PAGESIZE; i+=2)
{
// Set up little-endian word.
uint16_t w = *buf++;
w += (*buf++) << 8;
boot_page_fill (page + i, w);
}
boot_page_write (page);
boot_spm_busy_wait();
// Store buffer in flash page.
// Wait until the memory is written.
// Reenable RWW-section again. We need this if we want to jump back
// to the application after bootloading.
boot_rww_enable ();
// Re-enable interrupts (if they were ever enabled).
SREG = sreg;
}
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22.12
<avr/boot.h>: Bootloader Support Utilities
22.12.2
Define Documentation
22.12.2.1
#define boot_is_spm_interrupt(
(uint8_t)_BV(SPMIE))
230
) (__SPM_REG &
Check if the SPM interrupt is enabled.
22.12.2.2
#define boot_lock_bits_set( lock_bits ) __boot_lock_bits_set(lock_bits)
Set the bootloader lock bits.
Parameters
lock_bits A mask of which Boot Loader Lock Bits to set.
Note
In this context, a ’set bit’ will be written to a zero value. Note also that only BLBxx
bits can be programmed by this command.
For example, to disallow the SPM instruction from writing to the Boot Loader memory
section of flash, you would use this macro as such:
boot_lock_bits_set (_BV (BLB11));
Note
Like any lock bits, the Boot Loader Lock Bits, once set, cannot be cleared again
except by a chip erase which will in turn also erase the boot loader itself.
22.12.2.3
#define boot_lock_bits_set_safe( lock_bits )
Value:
do { \
boot_spm_busy_wait();
eeprom_busy_wait();
boot_lock_bits_set (lock_bits);
} while (0)
\
\
\
Same as boot_lock_bits_set() except waits for eeprom and spm operations to complete
before setting the lock bits.
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22.12
<avr/boot.h>: Bootloader Support Utilities
22.12.2.4
231
#define boot_lock_fuse_bits_get( address )
Value:
(__extension__({
uint8_t __result;
__asm__ __volatile__
(
"sts %1, %2\n\t"
"lpm %0, Z\n\t"
: "=r" (__result)
: "i" (_SFR_MEM_ADDR(__SPM_REG)),
"r" ((uint8_t)(__BOOT_LOCK_BITS_SET)),
"z" ((uint16_t)(address))
);
__result;
}))
\
\
\
\
\
\
\
\
\
\
\
\
Read the lock or fuse bits at address.
Parameter address can be any of GET_LOW_FUSE_BITS, GET_LOCK_BITS,
GET_EXTENDED_FUSE_BITS, or GET_HIGH_FUSE_BITS.
Note
The lock and fuse bits returned are the physical values, i.e. a bit returned as 0
means the corresponding fuse or lock bit is programmed.
22.12.2.5
#define boot_page_erase( address ) __boot_page_erase_normal(address)
Erase the flash page that contains address.
Note
address is a byte address in flash, not a word address.
22.12.2.6
#define boot_page_erase_safe( address )
Value:
do { \
boot_spm_busy_wait();
eeprom_busy_wait();
boot_page_erase (address);
} while (0)
\
\
\
Same as boot_page_erase() except it waits for eeprom and spm operations to complete
before erasing the page.
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22.12
<avr/boot.h>: Bootloader Support Utilities
22.12.2.7
232
#define boot_page_fill( address, data
) __boot_page_fill_normal(address, data)
Fill the bootloader temporary page buffer for flash address with data word.
Note
The address is a byte address. The data is a word. The AVR writes data to the
buffer a word at a time, but addresses the buffer per byte! So, increment your
address by 2 between calls, and send 2 data bytes in a word format! The LSB of
the data is written to the lower address; the MSB of the data is written to the higher
address.
22.12.2.8
#define boot_page_fill_safe( address, data )
Value:
do { \
boot_spm_busy_wait();
eeprom_busy_wait();
boot_page_fill(address, data);
} while (0)
\
\
\
Same as boot_page_fill() except it waits for eeprom and spm operations to complete
before filling the page.
22.12.2.9
#define boot_page_write( address ) __boot_page_write_normal(address)
Write the bootloader temporary page buffer to flash page that contains address.
Note
address is a byte address in flash, not a word address.
22.12.2.10
#define boot_page_write_safe( address )
Value:
do { \
boot_spm_busy_wait();
eeprom_busy_wait();
boot_page_write (address);
} while (0)
\
\
\
Same as boot_page_write() except it waits for eeprom and spm operations to complete
before writing the page.
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22.12
<avr/boot.h>: Bootloader Support Utilities
22.12.2.11
233
#define boot_rww_busy( ) (__SPM_REG &
(uint8_t)_BV(__COMMON_ASB))
Check if the RWW section is busy.
22.12.2.12
#define boot_rww_enable(
) __boot_rww_enable()
Enable the Read-While-Write memory section.
22.12.2.13
#define boot_rww_enable_safe(
)
Value:
do { \
boot_spm_busy_wait();
eeprom_busy_wait();
boot_rww_enable();
} while (0)
\
\
\
Same as boot_rww_enable() except waits for eeprom and spm operations to complete
before enabling the RWW mameory.
22.12.2.14
#define boot_signature_byte_get( addr )
Value:
(__extension__({
\
uint8_t __result;
__asm__ __volatile__
(
"sts %1, %2\n\t"
"lpm %0, Z" "\n\t"
: "=r" (__result)
: "i" (_SFR_MEM_ADDR(__SPM_REG)),
"r" ((uint8_t)(__BOOT_SIGROW_READ)),
"z" ((uint16_t)(addr))
);
__result;
}))
\
\
\
\
\
\
\
\
\
\
\
Read the Signature Row byte at address. For some MCU types, this function can
also retrieve the factory-stored oscillator calibration bytes.
Parameter address can be 0-0x1f as documented by the datasheet.
Note
The values are MCU type dependent.
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22.12
<avr/boot.h>: Bootloader Support Utilities
22.12.2.15
234
#define boot_spm_busy( ) (__SPM_REG &
(uint8_t)_BV(__SPM_ENABLE))
Check if the SPM instruction is busy.
22.12.2.16
#define boot_spm_busy_wait(
) do{}while(boot_spm_busy())
Wait while the SPM instruction is busy.
22.12.2.17
#define boot_spm_interrupt_disable(
(uint8_t)∼_BV(SPMIE))
) (__SPM_REG &=
Disable the SPM interrupt.
22.12.2.18
#define boot_spm_interrupt_enable(
(uint8_t)_BV(SPMIE))
) (__SPM_REG |=
Enable the SPM interrupt.
22.12.2.19
#define BOOTLOADER_SECTION __attribute__ ((section
(".bootloader")))
Used to declare a function or variable to be placed into a new section called
.bootloader. This section and its contents can then be relocated to any address (such as
the bootloader NRWW area) at link-time.
22.12.2.20
#define GET_EXTENDED_FUSE_BITS (0x0002)
address to read the extended fuse bits, using boot_lock_fuse_bits_get
22.12.2.21
#define GET_HIGH_FUSE_BITS (0x0003)
address to read the high fuse bits, using boot_lock_fuse_bits_get
22.12.2.22
#define GET_LOCK_BITS (0x0001)
address to read the lock bits, using boot_lock_fuse_bits_get
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22.13
<avr/cpufunc.h>: Special AVR CPU functions
22.12.2.23
235
#define GET_LOW_FUSE_BITS (0x0000)
address to read the low fuse bits, using boot_lock_fuse_bits_get
22.13 <avr/cpufunc.h>: Special AVR CPU functions
Defines
• #define _NOP()
• #define _MemoryBarrier()
22.13.1
Detailed Description
#include <avr/cpufunc.h>
This header file contains macros that access special functions of the AVR CPU which
do not fit into any of the other header files.
22.13.2
Define Documentation
22.13.2.1
#define _MemoryBarrier(
)
Implement a read/write memory barrier. A memory barrier
instructs the compiler to not cache any memory data in registers beyond the barrier.
This can sometimes be more effective than blocking certain optimizations by declaring
some object with a volatile qualifier.
See optim_code_reorder for things to be taken into account with respect to compiler
optimizations.
22.13.2.2
#define _NOP(
)
Execute a no operation (NOP)
CPU instruction. This should not be used to implement delays, better use the functions
from <util/delay_basic.h> or <util/delay.h> for this. For debugging purposes, a NOP
can be useful to have an instruction that is guaranteed to be not optimized away by the
compiler, so it can always become a breakpoint in the debugger.
22.14 <avr/eeprom.h>: EEPROM handling
Defines
• #define EEMEM __attribute__((section(".eeprom")))
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<avr/eeprom.h>: EEPROM handling
22.14
236
• #define eeprom_is_ready()
• #define eeprom_busy_wait() do {} while (!eeprom_is_ready())
Functions
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
uint8_t eeprom_read_byte (const uint8_t ∗__p) __ATTR_PURE__
uint16_t eeprom_read_word (const uint16_t ∗__p) __ATTR_PURE__
uint32_t eeprom_read_dword (const uint32_t ∗__p) __ATTR_PURE__
float eeprom_read_float (const float ∗__p) __ATTR_PURE__
void eeprom_read_block (void ∗__dst, const void ∗__src, size_t __n)
void eeprom_write_byte (uint8_t ∗__p, uint8_t __value)
void eeprom_write_word (uint16_t ∗__p, uint16_t __value)
void eeprom_write_dword (uint32_t ∗__p, uint32_t __value)
void eeprom_write_float (float ∗__p, float __value)
void eeprom_write_block (const void ∗__src, void ∗__dst, size_t __n)
void eeprom_update_byte (uint8_t ∗__p, uint8_t __value)
void eeprom_update_word (uint16_t ∗__p, uint16_t __value)
void eeprom_update_dword (uint32_t ∗__p, uint32_t __value)
void eeprom_update_float (float ∗__p, float __value)
void eeprom_update_block (const void ∗__src, void ∗__dst, size_t __n)
IAR C compatibility defines
•
•
•
•
#define _EEPUT(addr, val) eeprom_write_byte ((uint8_t ∗)(addr), (uint8_t)(val))
#define __EEPUT(addr, val) eeprom_write_byte ((uint8_t ∗)(addr), (uint8_t)(val))
#define _EEGET(var, addr) (var) = eeprom_read_byte ((const uint8_t ∗)(addr))
#define __EEGET(var, addr) (var) = eeprom_read_byte ((const uint8_t ∗)(addr))
22.14.1
Detailed Description
#include <avr/eeprom.h>
This header file declares the interface to some simple library routines suitable for handling the data EEPROM contained in the AVR microcontrollers. The implementation
uses a simple polled mode interface. Applications that require interrupt-controlled
EEPROM access to ensure that no time will be wasted in spinloops will have to deploy
their own implementation.
Notes:
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22.14
<avr/eeprom.h>: EEPROM handling
237
• In addition to the write functions there is a set of update ones. This functions read
each byte first and skip the burning if the old value is the same with new. The
scaning direction is from high address to low, to obtain quick return in common
cases.
• All of the read/write functions first make sure the EEPROM is ready to be accessed. Since this may cause long delays if a write operation is still pending,
time-critical applications should first poll the EEPROM e. g. using eeprom_is_ready() before attempting any actual I/O. But this functions are not wait until
SELFPRGEN in SPMCSR becomes zero. Do this manually, if your softwate
contains the Flash burning.
• As these functions modify IO registers, they are known to be non-reentrant. If
any of these functions are used from both, standard and interrupt context, the
applications must ensure proper protection (e.g. by disabling interrupts before
accessing them).
• All write functions force erase_and_write programming mode.
• For Xmega the EEPROM start address is 0, like other architectures. The reading
functions add the 0x2000 value to use EEPROM mapping into data space.
22.14.2
Define Documentation
22.14.2.1
#define __EEGET( var, addr ) (var) = eeprom_read_byte ((const
uint8_t ∗)(addr))
Read a byte from EEPROM. Compatibility define for IAR C.
22.14.2.2
#define __EEPUT( addr, val ) eeprom_write_byte ((uint8_t
∗)(addr), (uint8_t)(val))
Write a byte to EEPROM. Compatibility define for IAR C.
22.14.2.3
#define _EEGET( var, addr ) (var) = eeprom_read_byte ((const
uint8_t ∗)(addr))
Read a byte from EEPROM. Compatibility define for IAR C.
22.14.2.4
#define _EEPUT( addr, val ) eeprom_write_byte ((uint8_t ∗)(addr),
(uint8_t)(val))
Write a byte to EEPROM. Compatibility define for IAR C.
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22.14
<avr/eeprom.h>: EEPROM handling
22.14.2.5
238
#define EEMEM __attribute__((section(".eeprom")))
Attribute expression causing a variable to be allocated within the .eeprom section.
22.14.2.6
#define eeprom_busy_wait(
) do {} while (!eeprom_is_ready())
Loops until the eeprom is no longer busy.
Returns
Nothing.
22.14.2.7
#define eeprom_is_ready(
)
Returns
1 if EEPROM is ready for a new read/write operation, 0 if not.
22.14.3
Function Documentation
22.14.3.1
void eeprom_read_block ( void ∗ __dst, const void ∗ __src, size_t __n
)
Read a block of __n bytes from EEPROM address __src to SRAM __dst.
22.14.3.2
uint8_t eeprom_read_byte ( const uint8_t ∗ __p )
Read one byte from EEPROM address __p.
22.14.3.3
uint32_t eeprom_read_dword ( const uint32_t ∗ __p )
Read one 32-bit double word (little endian) from EEPROM address __p.
22.14.3.4
float eeprom_read_float ( const float ∗ __p )
Read one float value (little endian) from EEPROM address __p.
22.14.3.5
uint16_t eeprom_read_word ( const uint16_t ∗ __p )
Read one 16-bit word (little endian) from EEPROM address __p.
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22.14
<avr/eeprom.h>: EEPROM handling
22.14.3.6
239
void eeprom_update_block ( const void ∗ __src, void ∗ __dst, size_t
__n )
Update a block of __n bytes to EEPROM address __dst from __src.
Note
The argument order is mismatch with common functions like strcpy().
22.14.3.7
void eeprom_update_byte ( uint8_t ∗ __p, uint8_t __value )
Update a byte __value to EEPROM address __p.
22.14.3.8
void eeprom_update_dword ( uint32_t ∗ __p, uint32_t __value )
Update a 32-bit double word __value to EEPROM address __p.
22.14.3.9
void eeprom_update_float ( float ∗ __p, float __value )
Update a float __value to EEPROM address __p.
22.14.3.10
void eeprom_update_word ( uint16_t ∗ __p, uint16_t __value )
Update a word __value to EEPROM address __p.
22.14.3.11
void eeprom_write_block ( const void ∗ __src, void ∗ __dst, size_t
__n )
Write a block of __n bytes to EEPROM address __dst from __src.
Note
The argument order is mismatch with common functions like strcpy().
22.14.3.12
void eeprom_write_byte ( uint8_t ∗ __p, uint8_t __value )
Write a byte __value to EEPROM address __p.
22.14.3.13
void eeprom_write_dword ( uint32_t ∗ __p, uint32_t __value )
Write a 32-bit double word __value to EEPROM address __p.
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22.15
<avr/fuse.h>: Fuse Support
22.14.3.14
240
void eeprom_write_float ( float ∗ __p, float __value )
Write a float __value to EEPROM address __p.
22.14.3.15
void eeprom_write_word ( uint16_t ∗ __p, uint16_t __value )
Write a word __value to EEPROM address __p.
22.15 <avr/fuse.h>: Fuse Support
Introduction
The Fuse API allows a user to specify the fuse settings for the specific AVR device they
are compiling for. These fuse settings will be placed in a special section in the ELF
output file, after linking.
Programming tools can take advantage of the fuse information embedded in the ELF
file, by extracting this information and determining if the fuses need to be programmed
before programming the Flash and EEPROM memories. This also allows a single ELF
file to contain all the information needed to program an AVR.
To use the Fuse API, include the <avr/io.h> header file, which in turn automatically
includes the individual I/O header file and the <avr/fuse.h> file. These other two files
provides everything necessary to set the AVR fuses.
Fuse API
Each I/O header file must define the FUSE_MEMORY_SIZE macro which is defined
to the number of fuse bytes that exist in the AVR device.
A new type, __fuse_t, is defined as a structure. The number of fields in this structure
are determined by the number of fuse bytes in the FUSE_MEMORY_SIZE macro.
If FUSE_MEMORY_SIZE == 1, there is only a single field: byte, of type unsigned
char.
If FUSE_MEMORY_SIZE == 2, there are two fields: low, and high, of type unsigned
char.
If FUSE_MEMORY_SIZE == 3, there are three fields: low, high, and extended, of
type unsigned char.
If FUSE_MEMORY_SIZE > 3, there is a single field: byte, which is an array of
unsigned char with the size of the array being FUSE_MEMORY_SIZE.
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22.15
<avr/fuse.h>: Fuse Support
241
A convenience macro, FUSEMEM, is defined as a GCC attribute for a custom-named
section of ".fuse".
A convenience macro, FUSES, is defined that declares a variable, __fuse, of type __fuse_t with the attribute defined by FUSEMEM. This variable allows the end user to
easily set the fuse data.
Note
If a device-specific I/O header file has previously defined FUSEMEM, then FUSEMEM is not redefined. If a device-specific I/O header file has previously defined
FUSES, then FUSES is not redefined.
Each AVR device I/O header file has a set of defined macros which specify the actual
fuse bits available on that device. The AVR fuses have inverted values, logical 1 for
an unprogrammed (disabled) bit and logical 0 for a programmed (enabled) bit. The
defined macros for each individual fuse bit represent this in their definition by a bitwise inversion of a mask. For example, the FUSE_EESAVE fuse in the ATmega128 is
defined as:
#define FUSE_EESAVE
~_BV(3)
Note
The _BV macro creates a bit mask from a bit number. It is then inverted to represent logical values for a fuse memory byte.
To combine the fuse bits macros together to represent a whole fuse byte, use the bitwise
AND operator, like so:
(FUSE_BOOTSZ0 & FUSE_BOOTSZ1 & FUSE_EESAVE & FUSE_SPIEN & FUSE_JTAGEN)
Each device I/O header file also defines macros that provide default values for each fuse
byte that is available. LFUSE_DEFAULT is defined for a Low Fuse byte. HFUSE_DEFAULT is defined for a High Fuse byte. EFUSE_DEFAULT is defined for an Extended Fuse byte.
If FUSE_MEMORY_SIZE > 3, then the I/O header file defines macros that provide default values for each fuse byte like so: FUSE0_DEFAULT FUSE1_DEFAULT
FUSE2_DEFAULT FUSE3_DEFAULT FUSE4_DEFAULT ....
API Usage Example
Putting all of this together is easy. Using C99’s designated initializers:
#include <avr/io.h>
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22.15
<avr/fuse.h>: Fuse Support
242
FUSES =
{
.low = LFUSE_DEFAULT,
.high = (FUSE_BOOTSZ0 & FUSE_BOOTSZ1 & FUSE_EESAVE & FUSE_SPIEN & FUSE_JT
AGEN),
.extended = EFUSE_DEFAULT,
};
int main(void)
{
return 0;
}
Or, using the variable directly instead of the FUSES macro,
#include <avr/io.h>
__fuse_t __fuse __attribute__((section (".fuse"))) =
{
.low = LFUSE_DEFAULT,
.high = (FUSE_BOOTSZ0 & FUSE_BOOTSZ1 & FUSE_EESAVE & FUSE_SPIEN & FUSE_JT
AGEN),
.extended = EFUSE_DEFAULT,
};
int main(void)
{
return 0;
}
If you are compiling in C++, you cannot use the designated intializers so you must do:
#include <avr/io.h>
FUSES =
{
LFUSE_DEFAULT, // .low
(FUSE_BOOTSZ0 & FUSE_BOOTSZ1 & FUSE_EESAVE & FUSE_SPIEN & FUSE_JTAGEN), /
/ .high
EFUSE_DEFAULT, // .extended
};
int main(void)
{
return 0;
}
However there are a number of caveats that you need to be aware of to use this API
properly.
Be sure to include <avr/io.h> to get all of the definitions for the API. The FUSES
macro defines a global variable to store the fuse data. This variable is assigned to its
own linker section. Assign the desired fuse values immediately in the variable initialization.
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22.16
<avr/interrupt.h>: Interrupts
243
The .fuse section in the ELF file will get its values from the initial variable assignment
ONLY. This means that you can NOT assign values to this variable in functions and the
new values will not be put into the ELF .fuse section.
The global variable is declared in the FUSES macro has two leading underscores,
which means that it is reserved for the "implementation", meaning the library, so it
will not conflict with a user-named variable.
You must initialize ALL fields in the __fuse_t structure. This is because the fuse bits
in all bytes default to a logical 1, meaning unprogrammed. Normal uninitialized data
defaults to all locgial zeros. So it is vital that all fuse bytes are initialized, even with
default data. If they are not, then the fuse bits may not programmed to the desired
settings.
Be sure to have the -mmcu=device flag in your compile command line and your linker
command line to have the correct device selected and to have the correct I/O header
file included when you include <avr/io.h>.
You can print out the contents of the .fuse section in the ELF file by using this command
line:
avr-objdump -s -j .fuse <ELF file>
The section contents shows the address on the left, then the data going from lower
address to a higher address, left to right.
22.16 <avr/interrupt.h>: Interrupts
Global manipulation of the interrupt flag
The global interrupt flag is maintained in the I bit of the status register (SREG).
Handling interrupts frequently requires attention regarding atomic access to objects
that could be altered by code running within an interrupt context, see <util/atomic.h>.
Frequently, interrupts are being disabled for periods of time in order to perform certain
operations without being disturbed; see optim_code_reorder for things to be taken into
account with respect to compiler optimizations.
• #define sei()
• #define cli()
Macros for writing interrupt handler functions
• #define ISR(vector, attributes)
• #define SIGNAL(vector)
• #define EMPTY_INTERRUPT(vector)
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22.16
<avr/interrupt.h>: Interrupts
244
• #define ISR_ALIAS(vector, target_vector)
• #define reti()
• #define BADISR_vect
ISR attributes
•
•
•
•
22.16.1
#define ISR_BLOCK
#define ISR_NOBLOCK
#define ISR_NAKED
#define ISR_ALIASOF(target_vector)
Detailed Description
Note
This discussion of interrupts was originally taken from Rich Neswold’s document.
See Acknowledgments.
It’s nearly impossible to find compilers that
agree on how to handle interrupt code. Since the C language tries to stay away from
machine dependent details, each compiler writer is forced to design their method of
support.
Introduction to avr-libc’s interrupt handling
In the AVR-GCC environment, the vector table is predefined to point to interrupt routines with predetermined names. By using the appropriate name, your routine will be
called when the corresponding interrupt occurs. The device library provides a set of
default interrupt routines, which will get used if you don’t define your own.
Patching into the vector table is only one part of the problem. The compiler uses, by
convention, a set of registers when it’s normally executing compiler-generated code.
It’s important that these registers, as well as the status register, get saved and restored.
The extra code needed to do this is enabled by tagging the interrupt function with __attribute__((signal)).
These details seem to make interrupt routines a little messy, but all these details are
handled by the Interrupt API. An interrupt routine is defined with ISR(). This macro
register and mark the routine as an interrupt handler for the specified peripheral. The
following is an example definition of a handler for the ADC interrupt.
#include <avr/interrupt.h>
ISR(ADC_vect)
{
// user code here
}
Refer to the chapter explaining assembler programming for an explanation about interrupt routines written solely in assembler language.
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22.16
<avr/interrupt.h>: Interrupts
245
If an unexpected interrupt occurs (interrupt is enabled and no
handler is installed, which usually indicates a bug), then the default action is to reset
the device by jumping to the reset vector. You can override this by supplying a function named BADISR_vect which should be defined with ISR() as such. (The name
BADISR_vect is actually an alias for __vector_default. The latter must be used inside
assembly code in case <avr/interrupt.h> is not included.)
Catch-all interrupt vector
#include <avr/interrupt.h>
ISR(BADISR_vect)
{
// user code here
}
Nested interrupts The AVR hardware clears the global interrupt flag in SREG before
entering an interrupt vector. Thus, normally interrupts will remain disabled inside the
handler until the handler exits, where the RETI instruction (that is emitted by the compiler as part of the normal function epilogue for an interrupt handler) will eventually
re-enable further interrupts. For that reason, interrupt handlers normally do not nest.
For most interrupt handlers, this is the desired behaviour, for some it is even required in
order to prevent infinitely recursive interrupts (like UART interrupts, or level-triggered
external interrupts). In rare circumstances though it might be desired to re-enable the
global interrupt flag as early as possible in the interrupt handler, in order to not defer
any other interrupt more than absolutely needed. This could be done using an sei()
instruction right at the beginning of the interrupt handler, but this still leaves few instructions inside the compiler-generated function prologue to run with global interrupts
disabled. The compiler can be instructed to insert an SEI instruction right at the beginning of an interrupt handler by declaring the handler the following way:
ISR(XXX_vect, ISR_NOBLOCK)
{
...
}
where XXX_vect is the name of a valid interrupt vector for the MCU type in question,
as explained below.
In some circumstances, the actions to be taken upon
two different interrupts might be completely identical so a single implementation for
the ISR would suffice. For example, pin-change interrupts arriving from two different
ports could logically signal an event that is independent from the actual port (and thus
interrupt vector) where it happened. Sharing interrupt vector code can be accomplished
using the ISR_ALIASOF() attribute to the ISR macro:
Two vectors sharing the same code
ISR(PCINT0_vect)
{
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22.16
<avr/interrupt.h>: Interrupts
246
...
// Code to handle the event.
}
ISR(PCINT1_vect, ISR_ALIASOF(PCINT0_vect));
Note
There is no body to the aliased ISR.
Note that the ISR_ALIASOF() feature requires GCC 4.2 or above (or a patched version
of GCC 4.1.x). See the documentation of the ISR_ALIAS() macro for an implementation which is less elegant but could be applied to all compiler versions.
In rare circumstances, in interrupt vector does not need
any code to be implemented at all. The vector must be declared anyway, so when the
interrupt triggers it won’t execute the BADISR_vect code (which by default restarts the
application).
Empty interrupt service routines
This could for example be the case for interrupts that are solely enabled for the purpose
of getting the controller out of sleep_mode().
A handler for such an interrupt vector can be declared using the EMPTY_INTERRUPT()
macro:
EMPTY_INTERRUPT(ADC_vect);
Note
There is no body to this macro.
In some circumstances, the compiler-generated prologue and epilogue of the ISR might not be optimal for the job, and a manually defined ISR could
be considered particularly to speedup the interrupt handling.
Manually defined ISRs
One solution to this could be to implement the entire ISR as manual assembly code in
a separate (assembly) file. See Combining C and assembly source files for an example
of how to implement it that way.
Another solution is to still implement the ISR in C language but take over the compiler’s job of generating the prologue and epilogue. This can be done using the ISR_NAKED attribute to the ISR() macro. Note that the compiler does not generate anything as prologue or epilogue, so the final reti() must be provided by the actual implementation. SREG must be manually saved if the ISR code modifies it, and the
compiler-implied assumption of __zero_reg__ always being 0 could be wrong (e.
g. when interrupting right after of a MUL instruction).
ISR(TIMER1_OVF_vect, ISR_NAKED)
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22.16
<avr/interrupt.h>: Interrupts
247
{
PORTB |= _BV(0);
reti();
// results in SBI which does not affect SREG
}
Choosing the vector: Interrupt vector names
The interrupt is chosen by supplying one of
the symbols in following table.
There are currently two different styles present for naming the vectors. One form uses
names starting with SIG_, followed by a relatively verbose but arbitrarily chosen name
describing the interrupt vector. This has been the only available style in avr-libc up to
version 1.2.x.
Starting with avr-libc version 1.4.0, a second style of interrupt vector names has been
added, where a short phrase for the vector description is followed by _vect. The
short phrase matches the vector name as described in the datasheet of the respective
device (and in Atmel’s XML files), with spaces replaced by an underscore and other
non-alphanumeric characters dropped. Using the suffix _vect is intented to improve
portability to other C compilers available for the AVR that use a similar naming convention.
The historical naming style might become deprecated in a future release, so it is not
recommended for new projects.
Note
The ISR() macro cannot really spell-check the argument passed to them. Thus, by
misspelling one of the names below in a call to ISR(), a function will be created
that, while possibly being usable as an interrupt function, is not actually wired into
the interrupt vector table. The compiler will generate a warning if it detects a suspiciously looking name of a ISR() function (i.e. one that after macro replacement
does not start with "__vector_").
Vector name
Old
name
vector
Description
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
Applicable for device
22.16
<avr/interrupt.h>: Interrupts
248
ADC_vect
SIG_ADC
ADC Conversion
Complete
Com-
AT90S2333, AT90S4433, AT90S4434,
AT90S8535,
AT90PWM216,
AT90PWM2B,
AT90PWM316,
AT90PWM3B, AT90PWM3, AT90PWM2,
AT90PWM1, AT90CAN128, AT90CAN32,
AT90CAN64, ATmega103, ATmega128,
ATmega1284P, ATmega16, ATmega163,
ATmega165, ATmega165P, ATmega168P,
ATmega169, ATmega169P, ATmega32,
ATmega323, ATmega325, ATmega3250,
ATmega3250P, ATmega328P, ATmega329,
ATmega3290, ATmega3290P, ATmega48P,
ATmega64, ATmega645, ATmega6450,
ATmega649, ATmega6490, ATmega8,
ATmega8535, ATmega88P, ATmega168,
ATmega48, ATmega88, ATmega640, ATmega1280, ATmega1281, ATmega2560,
ATmega2561, ATmega324P, ATmega164P,
ATmega644P, ATmega644, ATtiny13, ATtiny15, ATtiny26, ATtiny43U, ATtiny48,
ATtiny24, ATtiny44, ATtiny84, ATtiny45,
ATtiny25, ATtiny85, ATtiny261, ATtiny461,
ATtiny861, AT90USB1287, AT90USB1286,
AT90USB647, AT90USB646
AT90PWM3, AT90PWM2, AT90PWM1
ANALOG_COMP_0_vect
ANALOG_COMP_1_vect
ANALOG_COMP_2_vect
ANALOG_COMP_vect
SIG_COMPARATOR0
SIG_COMPARATOR1
SIG_COMPARATOR2
SIG_COMPARATOR
Analog
parator 0
Analog
parator 1
Analog
parator 2
Analog
parator
Com-
AT90PWM3, AT90PWM2, AT90PWM1
Com-
AT90PWM3, AT90PWM2, AT90PWM1
Com-
AT90CAN128, AT90CAN32, AT90CAN64,
ATmega103, ATmega128, ATmega1284P,
ATmega165, ATmega165P, ATmega168P,
ATmega169, ATmega169P, ATmega325,
ATmega3250, ATmega3250P, ATmega328P,
ATmega329, ATmega3290, ATmega3290P,
ATmega48P, ATmega64,
ATmega645,
ATmega6450, ATmega649, ATmega6490,
ATmega88P, ATmega168,
ATmega48,
ATmega88, ATmega640, ATmega1280,
ATmega1281, ATmega2560, ATmega2561,
ATmega324P, ATmega164P, ATmega644P,
ATmega644, AT90USB162, AT90USB82,
AT90USB1287,
AT90USB1286,
AT90USB647, AT90USB646
AT90S1200, AT90S2313, AT90S2333,
AT90S4414, AT90S4433, AT90S4434,
AT90S8515,
AT90S8535,
ATmega16,
ATmega161, ATmega162, ATmega163,
ATmega32, ATmega323, ATmega8, ATmega8515,
ATmega8535,
ATtiny11,
ATtiny12, ATtiny13, ATtiny15, ATtiny2313,
ATtiny26, ATtiny28, ATtiny43U, ATtiny48,
ATtiny24, ATtiny44, ATtiny84, ATtiny45,
ATtiny25, ATtiny85, ATtiny261, ATtiny461,
ATtiny861
ANA_COMP_vect
SIG_Analog
COMPARATOR parator
Com-
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
22.16
<avr/interrupt.h>: Interrupts
CANIT_vect
SIG_CAN_INTERRUPT1
EEPROM_READY_vect
SIG_EEPROM_READY,
SIG_EE_READY
SIG_EEPROM_READY
EE_RDY_vect
CAN
Transfer
Complete
or
Error
249
AT90CAN128, AT90CAN32, AT90CAN64
ATtiny2313
EEPROM Ready
EE_READY_vect
SIG_EEPROM_READY
EEPROM Ready
EXT_INT0_vect
SIG_INTERRUPT0
External Interrupt
Request 0
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
AT90S2333, AT90S4433, AT90S4434,
AT90S8535,
ATmega16,
ATmega161,
ATmega162, ATmega163, ATmega32,
ATmega323, ATmega8, ATmega8515,
ATmega8535, ATtiny12, ATtiny13, ATtiny15, ATtiny26, ATtiny43U, ATtiny48,
ATtiny24, ATtiny44, ATtiny84, ATtiny45,
ATtiny25, ATtiny85, ATtiny261, ATtiny461,
ATtiny861
AT90PWM3, AT90PWM2, AT90PWM1,
AT90CAN128, AT90CAN32, AT90CAN64,
ATmega103, ATmega128, ATmega1284P,
ATmega165, ATmega165P, ATmega168P,
ATmega169, ATmega169P, ATmega325,
ATmega3250, ATmega3250P, ATmega328P,
ATmega329, ATmega3290, ATmega3290P,
ATmega32HVB, ATmega406, ATmega48P,
ATmega64, ATmega645, ATmega6450,
ATmega649, ATmega6490, ATmega88P,
ATmega168, ATmega48, ATmega88, ATmega640, ATmega1280, ATmega1281, ATmega2560, ATmega2561, ATmega324P, ATmega164P, ATmega644P, ATmega644, ATmega16HVA, AT90USB162, AT90USB82,
AT90USB1287,
AT90USB1286,
AT90USB647, AT90USB646
ATtiny24, ATtiny44, ATtiny84
22.16
<avr/interrupt.h>: Interrupts
INT0_vect
SIG_INTERRUPT0
External Interrupt
0
INT1_vect
SIG_INTERRUPT1
External Interrupt
Request 1
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
250
AT90S1200, AT90S2313, AT90S2323,
AT90S2333, AT90S2343, AT90S4414,
AT90S4433, AT90S4434, AT90S8515,
AT90S8535,
AT90PWM216,
AT90PWM2B,
AT90PWM316,
AT90PWM3B, AT90PWM3, AT90PWM2,
AT90PWM1, AT90CAN128, AT90CAN32,
AT90CAN64, ATmega103, ATmega128,
ATmega1284P, ATmega16, ATmega161,
ATmega162, ATmega163, ATmega165,
ATmega165P, ATmega168P, ATmega169,
ATmega169P, ATmega32, ATmega323,
ATmega325, ATmega3250, ATmega3250P,
ATmega328P, ATmega329, ATmega3290,
ATmega3290P,
ATmega32HVB,
ATmega406, ATmega48P, ATmega64, ATmega645,
ATmega6450,
ATmega649,
ATmega6490, ATmega8, ATmega8515,
ATmega8535, ATmega88P, ATmega168,
ATmega48, ATmega88, ATmega640, ATmega1280, ATmega1281, ATmega2560,
ATmega2561, ATmega324P, ATmega164P,
ATmega644P, ATmega644, ATmega16HVA,
ATtiny11, ATtiny12, ATtiny13, ATtiny15,
ATtiny22, ATtiny2313, ATtiny26, ATtiny28,
ATtiny43U, ATtiny48, ATtiny45, ATtiny25,
ATtiny85, ATtiny261, ATtiny461, ATtiny861,
AT90USB162,
AT90USB82,
AT90USB1287,
AT90USB1286,
AT90USB647, AT90USB646
AT90S2313, AT90S2333, AT90S4414,
AT90S4433, AT90S4434, AT90S8515,
AT90S8535,
AT90PWM216,
AT90PWM2B,
AT90PWM316,
AT90PWM3B, AT90PWM3, AT90PWM2,
AT90PWM1, AT90CAN128, AT90CAN32,
AT90CAN64, ATmega103, ATmega128,
ATmega1284P, ATmega16, ATmega161,
ATmega162, ATmega163, ATmega168P,
ATmega32, ATmega323, ATmega328P,
ATmega32HVB,
ATmega406,
ATmega48P, ATmega64, ATmega8, ATmega8515, ATmega8535, ATmega88P,
ATmega168, ATmega48, ATmega88, ATmega640, ATmega1280, ATmega1281,
ATmega2560, ATmega2561, ATmega324P,
ATmega164P, ATmega644P, ATmega644,
ATmega16HVA, ATtiny2313, ATtiny28,
ATtiny48, ATtiny261, ATtiny461, ATtiny861,
AT90USB162,
AT90USB82,
AT90USB1287,
AT90USB1286,
AT90USB647, AT90USB646
22.16
<avr/interrupt.h>: Interrupts
251
INT2_vect
SIG_INTERRUPT2
External Interrupt
Request 2
INT3_vect
SIG_INTERRUPT3
External Interrupt
Request 3
INT4_vect
SIG_INTERRUPT4
External Interrupt
Request 4
INT5_vect
SIG_INTERRUPT5
External Interrupt
Request 5
INT6_vect
SIG_INTERRUPT6
External Interrupt
Request 6
INT7_vect
SIG_INTERRUPT7
External Interrupt
Request 7
IO_PINS_vect
SIG_PIN,
SIG_PIN_CHANGE
SIG_LCD
External Interrupt
Request 0
SIG_PIN
Low-level Input
on Port B
LCD_vect
LOWLEVEL_IO_PINS_vect
LCD Start
Frame
of
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
AT90PWM3, AT90PWM2, AT90PWM1,
AT90CAN128, AT90CAN32, AT90CAN64,
ATmega103, ATmega128, ATmega1284P,
ATmega16, ATmega161, ATmega162,
ATmega32, ATmega323, ATmega32HVB,
ATmega406, ATmega64, ATmega8515, ATmega8535, ATmega640, ATmega1280,
ATmega1281,
ATmega2560,
ATmega2561, ATmega324P, ATmega164P,
ATmega644P,
ATmega644,
ATmega16HVA, AT90USB162, AT90USB82,
AT90USB1287,
AT90USB1286,
AT90USB647, AT90USB646
AT90PWM3, AT90PWM2, AT90PWM1,
AT90CAN128, AT90CAN32, AT90CAN64,
ATmega103, ATmega128, ATmega32HVB,
ATmega406, ATmega64, ATmega640,
ATmega1280, ATmega1281, ATmega2560,
ATmega2561, AT90USB162, AT90USB82,
AT90USB1287,
AT90USB1286,
AT90USB647, AT90USB646
AT90CAN128, AT90CAN32, AT90CAN64,
ATmega103,
ATmega128,
ATmega64,
ATmega640,
ATmega1280,
ATmega1281,
ATmega2560,
ATmega2561, AT90USB162, AT90USB82,
AT90USB1287,
AT90USB1286,
AT90USB647, AT90USB646
AT90CAN128, AT90CAN32, AT90CAN64,
ATmega103,
ATmega128,
ATmega64,
ATmega640,
ATmega1280,
ATmega1281,
ATmega2560,
ATmega2561, AT90USB162, AT90USB82,
AT90USB1287,
AT90USB1286,
AT90USB647, AT90USB646
AT90CAN128, AT90CAN32, AT90CAN64,
ATmega103,
ATmega128,
ATmega64,
ATmega640,
ATmega1280,
ATmega1281,
ATmega2560,
ATmega2561, AT90USB162, AT90USB82,
AT90USB1287,
AT90USB1286,
AT90USB647, AT90USB646
AT90CAN128, AT90CAN32, AT90CAN64,
ATmega103,
ATmega128,
ATmega64,
ATmega640,
ATmega1280,
ATmega1281,
ATmega2560,
ATmega2561, AT90USB162, AT90USB82,
AT90USB1287,
AT90USB1286,
AT90USB647, AT90USB646
ATtiny11, ATtiny12, ATtiny15, ATtiny26
ATmega169, ATmega169P, ATmega329,
ATmega3290, ATmega3290P, ATmega649,
ATmega6490
ATtiny28
22.16
<avr/interrupt.h>: Interrupts
OVRIT_vect
SIG_CAN_OVERFLOW1
SIG_PIN_CHANGE0
CAN
Timer
Overrun
Pin Change Interrupt Request 0
PCINT1_vect
SIG_PIN_CHANGE1
Pin Change Interrupt Request 1
PCINT2_vect
SIG_PIN_CHANGE2
Pin Change Interrupt Request 2
PCINT3_vect
SIG_PIN_CHANGE3
Pin Change Interrupt Request 3
PCINT_vect
SIG_PIN_CHANGE,
SIG_PCINT
SIG_PSC0_CAPTURE
SIG_PSC0_END_CYCLE
SIG_PSC1_CAPTURE
SIG_PSC1_END_CYCLE
SIG_PSC2_CAPTURE
PCINT0_vect
PSC0_CAPT_vect
PSC0_EC_vect
PSC1_CAPT_vect
PSC1_EC_vect
PSC2_CAPT_vect
252
AT90CAN128, AT90CAN32, AT90CAN64
ATmega162, ATmega165, ATmega165P,
ATmega168P, ATmega169, ATmega169P,
ATmega325, ATmega3250, ATmega3250P,
ATmega328P, ATmega329, ATmega3290,
ATmega3290P,
ATmega32HVB,
ATmega406,
ATmega48P,
ATmega645,
ATmega6450, ATmega649, ATmega6490,
ATmega88P, ATmega168,
ATmega48,
ATmega88, ATmega640, ATmega1280,
ATmega1281,
ATmega2560,
ATmega2561, ATmega324P, ATmega164P,
ATmega644P, ATmega644,
ATtiny13,
ATtiny43U, ATtiny48, ATtiny24, ATtiny44, ATtiny84, ATtiny45, ATtiny25,
ATtiny85, AT90USB162, AT90USB82,
AT90USB1287,
AT90USB1286,
AT90USB647, AT90USB646
ATmega162, ATmega165, ATmega165P,
ATmega168P, ATmega169, ATmega169P,
ATmega325, ATmega3250, ATmega3250P,
ATmega328P, ATmega329, ATmega3290,
ATmega3290P,
ATmega32HVB,
ATmega406,
ATmega48P,
ATmega645,
ATmega6450, ATmega649, ATmega6490,
ATmega88P, ATmega168,
ATmega48,
ATmega88, ATmega640, ATmega1280,
ATmega1281, ATmega2560, ATmega2561,
ATmega324P, ATmega164P, ATmega644P,
ATmega644, ATtiny43U, ATtiny48, ATtiny24, ATtiny44, ATtiny84, AT90USB162,
AT90USB82
ATmega3250, ATmega3250P, ATmega328P,
ATmega3290, ATmega3290P, ATmega48P,
ATmega6450, ATmega6490, ATmega88P,
ATmega168, ATmega48, ATmega88, ATmega640, ATmega1280, ATmega1281, ATmega2560, ATmega2561, ATmega324P, ATmega164P, ATmega644P, ATmega644, ATtiny48
ATmega3250, ATmega3250P, ATmega3290,
ATmega3290P, ATmega6450, ATmega6490,
ATmega324P, ATmega164P, ATmega644P,
ATmega644, ATtiny48
ATtiny2313, ATtiny261, ATtiny461, ATtiny861
PSC0
Capture
Event
PSC0 End Cycle
AT90PWM3, AT90PWM2, AT90PWM1
PSC1
Capture
Event
PSC1 End Cycle
AT90PWM3, AT90PWM2, AT90PWM1
PSC2
Event
AT90PWM3, AT90PWM2, AT90PWM1
Capture
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
AT90PWM3, AT90PWM2, AT90PWM1
AT90PWM3, AT90PWM2, AT90PWM1
22.16
<avr/interrupt.h>: Interrupts
253
PSC2_EC_vect
SPI_STC_vect
SIG_PSC2_END_CYCLE
SIG_SPI
PSC2 End Cycle
AT90PWM3, AT90PWM2, AT90PWM1
Serial Transfer
Complete
SPM_RDY_vect
SIG_SPM_READY
Store
Program
Memory Ready
SPM_READY_vect
SIG_SPM_READY
Store
Program
Memory Read
TIM0_COMPA_vect
SIG_OUTPUT_COMPARE0A
SIG_OUTPUT_COMPARE0B
SIG_OVERFLOW0
SIG_INPUT_CAPTURE1
Timer/Counter
Compare Match
A
Timer/Counter
Compare Match
B
Timer/Counter0
Overflow
Timer/Counter1
Capture Event
AT90S2333, AT90S4414, AT90S4433,
AT90S4434, AT90S8515, AT90S8535,
AT90PWM216,
AT90PWM2B,
AT90PWM316,
AT90PWM3B,
AT90PWM3, AT90PWM2, AT90PWM1,
AT90CAN128, AT90CAN32, AT90CAN64,
ATmega103, ATmega128, ATmega1284P,
ATmega16, ATmega161, ATmega162,
ATmega163, ATmega165, ATmega165P,
ATmega168P, ATmega169, ATmega169P,
ATmega32, ATmega323, ATmega325,
ATmega3250, ATmega3250P, ATmega328P,
ATmega329, ATmega3290, ATmega3290P,
ATmega32HVB, ATmega48P, ATmega64,
ATmega645, ATmega6450, ATmega649,
ATmega6490, ATmega8, ATmega8515,
ATmega8535, ATmega88P, ATmega168,
ATmega48, ATmega88, ATmega640, ATmega1280, ATmega1281, ATmega2560,
ATmega2561, ATmega324P, ATmega164P,
ATmega644P, ATmega644, ATmega16HVA,
ATtiny48, AT90USB162, AT90USB82,
AT90USB1287,
AT90USB1286,
AT90USB647, AT90USB646
ATmega16, ATmega162, ATmega32, ATmega323, ATmega8, ATmega8515, ATmega8535
AT90PWM3, AT90PWM2, AT90PWM1,
AT90CAN128, AT90CAN32, AT90CAN64,
ATmega128, ATmega1284P, ATmega165,
ATmega165P, ATmega168P, ATmega169,
ATmega169P, ATmega325, ATmega3250,
ATmega3250P, ATmega328P, ATmega329,
ATmega3290, ATmega3290P, ATmega406,
ATmega48P, ATmega64,
ATmega645,
ATmega6450, ATmega649, ATmega6490,
ATmega88P, ATmega168,
ATmega48,
ATmega88, ATmega640, ATmega1280,
ATmega1281, ATmega2560, ATmega2561,
ATmega324P, ATmega164P, ATmega644P,
ATmega644, AT90USB162, AT90USB82,
AT90USB1287,
AT90USB1286,
AT90USB647, AT90USB646
ATtiny13, ATtiny43U, ATtiny24, ATtiny44,
ATtiny84, ATtiny45, ATtiny25, ATtiny85
TIM0_COMPB_vect
TIM0_OVF_vect
TIM1_CAPT_vect
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
ATtiny13, ATtiny43U, ATtiny24, ATtiny44,
ATtiny84, ATtiny45, ATtiny25, ATtiny85
ATtiny13, ATtiny43U, ATtiny24, ATtiny44,
ATtiny84, ATtiny45, ATtiny25, ATtiny85
ATtiny24, ATtiny44, ATtiny84
22.16
<avr/interrupt.h>: Interrupts
TIM1_COMPA_vect
SIG_OUTPUT_COMPARE1A
SIG_OUTPUT_COMPARE1B
SIG_OVERFLOW1
SIG_INPUT_CAPTURE0
SIG_OUTPUT_COMPARE0A
Timer/Counter1
Compare Match
A
Timer/Counter1
Compare Match
B
Timer/Counter1
Overflow
ADC Conversion
Complete
TimerCounter0
Compare Match
A
TIMER0_COMPB_vect
SIG_OUTPUT_COMPARE0B,
SIG_OUTPUT_COMPARE0_B
Timer Counter 0
Compare Match
B
TIMER0_COMP_A_vect
SIG_OUTPUT_COMPARE0A,
SIG_OUTPUT_COMPARE0_A
SIG_OUTPUT_COMPARE0
Timer/Counter0
Compare Match
A
SIG_OVERFLOW0
Timer/Counter0
Overflow
TIM1_COMPB_vect
TIM1_OVF_vect
TIMER0_CAPT_vect
TIMER0_COMPA_vect
TIMER0_COMP_vect
TIMER0_OVF0_vect
Timer/Counter0
Compare Match
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
254
ATtiny24, ATtiny44, ATtiny84, ATtiny45,
ATtiny25, ATtiny85
ATtiny24, ATtiny44, ATtiny84, ATtiny45,
ATtiny25, ATtiny85
ATtiny24, ATtiny44, ATtiny84, ATtiny45,
ATtiny25, ATtiny85
ATtiny261, ATtiny461, ATtiny861
ATmega168, ATmega48, ATmega88, ATmega640, ATmega1280, ATmega1281,
ATmega2560,
ATmega2561,
ATmega324P, ATmega164P, ATmega644P,
ATmega644, ATmega16HVA, ATtiny2313,
ATtiny48, ATtiny261, ATtiny461, ATtiny861,
AT90USB162,
AT90USB82,
AT90USB1287,
AT90USB1286,
AT90USB647, AT90USB646
AT90PWM3, AT90PWM2, AT90PWM1,
ATmega1284P, ATmega168P, ATmega328P,
ATmega32HVB,
ATmega48P,
ATmega88P, ATmega168, ATmega48, ATmega88,
ATmega640,
ATmega1280,
ATmega1281, ATmega2560, ATmega2561,
ATmega324P, ATmega164P, ATmega644P,
ATmega644, ATmega16HVA, ATtiny2313,
ATtiny48, ATtiny261, ATtiny461, ATtiny861,
AT90USB162,
AT90USB82,
AT90USB1287,
AT90USB1286,
AT90USB647, AT90USB646
AT90PWM3, AT90PWM2, AT90PWM1
AT90CAN128, AT90CAN32, AT90CAN64,
ATmega103, ATmega128, ATmega16, ATmega161, ATmega162, ATmega165, ATmega165P, ATmega169, ATmega169P, ATmega32, ATmega323, ATmega325, ATmega3250, ATmega3250P, ATmega329, ATmega3290, ATmega3290P, ATmega64, ATmega645, ATmega6450, ATmega649, ATmega6490, ATmega8515, ATmega8535
AT90S2313, AT90S2323, AT90S2343, ATtiny22, ATtiny26
22.16
<avr/interrupt.h>: Interrupts
TIMER0_OVF_vect
SIG_OVERFLOW0
Timer/Counter0
Overflow
TIMER1_CAPT1_vect
TIMER1_CAPT_vect
SIG_INPUT_CAPTURE1
SIG_INPUT_CAPTURE1
Timer/Counter1
Capture Event
Timer/Counter
Capture Event
TIMER1_CMPA_vect
SIG_OUTPUT_COMPARE1A
Timer/Counter1
Compare Match
1A
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
255
AT90S1200, AT90S2333, AT90S4414,
AT90S4433, AT90S4434, AT90S8515,
AT90S8535,
AT90PWM216,
AT90PWM2B,
AT90PWM316,
AT90PWM3B, AT90PWM3, AT90PWM2,
AT90PWM1, AT90CAN128, AT90CAN32,
AT90CAN64, ATmega103, ATmega128,
ATmega1284P, ATmega16, ATmega161,
ATmega162, ATmega163, ATmega165,
ATmega165P, ATmega168P, ATmega169,
ATmega169P, ATmega32, ATmega323,
ATmega325, ATmega3250, ATmega3250P,
ATmega328P, ATmega329, ATmega3290,
ATmega3290P,
ATmega32HVB,
ATmega48P, ATmega64, ATmega645, ATmega6450, ATmega649, ATmega6490,
ATmega8, ATmega8515, ATmega8535,
ATmega88P, ATmega168,
ATmega48,
ATmega88, ATmega640, ATmega1280,
ATmega1281, ATmega2560, ATmega2561,
ATmega324P, ATmega164P, ATmega644P,
ATmega644, ATmega16HVA, ATtiny11,
ATtiny12, ATtiny15, ATtiny2313, ATtiny28,
ATtiny48, ATtiny261, ATtiny461, ATtiny861,
AT90USB162,
AT90USB82,
AT90USB1287,
AT90USB1286,
AT90USB647, AT90USB646
AT90S2313
AT90S2333, AT90S4414, AT90S4433,
AT90S4434, AT90S8515, AT90S8535,
AT90PWM216,
AT90PWM2B,
AT90PWM316,
AT90PWM3B,
AT90PWM3, AT90PWM2, AT90PWM1,
AT90CAN128, AT90CAN32, AT90CAN64,
ATmega103, ATmega128, ATmega1284P,
ATmega16, ATmega161, ATmega162,
ATmega163, ATmega165, ATmega165P,
ATmega168P, ATmega169, ATmega169P,
ATmega32, ATmega323, ATmega325,
ATmega3250,
ATmega3250P,
ATmega328P, ATmega329, ATmega3290,
ATmega3290P, ATmega48P, ATmega64,
ATmega645, ATmega6450, ATmega649,
ATmega6490, ATmega8, ATmega8515,
ATmega8535, ATmega88P, ATmega168,
ATmega48, ATmega88, ATmega640, ATmega1280, ATmega1281, ATmega2560,
ATmega2561, ATmega324P, ATmega164P,
ATmega644P, ATmega644, ATtiny2313,
ATtiny48, AT90USB162, AT90USB82,
AT90USB1287,
AT90USB1286,
AT90USB647, AT90USB646
ATtiny26
22.16
<avr/interrupt.h>: Interrupts
TIMER1_CMPB_vect
TIMER1_COMP1_vect
TIMER1_COMPA_vect
TIMER1_COMPB_vect
256
SIG_OUTPUT_COMPARE1B
SIG_OUTPUT_COMPARE1A
SIG_OUTPUT_COMPARE1A
Timer/Counter1
Compare Match
1B
Timer/Counter1
Compare Match
ATtiny26
Timer/Counter1
Compare Match
A
SIG_OUTPUT_COMPARE1B
Timer/Counter1
Compare MatchB
AT90S4414, AT90S4434, AT90S8515,
AT90S8535,
AT90PWM216,
AT90PWM2B,
AT90PWM316,
AT90PWM3B, AT90PWM3, AT90PWM2,
AT90PWM1, AT90CAN128, AT90CAN32,
AT90CAN64, ATmega103, ATmega128,
ATmega1284P, ATmega16, ATmega161,
ATmega162, ATmega163, ATmega165,
ATmega165P, ATmega168P, ATmega169,
ATmega169P, ATmega32, ATmega323,
ATmega325, ATmega3250, ATmega3250P,
ATmega328P, ATmega329, ATmega3290,
ATmega3290P,
ATmega32HVB,
ATmega48P, ATmega64, ATmega645, ATmega6450, ATmega649, ATmega6490,
ATmega8, ATmega8515, ATmega8535,
ATmega88P, ATmega168,
ATmega48,
ATmega88, ATmega640, ATmega1280,
ATmega1281, ATmega2560, ATmega2561,
ATmega324P, ATmega164P, ATmega644P,
ATmega644, ATmega16HVA, ATtiny2313,
ATtiny48, ATtiny261, ATtiny461, ATtiny861,
AT90USB162,
AT90USB82,
AT90USB1287,
AT90USB1286,
AT90USB647, AT90USB646
AT90S4414, AT90S4434, AT90S8515,
AT90S8535,
AT90PWM216,
AT90PWM2B,
AT90PWM316,
AT90PWM3B, AT90PWM3, AT90PWM2,
AT90PWM1, AT90CAN128, AT90CAN32,
AT90CAN64, ATmega103, ATmega128,
ATmega1284P, ATmega16, ATmega161,
ATmega162, ATmega163, ATmega165,
ATmega165P, ATmega168P, ATmega169,
ATmega169P, ATmega32, ATmega323,
ATmega325, ATmega3250, ATmega3250P,
ATmega328P, ATmega329, ATmega3290,
ATmega3290P,
ATmega32HVB,
ATmega48P, ATmega64, ATmega645, ATmega6450, ATmega649, ATmega6490,
ATmega8, ATmega8515, ATmega8535,
ATmega88P, ATmega168,
ATmega48,
ATmega88, ATmega640, ATmega1280,
ATmega1281, ATmega2560, ATmega2561,
ATmega324P, ATmega164P, ATmega644P,
ATmega644, ATmega16HVA, ATtiny2313,
ATtiny48, ATtiny261, ATtiny461, ATtiny861,
AT90USB162,
AT90USB82,
AT90USB1287,
AT90USB1286,
AT90USB647, AT90USB646
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
AT90S2313
22.16
<avr/interrupt.h>: Interrupts
TIMER1_COMPC_vect
SIG_OUTPUT_COMPARE1C
Timer/Counter1
Compare Match
C
TIMER1_COMPD_vect
SIG_OUTPUT_COMPARE0D
SIG_OUTPUT_COMPARE1A
SIG_OVERFLOW1
SIG_OVERFLOW1
Timer/Counter1
Compare Match
D
Timer/Counter1
Compare Match
TIMER2_COMPA_vect
SIG_OUTPUT_COMPARE2A
Timer/Counter2
Compare Match
A
TIMER2_COMPB_vect
SIG_OUTPUT_COMPARE2B
Timer/Counter2
Compare Match
A
TIMER1_COMP_vect
TIMER1_OVF1_vect
TIMER1_OVF_vect
Timer/Counter1
Overflow
Timer/Counter1
Overflow
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
257
AT90CAN128, AT90CAN32, AT90CAN64,
ATmega128, ATmega64, ATmega640,
ATmega1280, ATmega1281, ATmega2560,
ATmega2561, AT90USB162, AT90USB82,
AT90USB1287,
AT90USB1286,
AT90USB647, AT90USB646
ATtiny261, ATtiny461, ATtiny861
AT90S2333, AT90S4433, ATtiny15
AT90S2313, ATtiny26
AT90S2333, AT90S4414, AT90S4433,
AT90S4434, AT90S8515, AT90S8535,
AT90PWM216,
AT90PWM2B,
AT90PWM316,
AT90PWM3B,
AT90PWM3, AT90PWM2, AT90PWM1,
AT90CAN128, AT90CAN32, AT90CAN64,
ATmega103, ATmega128, ATmega1284P,
ATmega16, ATmega161, ATmega162,
ATmega163, ATmega165, ATmega165P,
ATmega168P, ATmega169, ATmega169P,
ATmega32, ATmega323, ATmega325,
ATmega3250, ATmega3250P, ATmega328P,
ATmega329, ATmega3290, ATmega3290P,
ATmega32HVB,
ATmega48P,
ATmega64,
ATmega645,
ATmega6450,
ATmega649, ATmega6490, ATmega8,
ATmega8515, ATmega8535, ATmega88P,
ATmega168, ATmega48, ATmega88, ATmega640, ATmega1280, ATmega1281,
ATmega2560, ATmega2561, ATmega324P,
ATmega164P, ATmega644P, ATmega644,
ATmega16HVA, ATtiny15, ATtiny2313,
ATtiny48, ATtiny261, ATtiny461, ATtiny861,
AT90USB162,
AT90USB82,
AT90USB1287,
AT90USB1286,
AT90USB647, AT90USB646
ATmega168, ATmega48, ATmega88, ATmega640, ATmega1280, ATmega1281,
ATmega2560,
ATmega2561,
ATmega324P, ATmega164P, ATmega644P, ATmega644, AT90USB1287, AT90USB1286,
AT90USB647, AT90USB646
ATmega168, ATmega48, ATmega88, ATmega640, ATmega1280, ATmega1281,
ATmega2560,
ATmega2561,
ATmega324P, ATmega164P, ATmega644P, ATmega644, AT90USB1287, AT90USB1286,
AT90USB647, AT90USB646
22.16
<avr/interrupt.h>: Interrupts
TIMER2_COMP_vect
SIG_OUTPUT_COMPARE2
Timer/Counter2
Compare Match
TIMER2_OVF_vect
SIG_OVERFLOW2
Timer/Counter2
Overflow
TIMER3_CAPT_vect
SIG_INPUT_CAPTURE3
Timer/Counter3
Capture Event
TIMER3_COMPA_vect
SIG_OUTPUT_COMPARE3A
Timer/Counter3
Compare Match
A
TIMER3_COMPB_vect
SIG_OUTPUT_COMPARE3B
Timer/Counter3
Compare Match
B
TIMER3_COMPC_vect
SIG_OUTPUT_COMPARE3C
Timer/Counter3
Compare Match
C
TIMER3_OVF_vect
SIG_OVERFLOW3
Timer/Counter3
Overflow
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
258
AT90S4434, AT90S8535, AT90CAN128,
AT90CAN32, AT90CAN64, ATmega103,
ATmega128, ATmega16, ATmega161, ATmega162, ATmega163, ATmega165, ATmega165P, ATmega169, ATmega169P, ATmega32, ATmega323, ATmega325, ATmega3250, ATmega3250P, ATmega329, ATmega3290, ATmega3290P, ATmega64, ATmega645, ATmega6450, ATmega649, ATmega6490, ATmega8, ATmega8535
AT90S4434, AT90S8535, AT90CAN128,
AT90CAN32, AT90CAN64, ATmega103,
ATmega128, ATmega1284P, ATmega16,
ATmega161, ATmega162, ATmega163,
ATmega165, ATmega165P, ATmega168P,
ATmega169, ATmega169P, ATmega32, ATmega323,
ATmega325,
ATmega3250,
ATmega3250P,
ATmega328P,
ATmega329, ATmega3290, ATmega3290P,
ATmega48P, ATmega64,
ATmega645,
ATmega6450, ATmega649, ATmega6490,
ATmega8, ATmega8535, ATmega88P,
ATmega168, ATmega48, ATmega88, ATmega640, ATmega1280, ATmega1281,
ATmega2560,
ATmega2561,
ATmega324P, ATmega164P, ATmega644P, ATmega644, AT90USB1287, AT90USB1286,
AT90USB647, AT90USB646
AT90CAN128, AT90CAN32, AT90CAN64,
ATmega128, ATmega1284P, ATmega162,
ATmega64, ATmega640, ATmega1280,
ATmega1281,
ATmega2560,
ATmega2561, AT90USB1287, AT90USB1286,
AT90USB647, AT90USB646
AT90CAN128, AT90CAN32, AT90CAN64,
ATmega128, ATmega1284P, ATmega162,
ATmega64, ATmega640, ATmega1280,
ATmega1281,
ATmega2560,
ATmega2561, AT90USB1287, AT90USB1286,
AT90USB647, AT90USB646
AT90CAN128, AT90CAN32, AT90CAN64,
ATmega128, ATmega1284P, ATmega162,
ATmega64, ATmega640, ATmega1280,
ATmega1281,
ATmega2560,
ATmega2561, AT90USB1287, AT90USB1286,
AT90USB647, AT90USB646
AT90CAN128, AT90CAN32, AT90CAN64,
ATmega128, ATmega64, ATmega640, ATmega1280, ATmega1281, ATmega2560, ATmega2561, AT90USB1287, AT90USB1286,
AT90USB647, AT90USB646
AT90CAN128, AT90CAN32, AT90CAN64,
ATmega128, ATmega1284P, ATmega162,
ATmega64, ATmega640, ATmega1280,
ATmega1281,
ATmega2560,
ATmega2561, AT90USB1287, AT90USB1286,
AT90USB647, AT90USB646
22.16
<avr/interrupt.h>: Interrupts
TIMER4_CAPT_vect
TIMER4_COMPA_vect
259
SIG_INPUT_CAPTURE4
SIG_OUTPUT_COMPARE4A
SIG_OUTPUT_COMPARE4B
SIG_OUTPUT_COMPARE4C
SIG_OVERFLOW4
SIG_INPUT_CAPTURE5
SIG_OUTPUT_COMPARE5A
SIG_OUTPUT_COMPARE5B
SIG_OUTPUT_COMPARE5C
SIG_OVERFLOW5
SIG_2WIRE_SERIAL
Timer/Counter4
Capture Event
Timer/Counter4
Compare Match
A
Timer/Counter4
Compare Match
B
Timer/Counter4
Compare Match
C
Timer/Counter4
Overflow
Timer/Counter5
Capture Event
Timer/Counter5
Compare Match
A
Timer/Counter5
Compare Match
B
Timer/Counter5
Compare Match
C
Timer/Counter5
Overflow
2-wire Serial Interface
TXDONE_vect
SIG_TXDONE
TXEMPTY_vect
SIG_TXBE
UART0_RX_vect
SIG_UART0_RECV
SIG_UART0_TRANS
SIG_UART0_DATA
SIG_UART1_RECV
Transmission
Done, Bit Timer
Flag 2 Interrupt
Transmit Buffer
Empty, Bit Itmer
Flag 0 Interrupt
UART0,
Rx
Complete
TIMER4_COMPB_vect
TIMER4_COMPC_vect
TIMER4_OVF_vect
TIMER5_CAPT_vect
TIMER5_COMPA_vect
TIMER5_COMPB_vect
TIMER5_COMPC_vect
TIMER5_OVF_vect
TWI_vect
UART0_TX_vect
UART0_UDRE_vect
UART1_RX_vect
UART0,
Complete
ATmega640, ATmega1280, ATmega1281,
ATmega2560, ATmega2561
ATmega640, ATmega1280, ATmega1281,
ATmega2560, ATmega2561
ATmega640, ATmega1280, ATmega1281,
ATmega2560, ATmega2561
ATmega640, ATmega1280, ATmega1281,
ATmega2560, ATmega2561
ATmega640, ATmega1280, ATmega1281,
ATmega2560, ATmega2561
ATmega640, ATmega1280, ATmega1281,
ATmega2560, ATmega2561
ATmega640, ATmega1280, ATmega1281,
ATmega2560, ATmega2561
ATmega640, ATmega1280, ATmega1281,
ATmega2560, ATmega2561
ATmega640, ATmega1280, ATmega1281,
ATmega2560, ATmega2561
ATmega640, ATmega1280, ATmega1281,
ATmega2560, ATmega2561
AT90CAN128, AT90CAN32, AT90CAN64,
ATmega128, ATmega1284P, ATmega16,
ATmega163, ATmega168P, ATmega32, ATmega323, ATmega328P, ATmega32HVB,
ATmega406,
ATmega48P, ATmega64,
ATmega8, ATmega8535, ATmega88P,
ATmega168, ATmega48, ATmega88, ATmega640, ATmega1280, ATmega1281,
ATmega2560, ATmega2561, ATmega324P,
ATmega164P, ATmega644P, ATmega644,
ATtiny48, AT90USB1287, AT90USB1286,
AT90USB647, AT90USB646
AT86RF401
AT86RF401
ATmega161
Tx
ATmega161
UART0
Data
Register Empty
ATmega161
UART1,
Complete
ATmega161
Rx
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
22.16
<avr/interrupt.h>: Interrupts
UART1_TX_vect
260
UART1,
Complete
UART_RX_vect
SIG_UART1_TRANS
SIG_UART1_DATA
SIG_UART_RECV
UART_TX_vect
SIG_UART_TRANS
UART, Tx Complete
UART_UDRE_vect
SIG_UART_DATA
UART Data Register Empty
USART0_RXC_vect
SIG_USART0_RECV
SIG_UART0_RECV
USART0,
Complete
Rx
USART0,
Complete
Rx
SIG_USART0_TRANS
SIG_UART0_TRANS
USART0,
Complete
Tx
USART0,
Complete
Tx
USART0_UDRE_vect
SIG_UART0_DATA
USART0
Data
Register Empty
USART1_RXC_vect
SIG_USART1_RECV
USART1,
Complete
UART1_UDRE_vect
USART0_RX_vect
USART0_TXC_vect
USART0_TX_vect
Tx
ATmega161
UART1
Data
Register Empty
ATmega161
UART, Rx Complete
AT90S2313, AT90S2333,
AT90S4433, AT90S4434,
AT90S8535, ATmega103,
ATmega8515
AT90S2313, AT90S2333,
AT90S4433, AT90S4434,
AT90S8535, ATmega103,
ATmega8515
AT90S2313, AT90S2333,
AT90S4433, AT90S4434,
AT90S8535, ATmega103,
ATmega8515
ATmega162
Rx
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
AT90S4414,
AT90S8515,
ATmega163,
AT90S4414,
AT90S8515,
ATmega163,
AT90S4414,
AT90S8515,
ATmega163,
AT90CAN128, AT90CAN32, AT90CAN64,
ATmega128, ATmega1284P, ATmega165,
ATmega165P, ATmega169, ATmega169P,
ATmega325, ATmega329, ATmega64, ATmega645, ATmega649, ATmega640, ATmega1280, ATmega1281, ATmega2560, ATmega2561, ATmega324P, ATmega164P, ATmega644P, ATmega644
ATmega162
AT90CAN128, AT90CAN32, AT90CAN64,
ATmega128, ATmega1284P, ATmega165,
ATmega165P, ATmega169, ATmega169P,
ATmega325, ATmega3250, ATmega3250P,
ATmega329, ATmega3290, ATmega3290P,
ATmega64, ATmega645, ATmega6450, ATmega649, ATmega6490, ATmega640, ATmega1280, ATmega1281, ATmega2560, ATmega2561, ATmega324P, ATmega164P, ATmega644P, ATmega644
AT90CAN128, AT90CAN32, AT90CAN64,
ATmega128, ATmega1284P, ATmega162,
ATmega165, ATmega165P, ATmega169,
ATmega169P, ATmega325, ATmega329,
ATmega64, ATmega645, ATmega649,
ATmega640, ATmega1280, ATmega1281,
ATmega2560, ATmega2561, ATmega324P,
ATmega164P, ATmega644P, ATmega644
ATmega162
22.16
<avr/interrupt.h>: Interrupts
261
USART1_RX_vect
SIG_UART1_RECV
USART1,
Complete
Rx
USART1_TXC_vect
SIG_USART1_TRANS
SIG_UART1_TRANS
USART1,
Complete
Tx
USART1,
Complete
Tx
USART1_UDRE_vect
SIG_UART1_DATA
USART1, Data
Register Empty
USART2_RX_vect
SIG_USART2_RECV
SIG_USART2_TRANS
SIG_USART2_DATA
SIG_USART3_RECV
SIG_USART3_TRANS
SIG_USART3_DATA
SIG_USART_RECV, SIG_UART_RECV
SIG_USART_RECV, SIG_UART_RECV
USART2,
Complete
Rx
USART2,
Complete
Tx
ATmega640, ATmega1280, ATmega1281,
ATmega2560, ATmega2561
USART2
Data
register Empty
ATmega640, ATmega1280, ATmega1281,
ATmega2560, ATmega2561
USART3,
Complete
Rx
ATmega640, ATmega1280, ATmega1281,
ATmega2560, ATmega2561
USART3,
Complete
Tx
ATmega640, ATmega1280, ATmega1281,
ATmega2560, ATmega2561
USART3
Data
register Empty
ATmega640, ATmega1280, ATmega1281,
ATmega2560, ATmega2561
USART,
Complete
Rx
ATmega16, ATmega32, ATmega323, ATmega8
USART,
Complete
Rx
AT90PWM3, AT90PWM2, AT90PWM1,
ATmega168P, ATmega3250, ATmega3250P,
ATmega328P, ATmega3290, ATmega3290P,
ATmega48P, ATmega6450, ATmega6490,
ATmega8535, ATmega88P, ATmega168,
ATmega48, ATmega88, ATtiny2313
USART1_TX_vect
USART2_TX_vect
USART2_UDRE_vect
USART3_RX_vect
USART3_TX_vect
USART3_UDRE_vect
USART_RXC_vect
USART_RX_vect
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
AT90CAN128, AT90CAN32, AT90CAN64,
ATmega128, ATmega1284P, ATmega64,
ATmega640, ATmega1280, ATmega1281,
ATmega2560,
ATmega2561,
ATmega324P, ATmega164P, ATmega644P,
ATmega644, AT90USB162, AT90USB82,
AT90USB1287,
AT90USB1286,
AT90USB647, AT90USB646
ATmega162
AT90CAN128, AT90CAN32, AT90CAN64,
ATmega128, ATmega1284P, ATmega64,
ATmega640, ATmega1280, ATmega1281,
ATmega2560,
ATmega2561,
ATmega324P, ATmega164P, ATmega644P,
ATmega644, AT90USB162, AT90USB82,
AT90USB1287,
AT90USB1286,
AT90USB647, AT90USB646
AT90CAN128, AT90CAN32, AT90CAN64,
ATmega128, ATmega1284P, ATmega162,
ATmega64, ATmega640, ATmega1280,
ATmega1281, ATmega2560, ATmega2561,
ATmega324P, ATmega164P, ATmega644P,
ATmega644, AT90USB162, AT90USB82,
AT90USB1287,
AT90USB1286,
AT90USB647, AT90USB646
ATmega640, ATmega1280, ATmega1281,
ATmega2560, ATmega2561
22.16
<avr/interrupt.h>: Interrupts
USART_TXC_vect
262
SIG_USART_TRANS,
SIG_UART_TRANS
SIG_USART_TRANS,
SIG_UART_TRANS
SIG_USART_DATA, SIG_UART_DATA
USART,
Complete
Tx
ATmega16, ATmega32, ATmega323, ATmega8
USART,
Complete
Tx
AT90PWM3, AT90PWM2, AT90PWM1,
ATmega168P, ATmega328P, ATmega48P,
ATmega8535, ATmega88P, ATmega168,
ATmega48, ATmega88, ATtiny2313
USART
Data
Register Empty
USI_OVERFLOW_vect
SIG_USI_OVERFLOW
USI Overflow
USI_OVF_vect
SIG_USI_OVERFLOW
USI Overflow
USI_START_vect
SIG_USI_START
USI Start Condition
USI_STRT_vect
USI_STR_vect
WATCHDOG_vect
SIG_USI_START
SIG_USI_START
SIG_WATCHDOG_TIMEOUT
SIG_WATCHDOG_TIMEOUT,
SIG_WDT_OVERFLOW
SIG_WDT,
SIG_WATCHDOG_TIMEOUT
USI Start
AT90PWM3, AT90PWM2, AT90PWM1,
ATmega16, ATmega168P, ATmega32, ATmega323, ATmega3250, ATmega3250P, ATmega328P, ATmega3290, ATmega3290P,
ATmega48P, ATmega6450, ATmega6490,
ATmega8, ATmega8535, ATmega88P, ATmega168, ATmega48, ATmega88, ATtiny2313
ATmega165, ATmega165P, ATmega169,
ATmega169P, ATmega325, ATmega3250,
ATmega3250P, ATmega329, ATmega3290,
ATmega3290P, ATmega645, ATmega6450,
ATmega649, ATmega6490, ATtiny2313
ATtiny26, ATtiny43U, ATtiny24, ATtiny44,
ATtiny84, ATtiny45, ATtiny25, ATtiny85,
ATtiny261, ATtiny461, ATtiny861
ATmega165, ATmega165P, ATmega169,
ATmega169P, ATmega325, ATmega3250,
ATmega3250P, ATmega329, ATmega3290,
ATmega3290P, ATmega645, ATmega6450,
ATmega649, ATmega6490, ATtiny2313,
ATtiny43U, ATtiny45, ATtiny25, ATtiny85,
ATtiny261, ATtiny461, ATtiny861
ATtiny26
USI START
ATtiny24, ATtiny44, ATtiny84
Watchdog Timeout
ATtiny24, ATtiny44, ATtiny84
Watchdog Timer
Overflow
ATtiny2313
Watchdog Timeout Interrupt
AT90PWM3, AT90PWM2, AT90PWM1,
ATmega1284P, ATmega168P, ATmega328P,
ATmega32HVB, ATmega406, ATmega48P,
ATmega88P, ATmega168,
ATmega48,
ATmega88, ATmega640, ATmega1280,
ATmega1281, ATmega2560, ATmega2561,
ATmega324P, ATmega164P, ATmega644P,
ATmega644, ATmega16HVA, ATtiny13,
ATtiny43U, ATtiny48, ATtiny45, ATtiny25,
ATtiny85, ATtiny261, ATtiny461, ATtiny861,
AT90USB162,
AT90USB82,
AT90USB1287,
AT90USB1286,
AT90USB647, AT90USB646
USART_TX_vect
USART_UDRE_vect
WDT_OVERFLOW_vect
WDT_vect
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22.16
<avr/interrupt.h>: Interrupts
22.16.2
Define Documentation
22.16.2.1
263
#define BADISR_vect
#include <avr/interrupt.h>
This is a vector which is aliased to __vector_default, the vector executed when an ISR
fires with no accompanying ISR handler. This may be used along with the ISR() macro
to create a catch-all for undefined but used ISRs for debugging purposes.
22.16.2.2
#define cli(
)
#include <avr/interrupt.h>
Disables all interrupts by clearing the global interrupt mask. This function actually
compiles into a single line of assembly, so there is no function call overhead. However,
the macro also implies a memory barrier which can cause additional loss of optimization.
In order to implement atomic access to multi-byte objects, consider using the macros
from <util/atomic.h>, rather than implementing them manually with cli() and sei().
22.16.2.3
#define EMPTY_INTERRUPT( vector )
#include <avr/interrupt.h>
Defines an empty interrupt handler function. This will not generate any prolog or
epilog code and will only return from the ISR. Do not define a function body as this
will define it for you. Example:
EMPTY_INTERRUPT(ADC_vect);
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22.16
<avr/interrupt.h>: Interrupts
22.16.2.4
264
#define ISR( vector, attributes )
#include <avr/interrupt.h>
Introduces an interrupt handler function (interrupt service routine) that runs with global
interrupts initially disabled by default with no attributes specified.
The attributes are optional and alter the behaviour and resultant generated code of the
interrupt routine. Multiple attributes may be used for a single function, with a space
seperating each attribute.
Valid attributes are ISR_BLOCK, ISR_NOBLOCK, ISR_NAKED and ISR_ALIASOF(vect).
vector must be one of the interrupt vector names that are valid for the particular
MCU type.
22.16.2.5
#define ISR_ALIAS( vector, target_vector )
#include <avr/interrupt.h>
Aliases a given vector to another one in the same manner as the ISR_ALIASOF attribute for the ISR() macro. Unlike the ISR_ALIASOF attribute macro however, this is
compatible for all versions of GCC rather than just GCC version 4.2 onwards.
Note
This macro creates a trampoline function for the aliased macro. This will result in
a two cycle penalty for the aliased vector compared to the ISR the vector is aliased
to, due to the JMP/RJMP opcode used.
Deprecated
For new code, the use of ISR(..., ISR_ALIASOF(...)) is recommended.
Example:
ISR(INT0_vect)
{
PORTB = 42;
}
ISR_ALIAS(INT1_vect, INT0_vect);
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22.16
<avr/interrupt.h>: Interrupts
22.16.2.6
265
#define ISR_ALIASOF( target_vector )
#include <avr/interrupt.h>
The ISR is linked to another ISR, specified by the vect parameter. This is compatible
with GCC 4.2 and greater only.
Use this attribute in the attributes parameter of the ISR macro.
22.16.2.7
#define ISR_BLOCK
# include <avr/interrupt.h>
Identical to an ISR with no attributes specified. Global interrupts are initially disabled
by the AVR hardware when entering the ISR, without the compiler modifying this state.
Use this attribute in the attributes parameter of the ISR macro.
22.16.2.8
#define ISR_NAKED
# include <avr/interrupt.h>
ISR is created with no prologue or epilogue code. The user code is responsible for
preservation of the machine state including the SREG register, as well as placing a
reti() at the end of the interrupt routine.
Use this attribute in the attributes parameter of the ISR macro.
22.16.2.9
#define ISR_NOBLOCK
# include <avr/interrupt.h>
ISR runs with global interrupts initially enabled. The interrupt enable flag is activated
by the compiler as early as possible within the ISR to ensure minimal processing delay
for nested interrupts.
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22.16
<avr/interrupt.h>: Interrupts
266
This may be used to create nested ISRs, however care should be taken to avoid stack
overflows, or to avoid infinitely entering the ISR for those cases where the AVR hardware does not clear the respective interrupt flag before entering the ISR.
Use this attribute in the attributes parameter of the ISR macro.
22.16.2.10
#define reti(
)
#include <avr/interrupt.h>
Returns from an interrupt routine, enabling global interrupts. This should be the last
command executed before leaving an ISR defined with the ISR_NAKED attribute.
This macro actually compiles into a single line of assembly, so there is no function call
overhead.
22.16.2.11
#define sei(
)
#include <avr/interrupt.h>
Enables interrupts by setting the global interrupt mask. This function actually compiles
into a single line of assembly, so there is no function call overhead. However, the macro
also implies a memory barrier which can cause additional loss of optimization.
In order to implement atomic access to multi-byte objects, consider using the macros
from <util/atomic.h>, rather than implementing them manually with cli() and sei().
22.16.2.12
#define SIGNAL( vector )
#include <avr/interrupt.h>
Introduces an interrupt handler function that runs with global interrupts initially disabled.
This is the same as the ISR macro without optional attributes.
Deprecated
Do not use SIGNAL() in new code. Use ISR() instead.
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
22.17
<avr/io.h>: AVR device-specific IO definitions
267
22.17 <avr/io.h>: AVR device-specific IO definitions
#include <avr/io.h>
This header file includes the apropriate IO definitions for the device that has been
specified by the -mmcu= compiler command-line switch. This is done by diverting to the appropriate file <avr/ioXXXX.h> which should never be included directly. Some register names common to all AVR devices are defined directly within
<avr/common.h>, which is included in <avr/io.h>, but most of the details
come from the respective include file.
Note that this file always includes the following files:
#include
#include
#include
#include
<avr/sfr_defs.h>
<avr/portpins.h>
<avr/common.h>
<avr/version.h>
See <avr/sfr_defs.h>: Special function registers for more details about that header file.
Included are definitions of the IO register set and their respective bit values as specified
in the Atmel documentation. Note that inconsistencies in naming conventions, so even
identical functions sometimes get different names on different devices.
Also included are the specific names useable for interrupt function definitions as documented here.
Finally, the following macros are defined:
• RAMEND
The last on-chip RAM address.
• XRAMEND
The last possible RAM location that is addressable. This is equal to RAMEND
for devices that do not allow for external RAM. For devices that allow external
RAM, this will be larger than RAMEND.
• E2END
The last EEPROM address.
• FLASHEND
The last byte address in the Flash program space.
• SPM_PAGESIZE
For devices with bootloader support, the flash pagesize (in bytes) to be used for
the SPM instruction.
• E2PAGESIZE
The size of the EEPROM page.
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22.18
<avr/lock.h>: Lockbit Support
268
22.18 <avr/lock.h>: Lockbit Support
Introduction
The Lockbit API allows a user to specify the lockbit settings for the specific AVR
device they are compiling for. These lockbit settings will be placed in a special section
in the ELF output file, after linking.
Programming tools can take advantage of the lockbit information embedded in the
ELF file, by extracting this information and determining if the lockbits need to be
programmed after programming the Flash and EEPROM memories. This also allows a
single ELF file to contain all the information needed to program an AVR.
To use the Lockbit API, include the <avr/io.h> header file, which in turn automatically
includes the individual I/O header file and the <avr/lock.h> file. These other two files
provides everything necessary to set the AVR lockbits.
Lockbit API
Each I/O header file may define up to 3 macros that controls what kinds of lockbits are
available to the user.
If __LOCK_BITS_EXIST is defined, then two lock bits are available to the user and 3
mode settings are defined for these two bits.
If __BOOT_LOCK_BITS_0_EXIST is defined, then the two BLB0 lock bits are available to the user and 4 mode settings are defined for these two bits.
If __BOOT_LOCK_BITS_1_EXIST is defined, then the two BLB1 lock bits are available to the user and 4 mode settings are defined for these two bits.
If __BOOT_LOCK_APPLICATION_TABLE_BITS_EXIST is defined then two lock
bits are available to set the locking mode for the Application Table Section (which is
used in the XMEGA family).
If __BOOT_LOCK_APPLICATION_BITS_EXIST is defined then two lock bits are
available to set the locking mode for the Application Section (which is used in the
XMEGA family).
If __BOOT_LOCK_BOOT_BITS_EXIST is defined then two lock bits are available
to set the locking mode for the Boot Loader Section (which is used in the XMEGA
family).
The AVR lockbit modes have inverted values, logical 1 for an unprogrammed (disabled) bit and logical 0 for a programmed (enabled) bit. The defined macros for each
individual lock bit represent this in their definition by a bit-wise inversion of a mask.
For example, the LB_MODE_3 macro is defined as:
#define LB_MODE_3
(0xFC)
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22.18
<avr/lock.h>: Lockbit Support
269
‘
To combine the lockbit mode macros together to represent a whole byte, use the bitwise
AND operator, like so:
(LB_MODE_3 & BLB0_MODE_2)
<avr/lock.h> also defines a macro that provides a default lockbit value: LOCKBITS_DEFAULT which is defined to be 0xFF.
See the AVR device specific datasheet for more details about these lock bits and the
available mode settings.
A convenience macro, LOCKMEM, is defined as a GCC attribute for a custom-named
section of ".lock".
A convenience macro, LOCKBITS, is defined that declares a variable, __lock, of type
unsigned char with the attribute defined by LOCKMEM. This variable allows the end
user to easily set the lockbit data.
Note
If a device-specific I/O header file has previously defined LOCKMEM, then LOCKMEM is not redefined. If a device-specific I/O header file has previously defined
LOCKBITS, then LOCKBITS is not redefined. LOCKBITS is currently known to
be defined in the I/O header files for the XMEGA devices.
API Usage Example
Putting all of this together is easy:
#include <avr/io.h>
LOCKBITS = (LB_MODE_1 & BLB0_MODE_3 & BLB1_MODE_4);
int main(void)
{
return 0;
}
Or:
#include <avr/io.h>
unsigned char __lock __attribute__((section (".lock"))) =
(LB_MODE_1 & BLB0_MODE_3 & BLB1_MODE_4);
int main(void)
{
return 0;
}
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<avr/pgmspace.h>: Program Space Utilities
22.19
270
However there are a number of caveats that you need to be aware of to use this API
properly.
Be sure to include <avr/io.h> to get all of the definitions for the API. The LOCKBITS
macro defines a global variable to store the lockbit data. This variable is assigned to
its own linker section. Assign the desired lockbit values immediately in the variable
initialization.
The .lock section in the ELF file will get its values from the initial variable assignment
ONLY. This means that you can NOT assign values to this variable in functions and the
new values will not be put into the ELF .lock section.
The global variable is declared in the LOCKBITS macro has two leading underscores,
which means that it is reserved for the "implementation", meaning the library, so it will
not conflict with a user-named variable.
You must initialize the lockbit variable to some meaningful value, even if it is the default value. This is because the lockbits default to a logical 1, meaning unprogrammed.
Normal uninitialized data defaults to all locgial zeros. So it is vital that all lockbits
are initialized, even with default data. If they are not, then the lockbits may not programmed to the desired settings and can possibly put your device into an unrecoverable
state.
Be sure to have the -mmcu=device flag in your compile command line and your linker
command line to have the correct device selected and to have the correct I/O header
file included when you include <avr/io.h>.
You can print out the contents of the .lock section in the ELF file by using this command
line:
avr-objdump -s -j .lock <ELF file>
22.19 <avr/pgmspace.h>: Program Space Utilities
Defines
•
•
•
•
•
•
•
•
#define PROGMEM __ATTR_PROGMEM__
#define PSTR(s) ((const PROGMEM char ∗)(s))
#define pgm_read_byte_near(address_short) __LPM((uint16_t)(address_short))
#define pgm_read_word_near(address_short) __LPM_word((uint16_t)(address_short))
#define pgm_read_dword_near(address_short) __LPM_dword((uint16_t)(address_short))
#define pgm_read_float_near(address_short) __LPM_float((uint16_t)(address_short))
#define pgm_read_byte_far(address_long) __ELPM((uint32_t)(address_long))
#define pgm_read_word_far(address_long) __ELPM_word((uint32_t)(address_long))
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<avr/pgmspace.h>: Program Space Utilities
22.19
271
• #define pgm_read_dword_far(address_long) __ELPM_dword((uint32_t)(address_long))
• #define pgm_read_float_far(address_long) __ELPM_float((uint32_t)(address_long))
• #define pgm_read_byte(address_short) pgm_read_byte_near(address_short)
• #define pgm_read_word(address_short) pgm_read_word_near(address_short)
• #define pgm_read_dword(address_short) pgm_read_dword_near(address_short)
• #define pgm_read_float(address_short) pgm_read_float_near(address_short)
• #define PGM_P const prog_char ∗
• #define PGM_VOID_P const prog_void ∗
Typedefs
•
•
•
•
•
•
•
•
•
•
•
typedef void PROGMEM prog_void
typedef char PROGMEM prog_char
typedef unsigned char PROGMEM prog_uchar
typedef int8_t PROGMEM prog_int8_t
typedef uint8_t PROGMEM prog_uint8_t
typedef int16_t PROGMEM prog_int16_t
typedef uint16_t PROGMEM prog_uint16_t
typedef int32_t PROGMEM prog_int32_t
typedef uint32_t PROGMEM prog_uint32_t
typedef int64_t PROGMEM prog_int64_t
typedef uint64_t PROGMEM prog_uint64_t
Functions
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
char ∗ strtok_P (char ∗s, PGM_P delim)
PGM_VOID_P memchr_P (PGM_VOID_P, int __val, size_t __len)
int memcmp_P (const void ∗, PGM_VOID_P, size_t) __ATTR_PURE__
int memcmp_PF (const void ∗, uint_farptr_t, size_t) __ATTR_PURE__
void ∗ memcpy_P (void ∗, PGM_VOID_P, size_t)
void ∗ memcpy_PF (void ∗dest, uint_farptr_t src, size_t len)
PGM_VOID_P memrchr_P (PGM_VOID_P, int __val, size_t __len)
int strcasecmp_P (const char ∗, PGM_P) __ATTR_PURE__
int strcasecmp_PF (const char ∗s1, uint_farptr_t s2) __ATTR_PURE__
char ∗ strcat_P (char ∗, PGM_P)
char ∗ strcat_PF (char ∗dest, uint_farptr_t src)
PGM_P strchr_P (PGM_P, int __val)
PGM_P strchrnul_P (PGM_P, int __val)
int strcmp_P (const char ∗, PGM_P) __ATTR_PURE__
int strcmp_PF (const char ∗s1, uint_farptr_t s2) __ATTR_PURE__
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22.19
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
22.19.1
<avr/pgmspace.h>: Program Space Utilities
272
char ∗ strcpy_P (char ∗, PGM_P)
char ∗ strcpy_PF (char ∗dest, uint_farptr_t src)
size_t strcspn_P (const char ∗__s, PGM_P __reject) __ATTR_PURE__
size_t strlcat_P (char ∗, PGM_P, size_t)
size_t strlcat_PF (char ∗dst, uint_farptr_t src, size_t siz)
size_t strlcpy_P (char ∗, PGM_P, size_t)
size_t strlcpy_PF (char ∗dst, uint_farptr_t src, size_t siz)
size_t strlen_P (PGM_P)
size_t strlen_PF (uint_farptr_t src)
int strncasecmp_P (const char ∗, PGM_P, size_t) __ATTR_PURE__
int strncasecmp_PF (const char ∗s1, uint_farptr_t s2, size_t n) __ATTR_PURE__
char ∗ strncat_P (char ∗, PGM_P, size_t)
char ∗ strncat_PF (char ∗dest, uint_farptr_t src, size_t len)
int strncmp_P (const char ∗, PGM_P, size_t) __ATTR_PURE__
int strncmp_PF (const char ∗s1, uint_farptr_t s2, size_t n) __ATTR_PURE__
char ∗ strncpy_P (char ∗, PGM_P, size_t)
char ∗ strncpy_PF (char ∗dest, uint_farptr_t src, size_t len)
size_t strnlen_P (PGM_P, size_t)
size_t strnlen_PF (uint_farptr_t src, size_t len)
char ∗ strpbrk_P (const char ∗__s, PGM_P __accept) __ATTR_PURE__
PGM_P strrchr_P (PGM_P, int __val)
char ∗ strsep_P (char ∗∗__sp, PGM_P __delim)
size_t strspn_P (const char ∗__s, PGM_P __accept) __ATTR_PURE__
char ∗ strstr_P (const char ∗, PGM_P) __ATTR_PURE__
char ∗ strstr_PF (const char ∗s1, uint_farptr_t s2)
char ∗ strtok_rP (char ∗__s, PGM_P __delim, char ∗∗__last)
void ∗ memccpy_P (void ∗, PGM_VOID_P, int __val, size_t)
void ∗ memmem_P (const void ∗, size_t, PGM_VOID_P, size_t) __ATTR_PURE__
char ∗ strcasestr_P (const char ∗, PGM_P) __ATTR_PURE__
Detailed Description
#include <avr/io.h>
#include <avr/pgmspace.h>
The functions in this module provide interfaces for a program to access data stored in
program space (flash memory) of the device. In order to use these functions, the target
device must support either the LPM or ELPM instructions.
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22.19
<avr/pgmspace.h>: Program Space Utilities
273
Note
These functions are an attempt to provide some compatibility with header files
that come with IAR C, to make porting applications between different compilers
easier. This is not 100% compatibility though (GCC does not have full support for
multiple address spaces yet).
If you are working with strings which are completely based in ram, use the standard string functions described in <string.h>: Strings.
If possible, put your constant tables in the lower 64 KB and use pgm_read_byte_near() or pgm_read_word_near() instead of pgm_read_byte_far() or pgm_read_word_far() since it is more efficient that way, and you can still use the upper 64K
for executable code. All functions that are suffixed with a _P require their arguments to be in the lower 64 KB of the flash ROM, as they do not use ELPM
instructions. This is normally not a big concern as the linker setup arranges any
program space constants declared using the macros from this header file so they
are placed right after the interrupt vectors, and in front of any executable code.
However, it can become a problem if there are too many of these constants, or for
bootloaders on devices with more than 64 KB of ROM. All these functions will not
work in that situation.
For Xmega devices, make sure the NVM controller command register (NVM.CMD
or NVM_CMD) is set to 0x00 (NOP) before using any of these functions.
22.19.2
Define Documentation
22.19.2.1
#define PGM_P const prog_char ∗
Used to declare a variable that is a pointer to a string in program space.
22.19.2.2
#define pgm_read_byte( address_short
) pgm_read_byte_near(address_short)
Read a byte from the program space with a 16-bit (near) address.
Note
The address is a byte address. The address is in the program space.
22.19.2.3
#define pgm_read_byte_far( address_long
) __ELPM((uint32_t)(address_long))
Read a byte from the program space with a 32-bit (far) address.
Note
The address is a byte address. The address is in the program space.
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22.19.2.4
274
#define pgm_read_byte_near( address_short
) __LPM((uint16_t)(address_short))
Read a byte from the program space with a 16-bit (near) address.
Note
The address is a byte address. The address is in the program space.
22.19.2.5
#define pgm_read_dword( address_short
) pgm_read_dword_near(address_short)
Read a double word from the program space with a 16-bit (near) address.
Note
The address is a byte address. The address is in the program space.
22.19.2.6
#define pgm_read_dword_far( address_long
) __ELPM_dword((uint32_t)(address_long))
Read a double word from the program space with a 32-bit (far) address.
Note
The address is a byte address. The address is in the program space.
22.19.2.7
#define pgm_read_dword_near( address_short
) __LPM_dword((uint16_t)(address_short))
Read a double word from the program space with a 16-bit (near) address.
Note
The address is a byte address. The address is in the program space.
22.19.2.8
#define pgm_read_float( address_short
) pgm_read_float_near(address_short)
Read a float from the program space with a 16-bit (near) address.
Note
The address is a byte address. The address is in the program space.
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22.19.2.9
275
#define pgm_read_float_far( address_long
) __ELPM_float((uint32_t)(address_long))
Read a float from the program space with a 32-bit (far) address.
Note
The address is a byte address. The address is in the program space.
22.19.2.10
#define pgm_read_float_near( address_short
) __LPM_float((uint16_t)(address_short))
Read a float from the program space with a 16-bit (near) address.
Note
The address is a byte address. The address is in the program space.
22.19.2.11
#define pgm_read_word( address_short
) pgm_read_word_near(address_short)
Read a word from the program space with a 16-bit (near) address.
Note
The address is a byte address. The address is in the program space.
22.19.2.12
#define pgm_read_word_far( address_long
) __ELPM_word((uint32_t)(address_long))
Read a word from the program space with a 32-bit (far) address.
Note
The address is a byte address. The address is in the program space.
22.19.2.13
#define pgm_read_word_near( address_short
) __LPM_word((uint16_t)(address_short))
Read a word from the program space with a 16-bit (near) address.
Note
The address is a byte address. The address is in the program space.
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22.19
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22.19.2.14
276
#define PGM_VOID_P const prog_void ∗
Used to declare a generic pointer to an object in program space.
22.19.2.15
#define PROGMEM __ATTR_PROGMEM__
Attribute to use in order to declare an object being located in flash ROM.
22.19.2.16
#define PSTR( s ) ((const PROGMEM char ∗)(s))
Used to declare a static pointer to a string in program space.
22.19.3
Typedef Documentation
22.19.3.1
prog_char
Type of a "char" object located in flash ROM.
22.19.3.2
prog_int16_t
Type of an "int16_t" object located in flash ROM.
22.19.3.3
prog_int32_t
Type of an "int32_t" object located in flash ROM.
22.19.3.4
prog_int64_t
Type of an "int64_t" object located in flash ROM.
Note
This type is not available when the compiler option -mint8 is in effect.
22.19.3.5
prog_int8_t
Type of an "int8_t" object located in flash ROM.
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22.19.3.6
277
prog_uchar
Type of an "unsigned char" object located in flash ROM.
22.19.3.7
prog_uint16_t
Type of an "uint16_t" object located in flash ROM.
22.19.3.8
prog_uint32_t
Type of an "uint32_t" object located in flash ROM.
22.19.3.9
prog_uint64_t
Type of an "uint64_t" object located in flash ROM.
Note
This type is not available when the compiler option -mint8 is in effect.
22.19.3.10
prog_uint8_t
Type of an "uint8_t" object located in flash ROM.
22.19.3.11
prog_void
Type of a "void" object located in flash ROM. Does not make much sense by itself,
but can be used to declare a "void ∗" object in flash ROM.
22.19.4
Function Documentation
22.19.4.1
void ∗ memccpy_P ( void ∗ dest, PGM_VOID_P src, int val, size_t
len )
This function is similar to memccpy() except that src is pointer to a string in
program space.
22.19.4.2
PGM_VOID_P memchr_P ( PGM_VOID_P s, int val, size_t len )
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Scan flash memory for a character.
The memchr_P() function scans the first len bytes of the flash memory area pointed
to by s for the character val. The first byte to match val (interpreted as an unsigned
character) stops the operation.
Returns
The memchr_P() function returns a pointer to the matching byte or NULL if the
character does not occur in the given memory area.
22.19.4.3
int memcmp_P ( const void ∗ s1, PGM_VOID_P s2, size_t len )
Compare memory areas.
The memcmp_P() function compares the first len bytes of the memory areas s1 and
flash s2. The comparision is performed using unsigned char operations.
Returns
The memcmp_P() function returns an integer less than, equal to, or greater than
zero if the first len bytes of s1 is found, respectively, to be less than, to match, or
be greater than the first len bytes of s2.
22.19.4.4
int memcmp_PF ( const void ∗ s1, uint_farptr_t s2, size_t len )
Compare memory areas.
The memcmp_PF() function compares the first len bytes of the memory areas s1
and flash s2. The comparision is performed using unsigned char operations. It is an
equivalent of memcmp_P() function, except that it is capable working on all FLASH
including the exteded area above 64kB.
Returns
The memcmp_PF() function returns an integer less than, equal to, or greater than
zero if the first len bytes of s1 is found, respectively, to be less than, to match, or
be greater than the first len bytes of s2.
22.19.4.5
void ∗ memcpy_P ( void ∗ dest, PGM_VOID_P src, size_t n )
The memcpy_P() function is similar to memcpy(), except the src string resides in
program space.
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Returns
The memcpy_P() function returns a pointer to dest.
22.19.4.6
void ∗ memcpy_PF ( void ∗ dest, uint_farptr_t src, size_t n )
Copy a memory block from flash to SRAM.
The memcpy_PF() function is similar to memcpy(), except the data is copied from the
program space and is addressed using a far pointer
Parameters
dst A pointer to the destination buffer
src A far pointer to the origin of data in flash memory
n The number of bytes to be copied
Returns
The memcpy_PF() function returns a pointer to dst. The contents of RAMPZ SFR
are undefined when the function returns
22.19.4.7
void ∗ memmem_P ( const void ∗ s1, size_t len1, PGM_VOID_P s2,
size_t len2 )
The memmem_P() function is similar to memmem() except that s2 is pointer to a
string in program space.
22.19.4.8
PGM_VOID_P memrchr_P ( PGM_VOID_P src, int val, size_t len )
The memrchr_P() function is like the memchr_P() function, except that it searches
backwards from the end of the len bytes pointed to by src instead of forwards from
the front. (Glibc, GNU extension.)
Returns
The memrchr_P() function returns a pointer to the matching byte or NULL if the
character does not occur in the given memory area.
22.19.4.9
int strcasecmp_P ( const char ∗ s1, PGM_P s2 )
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Compare two strings ignoring case.
The strcasecmp_P() function compares the two strings s1 and s2, ignoring the case of
the characters.
Parameters
s1 A pointer to a string in the devices SRAM.
s2 A pointer to a string in the devices Flash.
Returns
The strcasecmp_P() function returns an integer less than, equal to, or greater than
zero if s1 is found, respectively, to be less than, to match, or be greater than s2.
A consequence of the ordering used by strcasecmp_P() is that if s1 is an initial
substring of s2, then s1 is considered to be "less than" s2.
22.19.4.10
int strcasecmp_PF ( const char ∗ s1, uint_farptr_t s2 )
Compare two strings ignoring case.
The strcasecmp_PF() function compares the two strings s1 and s2, ignoring the case of
the characters
Parameters
s1 A pointer to the first string in SRAM
s2 A far pointer to the second string in Flash
Returns
The strcasecmp_PF() function returns an integer less than, equal to, or greater than
zero if s1 is found, respectively, to be less than, to match, or be greater than s2.
The contents of RAMPZ SFR are undefined when the function returns
22.19.4.11
char ∗ strcasestr_P ( const char ∗ s1, PGM_P s2 )
This funtion is similar to strcasestr() except that s2 is pointer to a string in program
space.
22.19.4.12
char ∗ strcat_P ( char ∗ dest, PGM_P src )
The strcat_P() function is similar to strcat() except that the src string must be located
in program space (flash).
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Returns
The strcat() function returns a pointer to the resulting string dest.
22.19.4.13
char ∗ strcat_PF ( char ∗ dst, uint_farptr_t src )
Concatenates two strings.
The strcat_PF() function is similar to strcat() except that the src string must be located
in program space (flash) and is addressed using a far pointer
Parameters
dst A pointer to the destination string in SRAM
src A far pointer to the string to be appended in Flash
Returns
The strcat_PF() function returns a pointer to the resulting string dst. The contents
of RAMPZ SFR are undefined when the function returns
22.19.4.14
PGM_P strchr_P ( PGM_P s, int val )
Locate character in program space string.
The strchr_P() function locates the first occurrence of val (converted to a char) in the
string pointed to by s in program space. The terminating null character is considered
to be part of the string.
The strchr_P() function is similar to strchr() except that s is pointer to a string in
program space.
Returns
The strchr_P() function returns a pointer to the matched character or NULL if the
character is not found.
22.19.4.15
PGM_P strchrnul_P ( PGM_P s, int c )
The strchrnul_P() function is like strchr_P() except that if c is not found
in s, then it returns a pointer to the null byte at the end of s, rather than NULL. (Glibc,
GNU extension.)
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Returns
The strchrnul_P() function returns a pointer to the matched character, or a pointer
to the null byte at the end of s (i.e., s+strlen(s)) if the character is not found.
22.19.4.16
int strcmp_P ( const char ∗ s1, PGM_P s2 )
The strcmp_P() function is similar to strcmp() except that s2 is pointer to a string in
program space.
Returns
The strcmp_P() function returns an integer less than, equal to, or greater than zero
if s1 is found, respectively, to be less than, to match, or be greater than s2. A
consequence of the ordering used by strcmp_P() is that if s1 is an initial substring
of s2, then s1 is considered to be "less than" s2.
22.19.4.17
int strcmp_PF ( const char ∗ s1, uint_farptr_t s2 )
Compares two strings.
The strcmp_PF() function is similar to strcmp() except that s2 is a far pointer to a string
in program space
Parameters
s1 A pointer to the first string in SRAM
s2 A far pointer to the second string in Flash
Returns
The strcmp_PF() function returns an integer less than, equal to, or greater than
zero if s1 is found, respectively, to be less than, to match, or be greater than s2.
The contents of RAMPZ SFR are undefined when the function returns
22.19.4.18
char ∗ strcpy_P ( char ∗ dest, PGM_P src )
The strcpy_P() function is similar to strcpy() except that src is a pointer to a string in
program space.
Returns
The strcpy_P() function returns a pointer to the destination string dest.
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22.19.4.19
283
char ∗ strcpy_PF ( char ∗ dst, uint_farptr_t src )
Duplicate a string.
The strcpy_PF() function is similar to strcpy() except that src is a far pointer to a string
in program space
Parameters
dst A pointer to the destination string in SRAM
src A far pointer to the source string in Flash
Returns
The strcpy_PF() function returns a pointer to the destination string dst. The contents of RAMPZ SFR are undefined when the funcion returns
22.19.4.20
size_t strcspn_P ( const char ∗ s, PGM_P reject )
The strcspn_P() function calculates the length of the initial segment
of s which consists entirely of characters not in reject. This function is similar to
strcspn() except that reject is a pointer to a string in program space.
Returns
The strcspn_P() function returns the number of characters in the initial segment of
s which are not in the string reject. The terminating zero is not considered as a
part of string.
22.19.4.21
size_t strlcat_P ( char ∗ dst, PGM_P src, size_t siz )
Concatenate two strings.
The strlcat_P() function is similar to strlcat(), except that the src string must be located
in program space (flash).
Appends src to string dst of size siz (unlike strncat(), siz is the full size of dst,
not space left). At most siz-1 characters will be copied. Always NULL terminates
(unless siz <= strlen(dst)).
Returns
The strlcat_P() function returns strlen(src) + MIN(siz, strlen(initial dst)). If retval
>= siz, truncation occurred.
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22.19.4.22
284
size_t strlcat_PF ( char ∗ dst, uint_farptr_t src, size_t n )
Concatenate two strings.
The strlcat_PF() function is similar to strlcat(), except that the src string must be located
in program space (flash) and is addressed using a far pointer
Appends src to string dst of size n (unlike strncat(), n is the full size of dst, not space
left). At most n-1 characters will be copied. Always NULL terminates (unless n <=
strlen(dst))
Parameters
dst A pointer to the destination string in SRAM
src A far pointer to the source string in Flash
n The total number of bytes allocated to the destination string
Returns
The strlcat_PF() function returns strlen(src) + MIN(n, strlen(initial dst)). If retval
>= n, truncation occurred. The contents of RAMPZ SFR are undefined when the
funcion returns
22.19.4.23
size_t strlcpy_P ( char ∗ dst, PGM_P src, size_t siz )
Copy a string from progmem to RAM.
Copy src to string dst of size siz. At most siz-1 characters will be copied.
Always NULL terminates (unless siz == 0). The strlcpy_P() function is similar to
strlcpy() except that the src is pointer to a string in memory space.
Returns
The strlcpy_P() function returns strlen(src). If retval >= siz, truncation occurred.
22.19.4.24
size_t strlcpy_PF ( char ∗ dst, uint_farptr_t src, size_t siz )
Copy a string from progmem to RAM.
Copy src to string dst of size siz. At most siz-1 characters will be copied. Always
NULL terminates (unless siz == 0).
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Returns
The strlcpy_PF() function returns strlen(src). If retval >= siz, truncation occurred.
The contents of RAMPZ SFR are undefined when the function returns
22.19.4.25
size_t strlen_P ( PGM_P src )
The strlen_P() function is similar to strlen(), except that src is a pointer to a string in
program space.
Returns
The strlen() function returns the number of characters in src.
22.19.4.26
size_t strlen_PF ( uint_farptr_t s )
Obtain the length of a string.
The strlen_PF() function is similar to strlen(), except that s is a far pointer to a string in
program space
Parameters
s A far pointer to the string in flash
Returns
The strlen_PF() function returns the number of characters in s. The contents of
RAMPZ SFR are undefined when the function returns
22.19.4.27
int strncasecmp_P ( const char ∗ s1, PGM_P s2, size_t n )
Compare two strings ignoring case.
The strncasecmp_P() function is similar to strcasecmp_P(), except it only compares the
first n characters of s1.
Parameters
s1 A pointer to a string in the devices SRAM.
s2 A pointer to a string in the devices Flash.
n The maximum number of bytes to compare.
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Returns
The strncasecmp_P() function returns an integer less than, equal to, or greater
than zero if s1 (or the first n bytes thereof) is found, respectively, to be less
than, to match, or be greater than s2. A consequence of the ordering used by
strncasecmp_P() is that if s1 is an initial substring of s2, then s1 is considered to
be "less than" s2.
22.19.4.28
int strncasecmp_PF ( const char ∗ s1, uint_farptr_t s2, size_t n )
Compare two strings ignoring case.
The strncasecmp_PF() function is similar to strcasecmp_PF(), except it only compares
the first n characters of s1 and the string in flash is addressed using a far pointer
Parameters
s1 A pointer to a string in SRAM
s2 A far pointer to a string in Flash
n The maximum number of bytes to compare
Returns
The strncasecmp_PF() function returns an integer less than, equal to, or greater
than zero if s1 (or the first n bytes thereof) is found, respectively, to be less than,
to match, or be greater than s2. The contents of RAMPZ SFR are undefined when
the function returns
22.19.4.29
char ∗ strncat_P ( char ∗ dest, PGM_P src, size_t len )
Concatenate two strings.
The strncat_P() function is similar to strncat(), except that the src string must be located
in program space (flash).
Returns
The strncat_P() function returns a pointer to the resulting string dest.
22.19.4.30
char ∗ strncat_PF ( char ∗ dst, uint_farptr_t src, size_t n )
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Concatenate two strings.
The strncat_PF() function is similar to strncat(), except that the src string must be
located in program space (flash) and is addressed using a far pointer
Parameters
dst A pointer to the destination string in SRAM
src A far pointer to the source string in Flash
n The maximum number of bytes to append
Returns
The strncat_PF() function returns a pointer to the resulting string dst. The contents
of RAMPZ SFR are undefined when the function returns
22.19.4.31
int strncmp_P ( const char ∗ s1, PGM_P s2, size_t n )
The strncmp_P() function is similar to strcmp_P() except it only compares the first (at
most) n characters of s1 and s2.
Returns
The strncmp_P() function returns an integer less than, equal to, or greater than zero
if s1 (or the first n bytes thereof) is found, respectively, to be less than, to match,
or be greater than s2.
22.19.4.32
int strncmp_PF ( const char ∗ s1, uint_farptr_t s2, size_t n )
Compare two strings with limited length.
The strncmp_PF() function is similar to strcmp_PF() except it only compares the first
(at most) n characters of s1 and s2
Parameters
s1 A pointer to the first string in SRAM
s2 A far pointer to the second string in Flash
n The maximum number of bytes to compare
Returns
The strncmp_PF() function returns an integer less than, equal to, or greater than
zero if s1 (or the first n bytes thereof) is found, respectively, to be less than, to
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match, or be greater than s2. The contents of RAMPZ SFR are undefined when
the function returns
22.19.4.33
char ∗ strncpy_P ( char ∗ dest, PGM_P src, size_t n )
The strncpy_P() function is similar to strcpy_P() except that not more than n bytes
of src are copied. Thus, if there is no null byte among the first n bytes of src, the result
will not be null-terminated.
In the case where the length of src is less than that of n, the remainder of dest will be
padded with nulls.
Returns
The strncpy_P() function returns a pointer to the destination string dest.
22.19.4.34
char ∗ strncpy_PF ( char ∗ dst, uint_farptr_t src, size_t n )
Duplicate a string until a limited length.
The strncpy_PF() function is similar to strcpy_PF() except that not more than n bytes
of src are copied. Thus, if there is no null byte among the first n bytes of src, the result
will not be null-terminated
In the case where the length of src is less than that of n, the remainder of dst will be
padded with nulls
Parameters
dst A pointer to the destination string in SRAM
src A far pointer to the source string in Flash
n The maximum number of bytes to copy
Returns
The strncpy_PF() function returns a pointer to the destination string dst. The contents of RAMPZ SFR are undefined when the function returns
22.19.4.35
size_t strnlen_P ( PGM_P src, size_t len )
Determine the length of a fixed-size string.
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The strnlen_P() function is similar to strnlen(), except that src is a pointer to a string
in program space.
Returns
The strnlen_P function returns strlen_P(src), if that is less than len, or len if
there is no ’\0’ character among the first len characters pointed to by src.
22.19.4.36
size_t strnlen_PF ( uint_farptr_t s, size_t len )
Determine the length of a fixed-size string.
The strnlen_PF() function is similar to strnlen(), except that s is a far pointer to a string
in program space
Parameters
s A far pointer to the string in Flash
len The maximum number of length to return
Returns
The strnlen_PF function returns strlen_P(s), if that is less than len, or len if there
is no ’\0’ character among the first len characters pointed to by s. The contents of
RAMPZ SFR are undefined when the function returns
22.19.4.37
char ∗ strpbrk_P ( const char ∗ s, PGM_P accept )
The strpbrk_P() function locates the first occurrence in the string s of any of the
characters in the flash string accept. This function is similar to strpbrk() except that
accept is a pointer to a string in program space.
Returns
The strpbrk_P() function returns a pointer to the character in s that matches one of
the characters in accept, or NULL if no such character is found. The terminating
zero is not considered as a part of string: if one or both args are empty, the result
will NULL.
22.19.4.38
PGM_P strrchr_P ( PGM_P s, int val )
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Locate character in string.
The strrchr_P() function returns a pointer to the last occurrence of the character val
in the flash string s.
Returns
The strrchr_P() function returns a pointer to the matched character or NULL if the
character is not found.
22.19.4.39
char ∗ strsep_P ( char ∗∗ sp, PGM_P delim )
Parse a string into tokens.
The strsep_P() function locates, in the string referenced by ∗sp, the first occurrence of
any character in the string delim (or the terminating ’\0’ character) and replaces it
with a ’\0’. The location of the next character after the delimiter character (or NULL,
if the end of the string was reached) is stored in ∗sp. An “empty” field, i.e. one
caused by two adjacent delimiter characters, can be detected by comparing the location
referenced by the pointer returned in ∗sp to ’\0’. This function is similar to strsep()
except that delim is a pointer to a string in program space.
Returns
The strsep_P() function returns a pointer to the original value of ∗sp. If ∗sp is
initially NULL, strsep_P() returns NULL.
22.19.4.40
size_t strspn_P ( const char ∗ s, PGM_P accept )
The strspn_P() function calculates the length of the initial segment of
s which consists entirely of characters in accept. This function is similar to strspn()
except that accept is a pointer to a string in program space.
Returns
The strspn_P() function returns the number of characters in the initial segment of
s which consist only of characters from accept. The terminating zero is not
considered as a part of string.
22.19.4.41
char ∗ strstr_P ( const char ∗ s1, PGM_P s2 )
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22.19
<avr/pgmspace.h>: Program Space Utilities
291
Locate a substring.
The strstr_P() function finds the first occurrence of the substring s2 in the string s1.
The terminating ’\0’ characters are not compared. The strstr_P() function is similar to
strstr() except that s2 is pointer to a string in program space.
Returns
The strstr_P() function returns a pointer to the beginning of the substring, or NULL
if the substring is not found. If s2 points to a string of zero length, the function
returns s1.
22.19.4.42
char ∗ strstr_PF ( const char ∗ s1, uint_farptr_t s2 )
Locate a substring.
The strstr_PF() function finds the first occurrence of the substring s2 in the string s1.
The terminating ’\0’ characters are not compared. The strstr_PF() function is similar
to strstr() except that s2 is a far pointer to a string in program space.
Returns
The strstr_PF() function returns a pointer to the beginning of the substring, or
NULL if the substring is not found. If s2 points to a string of zero length, the
function returns s1. The contents of RAMPZ SFR are undefined when the function returns
22.19.4.43
char∗ strtok_P ( char ∗ s, PGM_P delim )
Parses the string into tokens.
strtok_P() parses the string s into tokens. The first call to strtok_P() should have s as
its first argument. Subsequent calls should have the first argument set to NULL. If a
token ends with a delimiter, this delimiting character is overwritten with a ’\0’ and a
pointer to the next character is saved for the next call to strtok_P(). The delimiter string
delim may be different for each call.
The strtok_P() function is similar to strtok() except that delim is pointer to a string in
program space.
Returns
The strtok_P() function returns a pointer to the next token or NULL when no more
tokens are found.
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22.20
<avr/power.h>: Power Reduction Management
292
Note
strtok_P() is NOT reentrant. For a reentrant version of this function see strtok_rP().
22.19.4.44
char ∗ strtok_rP ( char ∗ string, PGM_P delim, char ∗∗ last )
Parses string into tokens.
The strtok_rP() function parses string into tokens. The first call to strtok_rP() should
have string as its first argument. Subsequent calls should have the first argument set to
NULL. If a token ends with a delimiter, this delimiting character is overwritten with
a ’\0’ and a pointer to the next character is saved for the next call to strtok_rP(). The
delimiter string delim may be different for each call. last is a user allocated char∗
pointer. It must be the same while parsing the same string. strtok_rP() is a reentrant
version of strtok_P().
The strtok_rP() function is similar to strtok_r() except that delim is pointer to a string
in program space.
Returns
The strtok_rP() function returns a pointer to the next token or NULL when no more
tokens are found.
22.20 <avr/power.h>: Power Reduction Management
#include <avr/power.h>
Many AVRs contain a Power Reduction Register (PRR) or Registers (PRRx) that allow
you to reduce power consumption by disabling or enabling various on-board peripherals as needed.
There are many macros in this header file that provide an easy interface to enable or
disable on-board peripherals to reduce power. See the table below.
Note
Not all AVR devices have a Power Reduction Register (for example the ATmega128).
On those devices without a Power Reduction Register, these macros are not available.
Not all AVR devices contain the same peripherals (for example, the LCD interface), or they will be named differently (for example, USART and USART0).
Please consult your device’s datasheet, or the header file, to find out which macros
are applicable to your device.
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22.20
<avr/power.h>: Power Reduction Management
293
Power Macro
Description
Applicable for device
power_adc_enable()
Enable the Analog to Digital
Converter module.
ATmega640, ATmega1280,
ATmega1281,
ATmega128RFA1,
ATmega2560, ATmega2561,
AT90USB646, AT90USB647,
AT90USB1286,
AT90USB1287, AT90PWM1,
AT90PWM2, AT90PWM2B,
AT90PWM3, AT90PWM3B,
AT90PWM216,
AT90PWM316, AT90PWM81,
ATmega165, ATmega165P,
ATmega325, ATmega325A,
ATmega325PA, ATmega3250,
ATmega3250A,
ATmega3250PA, ATmega645,
ATmega6450, ATmega169,
ATmega169P, ATmega329,
ATmega329A, ATmega3290,
ATmega3290A,
ATmega3290PA, ATmega649,
ATmega6490, ATmega164P,
ATmega324P, ATmega644,
ATmega48, ATmega88,
ATmega168, ATtiny24,
ATtiny44, ATtiny84,
ATtiny84A, ATtiny25,
ATtiny45, ATtiny85,
ATtiny261, ATtiny461,
ATtiny861
power_adc_disable()
Disable the Analog to Digital
Converter module.
ATmega640, ATmega1280,
ATmega1281,
ATmega128RFA1,
ATmega2560, ATmega2561,
AT90USB646, AT90USB647,
AT90USB1286,
AT90USB1287, AT90PWM1,
AT90PWM2, AT90PWM2B,
AT90PWM3, AT90PWM3B,
AT90PWM216,
AT90PWM316, AT90PWM81,
ATmega165, ATmega165P,
ATmega325, ATmega325A,
ATmega325PA, ATmega3250,
ATmega3250A,
ATmega3250PA, ATmega645,
ATmega6450, ATmega169,
ATmega169P, ATmega329,
ATmega329A, ATmega3290,
ATmega3290A,
ATmega3290PA, ATmega649,
ATmega6490, ATmega164P,
ATmega324P, ATmega644,
ATmega48, ATmega88,
ATmega168, ATtiny24,
ATtiny44, ATtiny84,
ATtiny84A, ATtiny25,
ATtiny45, ATtiny85,
ATtiny261, ATtiny461,
ATtiny861
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power_lcd_enable()
Enable the LCD module.
ATmega169, ATmega169P,
ATmega329, ATmega329A,
ATmega3290, ATmega3290A,
ATmega649, ATmega6490,
ATxmega128B1
22.21
Additional notes from <avr/sfr_defs.h>
294
Some of the newer AVRs contain a System Clock Prescale Register (CLKPR) that
allows you to decrease the system clock frequency and the power consumption when
the need for processing power is low. Below are two macros and an enumerated type
that can be used to interface to the Clock Prescale Register.
Note
Not all AVR devices have a Clock Prescale Register. On those devices without a
Clock Prescale Register, these macros are not available.
typedef enum
{
clock_div_1 = 0,
clock_div_2 = 1,
clock_div_4 = 2,
clock_div_8 = 3,
clock_div_16 = 4,
clock_div_32 = 5,
clock_div_64 = 6,
clock_div_128 = 7,
clock_div_256 = 8,
clock_div_1_rc = 15, // ATmega128RFA1 only
} clock_div_t;
Clock prescaler setting enumerations.
clock_prescale_set(x)
Set the clock prescaler register select bits, selecting a system clock division setting.
This function is inlined, even if compiler optimizations are disabled.
The type of x is clock_div_t.
clock_prescale_get()
Gets and returns the clock prescaler register setting. The return type is clock_div_t.
22.21
Additional notes from <avr/sfr defs.h>
The <avr/sfr_defs.h> file is included by all of the <avr/ioXXXX.h> files,
which use macros defined here to make the special function register definitions look
like C variables or simple constants, depending on the _SFR_ASM_COMPAT define.
Some examples from <avr/iocanxx.h> to show how to define such macros:
#define
#define
#define
#define
#define
PORTA
EEAR
UDR0
TCNT3
CANIDT
_SFR_IO8(0x02)
_SFR_IO16(0x21)
_SFR_MEM8(0xC6)
_SFR_MEM16(0x94)
_SFR_MEM32(0xF0)
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22.21
Additional notes from <avr/sfr_defs.h>
295
If _SFR_ASM_COMPAT is not defined, C programs can use names like PORTA directly
in C expressions (also on the left side of assignment operators) and GCC will do the
right thing (use short I/O instructions if possible). The __SFR_OFFSET definition is
not used in any way in this case.
Define _SFR_ASM_COMPAT as 1 to make these names work as simple constants (addresses of the I/O registers). This is necessary when included in preprocessed assembler (∗.S) source files, so it is done automatically if __ASSEMBLER__ is defined. By
default, all addresses are defined as if they were memory addresses (used in lds/sts
instructions). To use these addresses in in/out instructions, you must subtract 0x20
from them.
For more backwards compatibility, insert the following at the start of your old assembler source file:
#define __SFR_OFFSET 0
This automatically subtracts 0x20 from I/O space addresses, but it’s a hack, so it is
recommended to change your source: wrap such addresses in macros defined here, as
shown below. After this is done, the __SFR_OFFSET definition is no longer necessary
and can be removed.
Real example - this code could be used in a boot loader that is portable between devices
with SPMCR at different addresses.
<avr/iom163.h>: #define SPMCR _SFR_IO8(0x37)
<avr/iom128.h>: #define SPMCR _SFR_MEM8(0x68)
#if _SFR_IO_REG_P(SPMCR)
out
_SFR_IO_ADDR(SPMCR), r24
#else
sts
_SFR_MEM_ADDR(SPMCR), r24
#endif
You can use the in/out/cbi/sbi/sbic/sbis instructions, without the _SFR_IO_REG_P test, if you know that the register is in the I/O space (as with SREG, for
example). If it isn’t, the assembler will complain (I/O address out of range 0...0x3f),
so this should be fairly safe.
If you do not define __SFR_OFFSET (so it will be 0x20 by default), all special register
addresses are defined as memory addresses (so SREG is 0x5f), and (if code size and
speed are not important, and you don’t like the ugly #if above) you can always use
lds/sts to access them. But, this will not work if __SFR_OFFSET != 0x20, so use a
different macro (defined only if __SFR_OFFSET == 0x20) for safety:
sts
_SFR_ADDR(SPMCR), r24
In C programs, all 3 combinations of _SFR_ASM_COMPAT and __SFR_OFFSET are
supported - the _SFR_ADDR(SPMCR) macro can be used to get the address of the
SPMCR register (0x57 or 0x68 depending on device).
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<avr/sfr_defs.h>: Special function registers
22.22
296
22.22 <avr/sfr defs.h>: Special function registers
Modules
• Additional notes from <avr/sfr_defs.h>
Bit manipulation
• #define _BV(bit) (1 << (bit))
IO register bit manipulation
•
•
•
•
22.22.1
#define bit_is_set(sfr, bit) (_SFR_BYTE(sfr) & _BV(bit))
#define bit_is_clear(sfr, bit) (!(_SFR_BYTE(sfr) & _BV(bit)))
#define loop_until_bit_is_set(sfr, bit) do { } while (bit_is_clear(sfr, bit))
#define loop_until_bit_is_clear(sfr, bit) do { } while (bit_is_set(sfr, bit))
Detailed Description
When working with microcontrollers, many tasks usually consist of controlling internal
peripherals, or external peripherals that are connected to the device. The entire IO
address space is made available as memory-mapped IO, i.e. it can be accessed using
all the MCU instructions that are applicable to normal data memory. For most AVR
devices, the IO register space is mapped into the data memory address space with an
offset of 0x20 since the bottom of this space is reserved for direct access to the MCU
registers. (Actual SRAM is available only behind the IO register area, starting at some
specific address depending on the device.)
For example the user can access memory-mapped IO registers as if they were globally
defined variables like this:
PORTA = 0x33;
unsigned char foo = PINA;
The compiler will choose the correct instruction sequence to generate based on the
address of the register being accessed.
The advantage of using the memory-mapped registers in C programs is that it makes
the programs more portable to other C compilers for the AVR platform.
Note that special care must be taken when accessing some of the 16-bit timer IO registers where access from both the main program and within an interrupt context can
happen. See Why do some 16-bit timer registers sometimes get trashed?.
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22.22
<avr/sfr_defs.h>: Special function registers
297
Porting programs that use the deprecated sbi/cbi macros
Access to the AVR single bit set and clear instructions are provided via the standard C
bit manipulation commands. The sbi and cbi macros are no longer directly supported.
sbi (sfr,bit) can be replaced by sfr |= _BV(bit) .
i.e.: sbi(PORTB, PB1); is now PORTB |= _BV(PB1);
This actually is more flexible than having sbi directly, as the optimizer will use a hardware sbi if appropriate, or a read/or/write operation if not appropriate. You do not need
to keep track of which registers sbi/cbi will operate on.
Likewise, cbi (sfr,bit) is now sfr &= ∼(_BV(bit));
22.22.2
Define Documentation
22.22.2.1
#define _BV( bit ) (1 << (bit))
#include <avr/io.h>
Converts a bit number into a byte value.
Note
The bit shift is performed by the compiler which then inserts the result into the
code. Thus, there is no run-time overhead when using _BV().
22.22.2.2
#define bit_is_clear( sfr, bit ) (!(_SFR_BYTE(sfr) & _BV(bit)))
#include <avr/io.h>
Test whether bit bit in IO register sfr is clear. This will return non-zero if the bit is
clear, and a 0 if the bit is set.
22.22.2.3
#define bit_is_set( sfr, bit ) (_SFR_BYTE(sfr) & _BV(bit))
#include <avr/io.h>
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22.23
<avr/signature.h>: Signature Support
298
Test whether bit bit in IO register sfr is set. This will return a 0 if the bit is clear,
and non-zero if the bit is set.
22.22.2.4
#define loop_until_bit_is_clear( sfr, bit ) do { } while (bit_is_set(sfr,
bit))
#include <avr/io.h>
Wait until bit bit in IO register sfr is clear.
22.22.2.5
#define loop_until_bit_is_set( sfr, bit ) do { } while (bit_is_clear(sfr,
bit))
#include <avr/io.h>
Wait until bit bit in IO register sfr is set.
22.23 <avr/signature.h>: Signature Support
Introduction
The <avr/signature.h> header file allows the user to automatically and easily include
the device’s signature data in a special section of the final linked ELF file.
This value can then be used by programming software to compare the on-device signature with the signature recorded in the ELF file to look for a match before programming
the device.
API Usage Example
Usage is very simple; just include the header file:
#include <avr/signature.h>
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22.24
<avr/sleep.h>: Power Management and Sleep Modes
299
This will declare a constant unsigned char array and it is initialized with the three
signature bytes, MSB first, that are defined in the device I/O header file. This array is
then placed in the .signature section in the resulting linked ELF file.
The three signature bytes that are used to initialize the array are these defined macros
in the device I/O header file, from MSB to LSB: SIGNATURE_2, SIGNATURE_1,
SIGNATURE_0.
This header file should only be included once in an application.
22.24 <avr/sleep.h>: Power Management and Sleep Modes
Functions
• void sleep_enable (void)
• void sleep_disable (void)
• void sleep_cpu (void)
22.24.1
Detailed Description
#include <avr/sleep.h>
Use of the SLEEP instruction can allow an application to reduce its power comsumption considerably. AVR devices can be put into different sleep modes. Refer to the
datasheet for the details relating to the device you are using.
There are several macros provided in this header file to actually put the device into
sleep mode. The simplest way is to optionally set the desired sleep mode using set_sleep_mode() (it usually defaults to idle mode where the CPU is put on sleep but
all peripheral clocks are still running), and then call sleep_mode(). This macro
automatically sets the sleep enable bit, goes to sleep, and clears the sleep enable bit.
Example:
#include <avr/sleep.h>
...
set_sleep_mode(<mode>);
sleep_mode();
Note that unless your purpose is to completely lock the CPU (until a hardware reset),
interrupts need to be enabled before going to sleep.
As the sleep_mode() macro might cause race conditions in some situations, the
individual steps of manipulating the sleep enable (SE) bit, and actually issuing the
SLEEP instruction, are provided in the macros sleep_enable(), sleep_disable(),
and sleep_cpu(). This also allows for test-and-sleep scenarios that take care of not
missing the interrupt that will awake the device from sleep.
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22.24
<avr/sleep.h>: Power Management and Sleep Modes
300
Example:
#include <avr/interrupt.h>
#include <avr/sleep.h>
...
set_sleep_mode(<mode>);
cli();
if (some_condition)
{
sleep_enable();
sei();
sleep_cpu();
sleep_disable();
}
sei();
This sequence ensures an atomic test of some_condition with interrupts being disabled. If the condition is met, sleep mode will be prepared, and the SLEEP instruction
will be scheduled immediately after an SEI instruction. As the intruction right after
the SEI is guaranteed to be executed before an interrupt could trigger, it is sure the
device will really be put to sleep.
Some devices have the ability to disable the Brown Out Detector (BOD) before going
to sleep. This will also reduce power while sleeping. If the specific AVR device has this
ability then an additional macro is defined: sleep_bod_disable(). This macro
generates inlined assembly code that will correctly implement the timed sequence for
disabling the BOD before sleeping. However, there is a limited number of cycles after the BOD has been disabled that the device can be put into sleep mode, otherwise
the BOD will not truly be disabled. Recommended practice is to disable the BOD
(sleep_bod_disable()), set the interrupts (sei()), and then put the device to
sleep (sleep_cpu()), like so:
#include <avr/interrupt.h>
#include <avr/sleep.h>
...
set_sleep_mode(<mode>);
cli();
if (some_condition)
{
sleep_enable();
sleep_bod_disable();
sei();
sleep_cpu();
sleep_disable();
}
sei();
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22.25
<avr/version.h>: avr-libc version macros
22.24.2
Function Documentation
22.24.2.1
301
void sleep_cpu ( void )
Put the device into sleep mode. The SE bit must be set beforehand, and it is
recommended to clear it afterwards.
22.24.2.2
void sleep_disable ( void )
Clear the SE (sleep enable) bit.
22.24.2.3
void sleep_enable ( void )
Put the device in sleep mode. How the device is brought out of sleep
mode depends on the specific mode selected with the set_sleep_mode() function. See
the data sheet for your device for more details.
Set the SE (sleep enable) bit.
22.25 <avr/version.h>: avr-libc version macros
Defines
•
•
•
•
•
•
•
22.25.1
#define __AVR_LIBC_VERSION_STRING__ "1.7.1"
#define __AVR_LIBC_VERSION__ 10701UL
#define __AVR_LIBC_DATE_STRING__ "20110216"
#define __AVR_LIBC_DATE_ 20110216UL
#define __AVR_LIBC_MAJOR__ 1
#define __AVR_LIBC_MINOR__ 7
#define __AVR_LIBC_REVISION__ 1
Detailed Description
#include <avr/version.h>
This header file defines macros that contain version numbers and strings describing the
current version of avr-libc.
The version number itself basically consists of three pieces that are separated by a
dot: the major number, the minor number, and the revision number. For development
versions (which use an odd minor number), the string representation additionally gets
the date code (YYYYMMDD) appended.
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22.25
<avr/version.h>: avr-libc version macros
302
This file will also be included by <avr/io.h>. That way, portable tests can be
implemented using <avr/io.h> that can be used in code that wants to remain
backwards-compatible to library versions prior to the date when the library version
API had been added, as referenced but undefined C preprocessor macros automatically
evaluate to 0.
22.25.2
Define Documentation
22.25.2.1
#define __AVR_LIBC_DATE_ 20110216UL
Numerical representation of the release date.
22.25.2.2
#define __AVR_LIBC_DATE_STRING__ "20110216"
String literal representation of the release date.
22.25.2.3
#define __AVR_LIBC_MAJOR__ 1
Library major version number.
22.25.2.4
#define __AVR_LIBC_MINOR__ 7
Library minor version number.
22.25.2.5
#define __AVR_LIBC_REVISION__ 1
Library revision number.
22.25.2.6
#define __AVR_LIBC_VERSION__ 10701UL
Numerical representation of the current library version.
In the numerical representation, the major number is multiplied by 10000, the minor
number by 100, and all three parts are then added. It is intented to provide a monotonically increasing numerical value that can easily be used in numerical checks.
22.25.2.7
#define __AVR_LIBC_VERSION_STRING__ "1.7.1"
String literal representation of the current library version.
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<avr/wdt.h>: Watchdog timer handling
22.26
303
22.26 <avr/wdt.h>: Watchdog timer handling
Defines
•
•
•
•
•
•
•
•
•
•
•
•
•
22.26.1
#define wdt_reset() __asm__ __volatile__ ("wdr")
#define wdt_enable(value)
#define wdt_disable()
#define WDTO_15MS 0
#define WDTO_30MS 1
#define WDTO_60MS 2
#define WDTO_120MS 3
#define WDTO_250MS 4
#define WDTO_500MS 5
#define WDTO_1S 6
#define WDTO_2S 7
#define WDTO_4S 8
#define WDTO_8S 9
Detailed Description
#include <avr/wdt.h>
This header file declares the interface to some inline macros handling the watchdog
timer present in many AVR devices. In order to prevent the watchdog timer configuration from being accidentally altered by a crashing application, a special timed sequence
is required in order to change it. The macros within this header file handle the required
sequence automatically before changing any value. Interrupts will be disabled during
the manipulation.
Note
Depending on the fuse configuration of the particular device, further restrictions
might apply, in particular it might be disallowed to turn off the watchdog timer.
Note that for newer devices (ATmega88 and newer, effectively any AVR that has the option to also generate interrupts), the watchdog timer remains active even after a system
reset (except a power-on condition), using the fastest prescaler value (approximately
15 ms). It is therefore required to turn off the watchdog early during program startup,
the datasheet recommends a sequence like the following:
#include <stdint.h>
#include <avr/wdt.h>
uint8_t mcusr_mirror __attribute__ ((section (".noinit")));
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22.26
<avr/wdt.h>: Watchdog timer handling
304
void get_mcusr(void) \
__attribute__((naked)) \
__attribute__((section(".init3")));
void get_mcusr(void)
{
mcusr_mirror = MCUSR;
MCUSR = 0;
wdt_disable();
}
Saving the value of MCUSR in mcusr_mirror is only needed if the application
later wants to examine the reset source, but in particular, clearing the watchdog reset
flag before disabling the watchdog is required, according to the datasheet.
22.26.2
Define Documentation
22.26.2.1
#define wdt_disable(
)
Value:
__asm__ __volatile__ ( \
"in __tmp_reg__, __SREG__" "\n\t" \
"cli" "\n\t" \
"out %0, %1" "\n\t" \
"out %0, __zero_reg__" "\n\t" \
"out __SREG__,__tmp_reg__" "\n\t" \
: /* no outputs */ \
: "I" (_SFR_IO_ADDR(_WD_CONTROL_REG)), \
"r" ((uint8_t)(_BV(_WD_CHANGE_BIT) | _BV(WDE))) \
: "r0" \
)
Disable the watchdog timer, if possible. This attempts to turn off the Enable bit in the
watchdog control register. See the datasheet for details.
22.26.2.2
#define wdt_enable( value )
Value:
__asm__ __volatile__ ( \
"in __tmp_reg__,__SREG__" "\n\t"
\
"cli" "\n\t"
\
"wdr" "\n\t"
\
"out %0,%1" "\n\t" \
"out __SREG__,__tmp_reg__" "\n\t"
\
"out %0,%2" \
: /* no outputs */ \
: "I" (_SFR_IO_ADDR(_WD_CONTROL_REG)), \
"r" (_BV(_WD_CHANGE_BIT) | _BV(WDE)),
\
"r" ((uint8_t) ((value & 0x08 ? _WD_PS3_MASK : 0x00) | \
_BV(WDE) | (value & 0x07)) ) \
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22.26
<avr/wdt.h>: Watchdog timer handling
: "r0"
305
\
)
Enable the watchdog timer, configuring it for expiry after timeout (which is a combination of the WDP0 through WDP2 bits to write into the WDTCR register; For those
devices that have a WDTCSR register, it uses the combination of the WDP0 through
WDP3 bits).
See also the symbolic constants WDTO_15MS et al.
22.26.2.3
#define wdt_reset(
) __asm__ __volatile__ ("wdr")
Reset the watchdog
timer. When the watchdog timer is enabled, a call to this instruction is required before
the timer expires, otherwise a watchdog-initiated device reset will occur.
22.26.2.4
#define WDTO_120MS 3
See WDT0_15MS
22.26.2.5
#define WDTO_15MS 0
Symbolic constants for the watchdog timeout. Since the watchdog timer
is based on a free-running RC oscillator, the times are approximate only and apply to
a supply voltage of 5 V. At lower supply voltages, the times will increase. For older
devices, the times will be as large as three times when operating at Vcc = 3 V, while
the newer devices (e. g. ATmega128, ATmega8) only experience a negligible change.
Possible timeout values are: 15 ms, 30 ms, 60 ms, 120 ms, 250 ms, 500 ms, 1 s, 2 s.
(Some devices also allow for 4 s and 8 s.) Symbolic constants are formed by the prefix
WDTO_, followed by the time.
Example that would select a watchdog timer expiry of approximately 500 ms:
wdt_enable(WDTO_500MS);
22.26.2.6
#define WDTO_1S 6
See WDT0_15MS
22.26.2.7
#define WDTO_250MS 4
See WDT0_15MS
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22.26
<avr/wdt.h>: Watchdog timer handling
22.26.2.8
306
#define WDTO_2S 7
See WDT0_15MS
22.26.2.9
#define WDTO_30MS 1
See WDT0_15MS
22.26.2.10
#define WDTO_4S 8
See WDT0_15MS Note: This is only available on the ATtiny2313, ATtiny24, ATtiny44, ATtiny84, ATtiny84A, ATtiny25, ATtiny45, ATtiny85,
ATtiny261, ATtiny461, ATtiny861, ATmega48, ATmega88, ATmega168, ATmega48P,
ATmega88P, ATmega168P, ATmega328P, ATmega164P, ATmega324P, ATmega644P,
ATmega644, ATmega640, ATmega1280, ATmega1281, ATmega2560, ATmega2561,
ATmega8HVA, ATmega16HVA, ATmega32HVB, ATmega406, ATmega1284P, AT90PWM1,
AT90PWM2, AT90PWM2B, AT90PWM3, AT90PWM3B, AT90PWM216, AT90PWM316,
AT90PWM81, AT90PWM161, AT90USB82, AT90USB162, AT90USB646, AT90USB647,
AT90USB1286, AT90USB1287, ATtiny48, ATtiny88.
22.26.2.11
#define WDTO_500MS 5
See WDT0_15MS
22.26.2.12
#define WDTO_60MS 2
WDT0_15MS
22.26.2.13
#define WDTO_8S 9
See WDT0_15MS Note: This is only available on
the ATtiny2313, ATtiny24, ATtiny44, ATtiny84, ATtiny84A, ATtiny25, ATtiny45, ATtiny85, ATtiny261, ATtiny461, ATtiny861, ATmega48, ATmega48A, ATmega48PA,
ATmega88, ATmega168, ATmega48P, ATmega88P, ATmega168P, ATmega328P, ATmega164P, ATmega324P, ATmega644P, ATmega644, ATmega640, ATmega1280, ATmega1281, ATmega2560, ATmega2561, ATmega8HVA, ATmega16HVA, ATmega32HVB,
ATmega406, ATmega1284P, AT90PWM1, AT90PWM2, AT90PWM2B, AT90PWM3,
AT90PWM3B, AT90PWM216, AT90PWM316, AT90PWM81, AT90PWM161, AT90USB82,
AT90USB162, AT90USB646, AT90USB647, AT90USB1286, AT90USB1287, ATtiny48,
ATtiny88.
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<util/atomic.h> Atomically and Non-Atomically Executed Code Blocks
307
22.27
22.27 <util/atomic.h> Atomically and Non-Atomically Executed Code Blocks
Defines
•
•
•
•
•
•
22.27.1
#define ATOMIC_BLOCK(type)
#define NONATOMIC_BLOCK(type)
#define ATOMIC_RESTORESTATE
#define ATOMIC_FORCEON
#define NONATOMIC_RESTORESTATE
#define NONATOMIC_FORCEOFF
Detailed Description
#include <util/atomic.h>
Note
The macros in this header file require the ISO/IEC 9899:1999 ("ISO C99") feature
of for loop variables that are declared inside the for loop itself. For that reason, this
header file can only be used if the standard level of the compiler (option --std=) is
set to either c99 or gnu99.
The macros in this header file deal with code blocks that are guaranteed to be excuted
Atomically or Non-Atmomically. The term "Atomic" in this context refers to the unability of the respective code to be interrupted.
These macros operate via automatic manipulation of the Global Interrupt Status (I) bit
of the SREG register. Exit paths from both block types are all managed automatically
without the need for special considerations, i. e. the interrupt status will be restored to
the same value it has been when entering the respective block.
A typical example that requires atomic access is a 16 (or more) bit variable that is
shared between the main execution path and an ISR. While declaring such a variable
as volatile ensures that the compiler will not optimize accesses to it away, it does not
guarantee atomic access to it. Assuming the following example:
#include <inttypes.h>
#include <avr/interrupt.h>
#include <avr/io.h>
volatile uint16_t ctr;
ISR(TIMER1_OVF_vect)
{
ctr--;
}
...
int
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22.27
<util/atomic.h> Atomically and Non-Atomically Executed Code Blocks
308
main(void)
{
...
ctr = 0x200;
start_timer();
while (ctr != 0)
// wait
;
...
}
There is a chance where the main context will exit its wait loop when the variable ctr
just reached the value 0xFF. This happens because the compiler cannot natively access
a 16-bit variable atomically in an 8-bit CPU. So the variable is for example at 0x100,
the compiler then tests the low byte for 0, which succeeds. It then proceeds to test the
high byte, but that moment the ISR triggers, and the main context is interrupted. The
ISR will decrement the variable from 0x100 to 0xFF, and the main context proceeds.
It now tests the high byte of the variable which is (now) also 0, so it concludes the
variable has reached 0, and terminates the loop.
Using the macros from this header file, the above code can be rewritten like:
#include
#include
#include
#include
<inttypes.h>
<avr/interrupt.h>
<avr/io.h>
<util/atomic.h>
volatile uint16_t ctr;
ISR(TIMER1_OVF_vect)
{
ctr--;
}
...
int
main(void)
{
...
ctr = 0x200;
start_timer();
sei();
uint16_t ctr_copy;
do
{
ATOMIC_BLOCK(ATOMIC_FORCEON)
{
ctr_copy = ctr;
}
}
while (ctr_copy != 0);
...
}
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22.27
<util/atomic.h> Atomically and Non-Atomically Executed Code Blocks
309
This will install the appropriate interrupt protection before accessing variable ctr,
so it is guaranteed to be consistently tested. If the global interrupt state were uncertain before entering the ATOMIC_BLOCK, it should be executed with the parameter
ATOMIC_RESTORESTATE rather than ATOMIC_FORCEON.
See optim_code_reorder for things to be taken into account with respect to compiler
optimizations.
22.27.2
Define Documentation
22.27.2.1
#define ATOMIC_BLOCK( type )
Creates a block of code that is guaranteed to be executed atomically. Upon
entering the block the Global Interrupt Status flag in SREG is disabled, and re-enabled
upon exiting the block from any exit path.
Two possible macro parameters are permitted, ATOMIC_RESTORESTATE and ATOMIC_FORCEON.
22.27.2.2
#define ATOMIC_FORCEON
This is a possible parameter for ATOMIC_BLOCK. When used, it will
cause the ATOMIC_BLOCK to force the state of the SREG register on exit, enabling
the Global Interrupt Status flag bit. This saves on flash space as the previous value of
the SREG register does not need to be saved at the start of the block.
Care should be taken that ATOMIC_FORCEON is only used when it is known that
interrupts are enabled before the block’s execution or when the side effects of enabling
global interrupts at the block’s completion are known and understood.
22.27.2.3
#define ATOMIC_RESTORESTATE
This is a possible parameter for ATOMIC_BLOCK. When used,
it will cause the ATOMIC_BLOCK to restore the previous state of the SREG register,
saved before the Global Interrupt Status flag bit was disabled. The net effect of this
is to make the ATOMIC_BLOCK’s contents guaranteed atomic, without changing the
state of the Global Interrupt Status flag when execution of the block completes.
22.27.2.4
#define NONATOMIC_BLOCK( type )
Creates a block of code that is executed
non-atomically. Upon entering the block the Global Interrupt Status flag in SREG is
enabled, and disabled upon exiting the block from any exit path. This is useful when
nested inside ATOMIC_BLOCK sections, allowing for non-atomic execution of small
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22.28
<util/crc16.h>: CRC Computations
310
blocks of code while maintaining the atomic access of the other sections of the parent
ATOMIC_BLOCK.
Two possible macro parameters are permitted, NONATOMIC_RESTORESTATE and
NONATOMIC_FORCEOFF.
22.27.2.5
#define NONATOMIC_FORCEOFF
This is a possible parameter for NONATOMIC_BLOCK. When used, it
will cause the NONATOMIC_BLOCK to force the state of the SREG register on exit,
disabling the Global Interrupt Status flag bit. This saves on flash space as the previous
value of the SREG register does not need to be saved at the start of the block.
Care should be taken that NONATOMIC_FORCEOFF is only used when it is known
that interrupts are disabled before the block’s execution or when the side effects of
disabling global interrupts at the block’s completion are known and understood.
22.27.2.6
#define NONATOMIC_RESTORESTATE
This is a possible parameter for NONATOMIC_BLOCK. When used, it will cause
the NONATOMIC_BLOCK to restore the previous state of the SREG register, saved
before the Global Interrupt Status flag bit was enabled. The net effect of this is to make
the NONATOMIC_BLOCK’s contents guaranteed non-atomic, without changing the
state of the Global Interrupt Status flag when execution of the block completes.
22.28 <util/crc16.h>: CRC Computations
Functions
•
•
•
•
22.28.1
static __inline__ uint16_t _crc16_update (uint16_t __crc, uint8_t __data)
static __inline__ uint16_t _crc_xmodem_update (uint16_t __crc, uint8_t __data)
static __inline__ uint16_t _crc_ccitt_update (uint16_t __crc, uint8_t __data)
static __inline__ uint8_t _crc_ibutton_update (uint8_t __crc, uint8_t __data)
Detailed Description
#include <util/crc16.h>
This header file provides a optimized inline functions for calculating cyclic redundancy
checks (CRC) using common polynomials.
References:
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22.28
<util/crc16.h>: CRC Computations
311
See the Dallas Semiconductor app note 27 for 8051 assembler example and general
CRC optimization suggestions. The table on the last page of the app note is the key to
understanding these implementations.
Jack Crenshaw’s "Implementing CRCs" article in the January 1992 isue of Embedded
Systems Programming. This may be difficult to find, but it explains CRC’s in very clear
and concise terms. Well worth the effort to obtain a copy.
A typical application would look like:
// Dallas iButton test vector.
uint8_t serno[] = { 0x02, 0x1c, 0xb8, 0x01, 0, 0, 0, 0xa2 };
int
checkcrc(void)
{
uint8_t crc = 0, i;
for (i = 0; i < sizeof serno / sizeof serno[0]; i++)
crc = _crc_ibutton_update(crc, serno[i]);
return crc; // must be 0
}
22.28.2
Function Documentation
22.28.2.1
static __inline__ uint16_t _crc16_update ( uint16_t __crc, uint8_t
__data ) [static]
Optimized CRC-16 calculation.
Polynomial: x∧ 16 + x∧ 15 + x∧ 2 + 1 (0xa001)
Initial value: 0xffff
This CRC is normally used in disk-drive controllers.
The following is the equivalent functionality written in C.
uint16_t
crc16_update(uint16_t crc, uint8_t a)
{
int i;
crc ^= a;
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22.28
<util/crc16.h>: CRC Computations
for (i = 0;
{
if (crc
crc
else
crc
}
312
i < 8; ++i)
& 1)
= (crc >> 1) ^ 0xA001;
= (crc >> 1);
return crc;
}
22.28.2.2
static __inline__ uint16_t _crc_ccitt_update ( uint16_t __crc, uint8_t
__data ) [static]
Optimized CRC-CCITT calculation.
Polynomial: x∧ 16 + x∧ 12 + x∧ 5 + 1 (0x8408)
Initial value: 0xffff
This is the CRC used by PPP and IrDA.
See RFC1171 (PPP protocol) and IrDA IrLAP 1.1
Note
Although the CCITT polynomial is the same as that used by the Xmodem protocol,
they are quite different. The difference is in how the bits are shifted through the
alorgithm. Xmodem shifts the MSB of the CRC and the input first, while CCITT
shifts the LSB of the CRC and the input first.
The following is the equivalent functionality written in C.
uint16_t
crc_ccitt_update (uint16_t crc, uint8_t data)
{
data ^= lo8 (crc);
data ^= data << 4;
return ((((uint16_t)data << 8) | hi8 (crc)) ^ (uint8_t)(data >> 4)
^ ((uint16_t)data << 3));
}
22.28.2.3
static __inline__ uint8_t _crc_ibutton_update ( uint8_t __crc, uint8_t
__data ) [static]
Optimized Dallas (now Maxim) iButton 8-bit CRC calculation.
Polynomial: x∧ 8 + x∧ 5 + x∧ 4 + 1 (0x8C)
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22.28
<util/crc16.h>: CRC Computations
313
Initial value: 0x0
See http://www.maxim-ic.com/appnotes.cfm/appnote_number/27
The following is the equivalent functionality written in C.
uint8_t
_crc_ibutton_update(uint8_t crc, uint8_t data)
{
uint8_t i;
crc = crc ^
for (i = 0;
{
if (crc
crc
else
crc
}
data;
i < 8; i++)
& 0x01)
= (crc >> 1) ^ 0x8C;
>>= 1;
return crc;
}
22.28.2.4
static __inline__ uint16_t _crc_xmodem_update ( uint16_t __crc,
uint8_t __data ) [static]
Optimized CRC-XMODEM calculation.
Polynomial: x∧ 16 + x∧ 12 + x∧ 5 + 1 (0x1021)
Initial value: 0x0
This is the CRC used by the Xmodem-CRC protocol.
The following is the equivalent functionality written in C.
uint16_t
crc_xmodem_update (uint16_t crc, uint8_t data)
{
int i;
crc = crc ^ ((uint16_t)data << 8);
for (i=0; i<8; i++)
{
if (crc & 0x8000)
crc = (crc << 1) ^ 0x1021;
else
crc <<= 1;
}
return crc;
}
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22.29
<util/delay_basic.h>: Basic busy-wait delay loops
314
22.29 <util/delay basic.h>: Basic busy-wait delay loops
Functions
• void _delay_loop_1 (uint8_t __count)
• void _delay_loop_2 (uint16_t __count)
22.29.1
Detailed Description
#include <util/delay_basic.h>
The functions in this header file implement simple delay loops that perform a busywaiting. They are typically used to facilitate short delays in the program execution.
They are implemented as count-down loops with a well-known CPU cycle count per
loop iteration. As such, no other processing can occur simultaneously. It should be
kept in mind that the functions described here do not disable interrupts.
In general, for long delays, the use of hardware timers is much preferrable, as they
free the CPU, and allow for concurrent processing of other events while the timer is
running. However, in particular for very short delays, the overhead of setting up a
hardware timer is too much compared to the overall delay time.
Two inline functions are provided for the actual delay algorithms.
22.29.2
Function Documentation
22.29.2.1
void _delay_loop_1 ( uint8_t __count )
Delay loop using an 8-bit counter __count, so up to 256 iterations are possible.
(The value 256 would have to be passed as 0.) The loop executes three CPU cycles per
iteration, not including the overhead the compiler needs to setup the counter register.
Thus, at a CPU speed of 1 MHz, delays of up to 768 microseconds can be achieved.
22.29.2.2
void _delay_loop_2 ( uint16_t __count )
Delay loop using a 16-bit counter __count, so up to 65536 iterations
are possible. (The value 65536 would have to be passed as 0.) The loop executes four
CPU cycles per iteration, not including the overhead the compiler requires to setup the
counter register pair.
Thus, at a CPU speed of 1 MHz, delays of up to about 262.1 milliseconds can be
achieved.
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<util/parity.h>: Parity bit generation
22.30
315
22.30 <util/parity.h>: Parity bit generation
Defines
• #define parity_even_bit(val)
22.30.1
Detailed Description
#include <util/parity.h>
This header file contains optimized assembler code to calculate the parity bit for a byte.
22.30.2
Define Documentation
22.30.2.1
#define parity_even_bit( val )
Value:
(__extension__({
unsigned char __t;
__asm__ (
"mov __tmp_reg__,%0" "\n\t"
"swap %0" "\n\t"
"eor %0,__tmp_reg__" "\n\t"
"mov __tmp_reg__,%0" "\n\t"
"lsr %0" "\n\t"
"lsr %0" "\n\t"
"eor %0,__tmp_reg__"
: "=r" (__t)
: "0" ((unsigned char)(val))
: "r0"
);
(((__t + 1) >> 1) & 1);
}))
\
\
\
\
\
\
\
\
\
\
\
\
\
\
\
Returns
1 if val has an odd number of bits set.
22.31 <util/setbaud.h>: Helper macros for baud rate calculations
Defines
•
•
•
•
•
#define BAUD_TOL 2
#define UBRR_VALUE
#define UBRRL_VALUE
#define UBRRH_VALUE
#define USE_2X 0
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22.31
<util/setbaud.h>: Helper macros for baud rate calculations
22.31.1
Detailed Description
316
#define F_CPU 11059200
#define BAUD 38400
#include <util/setbaud.h>
This header file requires that on entry values are already defined for F_CPU and BAUD.
In addition, the macro BAUD_TOL will define the baud rate tolerance (in percent) that
is acceptable during the calculations. The value of BAUD_TOL will default to 2 %.
This header file defines macros suitable to setup the UART baud rate prescaler registers
of an AVR. All calculations are done using the C preprocessor. Including this header
file causes no other side effects so it is possible to include this file more than once
(supposedly, with different values for the BAUD parameter), possibly even within the
same function.
Assuming that the requested BAUD is valid for the given F_CPU then the macro
UBRR_VALUE is set to the required prescaler value. Two additional macros are provided for the low and high bytes of the prescaler, respectively: UBRRL_VALUE is set
to the lower byte of the UBRR_VALUE and UBRRH_VALUE is set to the upper byte.
An additional macro USE_2X will be defined. Its value is set to 1 if the desired BAUD
rate within the given tolerance could only be achieved by setting the U2X bit in the
UART configuration. It will be defined to 0 if U2X is not needed.
Example usage:
#include <avr/io.h>
#define F_CPU 4000000
static void
uart_9600(void)
{
#define BAUD 9600
#include <util/setbaud.h>
UBRRH = UBRRH_VALUE;
UBRRL = UBRRL_VALUE;
#if USE_2X
UCSRA |= (1 << U2X);
#else
UCSRA &= ~(1 << U2X);
#endif
}
static void
uart_38400(void)
{
#undef BAUD // avoid compiler warning
#define BAUD 38400
#include <util/setbaud.h>
UBRRH = UBRRH_VALUE;
UBRRL = UBRRL_VALUE;
#if USE_2X
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22.31
<util/setbaud.h>: Helper macros for baud rate calculations
317
UCSRA |= (1 << U2X);
#else
UCSRA &= ~(1 << U2X);
#endif
}
In this example, two functions are defined to setup the UART to run at 9600 Bd, and
38400 Bd, respectively. Using a CPU clock of 4 MHz, 9600 Bd can be achieved with
an acceptable tolerance without setting U2X (prescaler 25), while 38400 Bd require
U2X to be set (prescaler 12).
22.31.2
Define Documentation
22.31.2.1
#define BAUD_TOL 2
Input and output macro for <util/setbaud.h>
Define the acceptable baud rate tolerance in percent. If not set on entry, it will be set to
its default value of 2.
22.31.2.2
#define UBRR_VALUE
Output macro from <util/setbaud.h>
Contains the calculated baud rate prescaler value for the UBRR register.
22.31.2.3
#define UBRRH_VALUE
Output macro from <util/setbaud.h>
Contains the upper byte of the calculated prescaler value (UBRR_VALUE).
22.31.2.4
#define UBRRL_VALUE
Output macro from <util/setbaud.h>
Contains the lower byte of the calculated prescaler value (UBRR_VALUE).
22.31.2.5
#define USE_2X 0
Output bacro from <util/setbaud.h>
Contains the value 1 if the desired baud rate tolerance could only be achieved by setting
the U2X bit in the UART configuration. Contains 0 otherwise.
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22.32
<util/twi.h>: TWI bit mask definitions
22.32 <util/twi.h>: TWI bit mask definitions
TWSR values
Mnemonics:
TW_MT_xxx - master transmitter
TW_MR_xxx - master receiver
TW_ST_xxx - slave transmitter
TW_SR_xxx - slave receiver
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
#define TW_START 0x08
#define TW_REP_START 0x10
#define TW_MT_SLA_ACK 0x18
#define TW_MT_SLA_NACK 0x20
#define TW_MT_DATA_ACK 0x28
#define TW_MT_DATA_NACK 0x30
#define TW_MT_ARB_LOST 0x38
#define TW_MR_ARB_LOST 0x38
#define TW_MR_SLA_ACK 0x40
#define TW_MR_SLA_NACK 0x48
#define TW_MR_DATA_ACK 0x50
#define TW_MR_DATA_NACK 0x58
#define TW_ST_SLA_ACK 0xA8
#define TW_ST_ARB_LOST_SLA_ACK 0xB0
#define TW_ST_DATA_ACK 0xB8
#define TW_ST_DATA_NACK 0xC0
#define TW_ST_LAST_DATA 0xC8
#define TW_SR_SLA_ACK 0x60
#define TW_SR_ARB_LOST_SLA_ACK 0x68
#define TW_SR_GCALL_ACK 0x70
#define TW_SR_ARB_LOST_GCALL_ACK 0x78
#define TW_SR_DATA_ACK 0x80
#define TW_SR_DATA_NACK 0x88
#define TW_SR_GCALL_DATA_ACK 0x90
#define TW_SR_GCALL_DATA_NACK 0x98
#define TW_SR_STOP 0xA0
#define TW_NO_INFO 0xF8
#define TW_BUS_ERROR 0x00
#define TW_STATUS_MASK
#define TW_STATUS (TWSR & TW_STATUS_MASK)
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318
22.32
<util/twi.h>: TWI bit mask definitions
319
R/∼W bit in SLA+R/W address field.
• #define TW_READ 1
• #define TW_WRITE 0
22.32.1
Detailed Description
#include <util/twi.h>
This header file contains bit mask definitions for use with the AVR TWI interface.
22.32.2
Define Documentation
22.32.2.1
#define TW_BUS_ERROR 0x00
illegal start or stop condition
22.32.2.2
#define TW_MR_ARB_LOST 0x38
arbitration lost in SLA+R or NACK
22.32.2.3
#define TW_MR_DATA_ACK 0x50
data received, ACK returned
22.32.2.4
#define TW_MR_DATA_NACK 0x58
data received, NACK returned
22.32.2.5
#define TW_MR_SLA_ACK 0x40
SLA+R transmitted, ACK received
22.32.2.6
#define TW_MR_SLA_NACK 0x48
SLA+R transmitted, NACK received
22.32.2.7
#define TW_MT_ARB_LOST 0x38
arbitration lost in SLA+W or data
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22.32
<util/twi.h>: TWI bit mask definitions
22.32.2.8
320
#define TW_MT_DATA_ACK 0x28
data transmitted, ACK received
22.32.2.9
#define TW_MT_DATA_NACK 0x30
data transmitted, NACK received
22.32.2.10
#define TW_MT_SLA_ACK 0x18
SLA+W transmitted, ACK received
22.32.2.11
#define TW_MT_SLA_NACK 0x20
SLA+W transmitted, NACK received
22.32.2.12
#define TW_NO_INFO 0xF8
no state information available
22.32.2.13
#define TW_READ 1
SLA+R address
22.32.2.14
#define TW_REP_START 0x10
repeated start condition transmitted
22.32.2.15
#define TW_SR_ARB_LOST_GCALL_ACK 0x78
arbitration lost in SLA+RW, general call received, ACK returned
22.32.2.16
#define TW_SR_ARB_LOST_SLA_ACK 0x68
arbitration lost in SLA+RW, SLA+W received, ACK returned
22.32.2.17
#define TW_SR_DATA_ACK 0x80
data received, ACK returned
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22.32
<util/twi.h>: TWI bit mask definitions
22.32.2.18
321
#define TW_SR_DATA_NACK 0x88
data received, NACK returned
22.32.2.19
#define TW_SR_GCALL_ACK 0x70
general call received, ACK returned
22.32.2.20
#define TW_SR_GCALL_DATA_ACK 0x90
general call data received, ACK returned
22.32.2.21
#define TW_SR_GCALL_DATA_NACK 0x98
general call data received, NACK returned
22.32.2.22
#define TW_SR_SLA_ACK 0x60
SLA+W received, ACK returned
22.32.2.23
#define TW_SR_STOP 0xA0
stop or repeated start condition received while selected
22.32.2.24
#define TW_ST_ARB_LOST_SLA_ACK 0xB0
arbitration lost in SLA+RW, SLA+R received, ACK returned
22.32.2.25
#define TW_ST_DATA_ACK 0xB8
data transmitted, ACK received
22.32.2.26
#define TW_ST_DATA_NACK 0xC0
data transmitted, NACK received
22.32.2.27
#define TW_ST_LAST_DATA 0xC8
last data byte transmitted, ACK received
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22.33
<compat/deprecated.h>: Deprecated items
22.32.2.28
322
#define TW_ST_SLA_ACK 0xA8
SLA+R received, ACK returned
22.32.2.29
#define TW_START 0x08
start condition transmitted
22.32.2.30
#define TW_STATUS (TWSR & TW_STATUS_MASK)
TWSR, masked by TW_STATUS_MASK
22.32.2.31
#define TW_STATUS_MASK
Value:
(_BV(TWS7)|_BV(TWS6)|_BV(TWS5)|_BV(TWS4)|\
_BV(TWS3))
The lower 3 bits of TWSR are reserved on the ATmega163. The 2 LSB carry the
prescaler bits on the newer ATmegas.
22.32.2.32
#define TW_WRITE 0
SLA+W address
22.33 <compat/deprecated.h>: Deprecated items
Allowing specific system-wide interrupts
In addition to globally enabling interrupts, each device’s particular interrupt needs to
be enabled separately if interrupts for this device are desired. While some devices
maintain their interrupt enable bit inside the device’s register set, external and timer
interrupts have system-wide configuration registers.
Example:
// Enable timer 1 overflow interrupts.
timer_enable_int(_BV(TOIE1));
// Do some work...
// Disable all timer interrupts.
timer_enable_int(0);
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22.33
<compat/deprecated.h>: Deprecated items
323
Note
Be careful when you use these functions. If you already have a different interrupt
enabled, you could inadvertantly disable it by enabling another intterupt.
•
•
•
•
static __inline__ void timer_enable_int (unsigned char ints)
#define enable_external_int(mask) (__EICR = mask)
#define INTERRUPT(signame)
#define __INTR_ATTRS used
Obsolete IO macros
Back in a time when AVR-GCC and avr-libc could not handle IO port access in the direct assignment form as they are handled now, all IO port access had to be done through
specific macros that eventually resulted in inline assembly instructions performing the
desired action.
These macros became obsolete, as reading and writing IO ports can be done by simply
using the IO port name in an expression, and all bit manipulation (including those on
IO ports) can be done using generic C bit manipulation operators.
The macros in this group simulate the historical behaviour. While they are supposed to
be applied to IO ports, the emulation actually uses standard C methods, so they could
be applied to arbitrary memory locations as well.
•
•
•
•
•
•
22.33.1
#define inp(port) (port)
#define outp(val, port) (port) = (val)
#define inb(port) (port)
#define outb(port, val) (port) = (val)
#define sbi(port, bit) (port) |= (1 << (bit))
#define cbi(port, bit) (port) &= ∼(1 << (bit))
Detailed Description
This header file contains several items that used to be available in previous versions of
this library, but have eventually been deprecated over time.
#include <compat/deprecated.h>
These items are supplied within that header file for backward compatibility reasons
only, so old source code that has been written for previous library versions could easily
be maintained until its end-of-life. Use of any of these items in new code is strongly
discouraged.
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22.33
<compat/deprecated.h>: Deprecated items
22.33.2
Define Documentation
22.33.2.1
324
#define cbi( port, bit ) (port) &= ∼(1 << (bit))
Deprecated
Clear bit in IO port port.
22.33.2.2
#define enable_external_int( mask ) (__EICR = mask)
Deprecated
This macro gives access to the GIMSK register (or EIMSK register if using an AVR
Mega device or GICR register for others). Although this macro is essentially the same
as assigning to the register, it does adapt slightly to the type of device being used. This
macro is unavailable if none of the registers listed above are defined.
22.33.2.3
#define inb( port ) (port)
Deprecated
Read a value from an IO port port.
22.33.2.4
#define inp( port ) (port)
Deprecated
Read a value from an IO port port.
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22.33
<compat/deprecated.h>: Deprecated items
22.33.2.5
325
#define INTERRUPT( signame )
Value:
void signame (void) __attribute__ ((interrupt,__INTR_ATTRS));
void signame (void)
\
Deprecated
Introduces an interrupt handler function that runs with global interrupts initially enabled. This allows interrupt handlers to be interrupted.
As this macro has been used by too many unsuspecting people in the past, it has been
deprecated, and will be removed in a future version of the library. Users who want to
legitimately re-enable interrupts in their interrupt handlers as quickly as possible are
encouraged to explicitly declare their handlers as described above.
22.33.2.6
#define outb( port, val ) (port) = (val)
Deprecated
Write val to IO port port.
22.33.2.7
#define outp( val, port ) (port) = (val)
Deprecated
Write val to IO port port.
22.33.2.8
#define sbi( port, bit ) (port) |= (1 << (bit))
Deprecated
Set bit in IO port port.
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22.34
<compat/ina90.h>: Compatibility with IAR EWB 3.x
22.33.3
Function Documentation
22.33.3.1
326
static __inline__ void timer_enable_int ( unsigned char ints )
[static]
Deprecated
This function modifies the timsk register. The value you pass via ints is device
specific.
22.34 <compat/ina90.h>: Compatibility with IAR EWB 3.x
#include <compat/ina90.h>
This is an attempt to provide some compatibility with header files that come with IAR
C, to make porting applications between different compilers easier. No 100% compatibility though.
Note
For actual documentation, please see the IAR manual.
22.35
Demo projects
Modules
•
•
•
•
•
22.35.1
Combining C and assembly source files
A simple project
A more sophisticated project
Using the standard IO facilities
Example using the two-wire interface (TWI)
Detailed Description
Various small demo projects are provided to illustrate several aspects of using the opensource utilities for the AVR controller series. It should be kept in mind that these demos serve mainly educational purposes, and are normally not directly suitable for use
in any production environment. Usually, they have been kept as simple as sufficient to
demonstrate one particular feature.
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The simple project is somewhat like the "Hello world!" application for a microcontroller, about the most simple project that can be done. It is explained in good detail,
to allow the reader to understand the basic concepts behind using the tools on an AVR
microcontroller.
The more sophisticated demo project builds on top of that simple project, and adds
some controls to it. It touches a number of avr-libc’s basic concepts on its way.
A comprehensive example on using the standard IO facilities intends to explain that
complex topic, using a practical microcontroller peripheral setup with one RS-232 connection, and an HD44780-compatible industry-standard LCD display.
The Example using the two-wire interface (TWI) project explains the use of the twowire hardware interface (also known as "I2C") that is present on many AVR controllers.
Finally, the Combining C and assembly source files demo shows how C and assembly language source files can collaborate within one project. While the overall project
is managed by a C program part for easy maintenance, time-critical parts are written
directly in manually optimized assembly language for shortest execution times possible. Naturally, this kind of project is very closely tied to the hardware design, thus it is
custom-tailored to a particular controller type and peripheral setup. As an alternative to
the assembly-language solution, this project also offers a C-only implementation (deploying the exact same peripheral setup) based on a more sophisticated (and thus more
expensive) but pin-compatible controller.
While the simple demo is meant to run on about any AVR setup possible where a
LED could be connected to the OCR1[A] output, the large and stdio demos are mainly
targeted to the Atmel STK500 starter kit, and the TWI example requires a controller
where some 24Cxx two-wire EEPPROM can be connected to. For the STK500 demos,
the default CPU (either an AT90S8515 or an ATmega8515) should be removed from
its socket, and the ATmega16 that ships with the kit should be inserted into socket
SCKT3100A3. The ATmega16 offers an on-board ADC that is used in the large demo,
and all AVRs with an ADC feature a different pinout than the industry-standard compatible devices.
In order to fully utilize the large demo, a female 10-pin header with cable, connecting
to a 10 kOhm potentiometer will be useful.
For the stdio demo, an industry-standard HD44780-compatible LCD display of at least
16x1 characters will be needed. Among other things, the LCD4Linux project page
describes many things around these displays, including common pinouts.
22.36
Combining C and assembly source files
For time- or space-critical applications, it can often be desirable to combine C code
(for easy maintenance) and assembly code (for maximal speed or minimal code size)
together. This demo provides an example of how to do that.
The objective of the demo is to decode radio-controlled model PWM signals, and con-
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trol an output PWM based on the current input signal’s value. The incoming PWM
pulses follow a standard encoding scheme where a pulse width of 920 microseconds
denotes one end of the scale (represented as 0 % pulse width on output), and 2120
microseconds mark the other end (100 % output PWM). Normally, multiple channels
would be encoded that way in subsequent pulses, followed by a larger gap, so the entire frame will repeat each 14 through 20 ms, but this is ignored for the purpose of the
demo, so only a single input PWM channel is assumed.
The basic challenge is to use the cheapest controller available for the task, an ATtiny13
that has only a single timer channel. As this timer channel is required to run the outgoing PWM signal generation, the incoming PWM decoding had to be adjusted to the
constraints set by the outgoing PWM.
As PWM generation toggles the counting direction of timer 0 between up and down
after each 256 timer cycles, the current time cannot be deduced by reading TCNT0
only, but the current counting direction of the timer needs to be considered as well.
This requires servicing interrupts whenever the timer hits TOP (255) and BOTTOM (0)
to learn about each change of the counting direction. For PWM generation, it is usually
desired to run it at the highest possible speed so filtering the PWM frequency from the
modulated output signal is made easy. Thus, the PWM timer runs at full CPU speed.
This causes the overflow and compare match interrupts to be triggered each 256 CPU
clocks, so they must run with the minimal number of processor cycles possible in order
to not impose a too high CPU load by these interrupt service routines. This is the main
reason to implement the entire interrupt handling in fine-tuned assembly code rather
than in C.
In order to verify parts of the algorithm, and the underlying hardware, the demo has
been set up in a way so the pin-compatible but more expensive ATtiny45 (or its siblings
ATtiny25 and ATtiny85) could be used as well. In that case, no separate assembly code
is required, as two timer channels are avaible.
22.36.1
Hardware setup
The incoming PWM pulse train is fed into PB4. It will generate a pin change interrupt
there on eache edge of the incoming signal.
The outgoing PWM is generated through OC0B of timer channel 0 (PB1). For demonstration purposes, a LED should be connected to that pin (like, one of the LEDs of an
STK500).
The controllers run on their internal calibrated RC oscillators, 1.2 MHz on the ATtiny13, and 1.0 MHz on the ATtiny45.
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Combining C and assembly source files
22.36.2
A code walkthrough
22.36.2.1
329
asmdemo.c
After the usual include files, two variables are defined. The first one, pwm_incoming
is used to communicate the most recent pulse width detected by the incoming PWM
decoder up to the main loop.
The second variable actually only constitutes of a single bit, intbits.pwm_received.
This bit will be set whenever the incoming PWM decoder has updated pwm_incoming.
Both variables are marked volatile to ensure their readers will always pick up an updated value, as both variables will be set by interrupt service routines.
The function ioinit() initializes the microcontroller peripheral devices. In particular, it starts timer 0 to generate the outgoing PWM signal on OC0B. Setting OCR0A
to 255 (which is the TOP value of timer 0) is used to generate a timer 0 overflow A
interrupt on the ATtiny13. This interrupt is used to inform the incoming PWM decoder
that the counting direction of channel 0 is just changing from up to down. Likewise, an
overflow interrupt will be generated whenever the countdown reached BOTTOM (value
0), where the counter will again alter its counting direction to upwards. This information is needed in order to know whether the current counter value of TCNT0 is to be
evaluated from bottom or top.
Further, ioinit() activates the pin-change interrupt PCINT0 on any edge of PB4.
Finally, PB1 (OC0B) will be activated as an output pin, and global interrupts are being
enabled.
In the ATtiny45 setup, the C code contains an ISR for PCINT0. At each pin-change
interrupt, it will first be analyzed whether the interrupt was caused by a rising or a
falling edge. In case of the rising edge, timer 1 will be started with a prescaler of 16
after clearing the current timer value. Then, at the falling edge, the current timer value
will be recorded (and timer 1 stopped), the pin-change interrupt will be suspended, and
the upper layer will be notified that the incoming PWM measurement data is available.
Function main() first initializes the hardware by calling ioinit(), and then waits
until some incoming PWM value is available. If it is, the output PWM will be adjusted
by computing the relative value of the incoming PWM. Finally, the pin-change interrupt
is re-enabled, and the CPU is put to sleep.
22.36.2.2
project.h
In order for the interrupt service routines to be as fast as possible, some of the CPU
registers are set aside completely for use by these routines, so the compiler would not
use them for C code. This is arranged for in project.h.
The file is divided into one section that will be used by the assembly source code, and
another one to be used by C code. The assembly part is distinguished by the prepro-
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330
cessing macro __ASSEMBLER__ (which will be automatically set by the compiler
front-end when preprocessing an assembly-language file), and it contains just macros
that give symbolic names to a number of CPU registers. The preprocessor will then
replace the symbolic names by their right-hand side definitions before calling the assembler.
In C code, the compiler needs to see variable declarations for these objects. This is
done by using declarations that bind a variable permanently to a CPU register (see
How to permanently bind a variable to a register?). Even in case the C code never
has a need to access these variables, declaring the register binding that way causes the
compiler to not use these registers in C code at all.
The flags variable needs to be in the range of r16 through r31 as it is the target of a
load immediate (or SER) instruction that is not applicable to the entire register file.
22.36.2.3
isrs.S
This file is a preprocessed assembly source file. The C preprocessor will be run by
the compiler front-end first, resolving all #include, #define etc. directives. The
resulting program text will then be passed on to the assembler.
As the C preprocessor strips all C-style comments, preprocessed assembly source files
can have both, C-style (/∗ ... ∗/, // ...) as well as assembly-style (; ...)
comments.
At the top, the IO register definition file avr/io.h and the project declaration file
project.h are included. The remainder of the file is conditionally assembled only if
the target MCU type is an ATtiny13, so it will be completely ignored for the ATtiny45
option.
Next are the two interrupt service routines for timer 0 compare A match (timer 0 hits
TOP, as OCR0A is set to 255) and timer 0 overflow (timer 0 hits BOTTOM). As discussed above, these are kept as short as possible. They only save SREG (as the flags
will be modified by the INC instruction), increment the counter_hi variable which
forms the high part of the current time counter (the low part is formed by querying
TCNT0 directly), and clear or set the variable flags, respectively, in order to note
the current counting direction. The RETI instruction terminates these interrupt service
routines. Total cycle count is 8 CPU cycles, so together with the 4 CPU cycles needed
for interrupt setup, and the 2 cycles for the RJMP from the interrupt vector to the handler, these routines will require 14 out of each 256 CPU cycles, or about 5 % of the
overall CPU time.
The pin-change interrupt PCINT0 will be handled in the final part of this file. The
basic algorithm is to quickly evaluate the current system time by fetching the current
timer value of TCNT0, and combining it with the overflow part in counter_hi. If
the counter is currently counting down rather than up, the value fetched from TCNT0
must be negated. Finally, if this pin-change interrupt was triggered by a rising edge,
the time computed will be recorded as the start time only. Then, at the falling edge,
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this start time will be subracted from the current time to compute the actual pulse width
seen (left in pwm_incoming), and the upper layers are informed of the new value by
setting bit 0 in the intbits flags. At the same time, this pin-change interrupt will be
disabled so no new measurement can be performed until the upper layer had a chance
to process the current value.
22.36.3
The source code
The source code is installed under
$prefix/share/doc/avr-libc/examples/asmdemo/,
where $prefix is a configuration option. For Unix systems, it is usually set to either
/usr or /usr/local.
22.37
A simple project
At this point, you should have the GNU tools configured, built, and installed on your
system. In this chapter, we present a simple example of using the GNU tools in an AVR
project. After reading this chapter, you should have a better feel as to how the tools are
used and how a Makefile can be configured.
22.37.1
The Project
This project will use the pulse-width modulator (PWM) to ramp an LED on and off every
two seconds. An AT90S2313 processor will be used as the controller. The circuit for
this demonstration is shown in the schematic diagram. If you have a development kit,
you should be able to use it, rather than build the circuit, for this project.
Note
Meanwhile, the AT90S2313 became obsolete. Either use its successor, the (pincompatible) ATtiny2313 for the project, or perhaps the ATmega8 or one of its
successors (ATmega48/88/168) which have become quite popular since the original demo project had been established. For all these more modern devices, it is no
longer necessary to use an external crystal for clocking as they ship with the internal 1 MHz oscillator enabled, so C1, C2, and Q1 can be omitted. Normally, for
this experiment, the external circuitry on /RESET (R1, C3) can be omitted as well,
leaving only the AVR, the LED, the bypass capacitor C4, and perhaps R2. For the
ATmega8/48/88/168, use PB1 (pin 15 at the DIP-28 package) to connect the LED
to. Additionally, this demo has been ported to many different other AVRs. The location of the respective OC pin varies between different AVRs, and it is mandated
by the AVR hardware.
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VCC
IC1
4mhz
C2
Q1
C3
20K
.01uf
R1
C4
.1uf
18pf
GND
GND
19
18
17
16
15
14
13
12
(ICP)PD6
(T1)PD5
(T0)PD4
(INT1)PD3
(INT0)PD2
(TXD)PD1
(RXD)PD0
AT90S2313P
11
9
8
7
6
3
2
RESET
4
XTAL2
5
XTAL1
C1
18pf
(SCK)PB7
(MISO)PB6
(MOSI)PB5
PB4
(OCI)PB3
PB2
(AIN1)PB1
(AIN0)PB0
1
20 VCC
10 GND
R2*
LED5MM
D1
See note [8]
GND
Figure 5: Schematic of circuit for demo project
The source code is given in demo.c. For the sake of this example, create a file called
demo.c containing this source code. Some of the more important parts of the code
are:
Note [1]:
As the AVR microcontroller series has been developed during the past years, new
features have been added over time. Even though the basic concepts of the timer/counter1 are still the same as they used to be back in early 2001 when this simple demo was written initially, the names of registers and bits have been changed
slightly to reflect the new features. Also, the port and pin mapping of the output
compare match 1A (or 1 for older devices) pin which is used to control the LED
varies between different AVRs. The file iocompat.h tries to abstract between
all this differences using some preprocessor #ifdef statements, so the actual program itself can operate on a common set of symbolic names. The macros defined
by that file are:
• OCR the name of the OCR register used to control the PWM (usually either
OCR1 or OCR1A)
• DDROC the name of the DDR (data direction register) for the OC output
• OC1 the pin number of the OC1[A] output within its port
• TIMER1_TOP the TOP value of the timer used for the PWM (1023 for 10-bit
PWMs, 255 for devices that can only handle an 8-bit PWM)
• TIMER1_PWM_INIT the initialization bits to be set into control register 1A in
order to setup 10-bit (or 8-bit) phase and frequency correct PWM mode
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• TIMER1_CLOCKSOURCE the clock bits to set in the respective control register to start the PWM timer; usually the timer runs at full CPU clock for 10-bit
PWMs, while it runs on a prescaled clock for 8-bit PWMs
Note [2]:
ISR() is a macro that marks the function as an interrupt routine. In this case, the
function will get called when timer 1 overflows. Setting up interrupts is explained
in greater detail in <avr/interrupt.h>: Interrupts.
Note [3]:
The PWM is being used in 10-bit mode, so we need a 16-bit variable to remember
the current value.
Note [4]:
This section determines the new value of the PWM.
Note [5]:
Here’s where the newly computed value is loaded into the PWM register. Since
we are in an interrupt routine, it is safe to use a 16-bit assignment to the register.
Outside of an interrupt, the assignment should only be performed with interrupts
disabled if there’s a chance that an interrupt routine could also access this register
(or another register that uses TEMP), see the appropriate FAQ entry.
Note [6]:
This routine gets called after a reset. It initializes the PWM and enables interrupts.
Note [7]:
The main loop of the program does nothing -- all the work is done by the interrupt
routine! The sleep_mode() puts the processor on sleep until the next interrupt,
to conserve power. Of course, that probably won’t be noticable as we are still
driving a LED, it is merely mentioned here to demonstrate the basic principle.
Note [8]:
Early AVR devices saturate their outputs at rather low currents when sourcing current, so the LED can be connected directly, the resulting current through the LED
will be about 15 mA. For modern parts (at least for the ATmega 128), however
Atmel has drastically increased the IO source capability, so when operating at 5
V Vcc, R2 is needed. Its value should be about 150 Ohms. When operating the
circuit at 3 V, it can still be omitted though.
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22.37.2
The Source Code
334
/*
* ---------------------------------------------------------------------------* "THE BEER-WARE LICENSE" (Revision 42):
* <[email protected]> wrote this file. As long as you retain this notice you
* can do whatever you want with this stuff. If we meet some day, and you think
Joerg Wunsch
* this stuff is worth it, you can buy me a beer in return.
* ---------------------------------------------------------------------------*
* Simple AVR demonstration. Controls a LED that can be directly
* connected from OC1/OC1A to GND. The brightness of the LED is
* controlled with the PWM. After each period of the PWM, the PWM
* value is either incremented or decremented, that’s all.
*
* $Id: demo.c 1637 2008-03-17 21:49:41Z joerg_wunsch $
*/
#include
#include
#include
#include
<inttypes.h>
<avr/io.h>
<avr/interrupt.h>
<avr/sleep.h>
#include "iocompat.h"
/* Note [1] */
enum { UP, DOWN };
ISR (TIMER1_OVF_vect)
{
static uint16_t pwm;
static uint8_t direction;
/* Note [2] */
/* Note [3] */
switch (direction)
/* Note [4] */
{
case UP:
if (++pwm == TIMER1_TOP)
direction = DOWN;
break;
case DOWN:
if (--pwm == 0)
direction = UP;
break;
}
OCR = pwm;
/* Note [5] */
}
void
ioinit (void)
/* Note [6] */
{
/* Timer 1 is 10-bit PWM (8-bit PWM on some ATtinys). */
TCCR1A = TIMER1_PWM_INIT;
/*
* Start timer 1.
*
* NB: TCCR1A and TCCR1B could actually be the same register, so
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* take care to not clobber it.
*/
TCCR1B |= TIMER1_CLOCKSOURCE;
/*
* Run any device-dependent timer 1 setup hook if present.
*/
#if defined(TIMER1_SETUP_HOOK)
TIMER1_SETUP_HOOK();
#endif
/* Set PWM value to 0. */
OCR = 0;
/* Enable OC1 as output. */
DDROC = _BV (OC1);
/* Enable timer 1 overflow interrupt. */
TIMSK = _BV (TOIE1);
sei ();
}
int
main (void)
{
ioinit ();
/* loop forever, the interrupts are doing the rest */
for (;;)
sleep_mode();
/* Note [7] */
return (0);
}
22.37.3
Compiling and Linking
This first thing that needs to be done is compile the source. When compiling, the
compiler needs to know the processor type so the -mmcu option is specified. The
-Os option will tell the compiler to optimize the code for efficient space usage (at the
possible expense of code execution speed). The -g is used to embed debug info. The
debug info is useful for disassemblies and doesn’t end up in the .hex files, so I usually
specify it. Finally, the -c tells the compiler to compile and stop -- don’t link. This
demo is small enough that we could compile and link in one step. However, real-world
projects will have several modules and will typically need to break up the building of
the project into several compiles and one link.
$ avr-gcc -g -Os -mmcu=atmega8 -c demo.c
The compilation will create a demo.o file. Next we link it into a binary called
demo.elf.
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$ avr-gcc -g -mmcu=atmega8 -o demo.elf demo.o
It is important to specify the MCU type when linking. The compiler uses the -mmcu
option to choose start-up files and run-time libraries that get linked together. If this
option isn’t specified, the compiler defaults to the 8515 processor environment, which
is most certainly what you didn’t want.
22.37.4
Examining the Object File
Now we have a binary file. Can we do anything useful with it (besides put it into the
processor?) The GNU Binutils suite is made up of many useful tools for manipulating
object files that get generated. One tool is avr-objdump, which takes information
from the object file and displays it in many useful ways. Typing the command by itself
will cause it to list out its options.
For instance, to get a feel of the application’s size, the -h option can be used. The
output of this option shows how much space is used in each of the sections (the .stab
and .stabstr sections hold the debugging information and won’t make it into the ROM
file).
An even more useful option is -S. This option disassembles the binary file and intersperses the source code in the output! This method is much better, in my opinion, than
using the -S with the compiler because this listing includes routines from the libraries
and the vector table contents. Also, all the "fix-ups" have been satisfied. In other words,
the listing generated by this option reflects the actual code that the processor will run.
$ avr-objdump -h -S demo.elf > demo.lst
Here’s the output as saved in the demo.lst file:
demo.elf:
file format elf32-avr
Sections:
Idx Name
0 .text
1
2
3
4
5
6
7
Size
VMA
LMA
File off Algn
000000ca 00000000 00000000 00000074 2**1
CONTENTS, ALLOC, LOAD, READONLY, CODE
.bss
00000003 00800060 00800060 0000013e 2**0
ALLOC
.debug_aranges 00000020 00000000 00000000 0000013e 2**0
CONTENTS, READONLY, DEBUGGING
.debug_pubnames 00000035 00000000 00000000 0000015e 2**0
CONTENTS, READONLY, DEBUGGING
.debug_info
00000108 00000000 00000000 00000193 2**0
CONTENTS, READONLY, DEBUGGING
.debug_abbrev 000000cf 00000000 00000000 0000029b 2**0
CONTENTS, READONLY, DEBUGGING
.debug_line
00000165 00000000 00000000 0000036a 2**0
CONTENTS, READONLY, DEBUGGING
.debug_frame 00000040 00000000 00000000 000004d0 2**2
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CONTENTS, READONLY, DEBUGGING
000000cc 00000000 00000000 00000510 2**0
CONTENTS, READONLY, DEBUGGING
9 .debug_pubtypes 0000002b 00000000 00000000 000005dc 2**0
CONTENTS, READONLY, DEBUGGING
8 .debug_str
Disassembly of section .text:
00000000
0: 10
2: a0
4: b0
6: 01
<__ctors_end>:
e0
ldi r17, 0x00 ; 0
e6
ldi r26, 0x60 ; 96
e0
ldi r27, 0x00 ; 0
c0
rjmp .+2
; 0xa <.do_clear_bss_start>
00000008 <.do_clear_bss_loop>:
8: 1d 92
st X+, r1
0000000a
a: a3
c: b1
e: e1
<.do_clear_bss_start>:
36
cpi r26, 0x63 ; 99
07
cpc r27, r17
f7
brne .-8
; 0x8 <.do_clear_bss_loop>
00000010 <__vector_8>:
#include "iocompat.h" /* Note [1] */
enum { UP, DOWN };
ISR (TIMER1_OVF_vect) /* Note [2] */
{
10: 1f 92
push r1
12: 0f 92
push r0
14: 0f b6
in r0, 0x3f ; 63
16: 0f 92
push r0
18: 11 24
eor r1, r1
1a: 2f 93
push r18
1c: 8f 93
push r24
1e: 9f 93
push r25
static uint16_t pwm; /* Note [3] */
static uint8_t direction;
switch (direction) /* Note [4] */
20: 80 91 60 00 lds r24, 0x0060
24: 88 23
and r24, r24
26: b9 f4
brne .+46
; 0x56 <__SREG__+0x17>
{
case UP:
if (++pwm == TIMER1_TOP)
28: 80 91 61 00 lds r24, 0x0061
2c: 90 91 62 00 lds r25, 0x0062
30: 01 96
adiw r24, 0x01 ; 1
32: 90 93 62 00 sts 0x0062, r25
36: 80 93 61 00 sts 0x0061, r24
3a: 23 e0
ldi r18, 0x03 ; 3
3c: 8f 3f
cpi r24, 0xFF ; 255
3e: 92 07
cpc r25, r18
40: f9 f0
breq .+62
; 0x80 <__SREG__+0x41>
if (--pwm == 0)
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direction = UP;
break;
}
OCR = pwm; /* Note [5] */
42: 9b bd
out 0x2b, r25 ; 43
44: 8a bd
out 0x2a, r24 ; 42
}
46: 9f 91
pop r25
48: 8f 91
pop r24
4a: 2f 91
pop r18
4c: 0f 90
pop r0
4e: 0f be
out 0x3f, r0 ; 63
50: 0f 90
pop r0
52: 1f 90
pop r1
54: 18 95
reti
ISR (TIMER1_OVF_vect) /* Note [2] */
{
static uint16_t pwm; /* Note [3] */
static uint8_t direction;
switch (direction) /* Note [4] */
56: 81 30
cpi r24, 0x01 ; 1
58: 29 f0
breq .+10
; 0x64 <__SREG__+0x25>
5a: 80 91 61 00 lds r24, 0x0061
5e: 90 91 62 00 lds r25, 0x0062
62: ef cf
rjmp .-34
; 0x42 <__SREG__+0x3>
if (++pwm == TIMER1_TOP)
direction = DOWN;
break;
64:
68:
6c:
6e:
72:
76:
78:
7a:
7e:
case DOWN:
if (--pwm == 0)
80 91 61 00 lds r24, 0x0061
90 91 62 00 lds r25, 0x0062
01 97
sbiw r24, 0x01 ;
90 93 62 00 sts 0x0062, r25
80 93 61 00 sts 0x0061, r24
00 97
sbiw r24, 0x00 ;
21 f7
brne .-56
;
direction = UP;
10 92 60 00 sts 0x0060, r1
e1 cf
rjmp .-62
;
1
0
0x42 <__SREG__+0x3>
0x42 <__SREG__+0x3>
switch (direction) /* Note [4] */
{
case UP:
if (++pwm == TIMER1_TOP)
direction = DOWN;
80: 21 e0
ldi r18, 0x01 ; 1
82: 20 93 60 00 sts 0x0060, r18
86: dd cf
rjmp .-70
; 0x42 <__SREG__+0x3>
00000088 <ioinit>:
void
ioinit (void) /* Note [6] */
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{
/* Timer 1 is 10-bit PWM (8-bit PWM on some ATtinys). */
TCCR1A = TIMER1_PWM_INIT;
88: 83 e8
ldi r24, 0x83 ; 131
8a: 8f bd
out 0x2f, r24 ; 47
* Start timer 1.
*
* NB: TCCR1A and TCCR1B could actually be the same register, so
* take care to not clobber it.
*/
TCCR1B |= TIMER1_CLOCKSOURCE;
8c: 8e b5
in r24, 0x2e ; 46
8e: 81 60
ori r24, 0x01 ; 1
90: 8e bd
out 0x2e, r24 ; 46
#if defined(TIMER1_SETUP_HOOK)
TIMER1_SETUP_HOOK();
#endif
/* Set PWM value to 0. */
OCR = 0;
92: 1b bc
out 0x2b, r1 ; 43
94: 1a bc
out 0x2a, r1 ; 42
/* Enable OC1 as output. */
DDROC = _BV (OC1);
96: 82 e0
ldi r24, 0x02 ; 2
98: 87 bb
out 0x17, r24 ; 23
/* Enable timer 1 overflow interrupt. */
TIMSK = _BV (TOIE1);
9a: 84 e0
ldi r24, 0x04 ; 4
9c: 89 bf
out 0x39, r24 ; 57
sei ();
9e: 78 94
sei
}
a0: 08 95
ret
000000a2 <main>:
void
ioinit (void) /* Note [6] */
{
/* Timer 1 is 10-bit PWM (8-bit PWM on some ATtinys). */
TCCR1A = TIMER1_PWM_INIT;
a2: 83 e8
ldi r24, 0x83 ; 131
a4: 8f bd
out 0x2f, r24 ; 47
* Start timer 1.
*
* NB: TCCR1A and TCCR1B could actually be the same register, so
* take care to not clobber it.
*/
TCCR1B |= TIMER1_CLOCKSOURCE;
a6: 8e b5
in r24, 0x2e ; 46
a8: 81 60
ori r24, 0x01 ; 1
aa: 8e bd
out 0x2e, r24 ; 46
#if defined(TIMER1_SETUP_HOOK)
TIMER1_SETUP_HOOK();
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#endif
/* Set PWM value to 0. */
OCR = 0;
ac: 1b bc
out 0x2b, r1 ; 43
ae: 1a bc
out 0x2a, r1 ; 42
/* Enable OC1 as output. */
DDROC = _BV (OC1);
b0: 82 e0
ldi r24, 0x02 ; 2
b2: 87 bb
out 0x17, r24 ; 23
/* Enable timer 1 overflow interrupt. */
TIMSK = _BV (TOIE1);
b4: 84 e0
ldi r24, 0x04 ; 4
b6: 89 bf
out 0x39, r24 ; 57
sei ();
b8: 78 94
sei
ioinit ();
/* loop forever, the interrupts are doing the rest */
for (;;) /* Note [7] */
sleep_mode();
ba: 85 b7
in r24, 0x35 ; 53
bc: 80 68
ori r24, 0x80 ; 128
be: 85 bf
out 0x35, r24 ; 53
c0: 88 95
sleep
c2: 85 b7
in r24, 0x35 ; 53
c4: 8f 77
andi r24, 0x7F ; 127
c6: 85 bf
out 0x35, r24 ; 53
c8: f8 cf
rjmp .-16
; 0xba <main+0x18>
22.37.5
Linker Map Files
avr-objdump is very useful, but sometimes it’s necessary to see information about
the link that can only be generated by the linker. A map file contains this information.
A map file is useful for monitoring the sizes of your code and data. It also shows where
modules are loaded and which modules were loaded from libraries. It is yet another
view of your application. To get a map file, I usually add -Wl,-Map,demo.map to
my link command. Relink the application using the following command to generate
demo.map (a portion of which is shown below).
$ avr-gcc -g -mmcu=atmega8 -Wl,-Map,demo.map -o demo.elf demo.o
Some points of interest in the demo.map file are:
.rela.plt
*(.rela.plt)
.text
*(.vectors)
0x0000000000000000
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*(.vectors)
*(.progmem.gcc*)
*(.progmem*)
0x0000000000000000
0x0000000000000000
*(.trampolines)
.trampolines
0x0000000000000000
*(.trampolines*)
0x0000000000000000
*(.jumptables)
*(.jumptables*)
*(.lowtext)
*(.lowtext*)
0x0000000000000000
341
. = ALIGN (0x2)
__trampolines_start = .
0x0 linker stubs
__trampolines_end = .
__ctors_start = .
The .text segment (where program instructions are stored) starts at location 0x0.
*(.fini2)
*(.fini2)
*(.fini1)
*(.fini1)
*(.fini0)
*(.fini0)
0x00000000000000ca
.data
0x0000000000800060
0x0000000000800060
_etext = .
0x0 load address 0x00000000000000ca
PROVIDE (__data_start, .)
*(.data)
.data
0x0000000000800060
0x0 demo.o
.data
0x0000000000800060
0x0 /home/tools/hudson/workspace/avr8-g
nu-toolchain/avr8-gnu-toolchain-linux_x86_64/lib/gcc/avr/4.5.1/avr4/libgcc.a(_cle
ar_bss.o)
*(.data*)
*(.rodata)
*(.rodata*)
*(.gnu.linkonce.d*)
0x0000000000800060
. = ALIGN (0x2)
0x0000000000800060
_edata = .
0x0000000000800060
PROVIDE (__data_end, .)
.bss
0x0000000000800060
0x0000000000800060
0x3
PROVIDE (__bss_start, .)
*(.bss)
.bss
0x0000000000800060
0x3 demo.o
.bss
0x0000000000800063
0x0 /home/tools/hudson/workspace/avr8-g
nu-toolchain/avr8-gnu-toolchain-linux_x86_64/lib/gcc/avr/4.5.1/avr4/libgcc.a(_cle
ar_bss.o)
*(.bss*)
*(COMMON)
0x0000000000800063
PROVIDE (__bss_end, .)
0x00000000000000ca
__data_load_start = LOADADDR (.
data)
0x00000000000000ca
__data_load_end = (__data_load_
start + SIZEOF (.data))
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.noinit
0x0000000000800063
0x0000000000800063
342
0x0
PROVIDE (__noinit_start, .)
*(.noinit*)
0x0000000000800063
0x0000000000800063
0x0000000000800063
.eeprom
*(.eeprom*)
0x0000000000810000
PROVIDE (__noinit_end, .)
_end = .
PROVIDE (__heap_start, .)
0x0
0x0000000000810000
__eeprom_end = .
The last address in the .text segment is location 0x114 ( denoted by _etext ), so the
instructions use up 276 bytes of FLASH.
The .data segment (where initialized static variables are stored) starts at location 0x60,
which is the first address after the register bank on an ATmega8 processor.
The next available address in the .data segment is also location 0x60, so the application
has no initialized data.
The .bss segment (where uninitialized data is stored) starts at location 0x60.
The next available address in the .bss segment is location 0x63, so the application uses
3 bytes of uninitialized data.
The .eeprom segment (where EEPROM variables are stored) starts at location 0x0.
The next available address in the .eeprom segment is also location 0x0, so there aren’t
any EEPROM variables.
22.37.6
Generating Intel Hex Files
We have a binary of the application, but how do we get it into the processor? Most (if
not all) programmers will not accept a GNU executable as an input file, so we need to
do a little more processing. The next step is to extract portions of the binary and save
the information into .hex files. The GNU utility that does this is called avr-objcopy.
The ROM contents can be pulled from our project’s binary and put into the file demo.hex
using the following command:
$ avr-objcopy -j .text -j .data -O ihex demo.elf demo.hex
The resulting demo.hex file contains:
:1000000010E0A0E6B0E001C01D92A336B107E1F711
:100010001F920F920FB60F9211242F938F939F93DD
:10002000809160008823B9F4809161009091620012
:100030000196909362008093610023E08F3F9207C6
:10004000F9F09BBD8ABD9F918F912F910F900FBEAC
:100050000F901F901895813029F080916100909148
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:100060006200EFCF809161009091620001979093C0
:10007000620080936100009721F710926000E1CF49
:1000800021E020936000DDCF83E88FBD8EB58160D5
:100090008EBD1BBC1ABC82E087BB84E089BF78940C
:1000A000089583E88FBD8EB581608EBD1BBC1ABCE0
:1000B00082E087BB84E089BF789485B7806885BF7C
:0A00C000889585B78F7785BFF8CFCC
:00000001FF
The -j option indicates that we want the information from the .text and .data segment
extracted. If we specify the EEPROM segment, we can generate a .hex file that can be
used to program the EEPROM:
$ avr-objcopy -j .eeprom --change-section-lma .eeprom=0 -O ihex demo.elf demo_eeprom.hex
There is no demo_eeprom.hex file written, as that file would be empty.
Starting with version 2.17 of the GNU binutils, the avr-objcopy command that used
to generate the empty EEPROM files now aborts because of the empty input section
.eeprom, so these empty files are not generated. It also signals an error to the Makefile
which will be caught there, and makes it print a message about the empty file not being
generated.
22.37.7
Letting Make Build the Project
Rather than type these commands over and over, they can all be placed in a make file.
To build the demo project using make, save the following in a file called Makefile.
Note
This Makefile can only be used as input for the GNU version of make.
PRG
OBJ
#MCU_TARGET
#MCU_TARGET
#MCU_TARGET
#MCU_TARGET
#MCU_TARGET
#MCU_TARGET
#MCU_TARGET
#MCU_TARGET
#MCU_TARGET
#MCU_TARGET
#MCU_TARGET
#MCU_TARGET
#MCU_TARGET
#MCU_TARGET
#MCU_TARGET
#MCU_TARGET
#MCU_TARGET
= demo
= demo.o
= at90s2313
= at90s2333
= at90s4414
= at90s4433
= at90s4434
= at90s8515
= at90s8535
= atmega128
= atmega1280
= atmega1281
= atmega1284p
= atmega16
= atmega163
= atmega164p
= atmega165
= atmega165p
= atmega168
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#MCU_TARGET
#MCU_TARGET
#MCU_TARGET
#MCU_TARGET
#MCU_TARGET
#MCU_TARGET
#MCU_TARGET
#MCU_TARGET
#MCU_TARGET
#MCU_TARGET
#MCU_TARGET
#MCU_TARGET
#MCU_TARGET
#MCU_TARGET
#MCU_TARGET
#MCU_TARGET
#MCU_TARGET
#MCU_TARGET
#MCU_TARGET
MCU_TARGET
#MCU_TARGET
#MCU_TARGET
#MCU_TARGET
#MCU_TARGET
#MCU_TARGET
#MCU_TARGET
#MCU_TARGET
#MCU_TARGET
#MCU_TARGET
#MCU_TARGET
#MCU_TARGET
#MCU_TARGET
#MCU_TARGET
#MCU_TARGET
OPTIMIZE
=
=
=
=
=
=
=
=
=
=
=
=
=
=
=
=
=
=
=
atmega169
atmega169p
atmega2560
atmega2561
atmega32
atmega324p
atmega325
atmega3250
atmega329
atmega3290
atmega48
atmega64
atmega640
atmega644
atmega644p
atmega645
atmega6450
atmega649
atmega6490
= atmega8
= atmega8515
= atmega8535
= atmega88
= attiny2313
= attiny24
= attiny25
= attiny26
= attiny261
= attiny44
= attiny45
= attiny461
= attiny84
= attiny85
= attiny861
= -O2
DEFS
LIBS
=
=
# You should not have to change anything below here.
CC
= avr-gcc
# Override is only needed by avr-lib build system.
override CFLAGS
override LDFLAGS
OBJCOPY
OBJDUMP
= -g -Wall $(OPTIMIZE) -mmcu=$(MCU_TARGET) $(DEFS)
= -Wl,-Map,$(PRG).map
= avr-objcopy
= avr-objdump
all: $(PRG).elf lst text eeprom
$(PRG).elf: $(OBJ)
$(CC) $(CFLAGS) $(LDFLAGS) -o [email protected] $^ $(LIBS)
# dependency:
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demo.o: demo.c iocompat.h
clean:
rm -rf *.o $(PRG).elf *.eps *.png *.pdf *.bak
rm -rf *.lst *.map $(EXTRA_CLEAN_FILES)
lst:
$(PRG).lst
%.lst: %.elf
$(OBJDUMP) -h -S $< > [email protected]
# Rules for building the .text rom images
text: hex bin srec
hex: $(PRG).hex
bin: $(PRG).bin
srec: $(PRG).srec
%.hex: %.elf
$(OBJCOPY) -j .text -j .data -O ihex $< [email protected]
%.srec: %.elf
$(OBJCOPY) -j .text -j .data -O srec $< [email protected]
%.bin: %.elf
$(OBJCOPY) -j .text -j .data -O binary $< [email protected]
# Rules for building the .eeprom rom images
eeprom: ehex ebin esrec
ehex: $(PRG)_eeprom.hex
ebin: $(PRG)_eeprom.bin
esrec: $(PRG)_eeprom.srec
%_eeprom.hex: %.elf
$(OBJCOPY) -j .eeprom --change-section-lma .eeprom=0 -O ihex $< [email protected] \
|| { echo empty [email protected] not generated; exit 0; }
%_eeprom.srec: %.elf
$(OBJCOPY) -j .eeprom --change-section-lma .eeprom=0 -O srec $< [email protected] \
|| { echo empty [email protected] not generated; exit 0; }
%_eeprom.bin: %.elf
$(OBJCOPY) -j .eeprom --change-section-lma .eeprom=0 -O binary $< [email protected] \
|| { echo empty [email protected] not generated; exit 0; }
# Every thing below here is used by avr-libc’s build system and can be ignored
# by the casual user.
FIG2DEV
EXTRA_CLEAN_FILES
= fig2dev
= *.hex *.bin *.srec
dox: eps png pdf
eps: $(PRG).eps
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png: $(PRG).png
pdf: $(PRG).pdf
%.eps: %.fig
$(FIG2DEV) -L eps $< [email protected]
%.pdf: %.fig
$(FIG2DEV) -L pdf $< [email protected]
%.png: %.fig
$(FIG2DEV) -L png $< [email protected]
22.37.8
Reference to the source code
The source code is installed under
$prefix/share/doc/avr-libc/examples/demo/,
where $prefix is a configuration option. For Unix systems, it is usually set to either
/usr or /usr/local.
22.38
A more sophisticated project
This project extends the basic idea of the simple project to control a LED with a PWM
output, but adds methods to adjust the LED brightness. It employs a lot of the basic
concepts of avr-libc to achieve that goal.
Understanding this project assumes the simple project has been understood in full, as
well as being acquainted with the basic hardware concepts of an AVR microcontroller.
22.38.1
Hardware setup
The demo is set up in a way so it can be run on the ATmega16 that ships with the
STK500 development kit. The only external part needed is a potentiometer attached to
the ADC. It is connected to a 10-pin ribbon cable for port A, both ends of the potentiometer to pins 9 (GND) and 10 (VCC), and the wiper to pin 1 (port A0). A bypass
capacitor from pin 1 to pin 9 (like 47 nF) is recommendable.
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Figure 6: Setup of the STK500
The coloured patch cables are used to provide various interconnections. As there are
only four of them in the STK500, there are two options to connect them for this demo.
The second option for the yellow-green cable is shown in parenthesis in the table.
Alternatively, the "squid" cable from the JTAG ICE kit can be used if available.
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Port
D0
Header
1
Color
brown
Function
RxD
D1
2
grey
TxD
D2
3
black
button
"down"
D3
4
red
button "up"
D4
5
green
button
"ADC"
D5
6
blue
LED
D6
7
(green)
clock out
D7
8
white
GND
VCC
9
10
1-second
flash
unused
unused
Connect to
RXD of the
RS-232
header
TXD of the
RS-232
header
SW0 (pin 1
switches
header)
SW1 (pin 2
switches
header)
SW2 (pin 3
switches
header)
LED0 (pin 1
LEDs header)
LED1 (pin 2
LEDs header)
LED2 (pin 3
LEDs header)
Figure 7: Wiring of the STK500
The following picture shows the alternate wiring where LED1 is connected but SW2 is
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not:
Figure 8: Wiring option #2 of the STK500
As an alternative, this demo can also be run on the popular ATmega8 controller, or its
successor ATmega88 as well as the ATmega48 and ATmega168 variants of the latter.
These controllers do not have a port named "A", so their ADC inputs are located on
port C instead, thus the potentiometer needs to be attached to port C. Likewise, the
OC1A output is not on port D pin 5 but on port B pin 1 (PB1). Thus, the above
cabling scheme needs to be changed so that PB1 connects to the LED0 pin. (PD6
remains unconnected.) When using the STK500, use one of the jumper cables for this
connection. All other port D pins should be connected the same way as described for
the ATmega16 above.
When not using an STK500 starter kit, attach the LEDs through some resistor to Vcc
(low-active LEDs), and attach pushbuttons from the respective input pins to GND. The
internal pull-up resistors are enabled for the pushbutton pins, so no external resistors
are needed.
Finally, the demo has been ported to the ATtiny2313 as well. As this AVR does not
offer an ADC, everything related to handling the ADC is disabled in the code for that
MCU type. Also, port D of this controller type only features 6 pins, so the 1-second
flash LED had to be moved from PD6 to PD4. (PD4 is used as the ADC control button
on the other MCU types, but that is not needed here.) OC1A is located at PB3 on this
device.
The MCU_TARGET macro in the Makefile needs to be adjusted appropriately for the
alternative controller types.
The flash ROM and RAM consumption of this demo are way below the resources
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of even an ATmega48, and still well within the capabilities of an ATtiny2313. The
major advantage of experimenting with the ATmega16 (in addition that it ships together
with an STK500 anyway) is that it can be debugged online via JTAG. Likewise, the
ATmega48/88/168 and ATtiny2313 devices can be debugged through debugWire, using
the Atmel JTAG ICE mkII or the low-cost AVR Dragon.
Note that in the explanation below, all port/pin names are applicable to the ATmega16
setup.
22.38.2
Functional overview
PD6 will be toggled with each internal clock tick (approx. 10 ms). PD7 will flash once
per second.
PD0 and PD1 are configured as UART IO, and can be used to connect the demo kit to
a PC (9600 Bd, 8N1 frame format). The demo application talks to the serial port, and
it can be controlled from the serial port.
PD2 through PD4 are configured as inputs, and control the application unless control
has been taken over by the serial port. Shorting PD2 to GND will decrease the current
PWM value, shorting PD3 to GND will increase it.
While PD4 is shorted to GND, one ADC conversion for channel 0 (ADC input is on
PA0) will be triggered each internal clock tick, and the resulting value will be used as
the PWM value. So the brightness of the LED follows the analog input value on PC0.
VAREF on the STK500 should be set to the same value as VCC.
When running in serial control mode, the function of the watchdog timer can be demonstrated by typing an ‘r’. This will make the demo application run in a tight loop without
retriggering the watchdog so after some seconds, the watchdog will reset the MCU.
This situation can be figured out on startup by reading the MCUCSR register.
The current value of the PWM is backed up in an EEPROM cell after about 3 seconds
of idle time after the last change. If that EEPROM cell contains a reasonable (i. e.
non-erased) value at startup, it is taken as the initial value for the PWM. This virtually
preserves the last value across power cycles. By not updating the EEPROM immmediately but only after a timeout, EEPROM wear is reduced considerably compared to
immediately writing the value at each change.
22.38.3
A code walkthrough
This section explains the ideas behind individual parts of the code. The source code
has been divided into numbered parts, and the following subsections explain each of
these parts.
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Part 1: Macro definitions
A number of preprocessor macros are defined to improve readability and/or portability
of the application.
The first macros describe the IO pins our LEDs and pushbuttons are connected to. This
provides some kind of mini-HAL (hardware abstraction layer) so should some of the
connections be changed, they don’t need to be changed inside the code but only on
top. Note that the location of the PWM output itself is mandated by the hardware, so it
cannot be easily changed. As the ATmega48/88/168 controllers belong to a more recent
generation of AVRs, a number of register and bit names have been changed there, so
they are mapped back to their ATmega8/16 equivalents to keep the actual program code
portable.
The name F_CPU is the conventional name to describe the CPU clock frequency of
the controller. This demo project just uses the internal calibrated 1 MHz RC oscillator
that is enabled by default. Note that when using the <util/delay.h> functions,
F_CPU needs to be defined before including that file.
The remaining macros have their own comments in the source code. The macro
TMR1_SCALE shows how to use the preprocessor and the compiler’s constant expression computation to calculate the value of timer 1’s post-scaler in a way so it only
depends on F_CPU and the desired software clock frequency. While the formula looks
a bit complicated, using a macro offers the advantage that the application will automatically scale to new target softclock or master CPU frequencies without having to
manually re-calculate hardcoded constants.
22.38.3.2
Part 2: Variable definitions
The intflags structure demonstrates a way to allocate bit variables in memory. Each
of the interrupt service routines just sets one bit within that structure, and the application’s main loop then monitors the bits in order to act appropriately.
Like all variables that are used to communicate values between an interrupt service
routine and the main application, it is declared volatile.
The variable ee_pwm is not a variable in the classical C sense that could be used as an
lvalue or within an expression to obtain its value. Instead, the
__attribute__((section(".eeprom")))
marks it as belonging to the EEPROM section. This section is merely used as a placeholder so the compiler can arrange for each individual variable’s location in EEPROM.
The compiler will also keep track of initial values assigned, and usually the Makefile
is arranged to extract these initial values into a separate load file (largedemo_eeprom.∗ in this case) that can be used to initialize the EEPROM.
The actual EEPROM IO must be performed manually.
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Similarly, the variable mcucsr is kept in the .noinit section in order to prevent it from
being cleared upon application startup.
22.38.3.3
Part 3: Interrupt service routines
The ISR to handle timer 1’s overflow interrupt arranges for the software clock. While
timer 1 runs the PWM, it calls its overflow handler rather frequently, so the TMR1_SCALE value is used as a postscaler to reduce the internal software clock frequency
further. If the software clock triggers, it sets the tmr_int bitfield, and defers all
further tasks to the main loop.
The ADC ISR just fetches the value from the ADC conversion, disables the ADC
interrupt again, and announces the presence of the new value in the adc_int bitfield.
The interrupt is kept disabled while not needed, because the ADC will also be triggered
by executing the SLEEP instruction in idle mode (which is the default sleep mode).
Another option would be to turn off the ADC completely here, but that increases the
ADC’s startup time (not that it would matter much for this application).
22.38.3.4
Part 4: Auxiliary functions
The function handle_mcucsr() uses two __attribute__ declarators to achieve
specific goals. First, it will instruct the compiler to place the generated code into the
.init3 section of the output. Thus, it will become part of the application initialization
sequence. This is done in order to fetch (and clear) the reason of the last hardware reset
from MCUCSR as early as possible. There is a short period of time where the next reset
could already trigger before the current reason has been evaluated. This also explains
why the variable mcucsr that mirrors the register’s value needs to be placed into the
.noinit section, because otherwise the default initialization (which happens after .init3)
would blank the value again.
As the initialization code is not called using CALL/RET instructions but rather concatenated together, the compiler needs to be instructed to omit the entire function prologue and epilogue. This is performed by the naked attribute. So while syntactically,
handle_mcucsr() is a function to the compiler, the compiler will just emit the instructions for it without setting up any stack frame, and not even a RET instruction at
the end.
Function ioinit() centralizes all hardware setup. The very last part of that function
demonstrates the use of the EEPROM variable ee_pwm to obtain an EEPROM address
that can in turn be applied as an argument to eeprom_read_word().
The following functions handle UART character and string output. (UART input is handled by an ISR.) There are two string output functions, printstr() and printstr_p(). The latter function fetches the string from program memory. Both functions
translate a newline character into a carriage return/newline sequence, so a simple \n
can be used in the source code.
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The function set_pwm() propagates the new PWM value to the PWM, performing
range checking. When the value has been changed, the new percentage will be announced on the serial link. The current value is mirrored in the variable pwm so others
can use it in calculations. In order to allow for a simple calculation of a percentage
value without requiring floating-point mathematics, the maximal value of the PWM is
restricted to 1000 rather than 1023, so a simple division by 10 can be used. Due to the
nature of the human eye, the difference in LED brightness between 1000 and 1023 is
not noticable anyway.
22.38.3.5
Part 5: main()
At the start of main(), a variable mode is declared to keep the current mode of
operation. An enumeration is used to improve the readability. By default, the compiler
would allocate a variable of type int for an enumeration. The packed attribute declarator
instructs the compiler to use the smallest possible integer type (which would be an 8-bit
type here).
After some initialization actions, the application’s main loop follows. In an embedded
application, this is normally an infinite loop as there is nothing an application could
"exit" into anyway.
At the beginning of the loop, the watchdog timer will be retriggered. If that timer is
not triggered for about 2 seconds, it will issue a hardware reset. Care needs to be taken
that no code path blocks longer than this, or it needs to frequently perform watchdog
resets of its own. An example of such a code path would be the string IO functions: for
an overly large string to print (about 2000 characters at 9600 Bd), they might block for
too long.
The loop itself then acts on the interrupt indication bitfields as appropriate, and will
eventually put the CPU on sleep at its end to conserve power.
The first interrupt bit that is handled is the (software) timer, at a frequency of approximately 100 Hz. The CLOCKOUT pin will be toggled here, so e. g. an oscilloscope
can be used on that pin to measure the accuracy of our software clock. Then, the LED
flasher for LED2 ("We are alive"-LED) is built. It will flash that LED for about 50
ms, and pause it for another 950 ms. Various actions depending on the operation mode
follow. Finally, the 3-second backup timer is implemented that will write the PWM
value back to EEPROM once it is not changing anymore.
The ADC interrupt will just adjust the PWM value only.
Finally, the UART Rx interrupt will dispatch on the last character received from the
UART.
All the string literals that are used as informational messages within main() are
placed in program memory so no SRAM needs to be allocated for them. This is done
by using the PSTR macro, and passing the string to printstr_p().
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The source code
354
The source code is installed under
$prefix/share/doc/avr-libc/examples/largedemo/largedemo.c,
where $prefix is a configuration option. For Unix systems, it is usually set to either
/usr or /usr/local.
22.39
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This project illustrates how to use the standard IO facilities (stdio) provided by this
library. It assumes a basic knowledge of how the stdio subsystem is used in standard C
applications, and concentrates on the differences in this library’s implementation that
mainly result from the differences of the microcontroller environment, compared to a
hosted environment of a standard computer.
This demo is meant to supplement the documentation, not to replace it.
22.39.1
Hardware setup
The demo is set up in a way so it can be run on the ATmega16 that ships with the
STK500 development kit. The UART port needs to be connected to the RS-232 "spare"
port by a jumper cable that connects PD0 to RxD and PD1 to TxD. The RS-232 channel
is set up as standard input (stdin) and standard output (stdout), respectively.
In order to have a different device available for a standard error channel (stderr), an
industry-standard LCD display with an HD44780-compatible LCD controller has been
chosen. This display needs to be connected to port A of the STK500 in the following
way:
Port
A0
A1
A2
A3
A4
A5
A6
A7
GND
VCC
Header
1
2
3
4
5
6
7
8
9
10
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Function
LCD D4
LCD D5
LCD D6
LCD D7
LCD R/∼W
LCD E
LCD RS
unused
GND
Vcc
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Figure 9: Wiring of the STK500
The LCD controller is used in 4-bit mode, including polling the "busy" flag so the
R/∼W line from the LCD controller needs to be connected. Note that the LCD controller has yet another supply pin that is used to adjust the LCD’s contrast (V5). Typically, that pin connects to a potentiometer between Vcc and GND. Often, it might
work to just connect that pin to GND, while leaving it unconnected usually yields an
unreadable display.
Port A has been chosen as 7 pins are needed to connect the LCD, yet all other ports are
already partially in use: port B has the pins for in-system programming (ISP), port C
has the ports for JTAG (can be used for debugging), and port D is used for the UART
connection.
22.39.2
Functional overview
The project consists of the following files:
• stdiodemo.c This is the main example file.
• defines.h Contains some global defines, like the LCD wiring
• hd44780.c Implementation of an HD44780 LCD display driver
• hd44780.h Interface declarations for the HD44780 driver
• lcd.c Implementation of LCD character IO on top of the HD44780 driver
• lcd.h Interface declarations for the LCD driver
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• uart.c Implementation of a character IO driver for the internal UART
• uart.h Interface declarations for the UART driver
22.39.3
A code walkthrough
22.39.3.1
stdiodemo.c
As usual, include files go first. While conventionally, system header files (those in
angular brackets < ... >) go before application-specific header files (in double quotes),
defines.h comes as the first header file here. The main reason is that this file defines
the value of F_CPU which needs to be known before including <utils/delay.h>.
The function ioinit() summarizes all hardware initialization tasks. As this function
is declared to be module-internal only (static), the compiler will notice its simplicity, and with a reasonable optimization level in effect, it will inline that function. That
needs to be kept in mind when debugging, because the inlining might cause the debugger to "jump around wildly" at a first glance when single-stepping.
The definitions of uart_str and lcd_str set up two stdio streams. The initialization is done using the FDEV_SETUP_STREAM() initializer template macro, so a
static object can be constructed that can be used for IO purposes. This initializer macro
takes three arguments, two function macros to connect the corresponding output and
input functions, respectively, the third one describes the intent of the stream (read,
write, or both). Those functions that are not required by the specified intent (like the
input function for lcd_str which is specified to only perform output operations) can
be given as NULL.
The stream uart_str corresponds to input and output operations performed over the
RS-232 connection to a terminal (e.g. from/to a PC running a terminal program), while
the lcd_str stream provides a method to display character data on the LCD text
display.
The function delay_1s() suspends program execution for approximately one second. This is done using the _delay_ms() function from <util/delay.h>
which in turn needs the F_CPU macro in order to adjust the cycle counts. As the
_delay_ms() function has a limited range of allowable argument values (depending
on F_CPU), a value of 10 ms has been chosen as the base delay which would be safe
for CPU frequencies of up to about 26 MHz. This function is then called 100 times to
accomodate for the actual one-second delay.
In a practical application, long delays like this one were better be handled by a hardware
timer, so the main CPU would be free for other tasks while waiting, or could be put on
sleep.
At the beginning of main(), after initializing the peripheral devices, the default stdio
streams stdin, stdout, and stderr are set up by using the existing static FILE
stream objects. While this is not mandatory, the availability of stdin and stdout
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allows to use the shorthand functions (e.g. printf() instead of fprintf()), and
stderr can mnemonically be referred to when sending out diagnostic messages.
Just for demonstration purposes, stdin and stdout are connected to a stream that
will perform UART IO, while stderr is arranged to output its data to the LCD text
display.
Finally, a main loop follows that accepts simple "commands" entered via the RS-232
connection, and performs a few simple actions based on the commands.
First, a prompt is sent out using printf_P() (which takes a program space string).
The string is read into an internal buffer as one line of input, using fgets(). While it
would be also possible to use gets() (which implicitly reads from stdin), gets()
has no control that the user’s input does not overflow the input buffer provided so it
should never be used at all.
If fgets() fails to read anything, the main loop is left. Of course, normally the main
loop of a microcontroller application is supposed to never finish, but again, for demonstrational purposes, this explains the error handling of stdio. fgets() will return
NULL in case of an input error or end-of-file condition on input. Both these conditions are in the domain of the function that is used to establish the stream, uart_putchar() in this case. In short, this function returns EOF in case of a serial line
"break" condition (extended start condition) has been recognized on the serial line.
Common PC terminal programs allow to assert this condition as some kind of out-ofband signalling on an RS-232 connection.
When leaving the main loop, a goodbye message is sent to standard error output (i.e. to
the LCD), followed by three dots in one-second spacing, followed by a sequence that
will clear the LCD. Finally, main() will be terminated, and the library will add an
infinite loop, so only a CPU reset will be able to restart the application.
There are three "commands" recognized, each determined by the first letter of the line
entered (converted to lower case):
• The ’q’ (quit) command has the same effect of leaving the main loop.
• The ’l’ (LCD) command takes its second argument, and sends it to the LCD.
• The ’u’ (UART) command takes its second argument, and sends it back to the
UART connection.
Command recognition is done using sscanf() where the first format in the format
string just skips over the command itself (as the assignment suppression modifier ∗ is
given).
22.39.3.2
defines.h
This file just contains a few peripheral definitions.
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The F_CPU macro defines the CPU clock frequency, to be used in delay loops, as well
as in the UART baud rate calculation.
The macro UART_BAUD defines the RS-232 baud rate. Depending on the actual CPU
frequency, only a limited range of baud rates can be supported.
The remaining macros customize the IO port and pins used for the HD44780 LCD
driver. Each definition consists of a letter naming the port this pin is attached to, and a
respective bit number. For accessing the data lines, only the first data line gets its own
macro (line D4 on the HD44780, lines D0 through D3 are not used in 4-bit mode), all
other data lines are expected to be in ascending order next to D4.
22.39.3.3
hd44780.h
This file describes the public interface of the low-level LCD driver that interfaces to
the HD44780 LCD controller. Public functions are available to initialize the controller
into 4-bit mode, to wait for the controller’s busy bit to be clear, and to read or write one
byte from or to the controller.
As there are two different forms of controller IO, one to send a command or receive
the controller status (RS signal clear), and one to send or receive data to/from the
controller’s SRAM (RS asserted), macros are provided that build on the mentioned
function primitives.
Finally, macros are provided for all the controller commands to allow them to be used
symbolically. The HD44780 datasheet explains these basic functions of the controller
in more detail.
22.39.3.4
hd44780.c
This is the implementation of the low-level HD44780 LCD controller driver.
On top, a few preprocessor glueing tricks are used to establish symbolic access to
the hardware port pins the LCD controller is attached to, based on the application’s
definitions made in defines.h.
The hd44780_pulse_e() function asserts a short pulse to the controller’s E (enable) pin. Since reading back the data asserted by the LCD controller needs to be
performed while E is active, this function reads and returns the input data if the parameter readback is true. When called with a compile-time constant parameter that is
false, the compiler will completely eliminate the unused readback operation, as well as
the return value as part of its optimizations.
As the controller is used in 4-bit interface mode, all byte IO to/from the controller
needs to be handled as two nibble IOs. The functions hd44780_outnibble() and
hd44780_innibble() implement this. They do not belong to the public interface,
so they are declared static.
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Building upon these, the public functions hd44780_outbyte() and hd44780_inbyte() transfer one byte to/from the controller.
The function hd44780_wait_ready() waits for the controller to become ready,
by continuously polling the controller’s status (which is read by performing a byte read
with the RS signal cleard), and examining the BUSY flag within the status byte. This
function needs to be called before performing any controller IO.
Finally, hd44780_init() initializes the LCD controller into 4-bit mode, based on
the initialization sequence mandated by the datasheet. As the BUSY flag cannot be
examined yet at this point, this is the only part of this code where timed delays are
used. While the controller can perform a power-on reset when certain constraints on
the power supply rise time are met, always calling the software initialization routine
at startup ensures the controller will be in a known state. This function also puts the
interface into 4-bit mode (which would not be done automatically after a power-on
reset).
22.39.3.5
lcd.h
This function declares the public interface of the higher-level (character IO) LCD
driver.
22.39.3.6
lcd.c
The implementation of the higher-level LCD driver. This driver builds on top of the
HD44780 low-level LCD controller driver, and offers a character IO interface suitable
for direct use by the standard IO facilities. Where the low-level HD44780 driver deals
with setting up controller SRAM addresses, writing data to the controller’s SRAM,
and controlling display functions like clearing the display, or moving the cursor, this
high-level driver allows to just write a character to the LCD, in the assumption this will
somehow show up on the display.
Control characters can be handled at this level, and used to perform specific actions
on the LCD. Currently, there is only one control character that is being dealt with: a
newline character (\n) is taken as an indication to clear the display and set the cursor
into its initial position upon reception of the next character, so a "new line" of text
can be displayed. Therefore, a received newline character is remembered until more
characters have been sent by the application, and will only then cause the display to be
cleared before continuing. This provides a convenient abstraction where full lines of
text can be sent to the driver, and will remain visible at the LCD until the next line is
to be displayed.
Further control characters could be implemented, e. g. using a set of escape sequences.
That way, it would be possible to implement self-scrolling display lines etc.
The public function lcd_init() first calls the initialization entry point of the lowerlevel HD44780 driver, and then sets up the LCD in a way we’d like to (display cleared,
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non-blinking cursor enabled, SRAM addresses are increasing so characters will be
written left to right).
The public function lcd_putchar() takes arguments that make it suitable for being passed as a put() function pointer to the stdio stream initialization functions and
macros (fdevopen(), FDEV_SETUP_STREAM() etc.). Thus, it takes two arguments, the character to display itself, and a reference to the underlying stream object,
and it is expected to return 0 upon success.
This function remembers the last unprocessed newline character seen in the functionlocal static variable nl_seen. If a newline character is encountered, it will simply set
this variable to a true value, and return to the caller. As soon as the first non-newline
character is to be displayed with nl_seen still true, the LCD controller is told to clear
the display, put the cursor home, and restart at SRAM address 0. All other characters
are sent to the display.
The single static function-internal variable nl_seen works for this purpose. If multiple LCDs should be controlled using the same set of driver functions, that would not
work anymore, as a way is needed to distinguish between the various displays. This is
where the second parameter can be used, the reference to the stream itself: instead of
keeping the state inside a private variable of the function, it can be kept inside a private
object that is attached to the stream itself. A reference to that private object can be attached to the stream (e.g. inside the function lcd_init() that then also needs to be
passed a reference to the stream) using fdev_set_udata(), and can be accessed
inside lcd_putchar() using fdev_get_udata().
22.39.3.7
uart.h
Public interface definition for the RS-232 UART driver, much like in lcd.h except there
is now also a character input function available.
As the RS-232 input is line-buffered in this example, the macro RX_BUFSIZE determines the size of that buffer.
22.39.3.8
uart.c
This implements an stdio-compatible RS-232 driver using an AVR’s standard UART
(or USART in asynchronous operation mode). Both, character output as well as character input operations are implemented. Character output takes care of converting the
internal newline \n into its external representation carriage return/line feed (\r\n).
Character input is organized as a line-buffered operation that allows to minimally edit
the current line until it is "sent" to the application when either a carriage return (\r)
or newline (\n) character is received from the terminal. The line editing functions
implemented are:
• \b (back space) or \177 (delete) deletes the previous character
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∧u
•
∧w
•
∧r
361
(control-U, ASCII NAK) deletes the entire input buffer
(control-W, ASCII ETB) deletes the previous input word, delimited by white
space
(control-R, ASCII DC2) sends a \r, then reprints the buffer (refresh)
• \t (tabulator) will be replaced by a single space
The function uart_init() takes care of all hardware initialization that is required to
put the UART into a mode with 8 data bits, no parity, one stop bit (commonly referred
to as 8N1) at the baud rate configured in defines.h. At low CPU clock frequencies, the
U2X bit in the UART is set, reducing the oversampling from 16x to 8x, which allows
for a 9600 Bd rate to be achieved with tolerable error using the default 1 MHz RC
oscillator.
The public function uart_putchar() again has suitable arguments for direct use
by the stdio stream interface. It performs the \n into \r\n translation by recursively
calling itself when it sees a \n character. Just for demonstration purposes, the \a
(audible bell, ASCII BEL) character is implemented by sending a string to stderr,
so it will be displayed on the LCD.
The public function uart_getchar() implements the line editor. If there are characters available in the line buffer (variable rxp is not NULL), the next character will
be returned from the buffer without any UART interaction.
If there are no characters inside the line buffer, the input loop will be entered. Characters will be read from the UART, and processed accordingly. If the UART signalled a
framing error (FE bit set), typically caused by the terminal sending a line break condition (start condition held much longer than one character period), the function will
return an end-of-file condition using _FDEV_EOF. If there was a data overrun condition on input (DOR bit set), an error condition will be returned as _FDEV_ERR.
Line editing characters are handled inside the loop, potentially modifying the buffer
status. If characters are attempted to be entered beyond the size of the line buffer, their
reception is refused, and a \a character is sent to the terminal. If a \r or \n character is
seen, the variable rxp (receive pointer) is set to the beginning of the buffer, the loop is
left, and the first character of the buffer will be returned to the application. (If no other
characters have been entered, this will just be the newline character, and the buffer is
marked as being exhausted immediately again.)
22.39.4
The source code
The source code is installed under
$prefix/share/doc/avr-libc/examples/stdiodemo/,
where $prefix is a configuration option. For Unix systems, it is usually set to either
/usr or /usr/local.
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
22.40
Example using the two-wire interface (TWI)
22.40
Example using the two-wire interface (TWI)
362
Some newer devices of the ATmega series contain builtin support for interfacing the
microcontroller to a two-wire bus, called TWI. This is essentially the same called I2C
by Philips, but that term is avoided in Atmel’s documentation due to patenting issues.
For further documentation, see:
http://www.nxp.com/documents/user_manual/UM10204.pdf
22.40.1
Introduction into TWI
The two-wire interface consists of two signal lines named SDA (serial data) and SCL
(serial clock) (plus a ground line, of course). All devices participating in the bus are
connected together, using open-drain driver circuitry, so the wires must be terminated
using appropriate pullup resistors. The pullups must be small enough to recharge
the line capacity in short enough time compared to the desired maximal clock frequency, yet large enough so all drivers will not be overloaded. There are formulas in
the datasheet that help selecting the pullups.
Devices can either act as a master to the bus (i. e., they initiate a transfer), or as a
slave (they only act when being called by a master). The bus is multi-master capable,
and a particular device implementation can act as either master or slave at different
times. Devices are addressed using a 7-bit address (coordinated by Philips) transfered
as the first byte after the so-called start condition. The LSB of that byte is R/∼W, i. e.
it determines whether the request to the slave is to read or write data during the next
cycles. (There is also an option to have devices using 10-bit addresses but that is not
covered by this example.)
22.40.2
The TWI example project
The ATmega TWI hardware supports both, master and slave operation. This example
will only demonstrate how to use an AVR microcontroller as TWI master. The implementation is kept simple in order to concentrate on the steps that are required to talk to
a TWI slave, so all processing is done in polled-mode, waiting for the TWI interface to
indicate that the next processing step is due (by setting the TWINT interrupt bit). If it
is desired to have the entire TWI communication happen in "background", all this can
be implemented in an interrupt-controlled way, where only the start condition needs to
be triggered from outside the interrupt routine.
There is a variety of slave devices available that can be connected to a TWI bus. For the
purpose of this example, an EEPROM device out of the industry-standard 24Cxx series
has been chosen (where xx can be one of 01, 02, 04, 08, or 16) which are available from
various vendors. The choice was almost arbitrary, mainly triggered by the fact that an
EEPROM device is being talked to in both directions, reading and writing the slave
device, so the example will demonstrate the details of both.
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22.40
Example using the two-wire interface (TWI)
363
Usually, there is probably not much need to add more EEPROM to an ATmega system
that way: the smallest possible AVR device that offers hardware TWI support is the
ATmega8 which comes with 512 bytes of EEPROM, which is equivalent to an 24C04
device. The ATmega128 already comes with twice as much EEPROM as the 24C16
would offer. One exception might be to use an externally connected EEPROM device
that is removable; e. g. SDRAM PC memory comes with an integrated TWI EEPROM
that carries the RAM configuration information.
22.40.3
The Source Code
The source code is installed under
$prefix/share/doc/avr-libc/examples/twitest/twitest.c,
where $prefix is a configuration option. For Unix systems, it is usually set to either
/usr or /usr/local.
Note [1]
The header file <util/twi.h> contains some macro definitions for symbolic constants used in the TWI status register. These definitions match the names used in the
Atmel datasheet except that all names have been prefixed with TW_.
Note [2]
The clock is used in timer calculations done by the compiler, for the UART baud rate
and the TWI clock rate.
Note [3]
The address assigned for the 24Cxx EEPROM consists of 1010 in the upper four bits.
The following three bits are normally available as slave sub-addresses, allowing to
operate more than one device of the same type on a single bus, where the actual subaddress used for each device is configured by hardware strapping. However, since the
next data packet following the device selection only allows for 8 bits that are used as
an EEPROM address, devices that require more than 8 address bits (24C04 and above)
"steal" subaddress bits and use them for the EEPROM cell address bits 9 to 11 as required. This example simply assumes all subaddress bits are 0 for the smaller devices,
so the E0, E1, and E2 inputs of the 24Cxx must be grounded.
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22.40
Example using the two-wire interface (TWI)
364
Note [3a]
EEPROMs of type 24C32 and above cannot be addressed anymore even with the subaddress bit trick. Thus, they require the upper address bits being sent separately on the
bus. When activating the WORD_ADDRESS_16BIT define, the algorithm implements
that auxiliary address byte transmission.
Note [4]
For slow clocks, enable the 2 x U[S]ART clock multiplier, to improve the baud rate
error. This will allow a 9600 Bd communication using the standard 1 MHz calibrated
RC oscillator. See also the Baud rate tables in the datasheets.
Note [5]
The datasheet explains why a minimum TWBR value of 10 should be maintained when
running in master mode. Thus, for system clocks below 3.6 MHz, we cannot run the
bus at the intented clock rate of 100 kHz but have to slow down accordingly.
Note [6]
This function is used by the standard output facilities that are utilized in this example
for debugging and demonstration purposes.
Note [7]
In order to shorten the data to be sent over the TWI bus, the 24Cxx EEPROMs support
multiple data bytes transfered within a single request, maintaining an internal address
counter that is updated after each data byte transfered successfully. When reading
data, one request can read the entire device memory if desired (the counter would wrap
around and start back from 0 when reaching the end of the device).
Note [8]
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22.40
Example using the two-wire interface (TWI)
365
When reading the EEPROM, a first device selection must be made with write intent
(R/∼W bit set to 0 indicating a write operation) in order to transfer the EEPROM address to start reading from. This is called master transmitter mode. Each completion
of a particular step in TWI communication is indicated by an asserted TWINT bit in
TWCR. (An interrupt would be generated if allowed.) After performing any actions
that are needed for the next communication step, the interrupt condition must be manually cleared by setting the TWINT bit. Unlike with many other interrupt sources, this
would even be required when using a true interrupt routine, since as soon as TWINT is
re-asserted, the next bus transaction will start.
Note [9]
Since the TWI bus is multi-master capable, there is potential for a bus contention when
one master starts to access the bus. Normally, the TWI bus interface unit will detect this
situation, and will not initiate a start condition while the bus is busy. However, in case
two masters were starting at exactly the same time, the way bus arbitration works, there
is always a chance that one master could lose arbitration of the bus during any transmit
operation. A master that has lost arbitration is required by the protocol to immediately
cease talking on the bus; in particular it must not initiate a stop condition in order to not
corrupt the ongoing transfer from the active master. In this example, upon detecting a
lost arbitration condition, the entire transfer is going to be restarted. This will cause a
new start condition to be initiated, which will normally be delayed until the currently
active master has released the bus.
Note [10]
Next, the device slave is going to be reselected (using a so-called repeated start condition which is meant to guarantee that the bus arbitration will remain at the current
master) using the same slave address (SLA), but this time with read intent (R/∼W bit
set to 1) in order to request the device slave to start transfering data from the slave to
the master in the next packet.
Note [11]
If the EEPROM device is still busy writing one or more cells after a previous write
request, it will simply leave its bus interface drivers at high impedance, and does not
respond to a selection in any way at all. The master selecting the device will see the
high level at SDA after transfering the SLA+R/W packet as a NACK to its selection
request. Thus, the select process is simply started over (effectively causing a repeated
start condition), until the device will eventually respond. This polling procedure is
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22.40
Example using the two-wire interface (TWI)
366
recommended in the 24Cxx datasheet in order to minimize the busy wait time when
writing. Note that in case a device is broken and never responds to a selection (e. g.
since it is no longer present at all), this will cause an infinite loop. Thus the maximal
number of iterations made until the device is declared to be not responding at all, and
an error is returned, will be limited to MAX_ITER.
Note [12]
This is called master receiver mode: the bus master still supplies the SCL clock, but the
device slave drives the SDA line with the appropriate data. After 8 data bits, the master
responds with an ACK bit (SDA driven low) in order to request another data transfer
from the slave, or it can leave the SDA line high (NACK), indicating to the slave that
it is going to stop the transfer now. Assertion of ACK is handled by setting the TWEA
bit in TWCR when starting the current transfer.
Note [13]
The control word sent out in order to initiate the transfer of the next data packet is
initially set up to assert the TWEA bit. During the last loop iteration, TWEA is deasserted so the client will get informed that no further transfer is desired.
Note [14]
Except in the case of lost arbitration, all bus transactions must properly be terminated
by the master initiating a stop condition.
Note [15]
Writing to the EEPROM device is simpler than reading, since only a master transmitter
mode transfer is needed. Note that the first packet after the SLA+W selection is always
considered to be the EEPROM address for the next operation. (This packet is exactly
the same as the one above sent before starting to read the device.) In case a master
transmitter mode transfer is going to send more than one data packet, all following
packets will be considered data bytes to write at the indicated address. The internal
address pointer will be incremented after each write operation.
Note [16]
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23 Data Structure Documentation
367
24Cxx devices can become write-protected by strapping their ∼WC pin to logic high.
(Leaving it unconnected is explicitly allowed, and constitutes logic low level, i. e. no
write protection.) In case of a write protected device, all data transfer attempts will be
NACKed by the device. Note that some devices might not implement this.
23
Data Structure Documentation
23.1
div t Struct Reference
Data Fields
• int quot
• int rem
23.1.1
Detailed Description
Result type for function div().
23.1.2
Field Documentation
23.1.2.1
int div_t::quot
The Quotient.
23.1.2.2
int div_t::rem
The Remainder.
The documentation for this struct was generated from the following file:
• stdlib.h
23.2
ldiv t Struct Reference
Data Fields
• long quot
• long rem
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24 File Documentation
23.2.1
368
Detailed Description
Result type for function ldiv().
23.2.2
Field Documentation
23.2.2.1
long ldiv_t::quot
The Quotient.
23.2.2.2
long ldiv_t::rem
The Remainder.
The documentation for this struct was generated from the following file:
• stdlib.h
24
File Documentation
24.1
assert.h File Reference
Defines
• #define assert(expression)
24.1.1
Detailed Description
24.2
atoi.S File Reference
24.2.1
Detailed Description
24.3
atol.S File Reference
24.3.1
Detailed Description
24.4
atomic.h File Reference
Defines
• #define ATOMIC_BLOCK(type)
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24.5
•
•
•
•
•
boot.h File Reference
369
#define NONATOMIC_BLOCK(type)
#define ATOMIC_RESTORESTATE
#define ATOMIC_FORCEON
#define NONATOMIC_RESTORESTATE
#define NONATOMIC_FORCEOFF
24.4.1
Detailed Description
24.5
boot.h File Reference
Defines
•
•
•
•
•
•
•
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•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
#define BOOTLOADER_SECTION __attribute__ ((section (".bootloader")))
#define __COMMON_ASB RWWSB
#define __COMMON_ASRE RWWSRE
#define BLB12 5
#define BLB11 4
#define BLB02 3
#define BLB01 2
#define boot_spm_interrupt_enable() (__SPM_REG |= (uint8_t)_BV(SPMIE))
#define boot_spm_interrupt_disable() (__SPM_REG &= (uint8_t)∼_BV(SPMIE))
#define boot_is_spm_interrupt() (__SPM_REG & (uint8_t)_BV(SPMIE))
#define boot_rww_busy() (__SPM_REG & (uint8_t)_BV(__COMMON_ASB))
#define boot_spm_busy() (__SPM_REG & (uint8_t)_BV(__SPM_ENABLE))
#define boot_spm_busy_wait() do{}while(boot_spm_busy())
#define __BOOT_PAGE_ERASE (_BV(__SPM_ENABLE) | _BV(PGERS))
#define __BOOT_PAGE_WRITE (_BV(__SPM_ENABLE) | _BV(PGWRT))
#define __BOOT_PAGE_FILL _BV(__SPM_ENABLE)
#define __BOOT_RWW_ENABLE (_BV(__SPM_ENABLE) | _BV(__COMMON_ASRE))
#define __boot_page_fill_normal(address, data)
#define __boot_page_fill_alternate(address, data)
#define __boot_page_fill_extended(address, data)
#define __boot_page_erase_normal(address)
#define __boot_page_erase_alternate(address)
#define __boot_page_erase_extended(address)
#define __boot_page_write_normal(address)
#define __boot_page_write_alternate(address)
#define __boot_page_write_extended(address)
#define __boot_rww_enable()
#define __boot_rww_enable_alternate()
#define __boot_lock_bits_set(lock_bits)
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24.5
boot.h File Reference
370
•
•
•
•
•
•
•
#define __boot_lock_bits_set_alternate(lock_bits)
#define GET_LOW_FUSE_BITS (0x0000)
#define GET_LOCK_BITS (0x0001)
#define GET_EXTENDED_FUSE_BITS (0x0002)
#define GET_HIGH_FUSE_BITS (0x0003)
#define boot_lock_fuse_bits_get(address)
#define __BOOT_SIGROW_READ (_BV(__SPM_ENABLE) | _BV(SIGRD))
•
•
•
•
•
•
•
•
•
•
•
#define boot_signature_byte_get(addr)
#define boot_page_fill(address, data) __boot_page_fill_normal(address, data)
#define boot_page_erase(address) __boot_page_erase_normal(address)
#define boot_page_write(address) __boot_page_write_normal(address)
#define boot_rww_enable() __boot_rww_enable()
#define boot_lock_bits_set(lock_bits) __boot_lock_bits_set(lock_bits)
#define boot_page_fill_safe(address, data)
#define boot_page_erase_safe(address)
#define boot_page_write_safe(address)
#define boot_rww_enable_safe()
#define boot_lock_bits_set_safe(lock_bits)
24.5.1
Detailed Description
24.5.2
Define Documentation
24.5.2.1
#define __boot_lock_bits_set( lock_bits )
Value:
(__extension__({
uint8_t value = (uint8_t)(~(lock_bits));
__asm__ __volatile__
(
"ldi r30, 1\n\t"
"ldi r31, 0\n\t"
"mov r0, %2\n\t"
"sts %0, %1\n\t"
"spm\n\t"
:
: "i" (_SFR_MEM_ADDR(__SPM_REG)),
"r" ((uint8_t)(__BOOT_LOCK_BITS_SET)),
"r" (value)
: "r0", "r30", "r31"
);
}))
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\
\
\
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\
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\
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\
\
\
\
24.5
boot.h File Reference
24.5.2.2
371
#define __boot_lock_bits_set_alternate( lock_bits )
Value:
(__extension__({
uint8_t value = (uint8_t)(~(lock_bits));
__asm__ __volatile__
(
"ldi r30, 1\n\t"
"ldi r31, 0\n\t"
"mov r0, %2\n\t"
"sts %0, %1\n\t"
"spm\n\t"
".word 0xffff\n\t"
"nop\n\t"
:
: "i" (_SFR_MEM_ADDR(__SPM_REG)),
"r" ((uint8_t)(__BOOT_LOCK_BITS_SET)),
"r" (value)
: "r0", "r30", "r31"
);
}))
24.5.2.3
\
\
\
\
\
\
\
\
\
\
\
\
\
\
\
\
\
#define __boot_page_erase_alternate( address )
Value:
(__extension__({
__asm__ __volatile__
(
"sts %0, %1\n\t"
"spm\n\t"
".word 0xffff\n\t"
"nop\n\t"
:
: "i" (_SFR_MEM_ADDR(__SPM_REG)),
"r" ((uint8_t)(__BOOT_PAGE_ERASE)),
"z" ((uint16_t)(address))
);
}))
24.5.2.4
\
\
\
\
\
\
\
\
\
\
\
\
#define __boot_page_erase_extended( address )
Value:
(__extension__({
__asm__ __volatile__
(
"movw r30, %A3\n\t"
"sts %1, %C3\n\t"
"sts %0, %2\n\t"
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\
\
\
\
\
\
24.5
boot.h File Reference
"spm\n\t"
:
: "i" (_SFR_MEM_ADDR(__SPM_REG)),
"i" (_SFR_MEM_ADDR(RAMPZ)),
"r" ((uint8_t)(__BOOT_PAGE_ERASE)),
"r" ((uint32_t)(address))
: "r30", "r31"
);
372
\
\
\
\
\
\
\
\
}))
24.5.2.5
#define __boot_page_erase_normal( address )
Value:
(__extension__({
__asm__ __volatile__
(
"sts %0, %1\n\t"
"spm\n\t"
:
: "i" (_SFR_MEM_ADDR(__SPM_REG)),
"r" ((uint8_t)(__BOOT_PAGE_ERASE)),
"z" ((uint16_t)(address))
);
}))
24.5.2.6
\
\
\
\
\
\
\
\
\
\
#define __boot_page_fill_alternate( address, data )
Value:
(__extension__({
__asm__ __volatile__
(
"movw r0, %3\n\t"
"sts %0, %1\n\t"
"spm\n\t"
".word 0xffff\n\t"
"nop\n\t"
"clr r1\n\t"
:
: "i" (_SFR_MEM_ADDR(__SPM_REG)),
"r" ((uint8_t)(__BOOT_PAGE_FILL)),
"z" ((uint16_t)(address)),
"r" ((uint16_t)(data))
: "r0"
);
}))
24.5.2.7
\
\
\
\
\
\
\
\
\
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\
\
\
\
\
#define __boot_page_fill_extended( address, data )
Value:
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24.5
boot.h File Reference
(__extension__({
__asm__ __volatile__
(
"movw r0, %4\n\t"
"movw r30, %A3\n\t"
"sts %1, %C3\n\t"
"sts %0, %2\n\t"
"spm\n\t"
"clr r1\n\t"
:
: "i" (_SFR_MEM_ADDR(__SPM_REG)),
"i" (_SFR_MEM_ADDR(RAMPZ)),
"r" ((uint8_t)(__BOOT_PAGE_FILL)),
"r" ((uint32_t)(address)),
"r" ((uint16_t)(data))
: "r0", "r30", "r31"
);
}))
24.5.2.8
373
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\
#define __boot_page_fill_normal( address, data )
Value:
(__extension__({
__asm__ __volatile__
(
"movw r0, %3\n\t"
"sts %0, %1\n\t"
"spm\n\t"
"clr r1\n\t"
:
: "i" (_SFR_MEM_ADDR(__SPM_REG)),
"r" ((uint8_t)(__BOOT_PAGE_FILL)),
"z" ((uint16_t)(address)),
"r" ((uint16_t)(data))
: "r0"
);
}))
24.5.2.9
\
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\
\
\
\
#define __boot_page_write_alternate( address )
Value:
(__extension__({
__asm__ __volatile__
(
"sts %0, %1\n\t"
"spm\n\t"
".word 0xffff\n\t"
"nop\n\t"
:
: "i" (_SFR_MEM_ADDR(__SPM_REG)),
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24.5
boot.h File Reference
374
"r" ((uint8_t)(__BOOT_PAGE_WRITE)),
"z" ((uint16_t)(address))
);
\
\
\
}))
24.5.2.10
#define __boot_page_write_extended( address )
Value:
(__extension__({
__asm__ __volatile__
(
"movw r30, %A3\n\t"
"sts %1, %C3\n\t"
"sts %0, %2\n\t"
"spm\n\t"
:
: "i" (_SFR_MEM_ADDR(__SPM_REG)),
"i" (_SFR_MEM_ADDR(RAMPZ)),
"r" ((uint8_t)(__BOOT_PAGE_WRITE)),
"r" ((uint32_t)(address))
: "r30", "r31"
);
}))
24.5.2.11
\
\
\
\
\
\
\
\
\
\
\
\
\
\
#define __boot_page_write_normal( address )
Value:
(__extension__({
__asm__ __volatile__
(
"sts %0, %1\n\t"
"spm\n\t"
:
: "i" (_SFR_MEM_ADDR(__SPM_REG)),
"r" ((uint8_t)(__BOOT_PAGE_WRITE)),
"z" ((uint16_t)(address))
);
}))
24.5.2.12
#define __boot_rww_enable(
\
\
\
\
\
\
\
\
\
\
)
Value:
(__extension__({
__asm__ __volatile__
(
"sts %0, %1\n\t"
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\
\
\
\
24.6
cpufunc.h File Reference
375
"spm\n\t"
:
: "i" (_SFR_MEM_ADDR(__SPM_REG)),
"r" ((uint8_t)(__BOOT_RWW_ENABLE))
\
\
\
\
\
);
}))
24.5.2.13
#define __boot_rww_enable_alternate(
)
Value:
(__extension__({
__asm__ __volatile__
(
"sts %0, %1\n\t"
"spm\n\t"
".word 0xffff\n\t"
"nop\n\t"
:
: "i" (_SFR_MEM_ADDR(__SPM_REG)),
"r" ((uint8_t)(__BOOT_RWW_ENABLE))
);
}))
24.6
\
\
\
\
\
\
\
\
\
\
\
cpufunc.h File Reference
Defines
• #define _NOP()
• #define _MemoryBarrier()
24.6.1
Detailed Description
24.7
crc16.h File Reference
Functions
•
•
•
•
static __inline__ uint16_t _crc16_update (uint16_t __crc, uint8_t __data)
static __inline__ uint16_t _crc_xmodem_update (uint16_t __crc, uint8_t __data)
static __inline__ uint16_t _crc_ccitt_update (uint16_t __crc, uint8_t __data)
static __inline__ uint8_t _crc_ibutton_update (uint8_t __crc, uint8_t __data)
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
24.8
ctype.h File Reference
24.7.1
Detailed Description
24.8
ctype.h File Reference
376
Functions
Character classification routines
These functions perform character classification. They return true or false status
depending whether the character passed to the function falls into the function’s
classification (i.e. isdigit() returns true if its argument is any value ’0’ though ’9’,
inclusive). If the input is not an unsigned char value, all of this function return
false.
•
•
•
•
•
•
•
•
•
•
•
•
•
int isalnum (int __c)
int isalpha (int __c)
int isascii (int __c)
int isblank (int __c)
int iscntrl (int __c)
int isdigit (int __c)
int isgraph (int __c)
int islower (int __c)
int isprint (int __c)
int ispunct (int __c)
int isspace (int __c)
int isupper (int __c)
int isxdigit (int __c)
Character convertion routines
This realization permits all possible values of integer argument. The toascii() function clears all highest bits. The tolower() and toupper() functions return an input
argument as is, if it is not an unsigned char value.
• int toascii (int __c)
• int tolower (int __c)
• int toupper (int __c)
24.8.1
Detailed Description
24.9
delay basic.h File Reference
Functions
• void _delay_loop_1 (uint8_t __count)
• void _delay_loop_2 (uint16_t __count)
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
24.10
24.9.1
errno.h File Reference
Detailed Description
24.10
errno.h File Reference
Defines
• #define EDOM 33
• #define ERANGE 34
Variables
• int errno
24.10.1
Detailed Description
24.11
fdevopen.c File Reference
Functions
• FILE ∗ fdevopen (int(∗put)(char, FILE ∗), int(∗get)(FILE ∗))
24.11.1
Detailed Description
24.12
ffs.S File Reference
24.12.1
Detailed Description
24.13
ffsl.S File Reference
24.13.1
Detailed Description
24.14
ffsll.S File Reference
24.14.1
Detailed Description
24.15
fuse.h File Reference
Defines
• #define FUSEMEM __attribute__((section (".fuse")))
• #define FUSES __fuse_t __fuse FUSEMEM
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377
24.16
interrupt.h File Reference
24.15.1
Detailed Description
24.16
interrupt.h File Reference
378
Defines
Global manipulation of the interrupt flag
The global interrupt flag is maintained in the I bit of the status register (SREG).
Handling interrupts frequently requires attention regarding atomic access to objects that could be altered by code running within an interrupt context, see <util/atomic.h>.
Frequently, interrupts are being disabled for periods of time in order to perform
certain operations without being disturbed; see optim_code_reorder for things to
be taken into account with respect to compiler optimizations.
• #define sei()
• #define cli()
Macros for writing interrupt handler functions
•
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•
#define ISR(vector, attributes)
#define SIGNAL(vector)
#define EMPTY_INTERRUPT(vector)
#define ISR_ALIAS(vector, target_vector)
#define reti()
#define BADISR_vect
ISR attributes
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•
24.16.1
#define ISR_BLOCK
#define ISR_NOBLOCK
#define ISR_NAKED
#define ISR_ALIASOF(target_vector)
Detailed Description
@{
24.17
inttypes.h File Reference
Defines
macros for printf and scanf format specifiers
For C++, these are only included if __STDC_LIMIT_MACROS is defined before
including <inttypes.h>.
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24.17
inttypes.h File Reference
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#define PRId8 "d"
#define PRIdLEAST8 "d"
#define PRIdFAST8 "d"
#define PRIi8 "i"
#define PRIiLEAST8 "i"
#define PRIiFAST8 "i"
#define PRId16 "d"
#define PRIdLEAST16 "d"
#define PRIdFAST16 "d"
#define PRIi16 "i"
#define PRIiLEAST16 "i"
#define PRIiFAST16 "i"
#define PRId32 "ld"
#define PRIdLEAST32 "ld"
#define PRIdFAST32 "ld"
#define PRIi32 "li"
#define PRIiLEAST32 "li"
#define PRIiFAST32 "li"
#define PRIdPTR PRId16
#define PRIiPTR PRIi16
#define PRIo8 "o"
#define PRIoLEAST8 "o"
#define PRIoFAST8 "o"
#define PRIu8 "u"
#define PRIuLEAST8 "u"
#define PRIuFAST8 "u"
#define PRIx8 "x"
#define PRIxLEAST8 "x"
#define PRIxFAST8 "x"
#define PRIX8 "X"
#define PRIXLEAST8 "X"
#define PRIXFAST8 "X"
#define PRIo16 "o"
#define PRIoLEAST16 "o"
#define PRIoFAST16 "o"
#define PRIu16 "u"
#define PRIuLEAST16 "u"
#define PRIuFAST16 "u"
#define PRIx16 "x"
#define PRIxLEAST16 "x"
#define PRIxFAST16 "x"
#define PRIX16 "X"
#define PRIXLEAST16 "X"
#define PRIXFAST16 "X"
#define PRIo32 "lo"
#define PRIoLEAST32 "lo"
#define PRIoFAST32 "lo"
#define PRIu32 "lu"
#define PRIuLEAST32 "lu"
#define PRIuFAST32 "lu"
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inttypes.h File Reference
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#define PRIx32 "lx"
#define PRIxLEAST32 "lx"
#define PRIxFAST32 "lx"
#define PRIX32 "lX"
#define PRIXLEAST32 "lX"
#define PRIXFAST32 "lX"
#define PRIoPTR PRIo16
#define PRIuPTR PRIu16
#define PRIxPTR PRIx16
#define PRIXPTR PRIX16
#define SCNd16 "d"
#define SCNdLEAST16 "d"
#define SCNdFAST16 "d"
#define SCNi16 "i"
#define SCNiLEAST16 "i"
#define SCNiFAST16 "i"
#define SCNd32 "ld"
#define SCNdLEAST32 "ld"
#define SCNdFAST32 "ld"
#define SCNi32 "li"
#define SCNiLEAST32 "li"
#define SCNiFAST32 "li"
#define SCNdPTR SCNd16
#define SCNiPTR SCNi16
#define SCNo16 "o"
#define SCNoLEAST16 "o"
#define SCNoFAST16 "o"
#define SCNu16 "u"
#define SCNuLEAST16 "u"
#define SCNuFAST16 "u"
#define SCNx16 "x"
#define SCNxLEAST16 "x"
#define SCNxFAST16 "x"
#define SCNo32 "lo"
#define SCNoLEAST32 "lo"
#define SCNoFAST32 "lo"
#define SCNu32 "lu"
#define SCNuLEAST32 "lu"
#define SCNuFAST32 "lu"
#define SCNx32 "lx"
#define SCNxLEAST32 "lx"
#define SCNxFAST32 "lx"
#define SCNoPTR SCNo16
#define SCNuPTR SCNu16
#define SCNxPTR SCNx16
Typedefs
Far pointers for memory access >64K
• typedef int32_t int_farptr_t
• typedef uint32_t uint_farptr_t
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380
24.18
io.h File Reference
24.17.1
Detailed Description
24.18
io.h File Reference
24.18.1
Detailed Description
24.19
lock.h File Reference
Defines
• #define LOCKMEM __attribute__((section (".lock")))
• #define LOCKBITS unsigned char __lock LOCKMEM
• #define LOCKBITS_DEFAULT (0xFF)
24.19.1
Detailed Description
24.20
math.h File Reference
Defines
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#define M_E 2.7182818284590452354
#define M_LOG2E 1.4426950408889634074
#define M_LOG10E 0.43429448190325182765
#define M_LN2 0.69314718055994530942
#define M_LN10 2.30258509299404568402
#define M_PI 3.14159265358979323846
#define M_PI_2 1.57079632679489661923
#define M_PI_4 0.78539816339744830962
#define M_1_PI 0.31830988618379067154
#define M_2_PI 0.63661977236758134308
#define M_2_SQRTPI 1.12837916709551257390
#define M_SQRT2 1.41421356237309504880
#define M_SQRT1_2 0.70710678118654752440
#define NAN __builtin_nan("")
#define INFINITY __builtin_inf()
#define cosf cos
#define sinf sin
#define tanf tan
#define fabsf fabs
#define fmodf fmod
#define sqrtf sqrt
#define cbrtf cbrt
#define hypotf hypot
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math.h File Reference
#define squaref square
#define floorf floor
#define ceilf ceil
#define frexpf frexp
#define ldexpf ldexp
#define expf exp
#define coshf cosh
#define sinhf sinh
#define tanhf tanh
#define acosf acos
#define asinf asin
#define atanf atan
#define atan2f atan2
#define logf log
#define log10f log10
#define powf pow
#define isnanf isnan
#define isinff isinf
#define isfinitef isfinite
#define copysignf copysign
#define signbitf signbit
#define fdimf fdim
#define fmaf fma
#define fmaxf fmax
#define fminf fmin
#define truncf trunc
#define roundf round
#define lroundf lround
#define lrintf lrint
Functions
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double cos (double __x)
double sin (double __x)
double tan (double __x)
double fabs (double __x)
double fmod (double __x, double __y)
double modf (double __x, double ∗__iptr)
float modff (float __x, float ∗__iptr)
double sqrt (double __x)
double cbrt (double __x)
double hypot (double __x, double __y)
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382
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math.h File Reference
double square (double __x)
double floor (double __x)
double ceil (double __x)
double frexp (double __x, int ∗__pexp)
double ldexp (double __x, int __exp)
double exp (double __x)
double cosh (double __x)
double sinh (double __x)
double tanh (double __x)
double acos (double __x)
double asin (double __x)
double atan (double __x)
double atan2 (double __y, double __x)
double log (double __x)
double log10 (double __x)
double pow (double __x, double __y)
int isnan (double __x)
int isinf (double __x)
static int isfinite (double __x)
static double copysign (double __x, double __y)
int signbit (double __x)
double fdim (double __x, double __y)
double fma (double __x, double __y, double __z)
double fmax (double __x, double __y)
double fmin (double __x, double __y)
double trunc (double __x)
double round (double __x)
long lround (double __x)
long lrint (double __x)
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383
24.20
math.h File Reference
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
384
24.21
memccpy.S File Reference
24.20.1
Detailed Description
24.21
memccpy.S File Reference
24.21.1
Detailed Description
24.22
memchr.S File Reference
24.22.1
Detailed Description
24.23
memchr P.S File Reference
24.23.1
Detailed Description
24.24
memcmp.S File Reference
24.24.1
Detailed Description
24.25
memcmp P.S File Reference
24.25.1
Detailed Description
24.26
memcmp PF.S File Reference
24.26.1
Detailed Description
24.27
memcpy.S File Reference
24.27.1
Detailed Description
24.28
memcpy P.S File Reference
24.28.1
Detailed Description
24.29
memmem.S File Reference
24.29.1
Detailed Description
24.30
memmove.S File Reference
24.30.1
Detailed Description
24.31
memrchr.S File Reference
24.31.1
Detailed Description
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
24.32
memrchr P.S File Reference
24.32.1
Detailed Description
24.33
memset.S File Reference
385
24.35
pgmspace.h File Reference
24.34.1
Detailed Description
24.35
pgmspace.h File Reference
386
Defines
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#define __need_size_t
#define __ATTR_PROGMEM__ __attribute__((__progmem__))
#define __ATTR_PURE__ __attribute__((__pure__))
#define PROGMEM __ATTR_PROGMEM__
#define PSTR(s) ((const PROGMEM char ∗)(s))
#define __LPM_classic__(addr)
#define __LPM_enhanced__(addr)
#define __LPM_word_classic__(addr)
#define __LPM_word_enhanced__(addr)
#define __LPM_dword_classic__(addr)
#define __LPM_dword_enhanced__(addr)
#define __LPM_float_classic__(addr)
#define __LPM_float_enhanced__(addr)
#define __LPM(addr) __LPM_classic__(addr)
#define __LPM_word(addr) __LPM_word_classic__(addr)
#define __LPM_dword(addr) __LPM_dword_classic__(addr)
#define __LPM_float(addr) __LPM_float_classic__(addr)
#define pgm_read_byte_near(address_short) __LPM((uint16_t)(address_short))
#define pgm_read_word_near(address_short) __LPM_word((uint16_t)(address_short))
#define pgm_read_dword_near(address_short) __LPM_dword((uint16_t)(address_short))
#define pgm_read_float_near(address_short) __LPM_float((uint16_t)(address_short))
#define __ELPM_classic__(addr)
#define __ELPM_enhanced__(addr)
#define __ELPM_xmega__(addr)
#define __ELPM_word_classic__(addr)
#define __ELPM_word_enhanced__(addr)
#define __ELPM_word_xmega__(addr)
#define __ELPM_dword_classic__(addr)
#define __ELPM_dword_enhanced__(addr)
#define __ELPM_dword_xmega__(addr)
#define __ELPM_float_classic__(addr)
#define __ELPM_float_enhanced__(addr)
#define __ELPM_float_xmega__(addr)
#define __ELPM(addr) __ELPM_classic__(addr)
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
24.35
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pgmspace.h File Reference
387
#define __ELPM_word(addr) __ELPM_word_classic__(addr)
#define __ELPM_dword(addr) __ELPM_dword_classic__(addr)
#define __ELPM_float(addr) __ELPM_float_classic__(addr)
#define pgm_read_byte_far(address_long) __ELPM((uint32_t)(address_long))
#define pgm_read_word_far(address_long) __ELPM_word((uint32_t)(address_long))
#define pgm_read_dword_far(address_long) __ELPM_dword((uint32_t)(address_long))
#define pgm_read_float_far(address_long) __ELPM_float((uint32_t)(address_long))
#define pgm_read_byte(address_short) pgm_read_byte_near(address_short)
#define pgm_read_word(address_short) pgm_read_word_near(address_short)
#define pgm_read_dword(address_short) pgm_read_dword_near(address_short)
#define pgm_read_float(address_short) pgm_read_float_near(address_short)
#define PGM_P const prog_char ∗
#define PGM_VOID_P const prog_void ∗
#define pgm_get_far_address(var)
Typedefs
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typedef void PROGMEM prog_void
typedef char PROGMEM prog_char
typedef unsigned char PROGMEM prog_uchar
typedef int8_t PROGMEM prog_int8_t
typedef uint8_t PROGMEM prog_uint8_t
typedef int16_t PROGMEM prog_int16_t
typedef uint16_t PROGMEM prog_uint16_t
typedef int32_t PROGMEM prog_int32_t
typedef uint32_t PROGMEM prog_uint32_t
typedef int64_t PROGMEM prog_int64_t
typedef uint64_t PROGMEM prog_uint64_t
Functions
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PGM_VOID_P memchr_P (PGM_VOID_P, int __val, size_t __len)
int memcmp_P (const void ∗, PGM_VOID_P, size_t) __ATTR_PURE__
void ∗ memccpy_P (void ∗, PGM_VOID_P, int __val, size_t)
void ∗ memcpy_P (void ∗, PGM_VOID_P, size_t)
void ∗ memmem_P (const void ∗, size_t, PGM_VOID_P, size_t) __ATTR_PURE__
• PGM_VOID_P memrchr_P (PGM_VOID_P, int __val, size_t __len)
• char ∗ strcat_P (char ∗, PGM_P)
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
24.35
pgmspace.h File Reference
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PGM_P strchr_P (PGM_P, int __val)
PGM_P strchrnul_P (PGM_P, int __val)
int strcmp_P (const char ∗, PGM_P) __ATTR_PURE__
char ∗ strcpy_P (char ∗, PGM_P)
int strcasecmp_P (const char ∗, PGM_P) __ATTR_PURE__
char ∗ strcasestr_P (const char ∗, PGM_P) __ATTR_PURE__
size_t strcspn_P (const char ∗__s, PGM_P __reject) __ATTR_PURE__
size_t strlcat_P (char ∗, PGM_P, size_t)
size_t strlcpy_P (char ∗, PGM_P, size_t)
size_t strlen_P (PGM_P)
size_t strnlen_P (PGM_P, size_t)
int strncmp_P (const char ∗, PGM_P, size_t) __ATTR_PURE__
int strncasecmp_P (const char ∗, PGM_P, size_t) __ATTR_PURE__
char ∗ strncat_P (char ∗, PGM_P, size_t)
char ∗ strncpy_P (char ∗, PGM_P, size_t)
char ∗ strpbrk_P (const char ∗__s, PGM_P __accept) __ATTR_PURE__
PGM_P strrchr_P (PGM_P, int __val)
char ∗ strsep_P (char ∗∗__sp, PGM_P __delim)
size_t strspn_P (const char ∗__s, PGM_P __accept) __ATTR_PURE__
char ∗ strstr_P (const char ∗, PGM_P) __ATTR_PURE__
char ∗ strtok_P (char ∗__s, PGM_P __delim)
char ∗ strtok_rP (char ∗__s, PGM_P __delim, char ∗∗__last)
size_t strlen_PF (uint_farptr_t src)
size_t strnlen_PF (uint_farptr_t src, size_t len)
void ∗ memcpy_PF (void ∗dest, uint_farptr_t src, size_t len)
char ∗ strcpy_PF (char ∗dest, uint_farptr_t src)
char ∗ strncpy_PF (char ∗dest, uint_farptr_t src, size_t len)
char ∗ strcat_PF (char ∗dest, uint_farptr_t src)
size_t strlcat_PF (char ∗dst, uint_farptr_t src, size_t siz)
char ∗ strncat_PF (char ∗dest, uint_farptr_t src, size_t len)
int strcmp_PF (const char ∗s1, uint_farptr_t s2) __ATTR_PURE__
int strncmp_PF (const char ∗s1, uint_farptr_t s2, size_t n) __ATTR_PURE__
int strcasecmp_PF (const char ∗s1, uint_farptr_t s2) __ATTR_PURE__
int strncasecmp_PF (const char ∗s1, uint_farptr_t s2, size_t n) __ATTR_PURE__
• char ∗ strstr_PF (const char ∗s1, uint_farptr_t s2)
• size_t strlcpy_PF (char ∗dst, uint_farptr_t src, size_t siz)
• int memcmp_PF (const void ∗, uint_farptr_t, size_t) __ATTR_PURE__
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
24.35
pgmspace.h File Reference
24.35.1
Detailed Description
24.35.2
Define Documentation
24.35.2.1
389
#define __ELPM_classic__( addr )
Value:
(__extension__({
\
uint32_t __addr32 = (uint32_t)(addr); \
uint8_t __result;
\
__asm__
\
(
\
"out %2, %C1" "\n\t"
\
"mov r31, %B1" "\n\t"
\
"mov r30, %A1" "\n\t"
\
"elpm" "\n\t"
\
"mov %0, r0" "\n\t"
\
: "=r" (__result)
\
: "r" (__addr32),
\
"I" (_SFR_IO_ADDR(RAMPZ)) \
: "r0", "r30", "r31"
\
);
\
__result;
\
}))
24.35.2.2
#define __ELPM_dword_enhanced__( addr )
Value:
(__extension__({
uint32_t __addr32 = (uint32_t)(addr);
uint32_t __result;
__asm__
(
"out %2, %C1"
"\n\t"
"movw r30, %1" "\n\t"
"elpm %A0, Z+" "\n\t"
"elpm %B0, Z+" "\n\t"
"elpm %C0, Z+" "\n\t"
"elpm %D0, Z"
"\n\t"
: "=r" (__result)
: "r" (__addr32),
"I" (_SFR_IO_ADDR(RAMPZ))
: "r30", "r31"
);
__result;
}))
24.35.2.3
\
\
\
\
\
\
\
\
\
\
\
\
\
\
\
\
\
#define __ELPM_dword_xmega__( addr )
Value:
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
24.35
pgmspace.h File Reference
(__extension__({
uint32_t __addr32 = (uint32_t)(addr);
uint32_t __result;
__asm__
(
"in __tmp_reg__, %2" "\n\t"
"out %2, %C1"
"\n\t"
"movw r30, %1" "\n\t"
"elpm %A0, Z+" "\n\t"
"elpm %B0, Z+" "\n\t"
"elpm %C0, Z+" "\n\t"
"elpm %D0, Z"
"\n\t"
"out %2, __tmp_reg__"
: "=r" (__result)
: "r" (__addr32),
"I" (_SFR_IO_ADDR(RAMPZ))
: "r30", "r31"
);
__result;
}))
24.35.2.4
390
\
\
\
\
\
\
\
\
\
\
\
\
\
\
\
\
\
\
\
#define __ELPM_enhanced__( addr )
Value:
(__extension__({
\
uint32_t __addr32 = (uint32_t)(addr); \
uint8_t __result;
\
__asm__
\
(
\
"out %2, %C1" "\n\t"
\
"movw r30, %1" "\n\t"
\
"elpm %0, Z+" "\n\t"
\
: "=r" (__result)
\
: "r" (__addr32),
\
"I" (_SFR_IO_ADDR(RAMPZ)) \
: "r30", "r31"
\
);
\
__result;
\
}))
24.35.2.5
#define __ELPM_float_enhanced__( addr )
Value:
(__extension__({
\
uint32_t __addr32 = (uint32_t)(addr); \
float __result;
\
__asm__
\
(
\
"out %2, %C1"
"\n\t"
\
"movw r30, %1" "\n\t"
\
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
24.35
pgmspace.h File Reference
"elpm %A0, Z+" "\n\t"
"elpm %B0, Z+" "\n\t"
"elpm %C0, Z+" "\n\t"
"elpm %D0, Z"
"\n\t"
: "=r" (__result)
: "r" (__addr32),
"I" (_SFR_IO_ADDR(RAMPZ))
: "r30", "r31"
);
__result;
391
\
\
\
\
\
\
\
\
\
\
}))
24.35.2.6
#define __ELPM_float_xmega__( addr )
Value:
(__extension__({
uint32_t __addr32 = (uint32_t)(addr);
float __result;
__asm__
(
"in __tmp_reg__, %2" "\n\t"
"out %2, %C1"
"\n\t"
"movw r30, %1" "\n\t"
"elpm %A0, Z+" "\n\t"
"elpm %B0, Z+" "\n\t"
"elpm %C0, Z+" "\n\t"
"elpm %D0, Z"
"\n\t"
"out %2, __tmp_reg__"
: "=r" (__result)
: "r" (__addr32),
"I" (_SFR_IO_ADDR(RAMPZ))
: "r30", "r31"
);
__result;
}))
24.35.2.7
\
\
\
\
\
\
\
\
\
\
\
\
\
\
\
\
\
\
\
#define __ELPM_word_classic__( addr )
Value:
(__extension__({
uint32_t __addr32 =
uint16_t __result;
__asm__
(
"out %2, %C1"
"mov r31, %B1"
"mov r30, %A1"
"elpm"
"mov %A0, r0"
"in r0, %2"
\
(uint32_t)(addr); \
\
\
\
"\n\t"
\
"\n\t"
\
"\n\t"
\
"\n\t"
\
"\n\t"
\
"\n\t"
\
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
24.35
pgmspace.h File Reference
"adiw r30, 1"
"\n\t"
"adc r0, __zero_reg__" "\n\t"
"out %2, r0"
"\n\t"
"elpm"
"\n\t"
"mov %B0, r0"
"\n\t"
: "=r" (__result)
: "r" (__addr32),
"I" (_SFR_IO_ADDR(RAMPZ))
: "r0", "r30", "r31"
);
__result;
392
\
\
\
\
\
\
\
\
\
\
\
}))
24.35.2.8
#define __ELPM_word_enhanced__( addr )
Value:
(__extension__({
\
uint32_t __addr32 = (uint32_t)(addr); \
uint16_t __result;
\
__asm__
\
(
\
"out %2, %C1"
"\n\t"
\
"movw r30, %1" "\n\t"
\
"elpm %A0, Z+" "\n\t"
\
"elpm %B0, Z"
"\n\t"
\
: "=r" (__result)
\
: "r" (__addr32),
\
"I" (_SFR_IO_ADDR(RAMPZ))
\
: "r30", "r31"
\
);
\
__result;
\
}))
24.35.2.9
#define __ELPM_word_xmega__( addr )
Value:
(__extension__({
\
uint32_t __addr32 = (uint32_t)(addr); \
uint16_t __result;
\
__asm__
\
(
\
"in __tmp_reg__, %2" "\n\t"
\
"out %2, %C1"
"\n\t"
\
"movw r30, %1" "\n\t"
\
"elpm %A0, Z+" "\n\t"
\
"elpm %B0, Z"
"\n\t"
\
"out %2, __tmp_reg__"
\
: "=r" (__result)
\
: "r" (__addr32),
\
"I" (_SFR_IO_ADDR(RAMPZ))
\
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
24.35
pgmspace.h File Reference
: "r30", "r31"
);
__result;
393
\
\
\
}))
24.35.2.10
#define __ELPM_xmega__( addr )
Value:
(__extension__({
\
uint32_t __addr32 = (uint32_t)(addr); \
uint8_t __result;
\
__asm__
\
(
\
"in __tmp_reg__, %2" "\n\t" \
"out %2, %C1" "\n\t"
\
"movw r30, %1" "\n\t"
\
"elpm %0, Z+" "\n\t"
\
"out %2, __tmp_reg__"
\
: "=r" (__result)
\
: "r" (__addr32),
\
"I" (_SFR_IO_ADDR(RAMPZ)) \
: "r30", "r31"
\
);
\
__result;
\
}))
24.35.2.11
#define __LPM_classic__( addr )
Value:
(__extension__({
\
uint16_t __addr16 = (uint16_t)(addr); \
uint8_t __result;
\
__asm__
\
(
\
"lpm" "\n\t"
\
"mov %0, r0" "\n\t"
\
: "=r" (__result)
\
: "z" (__addr16)
\
: "r0"
\
);
\
__result;
\
}))
24.35.2.12
#define __LPM_dword_classic__( addr )
Value:
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
24.35
pgmspace.h File Reference
(__extension__({
uint16_t __addr16 = (uint16_t)(addr);
uint32_t __result;
__asm__
(
"lpm"
"\n\t"
"mov %A0, r0"
"\n\t"
"adiw r30, 1"
"\n\t"
"lpm"
"\n\t"
"mov %B0, r0"
"\n\t"
"adiw r30, 1"
"\n\t"
"lpm"
"\n\t"
"mov %C0, r0"
"\n\t"
"adiw r30, 1"
"\n\t"
"lpm"
"\n\t"
"mov %D0, r0"
"\n\t"
: "=r" (__result), "=z" (__addr16)
: "1" (__addr16)
: "r0"
);
__result;
}))
24.35.2.13
394
\
\
\
\
\
\
\
\
\
\
\
\
\
\
\
\
\
\
\
\
\
#define __LPM_dword_enhanced__( addr )
Value:
(__extension__({
uint16_t __addr16 = (uint16_t)(addr);
uint32_t __result;
__asm__
(
"lpm %A0, Z+"
"\n\t"
"lpm %B0, Z+"
"\n\t"
"lpm %C0, Z+"
"\n\t"
"lpm %D0, Z"
"\n\t"
: "=r" (__result), "=z" (__addr16)
: "1" (__addr16)
);
__result;
}))
24.35.2.14
\
\
\
\
\
\
\
\
\
\
\
\
\
#define __LPM_enhanced__( addr )
Value:
(__extension__({
\
uint16_t __addr16 = (uint16_t)(addr); \
uint8_t __result;
\
__asm__
\
(
\
"lpm %0, Z" "\n\t"
\
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
24.35
pgmspace.h File Reference
: "=r" (__result)
: "z" (__addr16)
);
__result;
395
\
\
\
\
}))
24.35.2.15
#define __LPM_float_classic__( addr )
Value:
(__extension__({
uint16_t __addr16 = (uint16_t)(addr);
float __result;
__asm__
(
"lpm"
"\n\t"
"mov %A0, r0"
"\n\t"
"adiw r30, 1"
"\n\t"
"lpm"
"\n\t"
"mov %B0, r0"
"\n\t"
"adiw r30, 1"
"\n\t"
"lpm"
"\n\t"
"mov %C0, r0"
"\n\t"
"adiw r30, 1"
"\n\t"
"lpm"
"\n\t"
"mov %D0, r0"
"\n\t"
: "=r" (__result), "=z" (__addr16)
: "1" (__addr16)
: "r0"
);
__result;
}))
24.35.2.16
\
\
\
\
\
\
\
\
\
\
\
\
\
\
\
\
\
\
\
\
\
#define __LPM_float_enhanced__( addr )
Value:
(__extension__({
uint16_t __addr16 = (uint16_t)(addr);
float __result;
__asm__
(
"lpm %A0, Z+"
"\n\t"
"lpm %B0, Z+"
"\n\t"
"lpm %C0, Z+"
"\n\t"
"lpm %D0, Z"
"\n\t"
: "=r" (__result), "=z" (__addr16)
: "1" (__addr16)
);
__result;
}))
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
\
\
\
\
\
\
\
\
\
\
\
\
\
24.35
pgmspace.h File Reference
24.35.2.17
396
#define __LPM_word_classic__( addr )
Value:
(__extension__({
uint16_t __addr16 = (uint16_t)(addr);
uint16_t __result;
__asm__
(
"lpm"
"\n\t"
"mov %A0, r0"
"\n\t"
"adiw r30, 1"
"\n\t"
"lpm"
"\n\t"
"mov %B0, r0"
"\n\t"
: "=r" (__result), "=z" (__addr16)
: "1" (__addr16)
: "r0"
);
__result;
}))
24.35.2.18
\
\
\
\
\
\
\
\
\
\
\
\
\
\
\
#define __LPM_word_enhanced__( addr )
Value:
(__extension__({
uint16_t __addr16 = (uint16_t)(addr);
uint16_t __result;
__asm__
(
"lpm %A0, Z+"
"\n\t"
"lpm %B0, Z"
"\n\t"
: "=r" (__result), "=z" (__addr16)
: "1" (__addr16)
);
__result;
}))
24.35.2.19
\
\
\
\
\
\
\
\
\
\
\
#define pgm_get_far_address( var )
Value:
({
\
uint_farptr_t tmp;
\
\
__asm__ __volatile__(
\
\
"ldi
"ldi
"ldi
"clr
%A0, lo8(%1)"
%B0, hi8(%1)"
%C0, hh8(%1)"
%D0"
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
"\n\t"
"\n\t"
"\n\t"
"\n\t"
\
\
\
\
24.36
power.h File Reference
397
:
\
"=d" (tmp)
\
:
\
"p"
(&(var))
);
tmp;
\
\
\
})
24.36
power.h File Reference
Defines
• #define clock_prescale_get() (clock_div_t)(CLKPR & (uint8_t)((1<<CLKPS0)|(1<<CLKPS1)|(1<<CLKPS2)|
Enumerations
• enum clock_div_t {
clock_div_1 = 0, clock_div_2 = 1, clock_div_4 = 2, clock_div_8 = 3,
clock_div_16 = 4, clock_div_32 = 5, clock_div_64 = 6, clock_div_128 = 7,
clock_div_256 = 8 }
Functions
• static __inline__ void clock_prescale_set (clock_div_t) __attribute__((__always_inline__))
24.36.1
Detailed Description
24.37
setbaud.h File Reference
Defines
•
•
•
•
•
#define BAUD_TOL 2
#define UBRR_VALUE
#define UBRRL_VALUE
#define UBRRH_VALUE
#define USE_2X 0
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
24.38
setjmp.h File Reference
24.37.1
Detailed Description
24.38
setjmp.h File Reference
Defines
• #define __ATTR_NORETURN__ __attribute__((__noreturn__))
Functions
• int setjmp (jmp_buf __jmpb)
• void longjmp (jmp_buf __jmpb, int __ret) __ATTR_NORETURN__
24.38.1
Detailed Description
24.39
signature.h File Reference
24.39.1
Detailed Description
24.40
sleep.h File Reference
Defines
• #define _SLEEP_CONTROL_REG MCUCR
• #define _SLEEP_ENABLE_MASK _BV(SE)
Functions
•
•
•
•
•
void sleep_enable (void)
void sleep_disable (void)
void sleep_cpu (void)
void sleep_mode (void)
void sleep_bod_disable (void)
24.40.1
Detailed Description
24.41
stdint.h File Reference
Defines
• #define __USING_MINT8 0
• #define __CONCATenate(left, right) left ## right
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
398
24.41
stdint.h File Reference
399
• #define __CONCAT(left, right) __CONCATenate(left, right)
Limits of specified-width integer types
C++ implementations should define these macros only when __STDC_LIMIT_MACROS is defined before <stdint.h> is included
•
•
•
•
•
•
•
•
•
•
•
•
#define INT8_MAX 0x7f
#define INT8_MIN (-INT8_MAX - 1)
#define UINT8_MAX (__CONCAT(INT8_MAX, U) ∗ 2U + 1U)
#define INT16_MAX 0x7fff
#define INT16_MIN (-INT16_MAX - 1)
#define UINT16_MAX (__CONCAT(INT16_MAX, U) ∗ 2U + 1U)
#define INT32_MAX 0x7fffffffL
#define INT32_MIN (-INT32_MAX - 1L)
#define UINT32_MAX (__CONCAT(INT32_MAX, U) ∗ 2UL + 1UL)
#define INT64_MAX 0x7fffffffffffffffLL
#define INT64_MIN (-INT64_MAX - 1LL)
#define UINT64_MAX (__CONCAT(INT64_MAX, U) ∗ 2ULL + 1ULL)
Limits of minimum-width integer types
•
•
•
•
•
•
•
•
•
•
•
•
#define INT_LEAST8_MAX INT8_MAX
#define INT_LEAST8_MIN INT8_MIN
#define UINT_LEAST8_MAX UINT8_MAX
#define INT_LEAST16_MAX INT16_MAX
#define INT_LEAST16_MIN INT16_MIN
#define UINT_LEAST16_MAX UINT16_MAX
#define INT_LEAST32_MAX INT32_MAX
#define INT_LEAST32_MIN INT32_MIN
#define UINT_LEAST32_MAX UINT32_MAX
#define INT_LEAST64_MAX INT64_MAX
#define INT_LEAST64_MIN INT64_MIN
#define UINT_LEAST64_MAX UINT64_MAX
Limits of fastest minimum-width integer types
•
•
•
•
•
•
•
•
•
•
•
•
#define INT_FAST8_MAX INT8_MAX
#define INT_FAST8_MIN INT8_MIN
#define UINT_FAST8_MAX UINT8_MAX
#define INT_FAST16_MAX INT16_MAX
#define INT_FAST16_MIN INT16_MIN
#define UINT_FAST16_MAX UINT16_MAX
#define INT_FAST32_MAX INT32_MAX
#define INT_FAST32_MIN INT32_MIN
#define UINT_FAST32_MAX UINT32_MAX
#define INT_FAST64_MAX INT64_MAX
#define INT_FAST64_MIN INT64_MIN
#define UINT_FAST64_MAX UINT64_MAX
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
24.41
stdint.h File Reference
400
Limits of integer types capable of holding object pointers
• #define INTPTR_MAX INT16_MAX
• #define INTPTR_MIN INT16_MIN
• #define UINTPTR_MAX UINT16_MAX
Limits of greatest-width integer types
• #define INTMAX_MAX INT64_MAX
• #define INTMAX_MIN INT64_MIN
• #define UINTMAX_MAX UINT64_MAX
Limits of other integer types
C++ implementations should define these macros only when __STDC_LIMIT_MACROS is defined before <stdint.h> is included
•
•
•
•
•
#define PTRDIFF_MAX INT16_MAX
#define PTRDIFF_MIN INT16_MIN
#define SIG_ATOMIC_MAX INT8_MAX
#define SIG_ATOMIC_MIN INT8_MIN
#define SIZE_MAX (__CONCAT(INT16_MAX, U))
Macros for integer constants
C++ implementations should define these macros only when __STDC_CONSTANT_MACROS is defined before <stdint.h> is included.
These definitions are valid for integer constants without suffix and for macros defined as integer constant without suffix
•
•
•
•
•
•
•
•
•
•
#define INT8_C(value) ((int8_t) value)
#define UINT8_C(value) ((uint8_t) __CONCAT(value, U))
#define INT16_C(value) value
#define UINT16_C(value) __CONCAT(value, U)
#define INT32_C(value) __CONCAT(value, L)
#define UINT32_C(value) __CONCAT(value, UL)
#define INT64_C(value) __CONCAT(value, LL)
#define UINT64_C(value) __CONCAT(value, ULL)
#define INTMAX_C(value) __CONCAT(value, LL)
#define UINTMAX_C(value) __CONCAT(value, ULL)
Typedefs
Exact-width integer types
Integer types having exactly the specified width
• typedef signed char int8_t
• typedef unsigned char uint8_t
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
24.41
stdint.h File Reference
•
•
•
•
•
•
401
typedef signed int int16_t
typedef unsigned int uint16_t
typedef signed long int int32_t
typedef unsigned long int uint32_t
typedef signed long long int int64_t
typedef unsigned long long int uint64_t
Integer types capable of holding object pointers
These allow you to declare variables of the same size as a pointer.
• typedef int16_t intptr_t
• typedef uint16_t uintptr_t
Minimum-width integer types
Integer types having at least the specified width
•
•
•
•
•
•
•
•
typedef int8_t int_least8_t
typedef uint8_t uint_least8_t
typedef int16_t int_least16_t
typedef uint16_t uint_least16_t
typedef int32_t int_least32_t
typedef uint32_t uint_least32_t
typedef int64_t int_least64_t
typedef uint64_t uint_least64_t
Fastest minimum-width integer types
Integer types being usually fastest having at least the specified width
•
•
•
•
•
•
•
•
typedef int8_t int_fast8_t
typedef uint8_t uint_fast8_t
typedef int16_t int_fast16_t
typedef uint16_t uint_fast16_t
typedef int32_t int_fast32_t
typedef uint32_t uint_fast32_t
typedef int64_t int_fast64_t
typedef uint64_t uint_fast64_t
Greatest-width integer types
Types designating integer data capable of representing any value of any integer
type in the corresponding signed or unsigned category
• typedef int64_t intmax_t
• typedef uint64_t uintmax_t
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
24.42
stdio.h File Reference
24.41.1
Detailed Description
24.42
stdio.h File Reference
Defines
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
#define __need_NULL
#define __need_size_t
#define FILE struct __file
#define stdin (__iob[0])
#define stdout (__iob[1])
#define stderr (__iob[2])
#define EOF (-1)
#define fdev_set_udata(stream, u) do { (stream)->udata = u; } while(0)
#define fdev_get_udata(stream) ((stream)->udata)
#define fdev_setup_stream(stream, put, get, rwflag)
#define _FDEV_SETUP_READ __SRD
#define _FDEV_SETUP_WRITE __SWR
#define _FDEV_SETUP_RW (__SRD|__SWR)
#define _FDEV_ERR (-1)
#define _FDEV_EOF (-2)
#define FDEV_SETUP_STREAM(put, get, rwflag)
#define fdev_close()
#define putc(__c, __stream) fputc(__c, __stream)
#define putchar(__c) fputc(__c, stdout)
#define getc(__stream) fgetc(__stream)
#define getchar() fgetc(stdin)
#define SEEK_SET 0
#define SEEK_CUR 1
#define SEEK_END 2
Functions
•
•
•
•
•
•
•
•
•
•
int fclose (FILE ∗__stream)
int vfprintf (FILE ∗__stream, const char ∗__fmt, va_list __ap)
int vfprintf_P (FILE ∗__stream, const char ∗__fmt, va_list __ap)
int fputc (int __c, FILE ∗__stream)
int printf (const char ∗__fmt,...)
int printf_P (const char ∗__fmt,...)
int vprintf (const char ∗__fmt, va_list __ap)
int sprintf (char ∗__s, const char ∗__fmt,...)
int sprintf_P (char ∗__s, const char ∗__fmt,...)
int snprintf (char ∗__s, size_t __n, const char ∗__fmt,...)
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
402
24.43
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
stdlib.h File Reference
403
int snprintf_P (char ∗__s, size_t __n, const char ∗__fmt,...)
int vsprintf (char ∗__s, const char ∗__fmt, va_list ap)
int vsprintf_P (char ∗__s, const char ∗__fmt, va_list ap)
int vsnprintf (char ∗__s, size_t __n, const char ∗__fmt, va_list ap)
int vsnprintf_P (char ∗__s, size_t __n, const char ∗__fmt, va_list ap)
int fprintf (FILE ∗__stream, const char ∗__fmt,...)
int fprintf_P (FILE ∗__stream, const char ∗__fmt,...)
int fputs (const char ∗__str, FILE ∗__stream)
int fputs_P (const char ∗__str, FILE ∗__stream)
int puts (const char ∗__str)
int puts_P (const char ∗__str)
size_t fwrite (const void ∗__ptr, size_t __size, size_t __nmemb, FILE ∗__stream)
int fgetc (FILE ∗__stream)
int ungetc (int __c, FILE ∗__stream)
char ∗ fgets (char ∗__str, int __size, FILE ∗__stream)
char ∗ gets (char ∗__str)
size_t fread (void ∗__ptr, size_t __size, size_t __nmemb, FILE ∗__stream)
void clearerr (FILE ∗__stream)
int feof (FILE ∗__stream)
int ferror (FILE ∗__stream)
int vfscanf (FILE ∗__stream, const char ∗__fmt, va_list __ap)
int vfscanf_P (FILE ∗__stream, const char ∗__fmt, va_list __ap)
int fscanf (FILE ∗__stream, const char ∗__fmt,...)
int fscanf_P (FILE ∗__stream, const char ∗__fmt,...)
int scanf (const char ∗__fmt,...)
int scanf_P (const char ∗__fmt,...)
int vscanf (const char ∗__fmt, va_list __ap)
int sscanf (const char ∗__buf, const char ∗__fmt,...)
int sscanf_P (const char ∗__buf, const char ∗__fmt,...)
int fflush (FILE ∗stream)
24.42.1
Detailed Description
24.43
stdlib.h File Reference
Data Structures
• struct div_t
• struct ldiv_t
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
24.43
stdlib.h File Reference
404
Defines
•
•
•
•
•
#define __need_NULL
#define __need_size_t
#define __need_wchar_t
#define __ptr_t void ∗
#define RAND_MAX 0x7FFF
Typedefs
• typedef int(∗ __compar_fn_t )(const void ∗, const void ∗)
Functions
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void abort (void) __ATTR_NORETURN__
int abs (int __i)
long labs (long __i)
void ∗ bsearch (const void ∗__key, const void ∗__base, size_t __nmemb, size_t
__size, int(∗__compar)(const void ∗, const void ∗))
div_t div (int __num, int __denom) __asm__("__divmodhi4")
ldiv_t ldiv (long __num, long __denom) __asm__("__divmodsi4")
void qsort (void ∗__base, size_t __nmemb, size_t __size, __compar_fn_t __compar)
long strtol (const char ∗__nptr, char ∗∗__endptr, int __base)
unsigned long strtoul (const char ∗__nptr, char ∗∗__endptr, int __base)
long atol (const char ∗__s) __ATTR_PURE__
int atoi (const char ∗__s) __ATTR_PURE__
void exit (int __status) __ATTR_NORETURN__
void ∗ malloc (size_t __size) __ATTR_MALLOC__
void free (void ∗__ptr)
void ∗ calloc (size_t __nele, size_t __size) __ATTR_MALLOC__
void ∗ realloc (void ∗__ptr, size_t __size) __ATTR_MALLOC__
double strtod (const char ∗__nptr, char ∗∗__endptr)
double atof (const char ∗__nptr)
int rand (void)
void srand (unsigned int __seed)
int rand_r (unsigned long ∗__ctx)
Variables
• size_t __malloc_margin
• char ∗ __malloc_heap_start
• char ∗ __malloc_heap_end
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
24.43
stdlib.h File Reference
405
Non-standard (i.e. non-ISO C) functions.
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#define RANDOM_MAX 0x7FFFFFFF
char ∗ itoa (int __val, char ∗__s, int __radix)
char ∗ ltoa (long int __val, char ∗__s, int __radix)
char ∗ utoa (unsigned int __val, char ∗__s, int __radix)
char ∗ ultoa (unsigned long int __val, char ∗__s, int __radix)
long random (void)
void srandom (unsigned long __seed)
long random_r (unsigned long ∗__ctx)
Conversion functions for double arguments.
Note that these functions are not located in the default library, libc.a, but in the
mathematical library, libm.a. So when linking the application, the -lm option needs
to be specified.
•
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#define DTOSTR_ALWAYS_SIGN 0x01
#define DTOSTR_PLUS_SIGN 0x02
#define DTOSTR_UPPERCASE 0x04
char ∗ dtostre (double __val, char ∗__s, unsigned char __prec, unsigned char
__flags)
• char ∗ dtostrf (double __val, signed char __width, unsigned char __prec, char
∗__s)
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24.43
stdlib.h File Reference
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
406
24.44
strcasecmp.S File Reference
24.43.1
Detailed Description
24.44
strcasecmp.S File Reference
24.44.1
Detailed Description
24.45
strcasecmp P.S File Reference
24.45.1
Detailed Description
24.46
strcasestr.S File Reference
24.46.1
Detailed Description
24.47
strcat.S File Reference
24.47.1
Detailed Description
24.48
strcat P.S File Reference
24.48.1
Detailed Description
24.49
strchr.S File Reference
24.49.1
Detailed Description
24.50
strchr P.S File Reference
24.50.1
Detailed Description
24.51
strchrnul.S File Reference
24.51.1
Detailed Description
24.52
strchrnul P.S File Reference
24.52.1
Detailed Description
24.53
strcmp.S File Reference
24.53.1
Detailed Description
24.54
strcmp P.S File Reference
24.54.1
Detailed Description
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
24.55
strcpy.S File Reference
24.55.1
Detailed Description
24.56
strcpy P.S File Reference
407
24.60
string.h File Reference
24.59.1
Detailed Description
24.60
string.h File Reference
408
Defines
•
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•
#define __need_NULL
#define __need_size_t
#define __ATTR_PURE__ __attribute__((__pure__))
#define _FFS(x)
Functions
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int ffs (int __val)
int ffsl (long __val)
int ffsll (long long __val)
void ∗ memccpy (void ∗, const void ∗, int, size_t)
void ∗ memchr (const void ∗, int, size_t) __ATTR_PURE__
int memcmp (const void ∗, const void ∗, size_t) __ATTR_PURE__
void ∗ memcpy (void ∗, const void ∗, size_t)
void ∗ memmem (const void ∗, size_t, const void ∗, size_t) __ATTR_PURE__
void ∗ memmove (void ∗, const void ∗, size_t)
void ∗ memrchr (const void ∗, int, size_t) __ATTR_PURE__
void ∗ memset (void ∗, int, size_t)
char ∗ strcat (char ∗, const char ∗)
char ∗ strchr (const char ∗, int) __ATTR_PURE__
char ∗ strchrnul (const char ∗, int) __ATTR_PURE__
int strcmp (const char ∗, const char ∗) __ATTR_PURE__
char ∗ strcpy (char ∗, const char ∗)
int strcasecmp (const char ∗, const char ∗) __ATTR_PURE__
char ∗ strcasestr (const char ∗, const char ∗) __ATTR_PURE__
size_t strcspn (const char ∗__s, const char ∗__reject) __ATTR_PURE__
char ∗ strdup (const char ∗s1)
size_t strlcat (char ∗, const char ∗, size_t)
size_t strlcpy (char ∗, const char ∗, size_t)
size_t strlen (const char ∗) __ATTR_PURE__
char ∗ strlwr (char ∗)
char ∗ strncat (char ∗, const char ∗, size_t)
int strncmp (const char ∗, const char ∗, size_t) __ATTR_PURE__
char ∗ strncpy (char ∗, const char ∗, size_t)
int strncasecmp (const char ∗, const char ∗, size_t) __ATTR_PURE__
size_t strnlen (const char ∗, size_t) __ATTR_PURE__
char ∗ strpbrk (const char ∗__s, const char ∗__accept) __ATTR_PURE__
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
24.60
•
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string.h File Reference
char ∗ strrchr (const char ∗, int) __ATTR_PURE__
char ∗ strrev (char ∗)
char ∗ strsep (char ∗∗, const char ∗)
size_t strspn (const char ∗__s, const char ∗__accept) __ATTR_PURE__
char ∗ strstr (const char ∗, const char ∗) __ATTR_PURE__
char ∗ strtok (char ∗, const char ∗)
char ∗ strtok_r (char ∗, const char ∗, char ∗∗)
char ∗ strupr (char ∗)
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409
24.60
string.h File Reference
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
410
24.61
strlcat.S File Reference
24.60.1
Detailed Description
24.61
strlcat.S File Reference
24.61.1
Detailed Description
24.62
strlcat P.S File Reference
24.62.1
Detailed Description
24.63
strlcpy.S File Reference
24.63.1
Detailed Description
24.64
strlcpy P.S File Reference
24.64.1
Detailed Description
24.65
strlen.S File Reference
24.65.1
Detailed Description
24.66
strlen P.S File Reference
24.66.1
Detailed Description
24.67
strlwr.S File Reference
24.67.1
Detailed Description
24.68
strncasecmp.S File Reference
24.68.1
Detailed Description
24.69
strncasecmp P.S File Reference
24.69.1
Detailed Description
24.70
strncat.S File Reference
24.70.1
Detailed Description
24.71
strncat P.S File Reference
24.71.1
Detailed Description
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
24.72
strncmp.S File Reference
24.72.1
Detailed Description
24.73
strncmp P.S File Reference
411
24.90
strtok_P.c File Reference
Variables
• static char ∗ p
24.89.1
Detailed Description
24.90
strtok P.c File Reference
Functions
• char ∗ strtok_P (char ∗s, PGM_P delim)
24.90.1
Detailed Description
24.91
strtok r.S File Reference
24.91.1
Detailed Description
24.92
strtok rP.S File Reference
24.92.1
Detailed Description
24.93
strupr.S File Reference
24.93.1
Detailed Description
24.94
twi.h File Reference
Defines
TWSR values
Mnemonics:
TW_MT_xxx - master transmitter
TW_MR_xxx - master receiver
TW_ST_xxx - slave transmitter
TW_SR_xxx - slave receiver
•
•
•
•
•
•
#define TW_START 0x08
#define TW_REP_START 0x10
#define TW_MT_SLA_ACK 0x18
#define TW_MT_SLA_NACK 0x20
#define TW_MT_DATA_ACK 0x28
#define TW_MT_DATA_NACK 0x30
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412
24.95
wdt.h File Reference
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#define TW_MT_ARB_LOST 0x38
#define TW_MR_ARB_LOST 0x38
#define TW_MR_SLA_ACK 0x40
#define TW_MR_SLA_NACK 0x48
#define TW_MR_DATA_ACK 0x50
#define TW_MR_DATA_NACK 0x58
#define TW_ST_SLA_ACK 0xA8
#define TW_ST_ARB_LOST_SLA_ACK 0xB0
#define TW_ST_DATA_ACK 0xB8
#define TW_ST_DATA_NACK 0xC0
#define TW_ST_LAST_DATA 0xC8
#define TW_SR_SLA_ACK 0x60
#define TW_SR_ARB_LOST_SLA_ACK 0x68
#define TW_SR_GCALL_ACK 0x70
#define TW_SR_ARB_LOST_GCALL_ACK 0x78
#define TW_SR_DATA_ACK 0x80
#define TW_SR_DATA_NACK 0x88
#define TW_SR_GCALL_DATA_ACK 0x90
#define TW_SR_GCALL_DATA_NACK 0x98
#define TW_SR_STOP 0xA0
#define TW_NO_INFO 0xF8
#define TW_BUS_ERROR 0x00
#define TW_STATUS_MASK
#define TW_STATUS (TWSR & TW_STATUS_MASK)
R/∼W bit in SLA+R/W address field.
• #define TW_READ 1
• #define TW_WRITE 0
24.94.1
Detailed Description
24.95
wdt.h File Reference
Defines
•
•
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#define wdt_reset() __asm__ __volatile__ ("wdr")
#define _WD_PS3_MASK 0x00
#define _WD_CONTROL_REG WDTCR
#define _WD_CHANGE_BIT WDCE
#define wdt_enable(value)
#define wdt_disable()
#define WDTO_15MS 0
#define WDTO_30MS 1
#define WDTO_60MS 2
#define WDTO_120MS 3
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413
24.95
•
•
•
•
•
•
24.95.1
wdt.h File Reference
#define WDTO_250MS 4
#define WDTO_500MS 5
#define WDTO_1S 6
#define WDTO_2S 7
#define WDTO_4S 8
#define WDTO_8S 9
Detailed Description
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
414
Index
<alloca.h>: Allocate space in the stack, <util/delay_basic.h>: Basic busy-wait de134
lay loops, 313
<assert.h>: Diagnostics, 135
<util/parity.h>: Parity bit generation, 314
<avr/boot.h>: Bootloader Support Utili- <util/setbaud.h>: Helper macros for baud
ties, 227
rate calculations, 314
<avr/cpufunc.h>: Special AVR CPU func- <util/twi.h>: TWI bit mask definitions,
tions, 234
317
<avr/eeprom.h>: EEPROM handling, 234 $PATH, 90
<avr/fuse.h>: Fuse Support, 239
$PREFIX, 90
<avr/interrupt.h>: Interrupts, 242
--prefix, 90
<avr/io.h>: AVR device-specific IO defi- _BV
nitions, 266
avr_sfr, 296
<avr/lock.h>: Lockbit Support, 267
_EEGET
<avr/pgmspace.h>: Program Space Utilavr_eeprom, 236
ities, 269
_EEPUT
<avr/power.h>: Power Reduction Manavr_eeprom, 236
agement, 291
_FDEV_EOF
<avr/sfr_defs.h>: Special function regisavr_stdio, 186
ters, 295
_FDEV_ERR
<avr/signature.h>: Signature Support, 297
avr_stdio, 186
<avr/sleep.h>: Power Management and _FDEV_SETUP_READ
Sleep Modes, 298
avr_stdio, 186
<avr/version.h>: avr-libc version macros, _FDEV_SETUP_RW
300
avr_stdio, 186
<avr/wdt.h>: Watchdog timer handling, _FDEV_SETUP_WRITE
302
avr_stdio, 186
<compat/deprecated.h>: Deprecated items, _FFS
321
avr_string, 214
<compat/ina90.h>: Compatibility with IAR_MemoryBarrier
EWB 3.x, 325
avr_cpufunc, 234
<ctype.h>: Character Operations, 136
_NOP
<errno.h>: System Errors, 139
avr_cpufunc, 234
<inttypes.h>: Integer Type conversions, __AVR_LIBC_DATE_
139
avr_version, 301
<math.h>: Mathematics, 152
__AVR_LIBC_DATE_STRING__
<setjmp.h>: Non-local goto, 166
avr_version, 301
<stdint.h>: Standard Integer Types, 168 __AVR_LIBC_MAJOR__
<stdio.h>: Standard IO facilities, 181
avr_version, 301
<stdlib.h>: General utilities, 201
__AVR_LIBC_MINOR__
<string.h>: Strings, 213
avr_version, 301
<util/atomic.h> Atomically and Non-Atomically
__AVR_LIBC_REVISION__
Executed Code Blocks, 306
avr_version, 301
<util/crc16.h>: CRC Computations, 309 __AVR_LIBC_VERSION_STRING__
INDEX
avr_version, 301
__AVR_LIBC_VERSION__
avr_version, 301
__EEGET
avr_eeprom, 236
__EEPUT
avr_eeprom, 236
__ELPM_classic__
pgmspace.h, 388
__ELPM_dword_enhanced__
pgmspace.h, 388
__ELPM_dword_xmega__
pgmspace.h, 388
__ELPM_enhanced__
pgmspace.h, 389
__ELPM_float_enhanced__
pgmspace.h, 389
__ELPM_float_xmega__
pgmspace.h, 390
__ELPM_word_classic__
pgmspace.h, 390
__ELPM_word_enhanced__
pgmspace.h, 391
__ELPM_word_xmega__
pgmspace.h, 391
__ELPM_xmega__
pgmspace.h, 392
__LPM_classic__
pgmspace.h, 392
__LPM_dword_classic__
pgmspace.h, 392
__LPM_dword_enhanced__
pgmspace.h, 393
__LPM_enhanced__
pgmspace.h, 393
__LPM_float_classic__
pgmspace.h, 394
__LPM_float_enhanced__
pgmspace.h, 394
__LPM_word_classic__
pgmspace.h, 394
__LPM_word_enhanced__
pgmspace.h, 395
__boot_lock_bits_set
boot.h, 369
__boot_lock_bits_set_alternate
416
boot.h, 369
__boot_page_erase_alternate
boot.h, 370
__boot_page_erase_extended
boot.h, 370
__boot_page_erase_normal
boot.h, 371
__boot_page_fill_alternate
boot.h, 371
__boot_page_fill_extended
boot.h, 371
__boot_page_fill_normal
boot.h, 372
__boot_page_write_alternate
boot.h, 372
__boot_page_write_extended
boot.h, 373
__boot_page_write_normal
boot.h, 373
__boot_rww_enable
boot.h, 373
__boot_rww_enable_alternate
boot.h, 374
__compar_fn_t
avr_stdlib, 203
__malloc_heap_end
avr_stdlib, 212
__malloc_heap_start
avr_stdlib, 212
__malloc_margin
avr_stdlib, 212
_crc16_update
util_crc, 310
_crc_ccitt_update
util_crc, 311
_crc_ibutton_update
util_crc, 311
_crc_xmodem_update
util_crc, 312
_delay_loop_1
util_delay_basic, 313
_delay_loop_2
util_delay_basic, 313
A more sophisticated project, 345
A simple project, 330
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
INDEX
417
abort
boot_lock_bits_set, 229
avr_stdlib, 203
boot_lock_bits_set_safe, 229
abs
boot_lock_fuse_bits_get, 229
avr_stdlib, 203
boot_page_erase, 230
acos
boot_page_erase_safe, 230
avr_math, 160
boot_page_fill, 230
acosf
boot_page_fill_safe, 231
avr_math, 155
boot_page_write, 231
Additional notes from <avr/sfr_defs.h>,
boot_page_write_safe, 231
293
boot_rww_busy, 231
alloca
boot_rww_enable, 232
alloca, 134
boot_rww_enable_safe, 232
asin
boot_signature_byte_get, 232
avr_math, 160
boot_spm_busy, 232
asinf
boot_spm_busy_wait, 233
avr_math, 155
boot_spm_interrupt_disable, 233
assert
boot_spm_interrupt_enable, 233
avr_assert, 135
BOOTLOADER_SECTION, 233
assert.h, 367
GET_EXTENDED_FUSE_BITS, 233
atan
GET_HIGH_FUSE_BITS, 233
avr_math, 160
GET_LOCK_BITS, 233
atan2
GET_LOW_FUSE_BITS, 233
avr_math, 161
avr_cpufunc
atan2f
_MemoryBarrier, 234
avr_math, 155
_NOP, 234
atanf
avr_eeprom
avr_math, 155
_EEGET, 236
atof
_EEPUT, 236
avr_stdlib, 203
__EEGET, 236
atoi
__EEPUT, 236
avr_stdlib, 204
EEMEM, 236
atoi.S, 367
eeprom_busy_wait, 237
atol
eeprom_is_ready, 237
avr_stdlib, 204
eeprom_read_block, 237
atol.S, 367
eeprom_read_byte, 237
atomic.h, 367
eeprom_read_dword, 237
ATOMIC_BLOCK
eeprom_read_float, 237
util_atomic, 308
eeprom_read_word, 237
ATOMIC_FORCEON
eeprom_update_block, 237
util_atomic, 308
eeprom_update_byte, 238
ATOMIC_RESTORESTATE
eeprom_update_dword, 238
util_atomic, 308
eeprom_update_float, 238
avr_assert
eeprom_update_word, 238
assert, 135
eeprom_write_block, 238
avr_boot
eeprom_write_byte, 238
boot_is_spm_interrupt, 229
eeprom_write_dword, 238
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
INDEX
eeprom_write_float, 238
eeprom_write_word, 239
avr_errno
EDOM, 139
ERANGE, 139
avr_interrupts
BADISR_vect, 262
cli, 262
EMPTY_INTERRUPT, 262
ISR, 262
ISR_ALIAS, 263
ISR_ALIASOF, 263
ISR_BLOCK, 264
ISR_NAKED, 264
ISR_NOBLOCK, 264
reti, 265
sei, 265
SIGNAL, 265
avr_inttypes
int_farptr_t, 152
PRId16, 142
PRId32, 142
PRId8, 142
PRIdFAST16, 143
PRIdFAST32, 143
PRIdFAST8, 143
PRIdLEAST16, 143
PRIdLEAST32, 143
PRIdLEAST8, 143
PRIdPTR, 143
PRIi16, 143
PRIi32, 143
PRIi8, 143
PRIiFAST16, 144
PRIiFAST32, 144
PRIiFAST8, 144
PRIiLEAST16, 144
PRIiLEAST32, 144
PRIiLEAST8, 144
PRIiPTR, 144
PRIo16, 144
PRIo32, 144
PRIo8, 144
PRIoFAST16, 145
PRIoFAST32, 145
PRIoFAST8, 145
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418
PRIoLEAST16, 145
PRIoLEAST32, 145
PRIoLEAST8, 145
PRIoPTR, 145
PRIu16, 145
PRIu32, 145
PRIu8, 145
PRIuFAST16, 146
PRIuFAST32, 146
PRIuFAST8, 146
PRIuLEAST16, 146
PRIuLEAST32, 146
PRIuLEAST8, 146
PRIuPTR, 146
PRIX16, 146
PRIx16, 146
PRIX32, 147
PRIx32, 146
PRIX8, 147
PRIx8, 147
PRIXFAST16, 147
PRIxFAST16, 147
PRIXFAST32, 147
PRIxFAST32, 147
PRIXFAST8, 147
PRIxFAST8, 147
PRIXLEAST16, 148
PRIxLEAST16, 147
PRIXLEAST32, 148
PRIxLEAST32, 148
PRIXLEAST8, 148
PRIxLEAST8, 148
PRIXPTR, 148
PRIxPTR, 148
SCNd16, 148
SCNd32, 148
SCNdFAST16, 148
SCNdFAST32, 149
SCNdLEAST16, 149
SCNdLEAST32, 149
SCNdPTR, 149
SCNi16, 149
SCNi32, 149
SCNiFAST16, 149
SCNiFAST32, 149
SCNiLEAST16, 149
INDEX
SCNiLEAST32, 149
SCNiPTR, 150
SCNo16, 150
SCNo32, 150
SCNoFAST16, 150
SCNoFAST32, 150
SCNoLEAST16, 150
SCNoLEAST32, 150
SCNoPTR, 150
SCNu16, 150
SCNu32, 150
SCNuFAST16, 151
SCNuFAST32, 151
SCNuLEAST16, 151
SCNuLEAST32, 151
SCNuPTR, 151
SCNx16, 151
SCNx32, 151
SCNxFAST16, 151
SCNxFAST32, 151
SCNxLEAST16, 151
SCNxLEAST32, 152
SCNxPTR, 152
uint_farptr_t, 152
avr_math
acos, 160
acosf, 155
asin, 160
asinf, 155
atan, 160
atan2, 161
atan2f, 155
atanf, 155
cbrt, 161
cbrtf, 155
ceil, 161
ceilf, 155
copysign, 161
copysignf, 155
cos, 161
cosf, 156
cosh, 161
coshf, 156
exp, 161
expf, 156
fabs, 161
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419
fabsf, 156
fdim, 161
fdimf, 156
floor, 162
floorf, 156
fma, 162
fmaf, 156
fmax, 162
fmaxf, 156
fmin, 162
fminf, 156
fmod, 162
fmodf, 156
frexp, 162
frexpf, 157
hypot, 163
hypotf, 157
INFINITY, 157
isfinite, 163
isfinitef, 157
isinf, 163
isinff, 157
isnan, 163
isnanf, 157
ldexp, 163
ldexpf, 157
log, 163
log10, 163
log10f, 157
logf, 157
lrint, 164
lrintf, 157
lround, 164
lroundf, 158
M_1_PI, 158
M_2_PI, 158
M_2_SQRTPI, 158
M_E, 158
M_LN10, 158
M_LN2, 158
M_LOG10E, 158
M_LOG2E, 158
M_PI, 158
M_PI_2, 159
M_PI_4, 159
M_SQRT1_2, 159
INDEX
M_SQRT2, 159
modf, 164
modff, 164
NAN, 159
pow, 165
powf, 159
round, 165
roundf, 159
signbit, 165
signbitf, 159
sin, 165
sinf, 159
sinh, 165
sinhf, 159
sqrt, 165
sqrtf, 160
square, 165
squaref, 160
tan, 166
tanf, 160
tanh, 166
tanhf, 160
trunc, 166
truncf, 160
avr_pgmspace
memccpy_P, 276
memchr_P, 276
memcmp_P, 277
memcmp_PF, 277
memcpy_P, 277
memcpy_PF, 278
memmem_P, 278
memrchr_P, 278
PGM_P, 272
pgm_read_byte, 272
pgm_read_byte_far, 272
pgm_read_byte_near, 272
pgm_read_dword, 273
pgm_read_dword_far, 273
pgm_read_dword_near, 273
pgm_read_float, 273
pgm_read_float_far, 273
pgm_read_float_near, 274
pgm_read_word, 274
pgm_read_word_far, 274
pgm_read_word_near, 274
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
420
PGM_VOID_P, 274
prog_char, 275
prog_int16_t, 275
prog_int32_t, 275
prog_int64_t, 275
prog_int8_t, 275
prog_uchar, 275
prog_uint16_t, 276
prog_uint32_t, 276
prog_uint64_t, 276
prog_uint8_t, 276
prog_void, 276
PROGMEM, 275
PSTR, 275
strcasecmp_P, 278
strcasecmp_PF, 279
strcasestr_P, 279
strcat_P, 279
strcat_PF, 280
strchr_P, 280
strchrnul_P, 280
strcmp_P, 281
strcmp_PF, 281
strcpy_P, 281
strcpy_PF, 281
strcspn_P, 282
strlcat_P, 282
strlcat_PF, 282
strlcpy_P, 283
strlcpy_PF, 283
strlen_P, 284
strlen_PF, 284
strncasecmp_P, 284
strncasecmp_PF, 285
strncat_P, 285
strncat_PF, 285
strncmp_P, 286
strncmp_PF, 286
strncpy_P, 287
strncpy_PF, 287
strnlen_P, 287
strnlen_PF, 288
strpbrk_P, 288
strrchr_P, 288
strsep_P, 289
strspn_P, 289
INDEX
strstr_P, 289
strstr_PF, 290
strtok_P, 290
strtok_rP, 291
avr_sfr
_BV, 296
bit_is_clear, 296
bit_is_set, 296
loop_until_bit_is_clear, 297
loop_until_bit_is_set, 297
avr_sleep
sleep_cpu, 300
sleep_disable, 300
sleep_enable, 300
avr_stdint
INT16_C, 172
INT16_MAX, 172
INT16_MIN, 172
int16_t, 178
INT32_C, 172
INT32_MAX, 172
INT32_MIN, 172
int32_t, 178
INT64_C, 172
INT64_MAX, 173
INT64_MIN, 173
int64_t, 178
INT8_C, 173
INT8_MAX, 173
INT8_MIN, 173
int8_t, 178
INT_FAST16_MAX, 173
INT_FAST16_MIN, 173
int_fast16_t, 178
INT_FAST32_MAX, 173
INT_FAST32_MIN, 173
int_fast32_t, 178
INT_FAST64_MAX, 173
INT_FAST64_MIN, 174
int_fast64_t, 178
INT_FAST8_MAX, 174
INT_FAST8_MIN, 174
int_fast8_t, 178
INT_LEAST16_MAX, 174
INT_LEAST16_MIN, 174
int_least16_t, 179
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
421
INT_LEAST32_MAX, 174
INT_LEAST32_MIN, 174
int_least32_t, 179
INT_LEAST64_MAX, 174
INT_LEAST64_MIN, 174
int_least64_t, 179
INT_LEAST8_MAX, 174
INT_LEAST8_MIN, 175
int_least8_t, 179
INTMAX_C, 175
INTMAX_MAX, 175
INTMAX_MIN, 175
intmax_t, 179
INTPTR_MAX, 175
INTPTR_MIN, 175
intptr_t, 179
PTRDIFF_MAX, 175
PTRDIFF_MIN, 175
SIG_ATOMIC_MAX, 175
SIG_ATOMIC_MIN, 175
SIZE_MAX, 176
UINT16_C, 176
UINT16_MAX, 176
uint16_t, 179
UINT32_C, 176
UINT32_MAX, 176
uint32_t, 179
UINT64_C, 176
UINT64_MAX, 176
uint64_t, 179
UINT8_C, 176
UINT8_MAX, 176
uint8_t, 180
UINT_FAST16_MAX, 176
uint_fast16_t, 180
UINT_FAST32_MAX, 177
uint_fast32_t, 180
UINT_FAST64_MAX, 177
uint_fast64_t, 180
UINT_FAST8_MAX, 177
uint_fast8_t, 180
UINT_LEAST16_MAX, 177
uint_least16_t, 180
UINT_LEAST32_MAX, 177
uint_least32_t, 180
UINT_LEAST64_MAX, 177
INDEX
uint_least64_t, 180
UINT_LEAST8_MAX, 177
uint_least8_t, 181
UINTMAX_C, 177
UINTMAX_MAX, 177
uintmax_t, 181
UINTPTR_MAX, 177
uintptr_t, 181
avr_stdio
_FDEV_EOF, 186
_FDEV_ERR, 186
_FDEV_SETUP_READ, 186
_FDEV_SETUP_RW, 186
_FDEV_SETUP_WRITE, 186
clearerr, 189
EOF, 186
fclose, 189
fdev_close, 186
fdev_get_udata, 187
fdev_set_udata, 187
FDEV_SETUP_STREAM, 187
fdev_setup_stream, 187
fdevopen, 189
feof, 190
ferror, 190
fflush, 190
fgetc, 190
fgets, 191
FILE, 188
fprintf, 191
fprintf_P, 191
fputc, 191
fputs, 191
fputs_P, 191
fread, 191
fscanf, 192
fscanf_P, 192
fwrite, 192
getc, 188
getchar, 188
gets, 192
printf, 192
printf_P, 192
putc, 188
putchar, 188
puts, 193
422
puts_P, 193
scanf, 193
scanf_P, 193
snprintf, 193
snprintf_P, 193
sprintf, 193
sprintf_P, 193
sscanf, 193
sscanf_P, 194
stderr, 188
stdin, 188
stdout, 189
ungetc, 194
vfprintf, 194
vfprintf_P, 197
vfscanf, 197
vfscanf_P, 199
vprintf, 200
vscanf, 200
vsnprintf, 200
vsnprintf_P, 200
vsprintf, 200
vsprintf_P, 200
avr_stdlib
__compar_fn_t, 203
__malloc_heap_end, 212
__malloc_heap_start, 212
__malloc_margin, 212
abort, 203
abs, 203
atof, 203
atoi, 204
atol, 204
bsearch, 204
calloc, 205
div, 205
DTOSTR_ALWAYS_SIGN, 202
DTOSTR_PLUS_SIGN, 202
DTOSTR_UPPERCASE, 203
dtostre, 205
dtostrf, 205
exit, 206
free, 206
itoa, 206
labs, 207
ldiv, 207
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
INDEX
ltoa, 207
malloc, 207
qsort, 208
rand, 208
RAND_MAX, 203
rand_r, 208
random, 208
RANDOM_MAX, 203
random_r, 209
realloc, 209
srand, 209
srandom, 209
strtod, 209
strtol, 210
strtoul, 210
ultoa, 211
utoa, 212
avr_string
_FFS, 214
ffs, 214
ffsl, 215
ffsll, 215
memccpy, 215
memchr, 215
memcmp, 215
memcpy, 216
memmem, 216
memmove, 216
memrchr, 217
memset, 217
strcasecmp, 217
strcasestr, 218
strcat, 218
strchr, 218
strchrnul, 219
strcmp, 219
strcpy, 219
strcspn, 220
strdup, 220
strlcat, 220
strlcpy, 221
strlen, 221
strlwr, 222
strncasecmp, 222
strncat, 222
strncmp, 222
423
strncpy, 223
strnlen, 223
strpbrk, 223
strrchr, 224
strrev, 224
strsep, 224
strspn, 225
strstr, 225
strtok, 225
strtok_r, 226
strupr, 226
avr_version
__AVR_LIBC_DATE_, 301
__AVR_LIBC_DATE_STRING__, 301
__AVR_LIBC_MAJOR__, 301
__AVR_LIBC_MINOR__, 301
__AVR_LIBC_REVISION__, 301
__AVR_LIBC_VERSION_STRING__, 301
__AVR_LIBC_VERSION__, 301
avr_watchdog
wdt_disable, 303
wdt_enable, 303
wdt_reset, 304
WDTO_120MS, 304
WDTO_15MS, 304
WDTO_1S, 304
WDTO_250MS, 304
WDTO_2S, 304
WDTO_30MS, 305
WDTO_4S, 305
WDTO_500MS, 305
WDTO_60MS, 305
WDTO_8S, 305
avrdude, usage, 120
avrprog, usage, 120
BADISR_vect
avr_interrupts, 262
BAUD_TOL
util_setbaud, 316
bit_is_clear
avr_sfr, 296
bit_is_set
avr_sfr, 296
boot.h, 368
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
INDEX
__boot_lock_bits_set, 369
__boot_lock_bits_set_alternate, 369
__boot_page_erase_alternate, 370
__boot_page_erase_extended, 370
__boot_page_erase_normal, 371
__boot_page_fill_alternate, 371
__boot_page_fill_extended, 371
__boot_page_fill_normal, 372
__boot_page_write_alternate, 372
__boot_page_write_extended, 373
__boot_page_write_normal, 373
__boot_rww_enable, 373
__boot_rww_enable_alternate, 374
boot_is_spm_interrupt
avr_boot, 229
boot_lock_bits_set
avr_boot, 229
boot_lock_bits_set_safe
avr_boot, 229
boot_lock_fuse_bits_get
avr_boot, 229
boot_page_erase
avr_boot, 230
boot_page_erase_safe
avr_boot, 230
boot_page_fill
avr_boot, 230
boot_page_fill_safe
avr_boot, 231
boot_page_write
avr_boot, 231
boot_page_write_safe
avr_boot, 231
boot_rww_busy
avr_boot, 231
boot_rww_enable
avr_boot, 232
boot_rww_enable_safe
avr_boot, 232
boot_signature_byte_get
avr_boot, 232
boot_spm_busy
avr_boot, 232
boot_spm_busy_wait
avr_boot, 233
boot_spm_interrupt_disable
424
avr_boot, 233
boot_spm_interrupt_enable
avr_boot, 233
BOOTLOADER_SECTION
avr_boot, 233
bsearch
avr_stdlib, 204
calloc
avr_stdlib, 205
cbi
deprecated_items, 323
cbrt
avr_math, 161
cbrtf
avr_math, 155
ceil
avr_math, 161
ceilf
avr_math, 155
clearerr
avr_stdio, 189
cli
avr_interrupts, 262
Combining C and assembly source files,
326
copysign
avr_math, 161
copysignf
avr_math, 155
cos
avr_math, 161
cosf
avr_math, 156
cosh
avr_math, 161
coshf
avr_math, 156
cpufunc.h, 374
crc16.h, 374
ctype
isalnum, 137
isalpha, 137
isascii, 137
isblank, 137
iscntrl, 137
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
INDEX
isdigit, 137
isgraph, 137
islower, 137
isprint, 137
ispunct, 137
isspace, 138
isupper, 138
isxdigit, 138
toascii, 138
tolower, 138
toupper, 138
ctype.h, 375
delay_basic.h, 375
Demo projects, 325
deprecated_items
cbi, 323
enable_external_int, 323
inb, 323
inp, 323
INTERRUPT, 323
outb, 324
outp, 324
sbi, 324
timer_enable_int, 325
disassembling, 335
div
avr_stdlib, 205
div_t, 366
quot, 366
rem, 366
DTOSTR_ALWAYS_SIGN
avr_stdlib, 202
DTOSTR_PLUS_SIGN
avr_stdlib, 202
DTOSTR_UPPERCASE
avr_stdlib, 203
dtostre
avr_stdlib, 205
dtostrf
avr_stdlib, 205
EDOM
avr_errno, 139
EEMEM
avr_eeprom, 236
425
eeprom_busy_wait
avr_eeprom, 237
eeprom_is_ready
avr_eeprom, 237
eeprom_read_block
avr_eeprom, 237
eeprom_read_byte
avr_eeprom, 237
eeprom_read_dword
avr_eeprom, 237
eeprom_read_float
avr_eeprom, 237
eeprom_read_word
avr_eeprom, 237
eeprom_update_block
avr_eeprom, 237
eeprom_update_byte
avr_eeprom, 238
eeprom_update_dword
avr_eeprom, 238
eeprom_update_float
avr_eeprom, 238
eeprom_update_word
avr_eeprom, 238
eeprom_write_block
avr_eeprom, 238
eeprom_write_byte
avr_eeprom, 238
eeprom_write_dword
avr_eeprom, 238
eeprom_write_float
avr_eeprom, 238
eeprom_write_word
avr_eeprom, 239
EMPTY_INTERRUPT
avr_interrupts, 262
enable_external_int
deprecated_items, 323
EOF
avr_stdio, 186
ERANGE
avr_errno, 139
errno.h, 376
Example using the two-wire interface (TWI),
361
exit
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
INDEX
426
avr_stdlib, 206
exp
avr_stdio, 190
fgets
avr_math, 161
expf
avr_math, 156
fabs
avr_math, 161
fabsf
avr_math, 156
FAQ, 61
fclose
avr_stdio, 189
fdev_close
avr_stdio, 186
fdev_get_udata
avr_stdio, 187
fdev_set_udata
avr_stdio, 187
FDEV_SETUP_STREAM
avr_stdio, 187
fdev_setup_stream
avr_stdio, 187
fdevopen
avr_stdio, 189
fdevopen.c, 376
fdim
avr_math, 161
fdimf
avr_math, 156
feof
avr_stdio, 190
ferror
avr_stdio, 190
fflush
avr_stdio, 190
ffs
avr_string, 214
ffs.S, 376
ffsl
avr_string, 215
ffsl.S, 376
ffsll
avr_string, 215
ffsll.S, 376
fgetc
avr_stdio, 191
FILE
avr_stdio, 188
floor
avr_math, 162
floorf
avr_math, 156
fma
avr_math, 162
fmaf
avr_math, 156
fmax
avr_math, 162
fmaxf
avr_math, 156
fmin
avr_math, 162
fminf
avr_math, 156
fmod
avr_math, 162
fmodf
avr_math, 156
fprintf
avr_stdio, 191
fprintf_P
avr_stdio, 191
fputc
avr_stdio, 191
fputs
avr_stdio, 191
fputs_P
avr_stdio, 191
fread
avr_stdio, 191
free
avr_stdlib, 206
frexp
avr_math, 162
frexpf
avr_math, 157
fscanf
avr_stdio, 192
fscanf_P
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
INDEX
avr_stdio, 192
fuse.h, 376
fwrite
avr_stdio, 192
GET_EXTENDED_FUSE_BITS
avr_boot, 233
GET_HIGH_FUSE_BITS
avr_boot, 233
GET_LOCK_BITS
avr_boot, 233
GET_LOW_FUSE_BITS
avr_boot, 233
getc
avr_stdio, 188
getchar
avr_stdio, 188
gets
avr_stdio, 192
hypot
avr_math, 163
hypotf
avr_math, 157
inb
deprecated_items, 323
INFINITY
avr_math, 157
inp
deprecated_items, 323
installation, 90
installation, avarice, 95
installation, avr-libc, 94
installation, avrdude, 94
installation, avrprog, 94
installation, binutils, 92
installation, gcc, 93
Installation, gdb, 95
installation, simulavr, 95
INT16_C
avr_stdint, 172
INT16_MAX
avr_stdint, 172
INT16_MIN
avr_stdint, 172
427
int16_t
avr_stdint, 178
INT32_C
avr_stdint, 172
INT32_MAX
avr_stdint, 172
INT32_MIN
avr_stdint, 172
int32_t
avr_stdint, 178
INT64_C
avr_stdint, 172
INT64_MAX
avr_stdint, 173
INT64_MIN
avr_stdint, 173
int64_t
avr_stdint, 178
INT8_C
avr_stdint, 173
INT8_MAX
avr_stdint, 173
INT8_MIN
avr_stdint, 173
int8_t
avr_stdint, 178
int_farptr_t
avr_inttypes, 152
INT_FAST16_MAX
avr_stdint, 173
INT_FAST16_MIN
avr_stdint, 173
int_fast16_t
avr_stdint, 178
INT_FAST32_MAX
avr_stdint, 173
INT_FAST32_MIN
avr_stdint, 173
int_fast32_t
avr_stdint, 178
INT_FAST64_MAX
avr_stdint, 173
INT_FAST64_MIN
avr_stdint, 174
int_fast64_t
avr_stdint, 178
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
INDEX
INT_FAST8_MAX
avr_stdint, 174
INT_FAST8_MIN
avr_stdint, 174
int_fast8_t
avr_stdint, 178
INT_LEAST16_MAX
avr_stdint, 174
INT_LEAST16_MIN
avr_stdint, 174
int_least16_t
avr_stdint, 179
INT_LEAST32_MAX
avr_stdint, 174
INT_LEAST32_MIN
avr_stdint, 174
int_least32_t
avr_stdint, 179
INT_LEAST64_MAX
avr_stdint, 174
INT_LEAST64_MIN
avr_stdint, 174
int_least64_t
avr_stdint, 179
INT_LEAST8_MAX
avr_stdint, 174
INT_LEAST8_MIN
avr_stdint, 175
int_least8_t
avr_stdint, 179
INTERRUPT
deprecated_items, 323
interrupt.h, 377
INTMAX_C
avr_stdint, 175
INTMAX_MAX
avr_stdint, 175
INTMAX_MIN
avr_stdint, 175
intmax_t
avr_stdint, 179
INTPTR_MAX
avr_stdint, 175
INTPTR_MIN
avr_stdint, 175
intptr_t
428
avr_stdint, 179
inttypes.h, 377
io.h, 380
isalnum
ctype, 137
isalpha
ctype, 137
isascii
ctype, 137
isblank
ctype, 137
iscntrl
ctype, 137
isdigit
ctype, 137
isfinite
avr_math, 163
isfinitef
avr_math, 157
isgraph
ctype, 137
isinf
avr_math, 163
isinff
avr_math, 157
islower
ctype, 137
isnan
avr_math, 163
isnanf
avr_math, 157
isprint
ctype, 137
ispunct
ctype, 137
ISR
avr_interrupts, 262
ISR_ALIAS
avr_interrupts, 263
ISR_ALIASOF
avr_interrupts, 263
ISR_BLOCK
avr_interrupts, 264
ISR_NAKED
avr_interrupts, 264
ISR_NOBLOCK
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
INDEX
avr_interrupts, 264
isspace
ctype, 138
isupper
ctype, 138
isxdigit
ctype, 138
itoa
avr_stdlib, 206
labs
avr_stdlib, 207
ldexp
avr_math, 163
ldexpf
avr_math, 157
ldiv
avr_stdlib, 207
ldiv_t, 366
quot, 367
rem, 367
lock.h, 380
log
avr_math, 163
log10
avr_math, 163
log10f
avr_math, 157
logf
avr_math, 157
longjmp
setjmp, 167
loop_until_bit_is_clear
avr_sfr, 297
loop_until_bit_is_set
avr_sfr, 297
lrint
avr_math, 164
lrintf
avr_math, 157
lround
avr_math, 164
lroundf
avr_math, 158
ltoa
avr_stdlib, 207
429
M_1_PI
avr_math, 158
M_2_PI
avr_math, 158
M_2_SQRTPI
avr_math, 158
M_E
avr_math, 158
M_LN10
avr_math, 158
M_LN2
avr_math, 158
M_LOG10E
avr_math, 158
M_LOG2E
avr_math, 158
M_PI
avr_math, 158
M_PI_2
avr_math, 159
M_PI_4
avr_math, 159
M_SQRT1_2
avr_math, 159
M_SQRT2
avr_math, 159
malloc
avr_stdlib, 207
math.h, 380
memccpy
avr_string, 215
memccpy.S, 384
memccpy_P
avr_pgmspace, 276
memchr
avr_string, 215
memchr.S, 384
memchr_P
avr_pgmspace, 276
memchr_P.S, 384
memcmp
avr_string, 215
memcmp.S, 384
memcmp_P
avr_pgmspace, 277
memcmp_P.S, 384
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
INDEX
memcmp_PF
avr_pgmspace, 277
memcmp_PF.S, 384
memcpy
avr_string, 216
memcpy.S, 384
memcpy_P
avr_pgmspace, 277
memcpy_P.S, 384
memcpy_PF
avr_pgmspace, 278
memmem
avr_string, 216
memmem.S, 384
memmem_P
avr_pgmspace, 278
memmove
avr_string, 216
memmove.S, 384
memrchr
avr_string, 217
memrchr.S, 384
memrchr_P
avr_pgmspace, 278
memrchr_P.S, 384
memset
avr_string, 217
memset.S, 384
modf
avr_math, 164
modff
avr_math, 164
NAN
avr_math, 159
NONATOMIC_BLOCK
util_atomic, 308
NONATOMIC_FORCEOFF
util_atomic, 309
NONATOMIC_RESTORESTATE
util_atomic, 309
outb
deprecated_items, 324
outp
deprecated_items, 324
430
parity.h, 384
parity_even_bit
util_parity, 314
pgm_get_far_address
pgmspace.h, 395
PGM_P
avr_pgmspace, 272
pgm_read_byte
avr_pgmspace, 272
pgm_read_byte_far
avr_pgmspace, 272
pgm_read_byte_near
avr_pgmspace, 272
pgm_read_dword
avr_pgmspace, 273
pgm_read_dword_far
avr_pgmspace, 273
pgm_read_dword_near
avr_pgmspace, 273
pgm_read_float
avr_pgmspace, 273
pgm_read_float_far
avr_pgmspace, 273
pgm_read_float_near
avr_pgmspace, 274
pgm_read_word
avr_pgmspace, 274
pgm_read_word_far
avr_pgmspace, 274
pgm_read_word_near
avr_pgmspace, 274
PGM_VOID_P
avr_pgmspace, 274
pgmspace.h, 385
__ELPM_classic__, 388
__ELPM_dword_enhanced__, 388
__ELPM_dword_xmega__, 388
__ELPM_enhanced__, 389
__ELPM_float_enhanced__, 389
__ELPM_float_xmega__, 390
__ELPM_word_classic__, 390
__ELPM_word_enhanced__, 391
__ELPM_word_xmega__, 391
__ELPM_xmega__, 392
__LPM_classic__, 392
__LPM_dword_classic__, 392
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
INDEX
__LPM_dword_enhanced__, 393
__LPM_enhanced__, 393
__LPM_float_classic__, 394
__LPM_float_enhanced__, 394
__LPM_word_classic__, 394
__LPM_word_enhanced__, 395
pgm_get_far_address, 395
pow
avr_math, 165
power.h, 396
powf
avr_math, 159
PRId16
avr_inttypes, 142
PRId32
avr_inttypes, 142
PRId8
avr_inttypes, 142
PRIdFAST16
avr_inttypes, 143
PRIdFAST32
avr_inttypes, 143
PRIdFAST8
avr_inttypes, 143
PRIdLEAST16
avr_inttypes, 143
PRIdLEAST32
avr_inttypes, 143
PRIdLEAST8
avr_inttypes, 143
PRIdPTR
avr_inttypes, 143
PRIi16
avr_inttypes, 143
PRIi32
avr_inttypes, 143
PRIi8
avr_inttypes, 143
PRIiFAST16
avr_inttypes, 144
PRIiFAST32
avr_inttypes, 144
PRIiFAST8
avr_inttypes, 144
PRIiLEAST16
avr_inttypes, 144
431
PRIiLEAST32
avr_inttypes, 144
PRIiLEAST8
avr_inttypes, 144
PRIiPTR
avr_inttypes, 144
printf
avr_stdio, 192
printf_P
avr_stdio, 192
PRIo16
avr_inttypes, 144
PRIo32
avr_inttypes, 144
PRIo8
avr_inttypes, 144
PRIoFAST16
avr_inttypes, 145
PRIoFAST32
avr_inttypes, 145
PRIoFAST8
avr_inttypes, 145
PRIoLEAST16
avr_inttypes, 145
PRIoLEAST32
avr_inttypes, 145
PRIoLEAST8
avr_inttypes, 145
PRIoPTR
avr_inttypes, 145
PRIu16
avr_inttypes, 145
PRIu32
avr_inttypes, 145
PRIu8
avr_inttypes, 145
PRIuFAST16
avr_inttypes, 146
PRIuFAST32
avr_inttypes, 146
PRIuFAST8
avr_inttypes, 146
PRIuLEAST16
avr_inttypes, 146
PRIuLEAST32
avr_inttypes, 146
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
INDEX
PRIuLEAST8
avr_inttypes, 146
PRIuPTR
avr_inttypes, 146
PRIX16
avr_inttypes, 146
PRIx16
avr_inttypes, 146
PRIX32
avr_inttypes, 147
PRIx32
avr_inttypes, 146
PRIX8
avr_inttypes, 147
PRIx8
avr_inttypes, 147
PRIXFAST16
avr_inttypes, 147
PRIxFAST16
avr_inttypes, 147
PRIXFAST32
avr_inttypes, 147
PRIxFAST32
avr_inttypes, 147
PRIXFAST8
avr_inttypes, 147
PRIxFAST8
avr_inttypes, 147
PRIXLEAST16
avr_inttypes, 148
PRIxLEAST16
avr_inttypes, 147
PRIXLEAST32
avr_inttypes, 148
PRIxLEAST32
avr_inttypes, 148
PRIXLEAST8
avr_inttypes, 148
PRIxLEAST8
avr_inttypes, 148
PRIXPTR
avr_inttypes, 148
PRIxPTR
avr_inttypes, 148
prog_char
avr_pgmspace, 275
432
prog_int16_t
avr_pgmspace, 275
prog_int32_t
avr_pgmspace, 275
prog_int64_t
avr_pgmspace, 275
prog_int8_t
avr_pgmspace, 275
prog_uchar
avr_pgmspace, 275
prog_uint16_t
avr_pgmspace, 276
prog_uint32_t
avr_pgmspace, 276
prog_uint64_t
avr_pgmspace, 276
prog_uint8_t
avr_pgmspace, 276
prog_void
avr_pgmspace, 276
PROGMEM
avr_pgmspace, 275
PSTR
avr_pgmspace, 275
PTRDIFF_MAX
avr_stdint, 175
PTRDIFF_MIN
avr_stdint, 175
putc
avr_stdio, 188
putchar
avr_stdio, 188
puts
avr_stdio, 193
puts_P
avr_stdio, 193
qsort
avr_stdlib, 208
quot
div_t, 366
ldiv_t, 367
rand
avr_stdlib, 208
RAND_MAX
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
INDEX
avr_stdlib, 203
rand_r
avr_stdlib, 208
random
avr_stdlib, 208
RANDOM_MAX
avr_stdlib, 203
random_r
avr_stdlib, 209
realloc
avr_stdlib, 209
rem
div_t, 366
ldiv_t, 367
reti
avr_interrupts, 265
round
avr_math, 165
roundf
avr_math, 159
sbi
deprecated_items, 324
scanf
avr_stdio, 193
scanf_P
avr_stdio, 193
SCNd16
avr_inttypes, 148
SCNd32
avr_inttypes, 148
SCNdFAST16
avr_inttypes, 148
SCNdFAST32
avr_inttypes, 149
SCNdLEAST16
avr_inttypes, 149
SCNdLEAST32
avr_inttypes, 149
SCNdPTR
avr_inttypes, 149
SCNi16
avr_inttypes, 149
SCNi32
avr_inttypes, 149
SCNiFAST16
433
avr_inttypes, 149
SCNiFAST32
avr_inttypes, 149
SCNiLEAST16
avr_inttypes, 149
SCNiLEAST32
avr_inttypes, 149
SCNiPTR
avr_inttypes, 150
SCNo16
avr_inttypes, 150
SCNo32
avr_inttypes, 150
SCNoFAST16
avr_inttypes, 150
SCNoFAST32
avr_inttypes, 150
SCNoLEAST16
avr_inttypes, 150
SCNoLEAST32
avr_inttypes, 150
SCNoPTR
avr_inttypes, 150
SCNu16
avr_inttypes, 150
SCNu32
avr_inttypes, 150
SCNuFAST16
avr_inttypes, 151
SCNuFAST32
avr_inttypes, 151
SCNuLEAST16
avr_inttypes, 151
SCNuLEAST32
avr_inttypes, 151
SCNuPTR
avr_inttypes, 151
SCNx16
avr_inttypes, 151
SCNx32
avr_inttypes, 151
SCNxFAST16
avr_inttypes, 151
SCNxFAST32
avr_inttypes, 151
SCNxLEAST16
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
INDEX
avr_inttypes, 151
SCNxLEAST32
avr_inttypes, 152
SCNxPTR
avr_inttypes, 152
sei
avr_interrupts, 265
setbaud.h, 396
setjmp
longjmp, 167
setjmp, 168
setjmp.h, 397
SIG_ATOMIC_MAX
avr_stdint, 175
SIG_ATOMIC_MIN
avr_stdint, 175
SIGNAL
avr_interrupts, 265
signature.h, 397
signbit
avr_math, 165
signbitf
avr_math, 159
sin
avr_math, 165
sinf
avr_math, 159
sinh
avr_math, 165
sinhf
avr_math, 159
SIZE_MAX
avr_stdint, 176
sleep.h, 397
sleep_cpu
avr_sleep, 300
sleep_disable
avr_sleep, 300
sleep_enable
avr_sleep, 300
snprintf
avr_stdio, 193
snprintf_P
avr_stdio, 193
sprintf
avr_stdio, 193
434
sprintf_P
avr_stdio, 193
sqrt
avr_math, 165
sqrtf
avr_math, 160
square
avr_math, 165
squaref
avr_math, 160
srand
avr_stdlib, 209
srandom
avr_stdlib, 209
sscanf
avr_stdio, 193
sscanf_P
avr_stdio, 194
stderr
avr_stdio, 188
stdin
avr_stdio, 188
stdint.h, 397
stdio.h, 401
stdlib.h, 402
stdout
avr_stdio, 189
strcasecmp
avr_string, 217
strcasecmp.S, 406
strcasecmp_P
avr_pgmspace, 278
strcasecmp_P.S, 406
strcasecmp_PF
avr_pgmspace, 279
strcasestr
avr_string, 218
strcasestr.S, 406
strcasestr_P
avr_pgmspace, 279
strcat
avr_string, 218
strcat.S, 406
strcat_P
avr_pgmspace, 279
strcat_P.S, 406
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
INDEX
strcat_PF
avr_pgmspace, 280
strchr
avr_string, 218
strchr.S, 406
strchr_P
avr_pgmspace, 280
strchr_P.S, 406
strchrnul
avr_string, 219
strchrnul.S, 406
strchrnul_P
avr_pgmspace, 280
strchrnul_P.S, 406
strcmp
avr_string, 219
strcmp.S, 406
strcmp_P
avr_pgmspace, 281
strcmp_P.S, 406
strcmp_PF
avr_pgmspace, 281
strcpy
avr_string, 219
strcpy.S, 406
strcpy_P
avr_pgmspace, 281
strcpy_P.S, 406
strcpy_PF
avr_pgmspace, 281
strcspn
avr_string, 220
strcspn.S, 406
strcspn_P
avr_pgmspace, 282
strcspn_P.S, 406
strdup
avr_string, 220
strdup.c, 406
string.h, 407
strlcat
avr_string, 220
strlcat.S, 410
strlcat_P
avr_pgmspace, 282
strlcat_P.S, 410
435
strlcat_PF
avr_pgmspace, 282
strlcpy
avr_string, 221
strlcpy.S, 410
strlcpy_P
avr_pgmspace, 283
strlcpy_P.S, 410
strlcpy_PF
avr_pgmspace, 283
strlen
avr_string, 221
strlen.S, 410
strlen_P
avr_pgmspace, 284
strlen_P.S, 410
strlen_PF
avr_pgmspace, 284
strlwr
avr_string, 222
strlwr.S, 410
strncasecmp
avr_string, 222
strncasecmp.S, 410
strncasecmp_P
avr_pgmspace, 284
strncasecmp_P.S, 410
strncasecmp_PF
avr_pgmspace, 285
strncat
avr_string, 222
strncat.S, 410
strncat_P
avr_pgmspace, 285
strncat_P.S, 410
strncat_PF
avr_pgmspace, 285
strncmp
avr_string, 222
strncmp.S, 410
strncmp_P
avr_pgmspace, 286
strncmp_P.S, 410
strncmp_PF
avr_pgmspace, 286
strncpy
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
INDEX
avr_string, 223
strncpy.S, 410
strncpy_P
avr_pgmspace, 287
strncpy_P.S, 410
strncpy_PF
avr_pgmspace, 287
strnlen
avr_string, 223
strnlen.S, 410
strnlen_P
avr_pgmspace, 287
strnlen_P.S, 410
strnlen_PF
avr_pgmspace, 288
strpbrk
avr_string, 223
strpbrk.S, 410
strpbrk_P
avr_pgmspace, 288
strpbrk_P.S, 410
strrchr
avr_string, 224
strrchr.S, 410
strrchr_P
avr_pgmspace, 288
strrchr_P.S, 410
strrev
avr_string, 224
strrev.S, 410
strsep
avr_string, 224
strsep.S, 410
strsep_P
avr_pgmspace, 289
strsep_P.S, 410
strspn
avr_string, 225
strspn.S, 410
strspn_P
avr_pgmspace, 289
strspn_P.S, 410
strstr
avr_string, 225
strstr.S, 410
strstr_P
436
avr_pgmspace, 289
strstr_P.S, 410
strstr_PF
avr_pgmspace, 290
strtod
avr_stdlib, 209
strtok
avr_string, 225
strtok.c, 410
strtok_P
avr_pgmspace, 290
strtok_P.c, 411
strtok_r
avr_string, 226
strtok_r.S, 411
strtok_rP
avr_pgmspace, 291
strtok_rP.S, 411
strtol
avr_stdlib, 210
strtoul
avr_stdlib, 210
strupr
avr_string, 226
strupr.S, 411
supported devices, 2
tan
avr_math, 166
tanf
avr_math, 160
tanh
avr_math, 166
tanhf
avr_math, 160
timer_enable_int
deprecated_items, 325
toascii
ctype, 138
tolower
ctype, 138
tools, optional, 91
tools, required, 91
toupper
ctype, 138
trunc
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
INDEX
avr_math, 166
truncf
avr_math, 160
TW_BUS_ERROR
util_twi, 318
TW_MR_ARB_LOST
util_twi, 318
TW_MR_DATA_ACK
util_twi, 318
TW_MR_DATA_NACK
util_twi, 318
TW_MR_SLA_ACK
util_twi, 318
TW_MR_SLA_NACK
util_twi, 318
TW_MT_ARB_LOST
util_twi, 318
TW_MT_DATA_ACK
util_twi, 318
TW_MT_DATA_NACK
util_twi, 319
TW_MT_SLA_ACK
util_twi, 319
TW_MT_SLA_NACK
util_twi, 319
TW_NO_INFO
util_twi, 319
TW_READ
util_twi, 319
TW_REP_START
util_twi, 319
TW_SR_ARB_LOST_GCALL_ACK
util_twi, 319
TW_SR_ARB_LOST_SLA_ACK
util_twi, 319
TW_SR_DATA_ACK
util_twi, 319
TW_SR_DATA_NACK
util_twi, 319
TW_SR_GCALL_ACK
util_twi, 320
TW_SR_GCALL_DATA_ACK
util_twi, 320
TW_SR_GCALL_DATA_NACK
util_twi, 320
TW_SR_SLA_ACK
437
util_twi, 320
TW_SR_STOP
util_twi, 320
TW_ST_ARB_LOST_SLA_ACK
util_twi, 320
TW_ST_DATA_ACK
util_twi, 320
TW_ST_DATA_NACK
util_twi, 320
TW_ST_LAST_DATA
util_twi, 320
TW_ST_SLA_ACK
util_twi, 320
TW_START
util_twi, 321
TW_STATUS
util_twi, 321
TW_STATUS_MASK
util_twi, 321
TW_WRITE
util_twi, 321
twi.h, 411
UBRR_VALUE
util_setbaud, 316
UBRRH_VALUE
util_setbaud, 316
UBRRL_VALUE
util_setbaud, 316
UINT16_C
avr_stdint, 176
UINT16_MAX
avr_stdint, 176
uint16_t
avr_stdint, 179
UINT32_C
avr_stdint, 176
UINT32_MAX
avr_stdint, 176
uint32_t
avr_stdint, 179
UINT64_C
avr_stdint, 176
UINT64_MAX
avr_stdint, 176
uint64_t
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
INDEX
avr_stdint, 179
UINT8_C
avr_stdint, 176
UINT8_MAX
avr_stdint, 176
uint8_t
avr_stdint, 180
uint_farptr_t
avr_inttypes, 152
UINT_FAST16_MAX
avr_stdint, 176
uint_fast16_t
avr_stdint, 180
UINT_FAST32_MAX
avr_stdint, 177
uint_fast32_t
avr_stdint, 180
UINT_FAST64_MAX
avr_stdint, 177
uint_fast64_t
avr_stdint, 180
UINT_FAST8_MAX
avr_stdint, 177
uint_fast8_t
avr_stdint, 180
UINT_LEAST16_MAX
avr_stdint, 177
uint_least16_t
avr_stdint, 180
UINT_LEAST32_MAX
avr_stdint, 177
uint_least32_t
avr_stdint, 180
UINT_LEAST64_MAX
avr_stdint, 177
uint_least64_t
avr_stdint, 180
UINT_LEAST8_MAX
avr_stdint, 177
uint_least8_t
avr_stdint, 181
UINTMAX_C
avr_stdint, 177
UINTMAX_MAX
avr_stdint, 177
uintmax_t
438
avr_stdint, 181
UINTPTR_MAX
avr_stdint, 177
uintptr_t
avr_stdint, 181
ultoa
avr_stdlib, 211
ungetc
avr_stdio, 194
USE_2X
util_setbaud, 316
Using the standard IO facilities, 353
util_atomic
ATOMIC_BLOCK, 308
ATOMIC_FORCEON, 308
ATOMIC_RESTORESTATE, 308
NONATOMIC_BLOCK, 308
NONATOMIC_FORCEOFF, 309
NONATOMIC_RESTORESTATE, 309
util_crc
_crc16_update, 310
_crc_ccitt_update, 311
_crc_ibutton_update, 311
_crc_xmodem_update, 312
util_delay_basic
_delay_loop_1, 313
_delay_loop_2, 313
util_parity
parity_even_bit, 314
util_setbaud
BAUD_TOL, 316
UBRR_VALUE, 316
UBRRH_VALUE, 316
UBRRL_VALUE, 316
USE_2X, 316
util_twi
TW_BUS_ERROR, 318
TW_MR_ARB_LOST, 318
TW_MR_DATA_ACK, 318
TW_MR_DATA_NACK, 318
TW_MR_SLA_ACK, 318
TW_MR_SLA_NACK, 318
TW_MT_ARB_LOST, 318
TW_MT_DATA_ACK, 318
TW_MT_DATA_NACK, 319
TW_MT_SLA_ACK, 319
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
INDEX
TW_MT_SLA_NACK, 319
wdt.h, 412
TW_NO_INFO, 319
wdt_disable
TW_READ, 319
avr_watchdog, 303
TW_REP_START, 319
wdt_enable
TW_SR_ARB_LOST_GCALL_ACK,
avr_watchdog, 303
319
wdt_reset
TW_SR_ARB_LOST_SLA_ACK, 319
avr_watchdog, 304
TW_SR_DATA_ACK, 319
WDTO_120MS
TW_SR_DATA_NACK, 319
avr_watchdog, 304
TW_SR_GCALL_ACK, 320
WDTO_15MS
TW_SR_GCALL_DATA_ACK, 320
avr_watchdog, 304
TW_SR_GCALL_DATA_NACK, 320 WDTO_1S
TW_SR_SLA_ACK, 320
avr_watchdog, 304
TW_SR_STOP, 320
WDTO_250MS
TW_ST_ARB_LOST_SLA_ACK, 320
avr_watchdog, 304
TW_ST_DATA_ACK, 320
WDTO_2S
TW_ST_DATA_NACK, 320
avr_watchdog, 304
TW_ST_LAST_DATA, 320
WDTO_30MS
TW_ST_SLA_ACK, 320
avr_watchdog, 305
TW_START, 321
WDTO_4S
TW_STATUS, 321
avr_watchdog, 305
TW_STATUS_MASK, 321
WDTO_500MS
TW_WRITE, 321
avr_watchdog, 305
utoa
WDTO_60MS
avr_stdlib, 212
avr_watchdog, 305
WDTO_8S
vfprintf
avr_watchdog, 305
avr_stdio, 194
vfprintf_P
avr_stdio, 197
vfscanf
avr_stdio, 197
vfscanf_P
avr_stdio, 199
vprintf
avr_stdio, 200
vscanf
avr_stdio, 200
vsnprintf
avr_stdio, 200
vsnprintf_P
avr_stdio, 200
vsprintf
avr_stdio, 200
vsprintf_P
avr_stdio, 200
Generated on Thu May 19 2011 13:29:12 for avr-libc by Doxygen
439
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