"user manual"

"user manual"
avr-libc Reference Manual
1.4.0
Generated by Doxygen 1.4.1
Sat Nov 19 23:00:48 2005
CONTENTS
i
Contents
1
2
3
4
5
AVR Libc
1
1.1
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1
1.2
General information about this library . . . . . . . . . . . . . . . . .
2
1.3
Supported Devices . . . . . . . . . . . . . . . . . . . . . . . . . . .
2
avr-libc Module Index
5
2.1
5
avr-libc Modules . . . . . . . . . . . . . . . . . . . . . . . . . . . .
avr-libc Data Structure Index
7
3.1
7
avr-libc Data Structures . . . . . . . . . . . . . . . . . . . . . . . . .
avr-libc Page Index
7
4.1
7
avr-libc Related Pages . . . . . . . . . . . . . . . . . . . . . . . . . .
avr-libc Module Documentation
8
<assert.h>: Diagnostics . . . . . . . . . . . . . . . . . . . . . . . .
8
5.1.1
Detailed Description . . . . . . . . . . . . . . . . . . . . . .
8
5.1.2
Define Documentation . . . . . . . . . . . . . . . . . . . . .
8
<avr/boot.h>: Bootloader Support Utilities . . . . . . . . . . . . . .
8
5.2.1
Detailed Description . . . . . . . . . . . . . . . . . . . . . .
8
5.2.2
Define Documentation . . . . . . . . . . . . . . . . . . . . .
10
<avr/eeprom.h>: EEPROM handling . . . . . . . . . . . . . . . . .
15
5.3.1
Detailed Description . . . . . . . . . . . . . . . . . . . . . .
15
5.3.2
Define Documentation . . . . . . . . . . . . . . . . . . . . .
16
5.3.3
Function Documentation . . . . . . . . . . . . . . . . . . . .
17
5.4
<avr/io.h>: AVR device-specific IO definitions . . . . . . . . . . . .
17
5.5
<avr/pgmspace.h>: Program Space String Utilities . . . . . . . . . .
18
5.5.1
Detailed Description . . . . . . . . . . . . . . . . . . . . . .
18
5.5.2
Define Documentation . . . . . . . . . . . . . . . . . . . . .
20
5.5.3
Typedef Documentation . . . . . . . . . . . . . . . . . . . .
22
5.5.4
Function Documentation . . . . . . . . . . . . . . . . . . . .
23
5.1
5.2
5.3
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CONTENTS
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5.6
Additional notes from <avr/sfr_defs.h> . . . . . . . . . . . . . . . .
26
5.7
<avr/sleep.h>: Power Management and Sleep Modes . . . . . . . . .
28
5.7.1
Detailed Description . . . . . . . . . . . . . . . . . . . . . .
28
5.7.2
Define Documentation . . . . . . . . . . . . . . . . . . . . .
28
5.7.3
Function Documentation . . . . . . . . . . . . . . . . . . . .
29
<avr/version.h>: avr-libc version macros . . . . . . . . . . . . . . .
29
5.8.1
Detailed Description . . . . . . . . . . . . . . . . . . . . . .
29
5.8.2
Define Documentation . . . . . . . . . . . . . . . . . . . . .
30
<avr/wdt.h>: Watchdog timer handling . . . . . . . . . . . . . . . .
31
5.9.1
Detailed Description . . . . . . . . . . . . . . . . . . . . . .
31
5.9.2
Define Documentation . . . . . . . . . . . . . . . . . . . . .
32
5.10 <compat/deprecated.h>: Deprecated items . . . . . . . . . . . . . .
34
5.10.1 Detailed Description . . . . . . . . . . . . . . . . . . . . . .
34
5.10.2 Define Documentation . . . . . . . . . . . . . . . . . . . . .
35
5.10.3 Function Documentation . . . . . . . . . . . . . . . . . . . .
36
5.11 <compat/ina90.h>: Compatibility with IAR EWB 3.x . . . . . . . .
37
5.12 <ctype.h>: Character Operations . . . . . . . . . . . . . . . . . . .
37
5.12.1 Detailed Description . . . . . . . . . . . . . . . . . . . . . .
37
5.12.2 Function Documentation . . . . . . . . . . . . . . . . . . . .
38
5.13 <errno.h>: System Errors . . . . . . . . . . . . . . . . . . . . . . .
39
5.13.1 Detailed Description . . . . . . . . . . . . . . . . . . . . . .
39
5.13.2 Define Documentation . . . . . . . . . . . . . . . . . . . . .
40
5.14 <inttypes.h>: Integer Type conversions . . . . . . . . . . . . . . . .
40
5.14.1 Detailed Description . . . . . . . . . . . . . . . . . . . . . .
40
5.14.2 Define Documentation . . . . . . . . . . . . . . . . . . . . .
43
5.14.3 Typedef Documentation . . . . . . . . . . . . . . . . . . . .
52
5.15 <math.h>: Mathematics . . . . . . . . . . . . . . . . . . . . . . . .
52
5.15.1 Detailed Description . . . . . . . . . . . . . . . . . . . . . .
52
5.15.2 Define Documentation . . . . . . . . . . . . . . . . . . . . .
53
5.15.3 Function Documentation . . . . . . . . . . . . . . . . . . . .
53
5.16 <setjmp.h>: Non-local goto . . . . . . . . . . . . . . . . . . . . . .
56
5.8
5.9
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5.16.1 Detailed Description . . . . . . . . . . . . . . . . . . . . . .
56
5.16.2 Function Documentation . . . . . . . . . . . . . . . . . . . .
58
5.17 <stdint.h>: Standard Integer Types . . . . . . . . . . . . . . . . . .
58
5.17.1 Detailed Description . . . . . . . . . . . . . . . . . . . . . .
58
5.17.2 Define Documentation . . . . . . . . . . . . . . . . . . . . .
62
5.17.3 Typedef Documentation . . . . . . . . . . . . . . . . . . . .
67
5.18 <stdio.h>: Standard IO facilities . . . . . . . . . . . . . . . . . . . .
70
5.18.1 Detailed Description . . . . . . . . . . . . . . . . . . . . . .
70
5.18.2 Define Documentation . . . . . . . . . . . . . . . . . . . . .
75
5.18.3 Function Documentation . . . . . . . . . . . . . . . . . . . .
77
5.19 <stdlib.h>: General utilities . . . . . . . . . . . . . . . . . . . . . .
88
5.19.1 Detailed Description . . . . . . . . . . . . . . . . . . . . . .
88
5.19.2 Define Documentation . . . . . . . . . . . . . . . . . . . . .
90
5.19.3 Typedef Documentation . . . . . . . . . . . . . . . . . . . .
91
5.19.4 Function Documentation . . . . . . . . . . . . . . . . . . . .
91
5.19.5 Variable Documentation . . . . . . . . . . . . . . . . . . . .
99
5.20 <string.h>: Strings . . . . . . . . . . . . . . . . . . . . . . . . . . .
99
5.20.1 Detailed Description . . . . . . . . . . . . . . . . . . . . . .
99
5.20.2 Define Documentation . . . . . . . . . . . . . . . . . . . . .
101
5.20.3 Function Documentation . . . . . . . . . . . . . . . . . . . .
101
5.21 <util/crc16.h>: CRC Computations . . . . . . . . . . . . . . . . . .
108
5.21.1 Detailed Description . . . . . . . . . . . . . . . . . . . . . .
108
5.21.2 Function Documentation . . . . . . . . . . . . . . . . . . . .
109
5.22 <util/delay.h>: Busy-wait delay loops . . . . . . . . . . . . . . . . .
111
5.22.1 Detailed Description . . . . . . . . . . . . . . . . . . . . . .
111
5.22.2 Function Documentation . . . . . . . . . . . . . . . . . . . .
112
5.23 <util/parity.h>: Parity bit generation . . . . . . . . . . . . . . . . . .
113
5.23.1 Detailed Description . . . . . . . . . . . . . . . . . . . . . .
113
5.23.2 Define Documentation . . . . . . . . . . . . . . . . . . . . .
113
5.24 <util/twi.h>: TWI bit mask definitions . . . . . . . . . . . . . . . .
114
5.24.1 Detailed Description . . . . . . . . . . . . . . . . . . . . . .
114
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6
5.24.2 Define Documentation . . . . . . . . . . . . . . . . . . . . .
115
5.25 <avr/interrupt.h>: Interrupts . . . . . . . . . . . . . . . . . . . . . .
118
5.25.1 Detailed Description . . . . . . . . . . . . . . . . . . . . . .
118
5.25.2 Define Documentation . . . . . . . . . . . . . . . . . . . . .
131
5.26 <avr/sfr_defs.h>: Special function registers . . . . . . . . . . . . . .
132
5.26.1 Detailed Description . . . . . . . . . . . . . . . . . . . . . .
132
5.26.2 Define Documentation . . . . . . . . . . . . . . . . . . . . .
134
5.27 Demo projects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
135
5.27.1 Detailed Description . . . . . . . . . . . . . . . . . . . . . .
135
5.28 A simple project . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
136
5.28.1 The Project . . . . . . . . . . . . . . . . . . . . . . . . . . .
136
5.28.2 The Source Code . . . . . . . . . . . . . . . . . . . . . . . .
137
5.28.3 Compiling and Linking . . . . . . . . . . . . . . . . . . . . .
140
5.28.4 Examining the Object File . . . . . . . . . . . . . . . . . . .
140
5.28.5 Linker Map Files . . . . . . . . . . . . . . . . . . . . . . . .
144
5.28.6 Intel Hex Files . . . . . . . . . . . . . . . . . . . . . . . . .
145
5.28.7 Make Build the Project . . . . . . . . . . . . . . . . . . . . .
146
5.29 Example using the two-wire interface (TWI) . . . . . . . . . . . . . .
148
5.29.1 Introduction into TWI . . . . . . . . . . . . . . . . . . . . .
148
5.29.2 The TWI example project . . . . . . . . . . . . . . . . . . .
148
5.29.3 The Source Code . . . . . . . . . . . . . . . . . . . . . . . .
149
avr-libc Data Structure Documentation
161
6.1
div_t Struct Reference . . . . . . . . . . . . . . . . . . . . . . . . .
161
6.1.1
Detailed Description . . . . . . . . . . . . . . . . . . . . . .
161
6.1.2
Field Documentation . . . . . . . . . . . . . . . . . . . . . .
162
ldiv_t Struct Reference . . . . . . . . . . . . . . . . . . . . . . . . .
162
6.2.1
Detailed Description . . . . . . . . . . . . . . . . . . . . . .
162
6.2.2
Field Documentation . . . . . . . . . . . . . . . . . . . . . .
162
6.2
7
iv
avr-libc Page Documentation
163
7.1
163
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . .
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CONTENTS
7.2
7.3
v
avr-libc and assembler programs . . . . . . . . . . . . . . . . . . . .
164
7.2.1
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . .
164
7.2.2
Invoking the compiler . . . . . . . . . . . . . . . . . . . . .
164
7.2.3
Example program . . . . . . . . . . . . . . . . . . . . . . . .
165
7.2.4
Pseudo-ops and operators . . . . . . . . . . . . . . . . . . .
168
Frequently Asked Questions . . . . . . . . . . . . . . . . . . . . . .
169
7.3.1
FAQ Index . . . . . . . . . . . . . . . . . . . . . . . . . . .
169
7.3.2
My program doesn’t recognize a variable updated within an
interrupt routine . . . . . . . . . . . . . . . . . . . . . . . .
171
7.3.3
I get "undefined reference to..." for functions like "sin()" . . .
171
7.3.4
How to permanently bind a variable to a register? . . . . . . .
171
7.3.5
How to modify MCUCR or WDTCR early? . . . . . . . . . .
172
7.3.6
What is all this _BV() stuff about? . . . . . . . . . . . . . . .
172
7.3.7
Can I use C++ on the AVR? . . . . . . . . . . . . . . . . . .
173
7.3.8
Shouldn’t I initialize all my variables? . . . . . . . . . . . . .
174
7.3.9
Why do some 16-bit timer registers sometimes get trashed? .
175
7.3.10 How do I use a #define’d constant in an asm statement? . . . .
176
7.3.11 Why does the PC randomly jump around when single-stepping
through my program in avr-gdb? . . . . . . . . . . . . . . . .
176
7.3.12 How do I trace an assembler file in avr-gdb? . . . . . . . . . .
177
7.3.13 How do I pass an IO port as a parameter to a function? . . . .
178
7.3.14 What registers are used by the C compiler? . . . . . . . . . .
180
7.3.15 How do I put an array of strings completely in ROM? . . . . .
182
7.3.16 How to use external RAM? . . . . . . . . . . . . . . . . . . .
184
7.3.17 Which -O flag to use? . . . . . . . . . . . . . . . . . . . . .
184
7.3.18 How do I relocate code to a fixed address? . . . . . . . . . . .
185
7.3.19 My UART is generating nonsense! My ATmega128 keeps
crashing! Port F is completely broken! . . . . . . . . . . . . .
186
7.3.20 Why do all my "foo...bar" strings eat up the SRAM? . . . . .
186
7.3.21 Why does the compiler compile an 8-bit operation that uses
bitwise operators into a 16-bit operation in assembly? . . . . .
187
7.3.22 How to detect RAM memory and variable overlap problems? .
188
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CONTENTS
7.4
7.5
7.6
7.7
vi
7.3.23 Is it really impossible to program the ATtinyXX in C? . . . .
188
7.3.24 What is this "clock skew detected" messsage? . . . . . . . . .
188
7.3.25 Why are (many) interrupt flags cleared by writing a logical 1?
189
7.3.26 Why have "programmed" fuses the bit value 0? . . . . . . . .
190
7.3.27 Which AVR-specific assembler operators are available? . . . .
190
Inline Asm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
190
7.4.1
GCC asm Statement . . . . . . . . . . . . . . . . . . . . . .
191
7.4.2
Assembler Code . . . . . . . . . . . . . . . . . . . . . . . .
193
7.4.3
Input and Output Operands . . . . . . . . . . . . . . . . . . .
193
7.4.4
Clobbers . . . . . . . . . . . . . . . . . . . . . . . . . . . .
197
7.4.5
Assembler Macros . . . . . . . . . . . . . . . . . . . . . . .
199
7.4.6
C Stub Functions . . . . . . . . . . . . . . . . . . . . . . . .
200
7.4.7
C Names Used in Assembler Code . . . . . . . . . . . . . . .
201
7.4.8
Links . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
202
Using malloc() . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
202
7.5.1
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . .
202
7.5.2
Internal vs. external RAM . . . . . . . . . . . . . . . . . . .
203
7.5.3
Tunables for malloc() . . . . . . . . . . . . . . . . . . . . . .
204
7.5.4
Implementation details . . . . . . . . . . . . . . . . . . . . .
205
Release Numbering and Methodology . . . . . . . . . . . . . . . . .
207
7.6.1
Release Version Numbering Scheme . . . . . . . . . . . . . .
207
7.6.2
Releasing AVR Libc . . . . . . . . . . . . . . . . . . . . . .
207
Memory Sections . . . . . . . . . . . . . . . . . . . . . . . . . . . .
210
7.7.1
The .text Section . . . . . . . . . . . . . . . . . . . . . . . .
210
7.7.2
The .data Section . . . . . . . . . . . . . . . . . . . . . . . .
211
7.7.3
The .bss Section . . . . . . . . . . . . . . . . . . . . . . . .
211
7.7.4
The .eeprom Section . . . . . . . . . . . . . . . . . . . . . .
211
7.7.5
The .noinit Section . . . . . . . . . . . . . . . . . . . . . . .
211
7.7.6
The .initN Sections . . . . . . . . . . . . . . . . . . . . . . .
212
7.7.7
The .finiN Sections . . . . . . . . . . . . . . . . . . . . . . .
213
7.7.8
Using Sections in Assembler Code . . . . . . . . . . . . . . .
214
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1 AVR Libc
7.7.9
1
Using Sections in C Code . . . . . . . . . . . . . . . . . . .
214
Installing the GNU Tool Chain . . . . . . . . . . . . . . . . . . . . .
215
7.8.1
Required Tools . . . . . . . . . . . . . . . . . . . . . . . . .
216
7.8.2
Optional Tools . . . . . . . . . . . . . . . . . . . . . . . . .
216
7.8.3
GNU Binutils for the AVR target . . . . . . . . . . . . . . . .
217
7.8.4
GCC for the AVR target . . . . . . . . . . . . . . . . . . . .
218
7.8.5
AVR Libc . . . . . . . . . . . . . . . . . . . . . . . . . . . .
218
7.8.6
UISP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
219
7.8.7
Avrdude . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
219
7.8.8
GDB for the AVR target . . . . . . . . . . . . . . . . . . . .
220
7.8.9
Simulavr . . . . . . . . . . . . . . . . . . . . . . . . . . . .
220
7.8.10 AVaRice . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
220
Using the avrdude program . . . . . . . . . . . . . . . . . . . . . . .
221
7.10 Using the GNU tools . . . . . . . . . . . . . . . . . . . . . . . . . .
223
7.10.1 Options for the C compiler avr-gcc . . . . . . . . . . . . . . .
223
7.10.2 Options for the assembler avr-as . . . . . . . . . . . . . . . .
228
7.10.3 Controlling the linker avr-ld . . . . . . . . . . . . . . . . . .
230
7.11 Todo List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
232
7.12 Deprecated List . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
232
7.8
7.9
1
1.1
AVR Libc
Introduction
The latest version of this document is always available
http://savannah.nongnu.org/projects/avr-libc/
from
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
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1.2
General information about this library
2
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 guarenteed 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 context, undefined behaviour
will result.
1.3
Supported Devices
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.
AT90S Type Devices:
• at90s1200 [1]
• at90s2313
• at90s2323
• at90s2333
• at90s2343
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1.3
Supported Devices
• at90s4414
• at90s4433
• at90s4434
• at90s8515
• at90c8534
• at90s8535
• at90can32
• at90can64
• at90can128
ATmega Type Devices:
• atmega8
• atmega103
• atmega128
• atmega1280
• atmega1281
• atmega16
• atmega161
• atmega162
• atmega163
• atmega164
• atmega165
• atmega168
• atmega169
• atmega32
• atmega323
• atmega324
• atmega325
Generated on Sat Nov 19 23:00:48 2005 for avr-libc by Doxygen
3
1.3
Supported Devices
• atmega3250
• atmega329
• atmega3290
• atmega48
• atmega64
• atmega640
• atmega644
• atmega645
• atmega6450
• atmega649
• atmega6490
• atmega8515
• atmega8535
• atmega88
ATtiny Type Devices:
• attiny11 [1]
• attiny12 [1]
• attiny13
• attiny15 [1]
• attiny22
• attiny25
• attiny26
• attiny28 [1]
• attiny2313
• attiny45
• attiny85
Generated on Sat Nov 19 23:00:48 2005 for avr-libc by Doxygen
4
2 avr-libc Module Index
5
Misc Devices:
• at94K [2]
• at76c711 [3]
• at43usb320
• at43usb355
• at86rf401
• at90pwm2/at90pwm3
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.
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.
2
avr-libc Module Index
2.1
avr-libc Modules
Here is a list of all modules:
<assert.h>: Diagnostics
8
<avr/boot.h>: Bootloader Support Utilities
8
<avr/eeprom.h>: EEPROM handling
15
<avr/io.h>: AVR device-specific IO definitions
17
<avr/pgmspace.h>: Program Space String Utilities
18
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2.1
avr-libc Modules
6
<avr/sleep.h>: Power Management and Sleep Modes
28
<avr/version.h>: avr-libc version macros
29
<avr/wdt.h>: Watchdog timer handling
31
<compat/deprecated.h>: Deprecated items
34
<compat/ina90.h>: Compatibility with IAR EWB 3.x
37
<ctype.h>: Character Operations
37
<errno.h>: System Errors
39
<inttypes.h>: Integer Type conversions
40
<math.h>: Mathematics
52
<setjmp.h>: Non-local goto
56
<stdint.h>: Standard Integer Types
58
<stdio.h>: Standard IO facilities
70
<stdlib.h>: General utilities
88
<string.h>: Strings
99
<util/crc16.h>: CRC Computations
108
<util/delay.h>: Busy-wait delay loops
111
<util/parity.h>: Parity bit generation
113
<util/twi.h>: TWI bit mask definitions
114
<avr/interrupt.h>: Interrupts
118
<avr/sfr_defs.h>: Special function registers
132
Additional notes from <avr/sfr_defs.h>
Demo projects
26
135
A simple project
136
Example using the two-wire interface (TWI)
148
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3 avr-libc Data Structure Index
3
7
avr-libc Data Structure Index
3.1
avr-libc Data Structures
Here are the data structures with brief descriptions:
div_t
161
ldiv_t
162
4
avr-libc Page Index
4.1
avr-libc Related Pages
Here is a list of all related documentation pages:
Acknowledgments
163
avr-libc and assembler programs
164
Frequently Asked Questions
169
Inline Asm
190
Using malloc()
202
Release Numbering and Methodology
207
Memory Sections
210
Installing the GNU Tool Chain
215
Using the avrdude program
221
Using the GNU tools
223
Todo List
232
Deprecated List
232
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5 avr-libc Module Documentation
5
8
avr-libc Module Documentation
5.1 <assert.h>: Diagnostics
5.1.1
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.
Defines
• #define assert(expression)
5.1.2
5.1.2.1
Define Documentation
#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).
5.2 <avr/boot.h>: Bootloader Support Utilities
5.2.1
Detailed Description
#include <avr/io.h>
#include <avr/boot.h>
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5.2
<avr/boot.h>: Bootloader Support Utilities
9
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.
Note:
Not all AVR processors provide bootloader support. See your processor datasheet
to see if it provides bootloader support.
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 ();
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<avr/boot.h>: Bootloader Support Utilities
5.2
10
// Re-enable interrupts (if they were ever enabled).
SREG = sreg;
}
Defines
• #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(SPMEN))
• #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_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)
5.2.2
Define Documentation
5.2.2.1 #define
BV(SPMIE))
boot_is_spm_interrupt()
(__SPM_REG
&
(uint8_t)_-
Check if the SPM interrupt is enabled.
5.2.2.2
#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.
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5.2
<avr/boot.h>: Bootloader Support Utilities
11
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 (BLB12));
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.
5.2.2.3
#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.
5.2.2.4
#define boot_lock_fuse_bits_get(address)
Value:
(__extension__({
uint8_t __result;
__asm__ __volatile__
(
"ldi r30, %3\n\t"
"ldi r31, 0\n\t"
"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),
"M" (address)
: "r0", "r30", "r31"
);
__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.
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5.2
<avr/boot.h>: Bootloader Support Utilities
12
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.
5.2.2.5
#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.
5.2.2.6
#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.
5.2.2.7
data)
#define boot_page_fill(address, data) __boot_page_fill_normal(address,
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.
5.2.2.8
#define boot_page_fill_safe(address, data)
Value:
do { \
boot_spm_busy_wait();
eeprom_busy_wait();
boot_page_fill(address, data);
} while (0)
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\
\
\
5.2
<avr/boot.h>: Bootloader Support Utilities
13
Same as boot_page_fill() except it waits for eeprom and spm operations to complete
before filling the page.
5.2.2.9
#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.
5.2.2.10
#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.
5.2.2.11 #define boot_rww_busy()
COMMON_ASB))
(__SPM_REG
&
(uint8_t)_BV(__-
Check if the RWW section is busy.
5.2.2.12
#define boot_rww_enable() __boot_rww_enable()
Enable the Read-While-Write memory section.
5.2.2.13
#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.
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5.2
<avr/boot.h>: Bootloader Support Utilities
5.2.2.14
14
#define boot_spm_busy() (__SPM_REG & (uint8_t)_BV(SPMEN))
Check if the SPM instruction is busy.
5.2.2.15
#define boot_spm_busy_wait() do{}while(boot_spm_busy())
Wait while the SPM instruction is busy.
5.2.2.16 #define boot_spm_interrupt_disable() (__SPM_REG &= (uint8_t)∼_BV(SPMIE))
Disable the SPM interrupt.
5.2.2.17 #define boot_spm_interrupt_enable() (__SPM_REG |= (uint8_t)_BV(SPMIE))
Enable the SPM interrupt.
5.2.2.18 #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.
5.2.2.19
#define GET_EXTENDED_FUSE_BITS (0x0002)
address to read the extended fuse bits, using boot_lock_fuse_bits_get
5.2.2.20
#define GET_HIGH_FUSE_BITS (0x0003)
address to read the high fuse bits, using boot_lock_fuse_bits_get
5.2.2.21
#define GET_LOCK_BITS (0x0001)
address to read the lock bits, using boot_lock_fuse_bits_get
5.2.2.22
#define GET_LOW_FUSE_BITS (0x0000)
address to read the low fuse bits, using boot_lock_fuse_bits_get
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<avr/eeprom.h>: EEPROM handling
5.3
15
5.3 <avr/eeprom.h>: EEPROM handling
5.3.1
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.
Note:
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, timecritical applications should first poll the EEPROM e. g. using eeprom_is_ready()
before attempting any actual I/O.
This header file declares inline functions that call the assembler subroutines directly. This prevents that the compiler generates push/pops for the call-clobbered
registers. This way also a specific calling convention could be used for the eeprom routines e.g. by passing values in __tmp_reg__, eeprom addresses in X and
memory addresses in Z registers. Method is optimized for code size.
Presently supported are two locations of the EEPROM register set:
0x1F,0x20,0x21 and 0x1C,0x1D,0x1E (see __EEPROM_REG_LOCATIONS__).
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).
avr-libc declarations
•
•
•
•
•
•
#define EEMEM __attribute__((section(".eeprom")))
#define eeprom_is_ready()
#define eeprom_busy_wait() do {} while (!eeprom_is_ready())
uint8_t eeprom_read_byte (const uint8_t ∗addr)
uint16_t eeprom_read_word (const uint16_t ∗addr)
void eeprom_read_block (void ∗pointer_ram, const void ∗pointer_eeprom,
size_t n)
• void eeprom_write_byte (uint8_t ∗addr, uint8_t value)
• void eeprom_write_word (uint16_t ∗addr, uint16_t value)
• void eeprom_write_block (const void ∗pointer_ram, void ∗pointer_eeprom,
size_t n)
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<avr/eeprom.h>: EEPROM handling
5.3
16
IAR C compatibility defines
• #define _EEPUT(addr, val) eeprom_write_byte ((uint8_t ∗)(addr), (uint8_t)(val))
• #define _EEGET(var, addr) (var) = eeprom_read_byte ((uint8_t ∗)(addr))
Defines
• #define __EEPROM_REG_LOCATIONS__ 1C1D1E
5.3.2
5.3.2.1
Define Documentation
#define __EEPROM_REG_LOCATIONS__ 1C1D1E
In order to be able to work without a requiring a multilib approach for dealing with
controllers having the EEPROM registers at different positions in memory space, the
eeprom functions evaluate __EEPROM_REG_LOCATIONS__: It is assumed to be
defined by the device io header and contains 6 uppercase hex digits encoding the addresses of EECR,EEDR and EEAR. First two letters: EECR address. Second two
letters: EEDR address. Last two letters: EEAR address. The default 1C1D1E corresponds to the register location that is valid for most controllers. The value of this define
symbol is used for appending it to the base name of the assembler functions.
5.3.2.2 #define _EEGET(var, addr) (var) = eeprom_read_byte ((uint8_t
∗)(addr))
Read a byte from EEPROM. Compatibility define for IAR C.
5.3.2.3 #define _EEPUT(addr, val) eeprom_write_byte ((uint8_t ∗)(addr),
(uint8_t)(val))
Write a byte to EEPROM. Compatibility define for IAR C.
5.3.2.4
#define EEMEM __attribute__((section(".eeprom")))
Attribute expression causing a variable to be allocated within the .eeprom section.
5.3.2.5
#define eeprom_busy_wait() do {} while (!eeprom_is_ready())
Loops until the eeprom is no longer busy.
Returns:
Nothing.
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5.4
<avr/io.h>: AVR device-specific IO definitions
5.3.2.6
17
#define eeprom_is_ready()
Returns:
1 if EEPROM is ready for a new read/write operation, 0 if not.
5.3.3
Function Documentation
5.3.3.1 void eeprom_read_block (void ∗ pointer_ram, const void ∗ pointer_eeprom, size_t n)
Read a block of n bytes from EEPROM address pointer_eeprom to pointer_ram. For constant n <= 256 bytes a library function is used. For block sizes unknown
at compile time or block sizes > 256 an inline loop is expanded.
5.3.3.2
uint8_t eeprom_read_byte (const uint8_t ∗ addr)
Read one byte from EEPROM address addr.
5.3.3.3
uint16_t eeprom_read_word (const uint16_t ∗ addr)
Read one 16-bit word (little endian) from EEPROM address addr.
5.3.3.4 void eeprom_write_block (const void ∗ pointer_ram, void ∗ pointer_eeprom, size_t n)
Write a block of n bytes to EEPROM address pointer_eeprom from pointer_ram.
5.3.3.5
void eeprom_write_byte (uint8_t ∗ addr, uint8_t value)
Write a byte value to EEPROM address addr.
5.3.3.6
void eeprom_write_word (uint16_t ∗ addr, uint16_t value)
Write a word value to EEPROM address addr.
5.4 <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
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<avr/pgmspace.h>: Program Space String Utilities
5.5
18
register names common to all AVR devices are defined directly within <avr/io.h>,
but most of the details come from the respective include file.
Note that this file always includes
#include <avr/sfr_defs.h>
See <avr/sfr_defs.h>: Special function registers for the details.
Included are definitions of the IO register set and their respective bit values as specified
in the Atmel documentation. Note that Atmel is not very consistent in its 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
A constant describing the last on-chip RAM location.
• XRAMEND
A constant describing the last possible location in RAM. This is equal to RAMEND for devices that do not allow for external RAM.
• E2END
A constant describing the address of the last EEPROM cell.
• FLASHEND
A constant describing the last byte address in flash ROM.
• SPM_PAGESIZE
For devices with bootloader support, the flash pagesize (in bytes) to be used for
the SPM instruction.
5.5
<avr/pgmspace.h>: Program Space String Utilities
5.5.1
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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<avr/pgmspace.h>: Program Space String Utilities
5.5
19
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 64K 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.
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_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_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_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
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<avr/pgmspace.h>: Program Space String Utilities
5.5
20
Functions
•
•
•
•
•
•
•
•
•
•
•
•
•
void ∗ memcpy_P (void ∗, PGM_VOID_P, size_t)
int strcasecmp_P (const char ∗, PGM_P) __ATTR_PURE__
char ∗ strcat_P (char ∗, PGM_P)
int strcmp_P (const char ∗, PGM_P) __ATTR_PURE__
char ∗ strcpy_P (char ∗, PGM_P)
size_t strlcat_P (char ∗, PGM_P, size_t)
size_t strlcpy_P (char ∗, PGM_P, size_t)
size_t strlen_P (PGM_P) __ATTR_CONST__
int strncasecmp_P (const char ∗, PGM_P, size_t) __ATTR_PURE__
char ∗ strncat_P (char ∗, PGM_P, size_t)
int strncmp_P (const char ∗, PGM_P, size_t) __ATTR_PURE__
char ∗ strncpy_P (char ∗, PGM_P, size_t)
size_t strnlen_P (PGM_P, size_t) __ATTR_CONST__
5.5.2
5.5.2.1
Define Documentation
#define PGM_P const prog_char ∗
Used to declare a variable that is a pointer to a string in program space.
5.5.2.2
short)
#define pgm_read_byte(address_short) pgm_read_byte_near(address_-
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.
5.5.2.3 #define
t)(address_long))
pgm_read_byte_far(address_long)
__ELPM((uint32_-
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.
5.5.2.4 #define
t)(address_short))
pgm_read_byte_near(address_short)
__LPM((uint16_-
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.
Generated on Sat Nov 19 23:00:48 2005 for avr-libc by Doxygen
5.5
<avr/pgmspace.h>: Program Space String Utilities
5.5.2.5 #define
pgm_read_dword(address_short)
near(address_short)
21
pgm_read_dword_-
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.
5.5.2.6 #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.
5.5.2.7 #define
pgm_read_dword_near(address_short)
dword((uint16_t)(address_short))
__LPM_-
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.
5.5.2.8 #define
near(address_short)
pgm_read_word(address_short)
pgm_read_word_-
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.
5.5.2.9 #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.
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5.5
<avr/pgmspace.h>: Program Space String Utilities
22
5.5.2.10 #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.
5.5.2.11
#define PGM_VOID_P const prog_void ∗
Used to declare a generic pointer to an object in program space.
5.5.2.12
#define PROGMEM __ATTR_PROGMEM__
Attribute to use in order to declare an object being located in flash ROM.
5.5.2.13
#define PSTR(s) ((const PROGMEM char ∗)(s))
Used to declare a static pointer to a string in program space.
5.5.3
5.5.3.1
Typedef Documentation
prog_char
Type of a "char" object located in flash ROM.
5.5.3.2
prog_int16_t
Type of an "int16_t" object located in flash ROM.
5.5.3.3
prog_int32_t
Type of an "int32_t" object located in flash ROM.
5.5.3.4
prog_int64_t
Type of an "int64_t" object located in flash ROM.
5.5.3.5
prog_int8_t
Type of an "int8_t" object located in flash ROM.
5.5.3.6
prog_uchar
Type of an "unsigned char" object located in flash ROM.
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5.5
<avr/pgmspace.h>: Program Space String Utilities
5.5.3.7
23
prog_uint16_t
Type of an "uint16_t" object located in flash ROM.
5.5.3.8
prog_uint32_t
Type of an "uint32_t" object located in flash ROM.
5.5.3.9
prog_uint64_t
Type of an "uint64_t" object located in flash ROM.
5.5.3.10
prog_uint8_t
Type of an "uint8_t" object located in flash ROM.
5.5.3.11
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.
5.5.4
5.5.4.1
Function Documentation
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.
Returns:
The memcpy_P() function returns a pointer to dest.
5.5.4.2
int strcasecmp_P (const char ∗ s1, PGM_P s2)
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.
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5.5
<avr/pgmspace.h>: Program Space String Utilities
5.5.4.3
24
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).
Returns:
The strcat() function returns a pointer to the resulting string dest.
5.5.4.4
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.
5.5.4.5
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.
5.5.4.6
size_t strlcat_P (char ∗ dst, PGM_P, 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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5.5
<avr/pgmspace.h>: Program Space String Utilities
5.5.4.7
25
size_t strlcpy_P (char ∗ dst, PGM_P, 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).
Returns:
The strlcpy_P() function returns strlen(src). If retval >= siz, truncation occurred.
5.5.4.8
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.
5.5.4.9
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.
Returns:
The strcasecmp_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.
5.5.4.10
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.
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5.6
Additional notes from <avr/sfr_defs.h>
5.5.4.11
26
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.
5.5.4.12
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.
5.5.4.13
size_t strnlen_P (PGM_P src, size_t len)
Determine the length of a fixed-size string.
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.
5.6
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/iom128.h> to show how to define such macros:
#define
#define
#define
#define
PORTA
TCNT1
PORTF
TCNT3
_SFR_IO8(0x1b)
_SFR_IO16(0x2c)
_SFR_MEM8(0x61)
_SFR_MEM16(0x88)
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5.6
Additional notes from <avr/sfr_defs.h>
27
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/sleep.h>: Power Management and Sleep Modes
5.7
28
5.7 <avr/sleep.h>: Power Management and Sleep Modes
5.7.1
Detailed Description
#include <avr/sleep.h>
Use of the SLEEP instruction can allow your application to reduce it’s 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.
Sleep Modes
Note:
Some of these modes are not available on all devices. See the datasheet for target
device for the available sleep modes.
•
•
•
•
•
•
#define SLEEP_MODE_IDLE 0
#define SLEEP_MODE_ADC _BV(SM0)
#define SLEEP_MODE_PWR_DOWN _BV(SM1)
#define SLEEP_MODE_PWR_SAVE (_BV(SM0) | _BV(SM1))
#define SLEEP_MODE_STANDBY (_BV(SM1) | _BV(SM2))
#define SLEEP_MODE_EXT_STANDBY (_BV(SM0) | _BV(SM1) | _BV(SM2))
Sleep Functions
• void set_sleep_mode (uint8_t mode)
• void sleep_mode (void)
5.7.2
5.7.2.1
Define Documentation
#define SLEEP_MODE_ADC _BV(SM0)
ADC Noise Reduction Mode.
5.7.2.2 #define SLEEP_MODE_EXT_STANDBY (_BV(SM0) | _BV(SM1) | _BV(SM2))
Extended Standby Mode.
5.7.2.3
#define SLEEP_MODE_IDLE 0
Idle mode.
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<avr/version.h>: avr-libc version macros
5.8
5.7.2.4
29
#define SLEEP_MODE_PWR_DOWN _BV(SM1)
Power Down Mode.
#define SLEEP_MODE_PWR_SAVE (_BV(SM0) | _BV(SM1))
5.7.2.5
Power Save Mode.
#define SLEEP_MODE_STANDBY (_BV(SM1) | _BV(SM2))
5.7.2.6
Standby Mode.
5.7.3
Function Documentation
5.7.3.1
void set_sleep_mode (uint8_t mode)
Select a sleep mode.
5.7.3.2
void sleep_mode (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.
5.8 <avr/version.h>: avr-libc version macros
5.8.1
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.
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 backwardscompatible 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.
Defines
• #define __AVR_LIBC_VERSION_STRING__ "1.4.0"
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<avr/version.h>: avr-libc version macros
5.8
•
•
•
•
•
•
30
#define __AVR_LIBC_VERSION__ 10400UL
#define __AVR_LIBC_DATE_STRING__ "20051119"
#define __AVR_LIBC_DATE_ 20051119UL
#define __AVR_LIBC_MAJOR__ 1
#define __AVR_LIBC_MINOR__ 4
#define __AVR_LIBC_REVISION__ 0
5.8.2
5.8.2.1
Define Documentation
#define __AVR_LIBC_DATE_ 20051119UL
Numerical representation of the release date.
5.8.2.2
#define __AVR_LIBC_DATE_STRING__ "20051119"
String literal representation of the release date.
5.8.2.3
#define __AVR_LIBC_MAJOR__ 1
Library major version number.
5.8.2.4
#define __AVR_LIBC_MINOR__ 4
Library minor version number.
5.8.2.5
#define __AVR_LIBC_REVISION__ 0
Library revision number.
5.8.2.6
#define __AVR_LIBC_VERSION__ 10400UL
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.
5.8.2.7
#define __AVR_LIBC_VERSION_STRING__ "1.4.0"
String literal representation of the current library version.
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<avr/wdt.h>: Watchdog timer handling
5.9
31
5.9 <avr/wdt.h>: Watchdog timer handling
5.9.1
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;
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 clearing in particular the watchdog reset
flag before disabling the watchdog is required, according to the datasheet.
Defines
• #define wdt_reset() __asm__ __volatile__ ("wdr")
• #define wdt_disable()
• #define wdt_enable(timeout) _wdt_write(timeout)
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<avr/wdt.h>: Watchdog timer handling
5.9
•
•
•
•
•
•
•
•
•
•
32
#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
5.9.2
5.9.2.1
Define Documentation
#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.
5.9.2.2
#define wdt_enable(timeout) _wdt_write(timeout)
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.
5.9.2.3
#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.
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5.9
<avr/wdt.h>: Watchdog timer handling
5.9.2.4
33
#define WDTO_120MS 3
See WDT0_15MS
5.9.2.5
#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);
5.9.2.6
#define WDTO_1S 6
See WDT0_15MS
5.9.2.7
#define WDTO_250MS 4
See WDT0_15MS
5.9.2.8
#define WDTO_2S 7
See WDT0_15MS
5.9.2.9
#define WDTO_30MS 1
See WDT0_15MS
5.9.2.10
#define WDTO_4S 8
See WDT0_15MS Note: This is only available on the ATtiny2313, ATtiny25, ATtiny45, ATtiny85, ATmega48, ATmega88, ATmega164, ATmega168, ATmega324,
ATmega644, ATmega640, ATmega1280, ATmega1281, AT90PWM2, and the
AT90PWM3.
5.9.2.11
#define WDTO_500MS 5
See WDT0_15MS
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<compat/deprecated.h>: Deprecated items
5.10
5.9.2.12
34
#define WDTO_60MS 2
WDT0_15MS
5.9.2.13
#define WDTO_8S 9
See WDT0_15MS Note: This is only available on the ATtiny2313, ATtiny25, ATtiny45, ATtiny85, ATmega48, ATmega88, ATmega164, ATmega168, ATmega324,
ATmega644, ATmega640, ATmega1280, ATmega1281, AT90PWM2, and the
AT90PWM3.
5.10 <compat/deprecated.h>: Deprecated items
5.10.1
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/deprected.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.
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);
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.
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5.10
<compat/deprecated.h>: Deprecated items
35
• #define enable_external_int(mask) (__EICR = mask)
• #define INTERRUPT(signame)
• static __inline__ void timer_enable_int (unsigned char ints)
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.
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#define inp(port) (port)
#define outp(port, val) (port) = (val)
#define sbi(port, bit) (port) |= (1 << (bit))
#define cbi(port, bit) (port) &= ∼(1 << (bit))
5.10.2
5.10.2.1
Define Documentation
#define cbi(port, bit) (port) &= ∼(1 << (bit))
Deprecated
Clear bit in IO port port.
5.10.2.2
#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.
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5.10
<compat/deprecated.h>: Deprecated items
5.10.2.3
36
#define inp(port) (port)
Deprecated
Read a value from an IO port port.
5.10.2.4
#define INTERRUPT(signame)
Value:
void signame (void) __attribute__ ((interrupt));
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.
5.10.2.5
#define outp(port, val) (port) = (val)
Deprecated
Write val to IO port port.
5.10.2.6
#define sbi(port, bit) (port) |= (1 << (bit))
Deprecated
Set bit in IO port port.
5.10.3
Function Documentation
5.10.3.1 static
[static]
__inline__
void
timer_enable_int
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(unsigned
char
ints)
5.11
<compat/ina90.h>: Compatibility with IAR EWB 3.x
37
Deprecated
This function modifies the timsk register. The value you pass via ints is device
specific.
5.11 <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.
5.12 <ctype.h>: Character Operations
5.12.1
Detailed Description
These functions perform various operations on characters.
#include <ctype.h>
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.)
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int isalnum (int __c) __ATTR_CONST__
int isalpha (int __c) __ATTR_CONST__
int isascii (int __c) __ATTR_CONST__
int isblank (int __c) __ATTR_CONST__
int iscntrl (int __c) __ATTR_CONST__
int isdigit (int __c) __ATTR_CONST__
int isgraph (int __c) __ATTR_CONST__
int islower (int __c) __ATTR_CONST__
int isprint (int __c) __ATTR_CONST__
int ispunct (int __c) __ATTR_CONST__
int isspace (int __c) __ATTR_CONST__
int isupper (int __c) __ATTR_CONST__
int isxdigit (int __c) __ATTR_CONST__
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<ctype.h>: Character Operations
38
Character convertion routines
If c is not an unsigned char value, or EOF, the behaviour of these functions is undefined.
• int toascii (int __c) __ATTR_CONST__
• int tolower (int __c) __ATTR_CONST__
• int toupper (int __c) __ATTR_CONST__
5.12.2
5.12.2.1
Function Documentation
int isalnum (int __c)
Checks for an alphanumeric character.
isdigit(c)).
5.12.2.2
int isalpha (int __c)
Checks for an alphabetic character.
islower(c)).
5.12.2.3
It is equivalent to (isalpha(c) ||
It is equivalent to (isupper(c) ||
int isascii (int __c)
Checks whether c is a 7-bit unsigned char value that fits into the ASCII character set.
5.12.2.4
int isblank (int __c)
Checks for a blank character, that is, a space or a tab.
5.12.2.5
int iscntrl (int __c)
Checks for a control character.
5.12.2.6
int isdigit (int __c)
Checks for a digit (0 through 9).
5.12.2.7
int isgraph (int __c)
Checks for any printable character except space.
5.12.2.8
int islower (int __c)
Checks for a lower-case character.
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5.13
<errno.h>: System Errors
5.12.2.9
39
int isprint (int __c)
Checks for any printable character including space.
5.12.2.10
int ispunct (int __c)
Checks for any printable character which is not a space or an alphanumeric character.
5.12.2.11
int isspace (int __c)
Checks for white-space characters. For the avr-libc library, these are: space, formfeed (’\f’), newline (’\n’), carriage return (’\r’), horizontal tab (’\t’), and vertical tab
(’\v’).
5.12.2.12
int isupper (int __c)
Checks for an uppercase letter.
5.12.2.13
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.
5.12.2.14
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.
5.12.2.15
int tolower (int __c)
Converts the letter c to lower case, if possible.
5.12.2.16
int toupper (int __c)
Converts the letter c to upper case, if possible.
5.13 <errno.h>: System Errors
5.13.1
Detailed Description
#include <errno.h>
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5.14
<inttypes.h>: Integer Type conversions
40
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.
Defines
• #define EDOM 33
• #define ERANGE 34
5.13.2
5.13.2.1
Define Documentation
#define EDOM 33
Domain error.
5.13.2.2
#define ERANGE 34
Range error.
5.14 <inttypes.h>: Integer Type conversions
5.14.1
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:
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<inttypes.h>: Integer Type conversions
5.14
41
#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);
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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#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"
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<inttypes.h>: Integer Type conversions
#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"
#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
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5.14
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<inttypes.h>: Integer Type conversions
#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
Far pointers for memory access >64K
• typedef int32_t int_farptr_t
• typedef uint32_t uint_farptr_t
5.14.2
5.14.2.1
Define Documentation
#define PRId16 "d"
decimal printf format for int16_t
5.14.2.2
#define PRId32 "ld"
decimal printf format for int32_t
5.14.2.3
#define PRId8 "d"
decimal printf format for int8_t
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5.14
<inttypes.h>: Integer Type conversions
5.14.2.4
#define PRIdFAST16 "d"
decimal printf format for int_fast16_t
5.14.2.5
#define PRIdFAST32 "ld"
decimal printf format for int_fast32_t
5.14.2.6
#define PRIdFAST8 "d"
decimal printf format for int_fast8_t
5.14.2.7
#define PRIdLEAST16 "d"
decimal printf format for int_least16_t
5.14.2.8
#define PRIdLEAST32 "ld"
decimal printf format for int_least32_t
5.14.2.9
#define PRIdLEAST8 "d"
decimal printf format for int_least8_t
5.14.2.10
#define PRIdPTR PRId16
decimal printf format for intptr_t
5.14.2.11
#define PRIi16 "i"
integer printf format for int16_t
5.14.2.12
#define PRIi32 "li"
integer printf format for int32_t
5.14.2.13
#define PRIi8 "i"
integer printf format for int8_t
5.14.2.14
#define PRIiFAST16 "i"
integer printf format for int_fast16_t
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5.14
<inttypes.h>: Integer Type conversions
5.14.2.15
#define PRIiFAST32 "li"
integer printf format for int_fast32_t
5.14.2.16
#define PRIiFAST8 "i"
integer printf format for int_fast8_t
5.14.2.17
#define PRIiLEAST16 "i"
integer printf format for int_least16_t
5.14.2.18
#define PRIiLEAST32 "li"
integer printf format for int_least32_t
5.14.2.19
#define PRIiLEAST8 "i"
integer printf format for int_least8_t
5.14.2.20
#define PRIiPTR PRIi16
integer printf format for intptr_t
5.14.2.21
#define PRIo16 "o"
octal printf format for uint16_t
5.14.2.22
#define PRIo32 "lo"
octal printf format for uint32_t
5.14.2.23
#define PRIo8 "o"
octal printf format for uint8_t
5.14.2.24
#define PRIoFAST16 "o"
octal printf format for uint_fast16_t
5.14.2.25
#define PRIoFAST32 "lo"
octal printf format for uint_fast32_t
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5.14
<inttypes.h>: Integer Type conversions
5.14.2.26
#define PRIoFAST8 "o"
octal printf format for uint_fast8_t
5.14.2.27
#define PRIoLEAST16 "o"
octal printf format for uint_least16_t
5.14.2.28
#define PRIoLEAST32 "lo"
octal printf format for uint_least32_t
5.14.2.29
#define PRIoLEAST8 "o"
octal printf format for uint_least8_t
5.14.2.30
#define PRIoPTR PRIo16
octal printf format for uintptr_t
5.14.2.31
#define PRIu16 "u"
decimal printf format for uint16_t
5.14.2.32
#define PRIu32 "lu"
decimal printf format for uint32_t
5.14.2.33
#define PRIu8 "u"
decimal printf format for uint8_t
5.14.2.34
#define PRIuFAST16 "u"
decimal printf format for uint_fast16_t
5.14.2.35
#define PRIuFAST32 "lu"
decimal printf format for uint_fast32_t
5.14.2.36
#define PRIuFAST8 "u"
decimal printf format for uint_fast8_t
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5.14
<inttypes.h>: Integer Type conversions
5.14.2.37
#define PRIuLEAST16 "u"
decimal printf format for uint_least16_t
5.14.2.38
#define PRIuLEAST32 "lu"
decimal printf format for uint_least32_t
5.14.2.39
#define PRIuLEAST8 "u"
decimal printf format for uint_least8_t
5.14.2.40
#define PRIuPTR PRIu16
decimal printf format for uintptr_t
5.14.2.41
#define PRIX16 "X"
uppercase hexadecimal printf format for uint16_t
5.14.2.42
#define PRIx16 "x"
hexadecimal printf format for uint16_t
5.14.2.43
#define PRIX32 "lX"
uppercase hexadecimal printf format for uint32_t
5.14.2.44
#define PRIx32 "lx"
hexadecimal printf format for uint32_t
5.14.2.45
#define PRIX8 "X"
uppercase hexadecimal printf format for uint8_t
5.14.2.46
#define PRIx8 "x"
hexadecimal printf format for uint8_t
5.14.2.47
#define PRIXFAST16 "X"
uppercase hexadecimal printf format for uint_fast16_t
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5.14
<inttypes.h>: Integer Type conversions
5.14.2.48
#define PRIxFAST16 "x"
hexadecimal printf format for uint_fast16_t
5.14.2.49
#define PRIXFAST32 "lX"
uppercase hexadecimal printf format for uint_fast32_t
5.14.2.50
#define PRIxFAST32 "lx"
hexadecimal printf format for uint_fast32_t
5.14.2.51
#define PRIXFAST8 "X"
uppercase hexadecimal printf format for uint_fast8_t
5.14.2.52
#define PRIxFAST8 "x"
hexadecimal printf format for uint_fast8_t
5.14.2.53
#define PRIXLEAST16 "X"
uppercase hexadecimal printf format for uint_least16_t
5.14.2.54
#define PRIxLEAST16 "x"
hexadecimal printf format for uint_least16_t
5.14.2.55
#define PRIXLEAST32 "lX"
uppercase hexadecimal printf format for uint_least32_t
5.14.2.56
#define PRIxLEAST32 "lx"
hexadecimal printf format for uint_least32_t
5.14.2.57
#define PRIXLEAST8 "X"
uppercase hexadecimal printf format for uint_least8_t
5.14.2.58
#define PRIxLEAST8 "x"
hexadecimal printf format for uint_least8_t
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5.14
<inttypes.h>: Integer Type conversions
5.14.2.59
#define PRIXPTR PRIX16
uppercase hexadecimal printf format for uintptr_t
5.14.2.60
#define PRIxPTR PRIx16
hexadecimal printf format for uintptr_t
5.14.2.61
#define SCNd16 "d"
decimal scanf format for int16_t
5.14.2.62
#define SCNd32 "ld"
decimal scanf format for int32_t
5.14.2.63
#define SCNdFAST16 "d"
decimal scanf format for int_fast16_t
5.14.2.64
#define SCNdFAST32 "ld"
decimal scanf format for int_fast32_t
5.14.2.65
#define SCNdLEAST16 "d"
decimal scanf format for int_least16_t
5.14.2.66
#define SCNdLEAST32 "ld"
decimal scanf format for int_least32_t
5.14.2.67
#define SCNdPTR SCNd16
decimal scanf format for intptr_t
5.14.2.68
#define SCNi16 "i"
generic-integer scanf format for int16_t
5.14.2.69
#define SCNi32 "li"
generic-integer scanf format for int32_t
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<inttypes.h>: Integer Type conversions
5.14.2.70
#define SCNiFAST16 "i"
generic-integer scanf format for int_fast16_t
5.14.2.71
#define SCNiFAST32 "li"
generic-integer scanf format for int_fast32_t
5.14.2.72
#define SCNiLEAST16 "i"
generic-integer scanf format for int_least16_t
5.14.2.73
#define SCNiLEAST32 "li"
generic-integer scanf format for int_least32_t
5.14.2.74
#define SCNiPTR SCNi16
generic-integer scanf format for intptr_t
5.14.2.75
#define SCNo16 "o"
octal scanf format for uint16_t
5.14.2.76
#define SCNo32 "lo"
octal scanf format for uint32_t
5.14.2.77
#define SCNoFAST16 "o"
octal scanf format for uint_fast16_t
5.14.2.78
#define SCNoFAST32 "lo"
octal scanf format for uint_fast32_t
5.14.2.79
#define SCNoLEAST16 "o"
octal scanf format for uint_least16_t
5.14.2.80
#define SCNoLEAST32 "lo"
octal scanf format for uint_least32_t
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<inttypes.h>: Integer Type conversions
5.14.2.81
#define SCNoPTR SCNo16
octal scanf format for uintptr_t
5.14.2.82
#define SCNu16 "u"
decimal scanf format for uint16_t
5.14.2.83
#define SCNu32 "lu"
decimal scanf format for uint32_t
5.14.2.84
#define SCNuFAST16 "u"
decimal scanf format for uint_fast16_t
5.14.2.85
#define SCNuFAST32 "lu"
decimal scanf format for uint_fast32_t
5.14.2.86
#define SCNuLEAST16 "u"
decimal scanf format for uint_least16_t
5.14.2.87
#define SCNuLEAST32 "lu"
decimal scanf format for uint_least32_t
5.14.2.88
#define SCNuPTR SCNu16
decimal scanf format for uintptr_t
5.14.2.89
#define SCNx16 "x"
hexadecimal scanf format for uint16_t
5.14.2.90
#define SCNx32 "lx"
hexadecimal scanf format for uint32_t
5.14.2.91
#define SCNxFAST16 "x"
hexadecimal scanf format for uint_fast16_t
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<math.h>: Mathematics
5.14.2.92
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#define SCNxFAST32 "lx"
hexadecimal scanf format for uint_fast32_t
5.14.2.93
#define SCNxLEAST16 "x"
hexadecimal scanf format for uint_least16_t
5.14.2.94
#define SCNxLEAST32 "lx"
hexadecimal scanf format for uint_least32_t
5.14.2.95
#define SCNxPTR SCNx16
hexadecimal scanf format for uintptr_t
5.14.3
5.14.3.1
Typedef Documentation
typedef int32_t int_farptr_t
signed integer type that can hold a pointer > 64 KB
5.14.3.2
typedef uint32_t uint_farptr_t
unsigned integer type that can hold a pointer > 64 KB
5.15 <math.h>: Mathematics
5.15.1
Detailed Description
#include <math.h>
This header file declares basic mathematics constants and functions.
Note:
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.
Defines
• #define M_PI 3.141592653589793238462643
• #define M_SQRT2 1.4142135623730950488016887
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5.15
<math.h>: Mathematics
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Functions
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double cos (double __x) __ATTR_CONST__
double fabs (double __x) __ATTR_CONST__
double fmod (double __x, double __y) __ATTR_CONST__
double modf (double __value, double ∗__iptr)
double sin (double __x) __ATTR_CONST__
double sqrt (double __x) __ATTR_CONST__
double tan (double __x) __ATTR_CONST__
double floor (double __x) __ATTR_CONST__
double ceil (double __x) __ATTR_CONST__
double frexp (double __value, int ∗__exp)
double ldexp (double __x, int __exp) __ATTR_CONST__
double exp (double __x) __ATTR_CONST__
double cosh (double __x) __ATTR_CONST__
double sinh (double __x) __ATTR_CONST__
double tanh (double __x) __ATTR_CONST__
double acos (double __x) __ATTR_CONST__
double asin (double __x) __ATTR_CONST__
double atan (double __x) __ATTR_CONST__
double atan2 (double __y, double __x) __ATTR_CONST__
double log (double __x) __ATTR_CONST__
double log10 (double __x) __ATTR_CONST__
double pow (double __x, double __y) __ATTR_CONST__
int isnan (double __x) __ATTR_CONST__
int isinf (double __x) __ATTR_CONST__
double square (double __x) __ATTR_CONST__
5.15.2
5.15.2.1
Define Documentation
#define M_PI 3.141592653589793238462643
The constant pi.
5.15.2.2
#define M_SQRT2 1.4142135623730950488016887
The square root of 2.
5.15.3
5.15.3.1
Function Documentation
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].
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5.15
<math.h>: Mathematics
5.15.3.2
54
double asin (double __x)
The asin() function computes the principal value of the arc sine of x. The returned
value is in the range [0, pi] radians. A domain error occurs for arguments not in the
range [-1, +1].
5.15.3.3
double atan (double __x)
The atan() function computes the principal value of the arc tangent of x. The returned
value is in the range [0, pi] radians. A domain error occurs for arguments not in the
range [-1, +1].
5.15.3.4
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. If both x and y are zero, the global variable
errno is set to EDOM.
5.15.3.5
double ceil (double __x)
The ceil() function returns the smallest integral value greater than or equal to x, expressed as a floating-point number.
5.15.3.6
double cos (double __x)
The cos() function returns the cosine of x, measured in radians.
5.15.3.7
double cosh (double __x)
The cosh() function returns the hyperbolic cosine of x.
5.15.3.8
double exp (double __x)
The exp() function returns the exponential value of x.
5.15.3.9
double fabs (double __x)
The fabs() function computes the absolute value of a floating-point number x.
5.15.3.10
double floor (double __x)
The floor() function returns the largest integral value less than or equal to x, expressed
as a floating-point number.
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5.15
<math.h>: Mathematics
5.15.3.11
55
double fmod (double __x, double __y)
The function fmod() returns the floating-point remainder of x / y.
5.15.3.12
double frexp (double __value, int ∗ __exp)
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 exp.
The frexp() function returns the value x, such that x is a double with magnitude in the
interval [1/2, 1) or zero, and value equals x times 2 raised to the power ∗exp. If
value is zero, both parts of the result are zero.
5.15.3.13
int isinf (double __x)
The function isinf() returns 1 if the argument x is either positive or negative infinity,
otherwise 0.
5.15.3.14
int isnan (double __x)
The function isnan() returns 1 if the argument x represents a "not-a-number" (NaN)
object, otherwise 0.
5.15.3.15
double ldexp (double __x, int __exp)
The ldexp() function multiplies a floating-point number by an integral power of 2.
The ldexp() function returns the value of x times 2 raised to the power exp.
If the resultant value would cause an overflow, the global variable errno is set to
ERANGE, and the value NaN is returned.
5.15.3.16
double log (double __x)
The log() function returns the natural logarithm of argument x.
If the argument is less than or equal 0, a domain error will occur.
5.15.3.17
double log10 (double __x)
The log10() function returns the logarithm of argument x to base 10.
If the argument is less than or equal 0, a domain error will occur.
5.15.3.18
double modf (double __value, double ∗ __iptr)
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5.16
<setjmp.h>: Non-local goto
56
The modf() function breaks the argument value 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 value.
5.15.3.19
double pow (double __x, double __y)
The function pow() returns the value of x to the exponent y.
5.15.3.20
double sin (double __x)
The sin() function returns the sine of x, measured in radians.
5.15.3.21
double sinh (double __x)
The sinh() function returns the hyperbolic sine of x.
5.15.3.22
double sqrt (double __x)
The sqrt() function returns the non-negative square root of x.
5.15.3.23
double square (double __x)
The function square() returns x ∗ x.
Note:
This function does not belong to the C standard definition.
5.15.3.24
double tan (double __x)
The tan() function returns the tangent of x, measured in radians.
5.15.3.25
double tanh (double __x)
The tanh() function returns the hyperbolic tangent of x.
5.16 <setjmp.h>: Non-local goto
5.16.1
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)
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<setjmp.h>: Non-local goto
5.16
57
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:
#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);
}
}
Functions
• int setjmp (jmp_buf __jmpb)
• void longjmp (jmp_buf __jmpb, int __ret) __ATTR_NORETURN__
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<stdint.h>: Standard Integer Types
5.17
5.16.2
5.16.2.1
58
Function Documentation
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().
Returns:
This function never returns.
5.16.2.2
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.
5.17 <stdint.h>: Standard Integer Types
5.17.1
Detailed Description
#include <stdint.h>
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5.17
<stdint.h>: Standard Integer Types
59
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.
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
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5.17
<stdint.h>: Standard Integer Types
60
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
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
•
•
•
•
•
#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
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5.17
•
•
•
•
•
•
•
•
•
•
<stdint.h>: Standard Integer Types
#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)
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.
• 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
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61
5.17
<stdint.h>: Standard Integer Types
62
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
5.17.2
5.17.2.1
Define Documentation
#define INT16_C(value) value
define a constant of type int16_t
5.17.2.2
#define INT16_MAX 0x7fff
largest positive value an int16_t can hold.
5.17.2.3
#define INT16_MIN (-INT16_MAX - 1)
smallest negative value an int16_t can hold.
5.17.2.4
#define INT32_C(value) __CONCAT(value, L)
define a constant of type int32_t
5.17.2.5
#define INT32_MAX 0x7fffffffL
largest positive value an int32_t can hold.
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5.17
<stdint.h>: Standard Integer Types
5.17.2.6
#define INT32_MIN (-INT32_MAX - 1L)
smallest negative value an int32_t can hold.
5.17.2.7
#define INT64_C(value) __CONCAT(value, LL)
define a constant of type int64_t
5.17.2.8
#define INT64_MAX 0x7fffffffffffffffLL
largest positive value an int64_t can hold.
5.17.2.9
#define INT64_MIN (-INT64_MAX - 1LL)
smallest negative value an int64_t can hold.
5.17.2.10
#define INT8_C(value) ((int8_t) value)
define a constant of type int8_t
5.17.2.11
#define INT8_MAX 0x7f
largest positive value an int8_t can hold.
5.17.2.12
#define INT8_MIN (-INT8_MAX - 1)
smallest negative value an int8_t can hold.
5.17.2.13
#define INT_FAST16_MAX INT16_MAX
largest positive value an int_fast16_t can hold.
5.17.2.14
#define INT_FAST16_MIN INT16_MIN
smallest negative value an int_fast16_t can hold.
5.17.2.15
#define INT_FAST32_MAX INT32_MAX
largest positive value an int_fast32_t can hold.
5.17.2.16
#define INT_FAST32_MIN INT32_MIN
smallest negative value an int_fast32_t can hold.
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5.17
<stdint.h>: Standard Integer Types
5.17.2.17
#define INT_FAST64_MAX INT64_MAX
largest positive value an int_fast64_t can hold.
5.17.2.18
#define INT_FAST64_MIN INT64_MIN
smallest negative value an int_fast64_t can hold.
5.17.2.19
#define INT_FAST8_MAX INT8_MAX
largest positive value an int_fast8_t can hold.
5.17.2.20
#define INT_FAST8_MIN INT8_MIN
smallest negative value an int_fast8_t can hold.
5.17.2.21
#define INT_LEAST16_MAX INT16_MAX
largest positive value an int_least16_t can hold.
5.17.2.22
#define INT_LEAST16_MIN INT16_MIN
smallest negative value an int_least16_t can hold.
5.17.2.23
#define INT_LEAST32_MAX INT32_MAX
largest positive value an int_least32_t can hold.
5.17.2.24
#define INT_LEAST32_MIN INT32_MIN
smallest negative value an int_least32_t can hold.
5.17.2.25
#define INT_LEAST64_MAX INT64_MAX
largest positive value an int_least64_t can hold.
5.17.2.26
#define INT_LEAST64_MIN INT64_MIN
smallest negative value an int_least64_t can hold.
5.17.2.27
#define INT_LEAST8_MAX INT8_MAX
largest positive value an int_least8_t can hold.
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5.17
<stdint.h>: Standard Integer Types
5.17.2.28
#define INT_LEAST8_MIN INT8_MIN
smallest negative value an int_least8_t can hold.
5.17.2.29
#define INTMAX_C(value) __CONCAT(value, LL)
define a constant of type intmax_t
5.17.2.30
#define INTMAX_MAX INT64_MAX
largest positive value an intmax_t can hold.
5.17.2.31
#define INTMAX_MIN INT64_MIN
smallest negative value an intmax_t can hold.
5.17.2.32
#define INTPTR_MAX INT16_MAX
largest positive value an intptr_t can hold.
5.17.2.33
#define INTPTR_MIN INT16_MIN
smallest negative value an intptr_t can hold.
5.17.2.34
#define PTRDIFF_MAX INT16_MAX
largest positive value a ptrdiff_t can hold.
5.17.2.35
#define PTRDIFF_MIN INT16_MIN
smallest negative value a ptrdiff_t can hold.
5.17.2.36
#define SIG_ATOMIC_MAX INT8_MAX
largest positive value a sig_atomic_t can hold.
5.17.2.37
#define SIG_ATOMIC_MIN INT8_MIN
smallest negative value a sig_atomic_t can hold.
5.17.2.38
#define SIZE_MAX (__CONCAT(INT16_MAX, U))
largest value a size_t can hold.
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5.17
<stdint.h>: Standard Integer Types
5.17.2.39
66
#define UINT16_C(value) __CONCAT(value, U)
define a constant of type uint16_t
5.17.2.40
#define UINT16_MAX (__CONCAT(INT16_MAX, U) ∗ 2U + 1U)
largest value an uint16_t can hold.
5.17.2.41
#define UINT32_C(value) __CONCAT(value, UL)
define a constant of type uint32_t
5.17.2.42
#define UINT32_MAX (__CONCAT(INT32_MAX, U) ∗ 2UL + 1UL)
largest value an uint32_t can hold.
5.17.2.43
#define UINT64_C(value) __CONCAT(value, ULL)
define a constant of type uint64_t
5.17.2.44
1ULL)
#define UINT64_MAX (__CONCAT(INT64_MAX, U) ∗ 2ULL +
largest value an uint64_t can hold.
5.17.2.45
#define UINT8_C(value) ((uint8_t) __CONCAT(value, U))
define a constant of type uint8_t
5.17.2.46
#define UINT8_MAX (__CONCAT(INT8_MAX, U) ∗ 2U + 1U)
largest value an uint8_t can hold.
5.17.2.47
#define UINT_FAST16_MAX UINT16_MAX
largest value an uint_fast16_t can hold.
5.17.2.48
#define UINT_FAST32_MAX UINT32_MAX
largest value an uint_fast32_t can hold.
5.17.2.49
#define UINT_FAST64_MAX UINT64_MAX
largest value an uint_fast64_t can hold.
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5.17
<stdint.h>: Standard Integer Types
5.17.2.50
#define UINT_FAST8_MAX UINT8_MAX
largest value an uint_fast8_t can hold.
5.17.2.51
#define UINT_LEAST16_MAX UINT16_MAX
largest value an uint_least16_t can hold.
5.17.2.52
#define UINT_LEAST32_MAX UINT32_MAX
largest value an uint_least32_t can hold.
5.17.2.53
#define UINT_LEAST64_MAX UINT64_MAX
largest value an uint_least64_t can hold.
5.17.2.54
#define UINT_LEAST8_MAX UINT8_MAX
largest value an uint_least8_t can hold.
5.17.2.55
#define UINTMAX_C(value) __CONCAT(value, ULL)
define a constant of type uintmax_t
5.17.2.56
#define UINTMAX_MAX UINT64_MAX
largest value an uintmax_t can hold.
5.17.2.57
#define UINTPTR_MAX UINT16_MAX
largest value an uintptr_t can hold.
5.17.3
5.17.3.1
Typedef Documentation
typedef signed int int16_t
16-bit signed type.
5.17.3.2
typedef signed long int int32_t
32-bit signed type.
5.17.3.3
typedef signed long long int int64_t
64-bit signed type.
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5.17
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5.17.3.4
typedef signed char int8_t
8-bit signed type.
5.17.3.5
typedef int16_t int_fast16_t
fastest signed int with at least 16 bits.
5.17.3.6
typedef int32_t int_fast32_t
fastest signed int with at least 32 bits.
5.17.3.7
typedef int64_t int_fast64_t
fastest signed int with at least 64 bits.
5.17.3.8
typedef int8_t int_fast8_t
fastest signed int with at least 8 bits.
5.17.3.9
typedef int16_t int_least16_t
signed int with at least 16 bits.
5.17.3.10
typedef int32_t int_least32_t
signed int with at least 32 bits.
5.17.3.11
typedef int64_t int_least64_t
signed int with at least 64 bits.
5.17.3.12
typedef int8_t int_least8_t
signed int with at least 8 bits.
5.17.3.13
typedef int64_t intmax_t
largest signed int available.
5.17.3.14
typedef int16_t intptr_t
Signed pointer compatible type.
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5.17
<stdint.h>: Standard Integer Types
5.17.3.15
typedef unsigned int uint16_t
16-bit unsigned type.
5.17.3.16
typedef unsigned long int uint32_t
32-bit unsigned type.
5.17.3.17
typedef unsigned long long int uint64_t
64-bit unsigned type.
5.17.3.18
typedef unsigned char uint8_t
8-bit unsigned type.
5.17.3.19
typedef uint16_t uint_fast16_t
fastest unsigned int with at least 16 bits.
5.17.3.20
typedef uint32_t uint_fast32_t
fastest unsigned int with at least 32 bits.
5.17.3.21
typedef uint64_t uint_fast64_t
fastest unsigned int with at least 64 bits.
5.17.3.22
typedef uint8_t uint_fast8_t
fastest unsigned int with at least 8 bits.
5.17.3.23
typedef uint16_t uint_least16_t
unsigned int with at least 16 bits.
5.17.3.24
typedef uint32_t uint_least32_t
unsigned int with at least 32 bits.
5.17.3.25
typedef uint64_t uint_least64_t
unsigned int with at least 64 bits.
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5.18
<stdio.h>: Standard IO facilities
5.17.3.26
70
typedef uint8_t uint_least8_t
unsigned int with at least 8 bits.
5.17.3.27
typedef uint64_t uintmax_t
largest unsigned int available.
5.17.3.28
typedef uint16_t uintptr_t
Unsigned pointer compatible type.
5.18 <stdio.h>: Standard IO facilities
5.18.1
Detailed Description
#include <stdio.h>
Introduction to the Standard IO facilities 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.
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.
Tunable options for code size vs. feature set 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.
Outline of the chosen API 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,
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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).
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
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
String Utilities) becomes very handy for declaring these format strings.
Running stdio without malloc() By default, fdevopen() as well as the floating-point
versions of the printf and scanf family require malloc(). As this is often not desired in
the limited environment of a microcontroller, an alternative option is provided to run
completely without malloc().
The macro fdev_setup_stream() is provided to prepare a user-supplied FILE buffer for
operation with stdio. If floating-point operation is desired, a user-supplied buffer can as
well be passed for the internal buffering for the floating-point numbers (and processing
of %[ scanf data).
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72
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’);
loop_until_bit_is_set(UCSRA, UDRE);
UDR = c;
return 0;
}
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
function-like 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:
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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, 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 will also save some execution time.
Defines
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#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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5.18.2
5.18.2.1
75
Define Documentation
#define _FDEV_EOF (-2)
Return code for an end-of-file condition during device read.
To be used in the get function of fdevopen().
5.18.2.2
#define _FDEV_ERR (-1)
Return code for an error condition during device read.
To be used in the get function of fdevopen().
5.18.2.3
#define _FDEV_SETUP_READ __SRD
fdev_setup_stream() with read intent
5.18.2.4
#define _FDEV_SETUP_RW (__SRD|__SWR)
fdev_setup_stream() with read/write intent
5.18.2.5
#define _FDEV_SETUP_WRITE __SWR
fdev_setup_stream() with write intent
5.18.2.6
#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.
5.18.2.7
#define fdev_close()
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.)
5.18.2.8
#define fdev_get_udata(stream) ((stream) → udata)
This macro retrieves a pointer to user defined data from a FILE stream object.
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76
#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.
5.18.2.10
#define FDEV_SETUP_STREAM(put, get, rwflag)
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().
5.18.2.11
#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().
5.18.2.12
#define FILE struct __file
FILE is the opaque structure that is passed around between the various standard IO
functions.
5.18.2.13
#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.
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5.18.2.14
77
#define getchar(void) fgetc(stdin)
The macro getchar reads a character from stdin. Return values and error handling
is identical to fgetc().
5.18.2.15
#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.
5.18.2.16
#define putchar(__c) fputc(__c, stdout)
The macro putchar sends character c to stdout.
5.18.2.17
#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).
5.18.2.18
#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.
5.18.2.19
#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.
5.18.3
5.18.3.1
Function Documentation
void clearerr (FILE ∗ __stream)
Clear the error and end-of-file flags of stream.
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78
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).
5.18.3.3
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.
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.
5.18.3.4
int feof (FILE ∗ __stream)
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Test the end-of-file flag of stream. This flag can only be cleared by a call to clearerr().
5.18.3.5
int ferror (FILE ∗ __stream)
Test the error flag of stream. This flag can only be cleared by a call to clearerr().
5.18.3.6
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.
5.18.3.7
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.
5.18.3.8
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.
5.18.3.9
int fprintf (FILE ∗ __stream, const char ∗ __fmt, ...)
The function fprintf performs formatted output to stream. See vfprintf()
for details.
5.18.3.10
int fprintf_P (FILE ∗ __stream, const char ∗ __fmt, ...)
Variant of fprintf() that uses a fmt string that resides in program memory.
5.18.3.11
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.
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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.
5.18.3.13
int fputs_P (const char ∗ __str, FILE ∗ __stream)
Variant of fputs() where str resides in program memory.
5.18.3.14
stream)
size_t fread (void ∗ __ptr, size_t __size, size_t __nmemb, FILE ∗ __-
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.
5.18.3.15
int fscanf (FILE ∗ __stream, const char ∗ __fmt, ...)
The function fscanf performs formatted input, reading the input data from stream.
See vfscanf() for details.
5.18.3.16
int fscanf_P (FILE ∗ __stream, const char ∗ __fmt, ...)
Variant of fscanf() using a fmt string in program memory.
5.18.3.17 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.
5.18.3.18
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.
5.18.3.19
int printf (const char ∗ __fmt, ...)
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The function printf performs formatted output to stream stderr.
vfprintf() for details.
5.18.3.20
81
See
int printf_P (const char ∗ __fmt, ...)
Variant of printf() that uses a fmt string that resides in program memory.
5.18.3.21
int puts (const char ∗ __str)
Write the string pointed to by str, and a trailing newline character, to stdout.
5.18.3.22
int puts_P (const char ∗ __str)
Variant of puts() where str resides in program memory.
5.18.3.23
int scanf (const char ∗ __fmt, ...)
The function scanf performs formatted input from stream stdin.
See vfscanf() for details.
5.18.3.24
int scanf_P (const char ∗ __fmt, ...)
Variant of scanf() where fmt resides in program memory.
5.18.3.25
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.
5.18.3.26
int snprintf_P (char ∗ __s, size_t __n, const char ∗ __fmt, ...)
Variant of snprintf() that uses a fmt string that resides in program memory.
5.18.3.27
int sprintf (char ∗ __s, const char ∗ __fmt, ...)
Variant of printf() that sends the formatted characters to string s.
5.18.3.28
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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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.
5.18.3.30
int sscanf_P (const char ∗ __buf, const char ∗ __fmt, ...)
Variant of sscanf() using a fmt string in program memory.
5.18.3.31
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.
5.18.3.32
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).
For x and X conversions, a non-zero result has the string ‘0x’ (or ‘0X’ for
X conversions) prepended to it.
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– 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-adjust173 ment 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 length modifier, that specifies that the argument for the d, i, o, u,
x, or X conversion is a "long int" rather than 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.
• 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.
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• A is written. No argument is converted. The complete conversion specification
is "%%".
• eE The double argument is rounded and converted in the format
"[-]d.ddde177dd" 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 none of the additional options that 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
If the full functionality including the floating point conversions is required, the following options should be used:
-Wl,-u,vfprintf -lprintf_flt -lm
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Limitations:
• The specified width and precision can be at most 127.
• For floating-point conversions, trailing digits will be lost if a number close to
DBL_MAX is converted with a precision > 0.
5.18.3.33
int vfprintf_P (FILE ∗ __stream, const char ∗ __fmt, va_list __ap)
Variant of vfprintf() that uses a fmt string that resides in program memory.
5.18.3.34
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,
• the character h indicating that the argument is a pointer to short int (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 127 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.
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• 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, 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.
• [ 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.
• p Matches a pointer value (as printed by p in printf()); the next pointer must be
a pointer to void.
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• 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 %[ conversion. These conversions will be available in the extended version provided by the library libscanf_flt.a. Note that either of these
conversions requires the availability of a buffer that needs to be obtained at run-time
using malloc(). If this buffer cannot be obtained, the operation is aborted, returning the
value EOF. 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. 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
In addition to the restrictions of the standard version, this version implements no field
width specification, no conversion assignment suppression flag (∗), no n specification,
and no general format character matching at all. All characters in fmt that do not
comprise a conversion specification will simply be ignored, including white space (that
is normally used to consume any amount of white space in the input stream). However,
the usual skip of initial white space in the formats that support it is implemented.
5.18.3.35
int vfscanf_P (FILE ∗ __stream, const char ∗ __fmt, va_list __ap)
Variant of vfscanf() using a fmt string in program memory.
5.18.3.36
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.
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5.18.3.37
88
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.
5.18.3.38
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.
5.18.3.39
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.
5.18.3.40
int vsprintf (char ∗ __s, const char ∗ __fmt, va_list ap)
Like sprintf() but takes a variable argument list for the arguments.
5.18.3.41
int vsprintf_P (char ∗ __s, const char ∗ __fmt, va_list ap)
Variant of vsprintf() that uses a fmt string that resides in program memory.
5.19 <stdlib.h>: General utilities
5.19.1
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.
Data Structures
• struct div_t
• struct ldiv_t
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Non-standard (i.e. non-ISO C) functions.
•
•
•
•
•
•
•
•
#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.
•
•
•
•
#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, char __width, char __prec, char ∗__s)
Defines
• #define RAND_MAX 0x7FFF
Typedefs
• typedef int(∗ __compar_fn_t )(const void ∗, const void ∗)
Functions
•
•
•
•
__inline__ void abort (void) __ATTR_NORETURN__
int abs (int __i) __ATTR_CONST__
long labs (long __i) __ATTR_CONST__
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") __ATTR_CONST__
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• ldiv_t ldiv (long __num, long __denom) __asm__("__divmodsi4") __ATTR_CONST__
• 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)
• __inline__ long atol (const char ∗__nptr) __ATTR_PURE__
• __inline__ int atoi (const char ∗__nptr) __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
5.19.2
5.19.2.1
Define Documentation
#define DTOSTR_ALWAYS_SIGN 0x01
Bit value that can be passed in flags to dtostre().
5.19.2.2
#define DTOSTR_PLUS_SIGN 0x02
Bit value that can be passed in flags to dtostre().
5.19.2.3
#define DTOSTR_UPPERCASE 0x04
Bit value that can be passed in flags to dtostre().
5.19.2.4
#define RAND_MAX 0x7FFF
Highest number that can be generated by rand().
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91
#define RANDOM_MAX 0x7FFFFFFF
Highest number that can be generated by random().
5.19.3
5.19.3.1
Typedef Documentation
typedef int(∗ __compar_fn_t)(const void ∗, const void ∗)
Comparision function type for qsort(), just for convenience.
5.19.4
5.19.4.1
Function Documentation
__inline__ void abort (void)
The abort() function causes abnormal program termination to occur. In the limited
AVR environment, execution is effectively halted by entering an infinite loop.
5.19.4.2
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.
5.19.4.3
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 **)NULL);
5.19.4.4
int atoi (const char ∗ string)
Convert a string to an integer.
The atoi() function converts the initial portion of the string pointed to by nptr to
integer representation.
It is equivalent to:
(int)strtol(nptr, (char **)NULL, 10);
except that atoi() does not detect errors.
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5.19.4.5
92
long int atol (const char ∗ string)
Convert a string to a long integer.
The atol() function converts the initial portion of the string pointed to by stringp to
integer representation.
It is equivalent to:
strtol(nptr, (char **)NULL, 10);
except that atol() does not detect errors.
5.19.4.6 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
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.
5.19.4.7
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.
5.19.4.8
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.
5.19.4.9 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.
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Conversion is done in the format "[-]d.ddde177dd" 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.
5.19.4.10
char∗ dtostrf (double __val, char __width, 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 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.
The dtostrf() function returns the pointer to the converted string s.
5.19.4.11
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.
In a C++ context, global destructors will be called before halting execution.
5.19.4.12
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.
5.19.4.13
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.
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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’.
If radix is 10 and val is negative, a minus sign will be prepended.
The itoa() function returns the pointer passed as s.
5.19.4.14
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.
5.19.4.15
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.
5.19.4.16
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.
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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’.
If radix is 10 and val is negative, a minus sign will be prepended.
The ltoa() function returns the pointer passed as s.
5.19.4.17
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.
5.19.4.18 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.
5.19.4.19
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.
5.19.4.20
int rand_r (unsigned long ∗ ctx)
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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.
5.19.4.21
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.
5.19.4.22
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.
5.19.4.23
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.
5.19.4.24
void srand (unsigned int __seed)
Pseudo-random number generator seeding; see rand().
5.19.4.25
void srandom (unsigned long __seed)
Pseudo-random number generator seeding; see random().
5.19.4.26
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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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 HUGE_VAL 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.
FIXME: HUGE_VAL needs to be defined somewhere. The bit pattern is 0x7fffffff, but
what number would this be?
5.19.4.27
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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5.19
<stdlib.h>: General utilities
5.19.4.28
base)
98
unsigned long strtoul (const char ∗ __nptr, char ∗∗ __endptr, int __-
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.
5.19.4.29
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.
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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5.20
<string.h>: Strings
99
The ultoa() function returns the pointer passed as s.
5.19.4.30
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.
5.19.5
5.19.5.1
Variable Documentation
char∗ __malloc_heap_end
malloc() tunable.
5.19.5.2
char∗ __malloc_heap_start
malloc() tunable.
5.19.5.3
size_t __malloc_margin
malloc() tunable.
5.20 <string.h>: Strings
5.20.1
Detailed Description
#include <string.h>
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5.20
<string.h>: Strings
100
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 String
Utilities.
Defines
• #define _FFS(x)
Functions
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
int ffs (int) __attribute__((const ))
int ffsl (long) __attribute__((const ))
int ffsll (long long) __attribute__((const ))
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 ∗ memmove (void ∗, const void ∗, size_t)
void ∗ memset (void ∗, int, size_t)
int strcasecmp (const char ∗, const char ∗) __ATTR_PURE__
char ∗ strcat (char ∗, const char ∗)
char ∗ strchr (const char ∗, int) __ATTR_PURE__
int strcmp (const char ∗, const char ∗) __ATTR_PURE__
char ∗ strcpy (char ∗, const char ∗)
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 ∗ strrchr (const char ∗, int) __ATTR_PURE__
char ∗ strrev (char ∗)
char ∗ strsep (char ∗∗, const char ∗)
char ∗ strstr (const char ∗, const char ∗) __ATTR_PURE__
char ∗ strtok_r (char ∗, const char ∗, char ∗∗)
char ∗ strupr (char ∗)
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5.20
<string.h>: Strings
5.20.2
5.20.2.1
101
Define Documentation
#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.
5.20.3
5.20.3.1
Function Documentation
int ffs (int val) const
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.
Note:
For expressions that are constant at compile time, consider using the _FFS macro
instead.
5.20.3.2
int ffsl (long val) const
Same as ffs(), for an argument of type long.
5.20.3.3
int ffsll (long long val) const
Same as ffs(), for an argument of type long long.
5.20.3.4
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.
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5.20
<string.h>: Strings
102
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.
5.20.3.5
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.
5.20.3.6
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.
5.20.3.7
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.
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5.20
<string.h>: Strings
5.20.3.8
103
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.
5.20.3.9
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.
5.20.3.10
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.
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.
5.20.3.11
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.
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5.20
<string.h>: Strings
5.20.3.12
104
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.
Returns:
The strchr() function returns a pointer to the matched character or NULL if the
character is not found.
5.20.3.13
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.
5.20.3.14
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.
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.
5.20.3.15
size_t strlcat (char ∗ dst, const char ∗ src, size_t siz)
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)).
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5.20
<string.h>: Strings
105
Returns:
The strlcat() function returns strlen(src) + MIN(siz, strlen(initial dst)). If retval >=
siz, truncation occurred.
5.20.3.16
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.
5.20.3.17
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.
Returns:
The strlen() function returns the number of characters in src.
5.20.3.18
char ∗ strlwr (char ∗ string)
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.
5.20.3.19
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
n characters of s1.
Returns:
The strncasecmp() 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.
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5.20
<string.h>: Strings
5.20.3.20
106
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.
5.20.3.21
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.
5.20.3.22
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.
5.20.3.23
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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5.20
<string.h>: Strings
5.20.3.24
107
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.
5.20.3.25
char ∗ strrev (char ∗ string)
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.
5.20.3.26
char ∗ strsep (char ∗∗ string, const char ∗ delim)
Parse a string into tokens.
The strsep() function locates, in the string referenced by ∗string, 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 ∗string. 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 ∗string to ’\0’.
Returns:
The strtok_r() function returns a pointer to the original value of ∗string. If ∗stringp
is initially NULL, strsep() returns NULL.
5.20.3.27
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.
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5.21
<util/crc16.h>: CRC Computations
108
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.
5.20.3.28
char ∗ strtok_r (char ∗ string, const char ∗ delim, char ∗∗ last)
Parses the string s into tokens.
strtok_r parses the string s 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.
5.20.3.29
char ∗ strupr (char ∗ string)
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.
5.21 <util/crc16.h>: CRC Computations
5.21.1
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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<util/crc16.h>: CRC Computations
5.21
109
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
}
Functions
•
•
•
•
5.21.2
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)
Function Documentation
5.21.2.1 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.
5.21.2.2 static __inline__ uint16_t _crc_ccitt_update (uint16_t __crc, uint8_t __data) [static]
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<util/crc16.h>: CRC Computations
5.21
110
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));
}
5.21.2.3 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)
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;
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<util/delay.h>: Busy-wait delay loops
5.22
111
}
return crc;
}
5.21.2.4 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;
}
5.22
<util/delay.h>: Busy-wait delay loops
5.22.1
Detailed Description
#define F_CPU 1000000UL // 1 MHz
//#define F_CPU 14.7456E6
#include <util/delay.h>
Note:
As an alternative method, it is possible to pass the F_CPU macro down to the compiler from the Makefile. Obviously, in that case, no #define statement should
be used.
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.
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5.22
<util/delay.h>: Busy-wait delay loops
112
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.
Two wrapper functions allow the specification of microsecond, and millisecond delays
directly, using the application-supplied macro F_CPU as the CPU clock frequency (in
Hertz). These functions operate on double typed arguments, however when optimization is turned on, the entire floating-point calculation will be done at compile-time.
Note:
When using _delay_us() and _delay_ms(), the expressions passed as arguments to
these functions shall be compile-time constants, otherwise the floating-point calculations to setup the loops will be done at run-time, thereby drastically increasing
both the resulting code size, as well as the time required to setup the loops.
Functions
•
•
•
•
void _delay_loop_1 (uint8_t __count)
void _delay_loop_2 (uint16_t __count)
void _delay_us (double __us)
void _delay_ms (double __ms)
5.22.2
5.22.2.1
Function Documentation
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.
5.22.2.2
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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5.23
<util/parity.h>: Parity bit generation
5.22.2.3
113
void _delay_ms (double __ms)
Perform a delay of __ms milliseconds, using _delay_loop_2().
The macro F_CPU is supposed to be defined to a constant defining the CPU clock
frequency (in Hertz).
The maximal possible delay is 262.14 ms / F_CPU in MHz.
5.22.2.4
void _delay_us (double __us)
Perform a delay of __us microseconds, using _delay_loop_1().
The macro F_CPU is supposed to be defined to a constant defining the CPU clock
frequency (in Hertz).
The maximal possible delay is 768 us / F_CPU in MHz.
5.23 <util/parity.h>: Parity bit generation
5.23.1
Detailed Description
#include <util/parity.h>
This header file contains optimized assembler code to calculate the parity bit for a byte.
Defines
• #define parity_even_bit(val)
5.23.2
5.23.2.1
Define Documentation
#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"
Generated on Sat Nov 19 23:00:48 2005 for avr-libc by Doxygen
\
\
\
\
\
\
\
\
\
\
\
\
\
5.24
<util/twi.h>: TWI bit mask definitions
);
(((__t + 1) >> 1) & 1);
114
\
\
}))
Returns:
1 if val has an odd number of bits set.
5.24 <util/twi.h>: TWI bit mask definitions
5.24.1
Detailed Description
#include <util/twi.h>
This header file contains bit mask definitions for use with the AVR TWI interface.
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
Generated on Sat Nov 19 23:00:48 2005 for avr-libc by Doxygen
5.24
•
•
•
•
•
•
•
•
•
•
•
•
<util/twi.h>: TWI bit mask definitions
#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
5.24.2
5.24.2.1
Define Documentation
#define TW_BUS_ERROR 0x00
illegal start or stop condition
5.24.2.2
#define TW_MR_ARB_LOST 0x38
arbitration lost in SLA+R or NACK
5.24.2.3
#define TW_MR_DATA_ACK 0x50
data received, ACK returned
5.24.2.4
#define TW_MR_DATA_NACK 0x58
data received, NACK returned
5.24.2.5
#define TW_MR_SLA_ACK 0x40
SLA+R transmitted, ACK received
5.24.2.6
#define TW_MR_SLA_NACK 0x48
SLA+R transmitted, NACK received
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115
5.24
<util/twi.h>: TWI bit mask definitions
5.24.2.7
#define TW_MT_ARB_LOST 0x38
arbitration lost in SLA+W or data
5.24.2.8
#define TW_MT_DATA_ACK 0x28
data transmitted, ACK received
5.24.2.9
#define TW_MT_DATA_NACK 0x30
data transmitted, NACK received
5.24.2.10
#define TW_MT_SLA_ACK 0x18
SLA+W transmitted, ACK received
5.24.2.11
#define TW_MT_SLA_NACK 0x20
SLA+W transmitted, NACK received
5.24.2.12
#define TW_NO_INFO 0xF8
no state information available
5.24.2.13
#define TW_READ 1
SLA+R address
5.24.2.14
#define TW_REP_START 0x10
repeated start condition transmitted
5.24.2.15
#define TW_SR_ARB_LOST_GCALL_ACK 0x78
arbitration lost in SLA+RW, general call received, ACK returned
5.24.2.16
#define TW_SR_ARB_LOST_SLA_ACK 0x68
arbitration lost in SLA+RW, SLA+W received, ACK returned
5.24.2.17
#define TW_SR_DATA_ACK 0x80
data received, ACK returned
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116
5.24
<util/twi.h>: TWI bit mask definitions
5.24.2.18
#define TW_SR_DATA_NACK 0x88
data received, NACK returned
5.24.2.19
#define TW_SR_GCALL_ACK 0x70
general call received, ACK returned
5.24.2.20
#define TW_SR_GCALL_DATA_ACK 0x90
general call data received, ACK returned
5.24.2.21
#define TW_SR_GCALL_DATA_NACK 0x98
general call data received, NACK returned
5.24.2.22
#define TW_SR_SLA_ACK 0x60
SLA+W received, ACK returned
5.24.2.23
#define TW_SR_STOP 0xA0
stop or repeated start condition received while selected
5.24.2.24
#define TW_ST_ARB_LOST_SLA_ACK 0xB0
arbitration lost in SLA+RW, SLA+R received, ACK returned
5.24.2.25
#define TW_ST_DATA_ACK 0xB8
data transmitted, ACK received
5.24.2.26
#define TW_ST_DATA_NACK 0xC0
data transmitted, NACK received
5.24.2.27
#define TW_ST_LAST_DATA 0xC8
last data byte transmitted, ACK received
5.24.2.28
#define TW_ST_SLA_ACK 0xA8
SLA+R received, ACK returned
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117
5.25
<avr/interrupt.h>: Interrupts
5.24.2.29
118
#define TW_START 0x08
start condition transmitted
5.24.2.30
#define TW_STATUS (TWSR & TW_STATUS_MASK)
TWSR, masked by TW_STATUS_MASK
5.24.2.31
#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.
5.24.2.32
#define TW_WRITE 0
SLA+W address
5.25 <avr/interrupt.h>: Interrupts
5.25.1
Detailed Description
Note:
This discussion of interrupts was originally taken from Rich Neswold’s document.
See Acknowledgments.
Introduction to avr-libc’s interrupt handling 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.
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)).
Generated on Sat Nov 19 23:00:48 2005 for avr-libc by Doxygen
5.25
<avr/interrupt.h>: Interrupts
119
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.
Catch-all interrupt vector 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 __vector_default which should be defined with ISR() as such.
#include <avr/interrupt.h>
ISR(__vector_default)
{
// 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:
void XXX_vect(void) __attribute__((interrupt));
void XXX_vect(void) {
...
}
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5.25
<avr/interrupt.h>: Interrupts
120
where XXX_vect is the name of a valid interrupt vector for the MCU type in question,
as explained below.
Chosing 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
ADC_vect
Old
vector
name
SIG_ADC
ANALOG_COMP_0_vect
ANALOG_COMP_1_vect
SIG_COMPARATOR0
SIG_COMPARATOR1
Description
Applicable for device
ADC Conversion
Complete
Com-
AT90S2333, AT90S4433, AT90S4434,
AT90S8535, AT90PWM3, AT90PWM2,
AT90CAN128, AT90CAN32, AT90CAN64,
ATmega103, ATmega128, ATmega16,
ATmega163, ATmega165, ATmega169,
ATmega32, ATmega323, ATmega325,
ATmega3250, ATmega329, ATmega3290,
ATmega64, ATmega645, ATmega6450,
ATmega649, ATmega6490, ATmega8,
ATmega8535, ATmega168, ATmega48,
ATmega88, ATmega640, ATmega1280,
ATmega1281, ATmega324, ATmega164,
ATmega644, ATtiny13, ATtiny15, ATtiny26,
ATtiny45
AT90PWM3, AT90PWM2
Com-
AT90PWM3, AT90PWM2
Analog
parator 0
Analog
parator 1
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5.25
<avr/interrupt.h>: Interrupts
Vector name
ANALOG_COMP_2_vect
ANALOG_COMP_vect
Old
vector
name
SIG_COMPARATOR2
SIG_COMPARATOR
ANA_COMP_vect
SIG_Analog
COMPARATOR parator
CANIT_vect
SIG_CAN_INTERRUPT1
EEPROM_READY_vect
SIG_EEPROM_READY,
SIG_EE_READY
SIG_EEPROM_READY
EE_RDY_vect
EE_READY_vect
SIG_EEPROM_READY
121
Description
Applicable for device
Analog
parator 2
Analog
parator
Com-
AT90PWM3, AT90PWM2
Com-
AT90CAN128, AT90CAN32, AT90CAN64,
ATmega103, ATmega128, ATmega165, ATmega169, ATmega325, ATmega3250, ATmega329, ATmega3290, ATmega64, ATmega645, ATmega6450, ATmega649, ATmega6490, ATmega168, ATmega48, ATmega88, ATmega640, ATmega1280, ATmega1281, ATmega324, ATmega164, ATmega644
AT90S1200, AT90S2313, AT90S2333,
AT90S4414, AT90S4433, AT90S4434,
AT90S8515,
AT90S8535,
ATmega16,
ATmega161, ATmega162, ATmega163,
ATmega32, ATmega323, ATmega8, ATmega8515,
ATmega8535,
ATtiny11,
ATtiny12, ATtiny13, ATtiny15, ATtiny2313,
ATtiny26, ATtiny28, ATtiny45
AT90CAN128, AT90CAN32, AT90CAN64
Com-
CAN
Transfer
Complete
or
Error
ATtiny2313
EEPROM Ready
EEPROM Ready
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AT90S2333, AT90S4433, AT90S4434,
AT90S8535,
ATmega16,
ATmega161,
ATmega162, ATmega163, ATmega32,
ATmega323, ATmega8, ATmega8515, ATmega8535, ATtiny12, ATtiny13, ATtiny15,
ATtiny26, ATtiny45
AT90PWM3, AT90PWM2, AT90CAN128,
AT90CAN32, AT90CAN64, ATmega103,
ATmega128, ATmega165, ATmega169, ATmega325, ATmega3250, ATmega329, ATmega3290, ATmega64, ATmega645, ATmega6450, ATmega649, ATmega6490, ATmega168, ATmega48, ATmega88, ATmega640, ATmega1280, ATmega1281, ATmega324, ATmega164, ATmega644
5.25
<avr/interrupt.h>: Interrupts
Vector name
122
Old
vector
name
SIG_INTERRUPT0
Description
Applicable for device
External Interrupt
0
INT1_vect
SIG_INTERRUPT1
External Interrupt
Request 1
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
AT90S1200, AT90S2313, AT90S2323,
AT90S2333, AT90S2343, AT90S4414,
AT90S4433, AT90S4434, AT90S8515,
AT90S8535, AT90PWM3, AT90PWM2,
AT90CAN128, AT90CAN32, AT90CAN64,
ATmega103, ATmega128, ATmega16,
ATmega161, ATmega162, ATmega163,
ATmega165, ATmega169, ATmega32,
ATmega323, ATmega325, ATmega3250,
ATmega329, ATmega3290, ATmega64,
ATmega645, ATmega6450, ATmega649,
ATmega6490, ATmega8, ATmega8515,
ATmega8535, ATmega168, ATmega48,
ATmega88, ATmega640, ATmega1280,
ATmega1281, ATmega324, ATmega164,
ATmega644, ATtiny11, ATtiny12, ATtiny13, ATtiny15, ATtiny22, ATtiny2313,
ATtiny26, ATtiny28, ATtiny45
AT90S2313, AT90S2333, AT90S4414,
AT90S4433, AT90S4434, AT90S8515,
AT90S8535, AT90PWM3, AT90PWM2,
AT90CAN128, AT90CAN32, AT90CAN64,
ATmega103, ATmega128, ATmega16,
ATmega161, ATmega162, ATmega163,
ATmega32,
ATmega323,
ATmega64,
ATmega8, ATmega8515, ATmega8535,
ATmega168, ATmega48, ATmega88, ATmega640, ATmega1280, ATmega1281,
ATmega324, ATmega164, ATmega644,
ATtiny2313, ATtiny28
AT90PWM3, AT90PWM2, AT90CAN128,
AT90CAN32, AT90CAN64, ATmega103,
ATmega128, ATmega16, ATmega161, ATmega162, ATmega32, ATmega323, ATmega64, ATmega8515, ATmega8535, ATmega640, ATmega1280, ATmega1281, ATmega324, ATmega164, ATmega644
AT90PWM3, AT90PWM2, AT90CAN128,
AT90CAN32, AT90CAN64, ATmega103,
ATmega128, ATmega64, ATmega640, ATmega1280, ATmega1281
AT90CAN128, AT90CAN32, AT90CAN64,
ATmega103, ATmega128, ATmega64, ATmega640, ATmega1280, ATmega1281
AT90CAN128, AT90CAN32, AT90CAN64,
ATmega103, ATmega128, ATmega64, ATmega640, ATmega1280, ATmega1281
AT90CAN128, AT90CAN32, AT90CAN64,
ATmega103, ATmega128, ATmega64, ATmega640, ATmega1280, ATmega1281
AT90CAN128, AT90CAN32, AT90CAN64,
ATmega103, ATmega128, ATmega64, ATmega640, ATmega1280, ATmega1281
INT0_vect
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5.25
<avr/interrupt.h>: Interrupts
Vector name
Description
Applicable for device
External Interrupt
Request 0
ATtiny11, ATtiny12, ATtiny15, ATtiny26
ATmega169, ATmega329, ATmega3290,
ATmega649, ATmega6490
ATtiny28
SIG_CAN_OVERFLOW1
SIG_PIN_CHANGE0
LCD Start of
Frame
Low-level Input
on Port B
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
SIG_PSC2_END_CYCLE
IO_PINS_vect
LCD_vect
LOWLEVEL_IO_PINS_vect
OVRIT_vect
PCINT0_vect
PSC0_CAPT_vect
PSC0_EC_vect
PSC1_CAPT_vect
PSC1_EC_vect
PSC2_CAPT_vect
PSC2_EC_vect
Old
vector
name
SIG_PIN,
SIG_PIN_CHANGE
SIG_LCD
123
SIG_PIN
PSC0
Capture
Event
PSC0 End Cycle
PSC1
Capture
Event
PSC1 End Cycle
PSC2
Capture
Event
PSC2 End Cycle
Generated on Sat Nov 19 23:00:48 2005 for avr-libc by Doxygen
AT90CAN128, AT90CAN32, AT90CAN64
ATmega162, ATmega165, ATmega169, ATmega325, ATmega3250, ATmega329, ATmega3290, ATmega645, ATmega6450, ATmega649, ATmega6490, ATmega168, ATmega48, ATmega88, ATmega640, ATmega1280, ATmega1281, ATmega324, ATmega164, ATmega644, ATtiny13, ATtiny45
ATmega162, ATmega165, ATmega169, ATmega325, ATmega3250, ATmega329, ATmega3290, ATmega645, ATmega6450, ATmega649, ATmega6490, ATmega168, ATmega48, ATmega88, ATmega640, ATmega1280, ATmega1281, ATmega324, ATmega164, ATmega644
ATmega3250, ATmega3290, ATmega6450,
ATmega6490, ATmega168, ATmega48, ATmega88, ATmega640, ATmega1280, ATmega1281, ATmega324, ATmega164, ATmega644
ATmega3250, ATmega3290, ATmega6450,
ATmega6490, ATmega324, ATmega164,
ATmega644
ATtiny2313
AT90PWM3, AT90PWM2
AT90PWM3, AT90PWM2
AT90PWM3, AT90PWM2
AT90PWM3, AT90PWM2
AT90PWM3, AT90PWM2
AT90PWM3, AT90PWM2
5.25
<avr/interrupt.h>: Interrupts
Vector name
124
Description
Applicable for device
SPI_STC_vect
Old
vector
name
SIG_SPI
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_OUTPUT_COMPARE1A
SIG_OUTPUT_COMPARE1B
SIG_OVERFLOW1
SIG_OUTPUT_COMPARE0A
Timer/Counter
Compare Match
A
Timer/Counter
Compare Match
B
Timer/Counter0
Overflow
Timer/Counter1
Compare Match
1A
Timer/Counter1
Compare Match
B
Timer/Counter1
Overflow
TimerCounter0
Compare Match
A
AT90S2333, AT90S4414, AT90S4433,
AT90S4434, AT90S8515, AT90S8535,
AT90PWM3, AT90PWM2, AT90CAN128,
AT90CAN32, AT90CAN64, ATmega103,
ATmega128, ATmega16, ATmega161,
ATmega162, ATmega163, ATmega165,
ATmega169, ATmega32, ATmega323,
ATmega325, ATmega3250, ATmega329,
ATmega3290, ATmega64, ATmega645,
ATmega6450, ATmega649, ATmega6490,
ATmega8, ATmega8515, ATmega8535,
ATmega168, ATmega48, ATmega88, ATmega640, ATmega1280, ATmega1281,
ATmega324, ATmega164, ATmega644
ATmega16, ATmega162, ATmega32, ATmega323, ATmega8, ATmega8515, ATmega8535
AT90PWM3, AT90PWM2, AT90CAN128,
AT90CAN32, AT90CAN64, ATmega128,
ATmega165, ATmega169, ATmega325, ATmega3250, ATmega329, ATmega3290, ATmega64, ATmega645, ATmega6450, ATmega649, ATmega6490, ATmega168, ATmega48, ATmega88, ATmega640, ATmega1280, ATmega1281, ATmega324, ATmega164, ATmega644
ATtiny13, ATtiny45
SIG_OUTPUT_COMPARE0B,
SIG_OUTPUT_COMPARE0_B
Timer Counter 0
Compare Match
B
TIM0_COMPB_vect
TIM0_OVF_vect
TIM1_COMPA_vect
TIM1_COMPB_vect
TIM1_OVF_vect
TIMER0_COMPA_vect
TIMER0_COMPB_vect
Generated on Sat Nov 19 23:00:48 2005 for avr-libc by Doxygen
ATtiny13, ATtiny45
ATtiny13, ATtiny45
ATtiny45
ATtiny45
ATtiny45
ATmega168, ATmega48, ATmega88, ATmega640, ATmega1280, ATmega1281, ATmega324, ATmega164, ATmega644, ATtiny2313
AT90PWM3, AT90PWM2, ATmega168,
ATmega48, ATmega88, ATmega640, ATmega1280, ATmega1281, ATmega324, ATmega164, ATmega644, ATtiny2313
5.25
<avr/interrupt.h>: Interrupts
Vector name
TIMER0_COMP_A_vect
TIMER0_COMP_vect
Old
vector
name
SIG_OUTPUT_COMPARE0A,
SIG_OUTPUT_COMPARE0_A
SIG_OUTPUT_COMPARE0
125
Description
Applicable for device
Timer/Counter0
Compare Match
A
AT90PWM3, AT90PWM2
Timer/Counter0
Compare Match
AT90CAN128, AT90CAN32, AT90CAN64,
ATmega103, ATmega128, ATmega16, ATmega161, ATmega162, ATmega165, ATmega169, ATmega32, ATmega323, ATmega325, ATmega3250, ATmega329, ATmega3290, ATmega64, ATmega645, ATmega6450, ATmega649, ATmega6490, ATmega8515, ATmega8535
AT90S2313, AT90S2323, AT90S2343, ATtiny22, ATtiny26
AT90S1200, AT90S2333, AT90S4414,
AT90S4433, AT90S4434, AT90S8515,
AT90S8535, AT90PWM3, AT90PWM2,
AT90CAN128, AT90CAN32, AT90CAN64,
ATmega103, ATmega128, ATmega16,
ATmega161, ATmega162, ATmega163,
ATmega165, ATmega169, ATmega32,
ATmega323, ATmega325, ATmega3250,
ATmega329, ATmega3290, ATmega64,
ATmega645, ATmega6450, ATmega649,
ATmega6490, ATmega8, ATmega8515,
ATmega8535, ATmega168, ATmega48,
ATmega88, ATmega640, ATmega1280,
ATmega1281, ATmega324, ATmega164,
ATmega644, ATtiny11, ATtiny12, ATtiny15,
ATtiny2313, ATtiny28
AT90S2313
TIMER0_OVF0_vect
TIMER0_OVF_vect
SIG_OVERFLOW0
SIG_OVERFLOW0
Timer/Counter0
Overflow
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 Sat Nov 19 23:00:48 2005 for avr-libc by Doxygen
AT90S2333, AT90S4414, AT90S4433,
AT90S4434, AT90S8515, AT90S8535,
AT90PWM3, AT90PWM2, AT90CAN128,
AT90CAN32, AT90CAN64, ATmega103,
ATmega128, ATmega16, ATmega161,
ATmega162, ATmega163, ATmega165,
ATmega169, ATmega32, ATmega323,
ATmega325, ATmega3250, ATmega329,
ATmega3290, ATmega64, ATmega645,
ATmega6450, ATmega649, ATmega6490,
ATmega8, ATmega8515, ATmega8535,
ATmega168, ATmega48, ATmega88, ATmega640, ATmega1280, ATmega1281,
ATmega324, ATmega164, ATmega644,
ATtiny2313
ATtiny26
5.25
<avr/interrupt.h>: Interrupts
Vector name
TIMER1_CMPB_vect
TIMER1_COMP1_vect
TIMER1_COMPA_vect
Old
vector
name
SIG_OUTPUT_COMPARE1B
SIG_OUTPUT_COMPARE1A
SIG_OUTPUT_COMPARE1A
Description
Applicable for device
Timer/Counter1
Compare Match
1B
Timer/Counter1
Compare Match
ATtiny26
Timer/Counter1
Compare Match
A
TIMER1_COMPB_vect
SIG_OUTPUT_COMPARE1B
Timer/Counter1
Compare MatchB
TIMER1_COMPC_vect
SIG_OUTPUT_COMPARE1C
SIG_OUTPUT_COMPARE1A
SIG_OVERFLOW1
Timer/Counter1
Compare Match
C
Timer/Counter1
Compare Match
TIMER1_COMP_vect
TIMER1_OVF1_vect
126
Timer/Counter1
Overflow
Generated on Sat Nov 19 23:00:48 2005 for avr-libc by Doxygen
AT90S2313
AT90S4414, AT90S4434, AT90S8515,
AT90S8535, AT90PWM3, AT90PWM2,
AT90CAN128, AT90CAN32, AT90CAN64,
ATmega103, ATmega128, ATmega16,
ATmega161, ATmega162, ATmega163,
ATmega165, ATmega169, ATmega32,
ATmega323, ATmega325, ATmega3250,
ATmega329, ATmega3290, ATmega64,
ATmega645, ATmega6450, ATmega649,
ATmega6490, ATmega8, ATmega8515,
ATmega8535, ATmega168, ATmega48,
ATmega88, ATmega640, ATmega1280,
ATmega1281, ATmega324, ATmega164,
ATmega644, ATtiny2313
AT90S4414, AT90S4434, AT90S8515,
AT90S8535, AT90PWM3, AT90PWM2,
AT90CAN128, AT90CAN32, AT90CAN64,
ATmega103, ATmega128, ATmega16,
ATmega161, ATmega162, ATmega163,
ATmega165, ATmega169, ATmega32,
ATmega323, ATmega325, ATmega3250,
ATmega329, ATmega3290, ATmega64,
ATmega645, ATmega6450, ATmega649,
ATmega6490, ATmega8, ATmega8515,
ATmega8535, ATmega168, ATmega48,
ATmega88, ATmega640, ATmega1280,
ATmega1281, ATmega324, ATmega164,
ATmega644, ATtiny2313
AT90CAN128, AT90CAN32, AT90CAN64,
ATmega128, ATmega64, ATmega640, ATmega1280, ATmega1281
AT90S2333, AT90S4433, ATtiny15
AT90S2313, ATtiny26
5.25
<avr/interrupt.h>: Interrupts
Vector name
127
Old
vector
name
SIG_OVERFLOW1
Description
Applicable for device
Timer/Counter1
Overflow
SIG_OUTPUT_COMPARE2A
SIG_OUTPUT_COMPARE2B
SIG_OUTPUT_COMPARE2
Timer/Counter2
Compare Match
A
Timer/Counter2
Compare Match
A
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
SIG_OUTPUT_COMPARE3B
SIG_OUTPUT_COMPARE3C
Timer/Counter3
Compare Match
A
Timer/Counter3
Compare Match
B
Timer/Counter3
Compare Match
C
AT90S2333, AT90S4414, AT90S4433,
AT90S4434, AT90S8515, AT90S8535,
AT90PWM3, AT90PWM2, AT90CAN128,
AT90CAN32, AT90CAN64, ATmega103,
ATmega128, ATmega16, ATmega161,
ATmega162, ATmega163, ATmega165,
ATmega169, ATmega32, ATmega323,
ATmega325, ATmega3250, ATmega329,
ATmega3290, ATmega64, ATmega645,
ATmega6450, ATmega649, ATmega6490,
ATmega8, ATmega8515, ATmega8535,
ATmega168, ATmega48, ATmega88, ATmega640, ATmega1280, ATmega1281,
ATmega324, ATmega164, ATmega644,
ATtiny15, ATtiny2313
ATmega168, ATmega48, ATmega88, ATmega640, ATmega1280, ATmega1281, ATmega324, ATmega164, ATmega644
ATmega168, ATmega48, ATmega88, ATmega640, ATmega1280, ATmega1281, ATmega324, ATmega164, ATmega644
AT90S4434, AT90S8535, AT90CAN128,
AT90CAN32, AT90CAN64, ATmega103,
ATmega128, ATmega16, ATmega161, ATmega162, ATmega163, ATmega165, ATmega169, ATmega32, ATmega323, ATmega325, ATmega3250, ATmega329, ATmega3290, ATmega64, ATmega645, ATmega6450, ATmega649, ATmega6490, ATmega8, ATmega8535
AT90S4434, AT90S8535, AT90CAN128,
AT90CAN32, AT90CAN64, ATmega103,
ATmega128, ATmega16, ATmega161, ATmega162, ATmega163, ATmega165, ATmega169, ATmega32, ATmega323, ATmega325, ATmega3250, ATmega329, ATmega3290, ATmega64, ATmega645, ATmega6450, ATmega649, ATmega6490, ATmega8, ATmega8535, ATmega168, ATmega48, ATmega88, ATmega640, ATmega1280, ATmega1281, ATmega324, ATmega164, ATmega644
AT90CAN128, AT90CAN32, AT90CAN64,
ATmega128, ATmega162, ATmega64, ATmega640, ATmega1280, ATmega1281
AT90CAN128, AT90CAN32, AT90CAN64,
ATmega128, ATmega162, ATmega64, ATmega640, ATmega1280, ATmega1281
AT90CAN128, AT90CAN32, AT90CAN64,
ATmega128, ATmega162, ATmega64, ATmega640, ATmega1280, ATmega1281
AT90CAN128, AT90CAN32, AT90CAN64,
ATmega128, ATmega64, ATmega640, ATmega1280, ATmega1281
TIMER1_OVF_vect
TIMER2_COMPA_vect
TIMER2_COMPB_vect
TIMER2_COMP_vect
TIMER3_COMPB_vect
TIMER3_COMPC_vect
Generated on Sat Nov 19 23:00:48 2005 for avr-libc by Doxygen
5.25
<avr/interrupt.h>: Interrupts
Vector name
128
Old
vector
name
SIG_OVERFLOW3
Description
Applicable for device
Timer/Counter3
Overflow
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
AT90CAN128, AT90CAN32, AT90CAN64,
ATmega128, ATmega162, ATmega64, ATmega640, ATmega1280, ATmega1281
ATmega640, ATmega1280, ATmega1281
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
TIMER3_OVF_vect
TIMER4_CAPT_vect
TIMER4_COMPA_vect
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
ATmega640, ATmega1280, ATmega1281
ATmega640, ATmega1280, ATmega1281
ATmega640, ATmega1280, ATmega1281
ATmega640, ATmega1280, ATmega1281
ATmega640, ATmega1280, ATmega1281
ATmega640, ATmega1280, ATmega1281
ATmega640, ATmega1280, ATmega1281
ATmega640, ATmega1280, ATmega1281
AT90CAN128, AT90CAN32, AT90CAN64,
ATmega128, ATmega16, ATmega163, ATmega32, ATmega323, ATmega64, ATmega8, ATmega8535, ATmega168, ATmega48, ATmega88, ATmega640, ATmega1280, ATmega1281, ATmega324, ATmega164, ATmega644
AT86RF401
AT86RF401
ATmega161
Tx
ATmega161
UART0
Data
Register Empty
ATmega161
UART1,
Complete
ATmega161
Rx
Generated on Sat Nov 19 23:00:48 2005 for avr-libc by Doxygen
5.25
<avr/interrupt.h>: Interrupts
Vector name
129
UART_RX_vect
Old
vector
name
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
USART0,
Complete
Tx
USART0,
Complete
Tx
UART1_TX_vect
UART1_UDRE_vect
USART0_RX_vect
USART0_TXC_vect
USART0_TX_vect
SIG_USART0_TRANS
SIG_UART0_TRANS
Description
UART1,
Complete
Applicable for device
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
USART0_UDRE_vect
SIG_UART0_DATA
USART0
Data
Register Empty
USART1_RXC_vect
SIG_USART1_RECV
SIG_UART1_RECV
USART1,
Complete
Rx
USART1,
Complete
Rx
USART1,
Complete
Tx
USART1_RX_vect
USART1_TXC_vect
SIG_USART1_TRANS
Generated on Sat Nov 19 23:00:48 2005 for avr-libc by Doxygen
AT90S4414,
AT90S8515,
ATmega163,
AT90S4414,
AT90S8515,
ATmega163,
AT90S4414,
AT90S8515,
ATmega163,
AT90CAN128, AT90CAN32, AT90CAN64,
ATmega128, ATmega165, ATmega169, ATmega325, ATmega329, ATmega64, ATmega645, ATmega649, ATmega640, ATmega1280, ATmega1281, ATmega324, ATmega164, ATmega644
ATmega162
AT90CAN128, AT90CAN32, AT90CAN64,
ATmega128, ATmega165, ATmega169, ATmega325, ATmega3250, ATmega329, ATmega3290, ATmega64, ATmega645, ATmega6450, ATmega649, ATmega6490, ATmega640, ATmega1280, ATmega1281, ATmega324, ATmega164, ATmega644
AT90CAN128, AT90CAN32, AT90CAN64,
ATmega128, ATmega162, ATmega165, ATmega169, ATmega325, ATmega329, ATmega64, ATmega645, ATmega649, ATmega640, ATmega1280, ATmega1281, ATmega324, ATmega164, ATmega644
ATmega162
AT90CAN128, AT90CAN32, AT90CAN64,
ATmega128, ATmega64, ATmega640, ATmega1280, ATmega1281, ATmega324, ATmega164, ATmega644
ATmega162
5.25
<avr/interrupt.h>: Interrupts
Vector name
130
Old
vector
name
SIG_UART1_TRANS
Description
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
SIG_USART_TRANS,
SIG_UART_TRANS
SIG_USART_TRANS,
SIG_UART_TRANS
SIG_USART_DATA, SIG_UART_DATA
USART2,
Complete
Rx
AT90CAN128, AT90CAN32, AT90CAN64,
ATmega128, ATmega64, ATmega640, ATmega1280, ATmega1281, ATmega324, ATmega164, ATmega644
AT90CAN128, AT90CAN32, AT90CAN64,
ATmega128, ATmega162, ATmega64, ATmega640, ATmega1280, ATmega1281, ATmega324, ATmega164, ATmega644
ATmega640, ATmega1280, ATmega1281
USART2,
Complete
Tx
ATmega640, ATmega1280, ATmega1281
USART2
Data
register Empty
ATmega640, ATmega1280, ATmega1281
USART3,
Complete
Rx
ATmega640, ATmega1280, ATmega1281
USART3,
Complete
Tx
ATmega640, ATmega1280, ATmega1281
USART3
Data
register Empty
ATmega640, ATmega1280, ATmega1281
USART,
Complete
Rx
ATmega16, ATmega32, ATmega323, ATmega8
USART,
Complete
Rx
USART,
Complete
Tx
AT90PWM3, AT90PWM2, ATmega3250,
ATmega3290, ATmega6450, ATmega6490,
ATmega8535, ATmega168, ATmega48, ATmega88, ATtiny2313
ATmega16, ATmega32, ATmega323, ATmega8
USART,
Complete
Tx
AT90PWM3, AT90PWM2, ATmega8535,
ATmega168, ATmega48, ATmega88, ATtiny2313
USART
Data
Register Empty
AT90PWM3, AT90PWM2, ATmega16, ATmega32, ATmega323, ATmega3250, ATmega3290, ATmega6450, ATmega6490, ATmega8, ATmega8535, ATmega168, ATmega48, ATmega88, ATtiny2313
ATmega165, ATmega169, ATmega325, ATmega3250, ATmega329, ATmega3290, ATmega645, ATmega6450, ATmega649, ATmega6490, 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
USART_TXC_vect
USART_TX_vect
USART_UDRE_vect
USI_OVERFLOW_vect
SIG_USI_OVERFLOW
USART1,
Complete
Applicable for device
Tx
USI Overflow
Generated on Sat Nov 19 23:00:48 2005 for avr-libc by Doxygen
5.25
<avr/interrupt.h>: Interrupts
Vector name
USI_OVF_vect
USI_START_vect
USI_STRT_vect
WDT_OVERFLOW_vect
WDT_vect
Old
vector
name
SIG_USI_OVERFLOW
SIG_USI_START
SIG_USI_START
SIG_WATCHDOG_TIMEOUT,
SIG_WDT_OVERFLOW
SIG_WDT,
SIG_WATCHDOG_TIMEOUT
131
Description
Applicable for device
USI Overflow
ATtiny26, ATtiny45
USI Start Condition
ATmega165, ATmega169, ATmega325, ATmega3250, ATmega329, ATmega3290, ATmega645, ATmega6450, ATmega649, ATmega6490, ATtiny2313, ATtiny45
ATtiny26
USI Start
Watchdog Timer
Overflow
ATtiny2313
Watchdog Timeout Interrupt
AT90PWM3, AT90PWM2, ATmega168,
ATmega48, ATmega88, ATmega640, ATmega1280, ATmega1281, ATmega324, ATmega164, ATmega644, ATtiny13, ATtiny45
Macros for writing interrupt handler functions
• #define ISR(vector)
• #define SIGNAL(signame)
• #define EMPTY_INTERRUPT(vector)
5.25.2
5.25.2.1
Define Documentation
#define EMPTY_INTERRUPT(vector)
Value:
void vector (void) __attribute__ ((naked));
\
void vector (void) { __asm__ __volatile__ ("reti" ::); }
#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);
5.25.2.2
#define ISR(vector)
Value:
Generated on Sat Nov 19 23:00:48 2005 for avr-libc by Doxygen
5.26
<avr/sfr_defs.h>: Special function registers
void vector (void) __attribute__ ((signal));
void vector (void)
132
\
#include <avr/interrupt.h>
Introduces an interrupt handler function (interrupt service routine) that runs with global
interrupts initially disabled.
vector must be one of the interrupt vector names that are valid for the particular
MCU type.
5.25.2.3
#define SIGNAL(signame)
Value:
void signame (void) __attribute__ ((signal));
void signame (void)
\
#include <avr/interrupt.h>
Introduces an interrupt handler function that runs with global interrupts initially disabled.
This is the same as the ISR macro.
Note:
Do not use anymore in new code, it will be deprecated in a future release.
5.26 <avr/sfr_defs.h>: Special function registers
5.26.1
Detailed Description
When working with microcontrollers, many of the tasks usually consist of controlling
the peripherals that are connected to the device, respectively programming the subsystems that are contained in the controller (which by itself communicate with the circuitry
connected to the controller).
The AVR series of microcontrollers offers two different paradigms to perform this task.
There’s a separate IO address space available (as it is known from some high-level
CISC CPUs) that can be addressed with specific IO instructions that are applicable to
some or all of the IO address space (in, out, sbi etc.). The entire IO address space
is also made available as memory-mapped IO, i. e. it can be accessed using all the
MCU instructions that are applicable to normal data memory. 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 either address 0x60, or 0x100
depending on the device.)
Generated on Sat Nov 19 23:00:48 2005 for avr-libc by Doxygen
5.26
<avr/sfr_defs.h>: Special function registers
133
AVR Libc supports both these paradigms. While by default, the implementation uses
memory-mapped IO access, this is hidden from the programmer. So the programmer
can access IO registers either with a special function like outb():
#include <avr/io.h>
outb(PORTA, 0x33);
or they can assign a value directly to the symbolic address:
PORTA = 0x33;
The compiler’s choice of which method to use when actually accessing the IO port is
completely independent of the way the programmer chooses to write the code. So even
if the programmer uses the memory-mapped paradigm and writes
PORTA |= 0x40;
the compiler can optimize this into the use of an sbi instruction (of course, provided
the target address is within the allowable range for this instruction, and the right-hand
side of the expression is a constant value known at compile-time).
The advantage of using the memory-mapped paradigm in C programs is that it makes
the programs more portable to other C compilers for the AVR platform. Some people
might also feel that this is more readable. For example, the following two statements
would be equivalent:
outb(DDRD, inb(DDRD) & ~LCDBITS);
DDRD &= ~LCDBITS;
The generated code is identical for both. Without optimization, the compiler strictly
generates code following the memory-mapped paradigm, while with optimization
turned on, code is generated using the (faster and smaller) in/out MCU instructions.
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?.
Porting programs that use sbi/cbi
As described above, access to the AVR single bit set and clear instructions are provided
via the standard C bit manipulation commands. The sbi and cbi commands are no
longer directly supported. sbi (sfr,bit) can be replaced by sfr |= _BV(bit) .
ie: sbi(PORTB, PB1); is now PORTB |= _BV(PB1);
Generated on Sat Nov 19 23:00:48 2005 for avr-libc by Doxygen
5.26
<avr/sfr_defs.h>: Special function registers
134
This actually is more flexible than having sbi directly, as the optimizer will use a hardware sbi if appropriate, or a read/or/write if not. You do not need to keep track of which
registers sbi/cbi will operate on.
Likewise, cbi (sfr,bit) is now sfr &= ∼(_BV(bit));
Modules
• Additional notes from <avr/sfr_defs.h>
Bit manipulation
• #define _BV(bit) (1 << (bit))
IO register bit manipulation
•
•
•
•
#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))
5.26.2
5.26.2.1
Define Documentation
#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().
5.26.2.2
#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.
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5.27
Demo projects
5.26.2.3
135
#define bit_is_set(sfr, bit) (_SFR_BYTE(sfr) & _BV(bit))
#include <avr/io.h>
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.
5.26.2.4
#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.
5.26.2.5
#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.
5.27
Demo projects
5.27.1
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.
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 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.
Modules
• A simple project
• Example using the two-wire interface (TWI)
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136
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.
5.28.1
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.
VCC
IC1
.1uf
C4
18pf
GND
GND
C2
18pf
4mhz
C1
Q1
.01uf
20K
C3
R1
(SCK)PB7
(MISO)PB6
(MOSI)PB5
PB4
(OCI)PB3
PB2
(AIN1)PB1
(AIN0)PB0
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
1
RESET
4
XTAL2
5
XTAL1
20 VCC
10 GND
R2*
LED5MM
D1
See note [7]
GND
Figure 1: 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:
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137
Note [1]:
The PWM is being used in 10-bit mode, so we need a 16-bit variable to remember
the current value.
Note [2]:
ISR() is a macro that marks the function as an interrupt routine. In this case,
the function will get called when the timer overflows. Setting up interrupts is
explained in greater detail in <avr/interrupt.h>: Interrupts.
Note [3]:
This section determines the new value of the PWM.
Note [4]:
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 [5]:
This routine gets called after a reset. It initializes the PWM and enables interrupts.
Note [6]:
The main loop of the program does nothing – all the work is done by the interrupt
routine! If this was a real product, we’d probably put a SLEEP instruction in this
loop to conserve power.
Note [7]:
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.
5.28.2
/*
*
*
*
*
*
*
*
*
*
The Source Code
---------------------------------------------------------------------------"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
this stuff is worth it, you can buy me a beer in return.
Joerg Wunsch
---------------------------------------------------------------------------Simple AVR demonstration. Controls a LED that can be directly
connected from OC1/OC1A to GND. The brightness of the LED is
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5.28
A simple project
* controlled with the PWM. After each period of the PWM, the PWM
* value is either incremented or decremented, that’s all.
*
* $Id: demo.c,v 1.6 2005/11/04 22:55:15 joerg_wunsch Exp $
*/
#include <inttypes.h>
#include <avr/io.h>
#include <avr/interrupt.h>
#if defined(__AVR_AT90S2313__)
# define OC1 PB3
# define OCR OCR1
# define DDROC DDRB
#elif defined(__AVR_AT90S2333__) || defined(__AVR_AT90S4433__)
# define OC1 PB1
# define DDROC DDRB
# define OCR OCR1
#elif defined(__AVR_AT90S4414__) || defined(__AVR_AT90S8515__) || \
defined(__AVR_AT90S4434__) || defined(__AVR_AT90S8535__) || \
defined(__AVR_ATmega163__)
# define OC1 PD5
# define DDROC DDRD
# define OCR OCR1A
#elif defined(__AVR_ATmega8__)
# define OC1 PB1
# define DDROC DDRB
# define OCR OCR1A
# define PWM10 WGM10
# define PWM11 WGM11
#elif defined(__AVR_ATmega32__) || defined(__AVR_ATmega16__)
# define OC1 PD5
# define DDROC DDRD
# define OCR OCR1A
# define PWM10 WGM10
# define PWM11 WGM11
#elif defined(__AVR_ATmega64__) || defined(__AVR_ATmega128__)
# define OC1 PB5
# define DDROC DDRB
# define OCR OCR1A
# define PWM10 WGM10
# define PWM11 WGM11
#else
# error "Don’t know what kind of MCU you are compiling for"
#endif
#if defined(COM11)
# define XCOM11 COM11
#elif defined(COM1A1)
# define XCOM11 COM1A1
#else
# error "need either COM1A1 or COM11"
#endif
enum { UP, DOWN };
volatile uint16_t pwm; /* Note [1] */
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138
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volatile uint8_t direction;
ISR (TIMER1_OVF_vect) /* Note [2] */
{
switch (direction) /* Note [3] */
{
case UP:
if (++pwm == 1023)
direction = DOWN;
break;
case DOWN:
if (--pwm == 0)
direction = UP;
break;
}
OCR = pwm; /* Note [4] */
}
void
ioinit (void) /* Note [5] */
{
/* tmr1 is 10-bit PWM */
TCCR1A = _BV (PWM10) | _BV (PWM11) | _BV (XCOM11);
/* tmr1 running on full MCU clock */
TCCR1B = _BV (CS10);
/* set PWM value to 0 */
OCR = 0;
/* enable OC1 and PB2 as output */
DDROC = _BV (OC1);
/* enable interrupts */
TIMSK = _BV (TOIE1);
sei ();
}
int
main (void)
{
ioinit ();
/* loop forever, the interrupts are doing the rest */
for (;;) /* Note [6] */
;
return (0);
}
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5.28.3
140
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=at90s2333 -c demo.c
The compilation will create a demo.o file. Next we link it into a binary called
demo.elf.
$ avr-gcc -g -mmcu=at90s2333 -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.
5.28.4
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:
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5.28
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demo.elf:
141
file format elf32-avr
Sections:
Idx Name
0 .text
Size
VMA
LMA
File off
000000e0 00000000 00000000 00000094
CONTENTS, ALLOC, LOAD, READONLY, CODE
1 .data
00000000 00800060 000000e0 00000174
CONTENTS, ALLOC, LOAD, DATA
2 .bss
00000003 00800060 00800060 00000174
ALLOC
3 .noinit
00000000 00800063 00800063 00000174
CONTENTS
4 .eeprom
00000000 00810000 00810000 00000174
CONTENTS
5 .stab
00000768 00000000 00000000 00000174
CONTENTS, READONLY, DEBUGGING
6 .stabstr
000007da 00000000 00000000 000008dc
CONTENTS, READONLY, DEBUGGING
Disassembly of section .text:
00000000
0: 12
2: 6d
4: 6c
6: 6b
8: 6a
a: 69
c: 68
e: 67
10: 11
12: 65
14: 64
16: 63
18: 62
1a: 61
1c: 60
1e: 5f
20: 5e
22: 5d
24: 5c
<__vectors>:
c0
rjmp
c0
rjmp
c0
rjmp
c0
rjmp
c0
rjmp
c0
rjmp
c0
rjmp
c0
rjmp
c0
rjmp
c0
rjmp
c0
rjmp
c0
rjmp
c0
rjmp
c0
rjmp
c0
rjmp
c0
rjmp
c0
rjmp
c0
rjmp
c0
rjmp
00000026
26: 11
28: 1f
2a: cf
2c: d4
2e: de
30: cd
32: 4f
<__ctors_end>:
24
eor r1, r1
be
out 0x3f, r1 ; 63
e5
ldi r28, 0x5F ; 95
e0
ldi r29, 0x04 ; 4
bf
out 0x3e, r29 ; 62
bf
out 0x3d, r28 ; 61
c0
rjmp .+158
; 0xd2 <main>
.+36
.+218
.+216
.+214
.+212
.+210
.+208
.+206
.+34
.+202
.+200
.+198
.+196
.+194
.+192
.+190
.+188
.+186
.+184
;
;
;
;
;
;
;
;
;
;
;
;
;
;
;
;
;
;
;
0x26
0xde
0xde
0xde
0xde
0xde
0xde
0xde
0x34
0xde
0xde
0xde
0xde
0xde
0xde
0xde
0xde
0xde
0xde
00000034 <__vector_8>:
volatile uint16_t pwm; /* Note [1] */
volatile uint8_t direction;
ISR (TIMER1_OVF_vect) /* Note [2] */
{
34: 1f 92
push r1
Generated on Sat Nov 19 23:00:48 2005 for avr-libc by Doxygen
Algn
2**0
2**0
2**0
2**0
2**0
2**2
2**0
<__ctors_end>
<__bad_interrupt>
<__bad_interrupt>
<__bad_interrupt>
<__bad_interrupt>
<__bad_interrupt>
<__bad_interrupt>
<__bad_interrupt>
<__vector_8>
<__bad_interrupt>
<__bad_interrupt>
<__bad_interrupt>
<__bad_interrupt>
<__bad_interrupt>
<__bad_interrupt>
<__bad_interrupt>
<__bad_interrupt>
<__bad_interrupt>
<__bad_interrupt>
5.28
A simple project
36: 0f 92
push r0
38: 0f b6
in r0, 0x3f ; 63
3a: 0f 92
push r0
3c: 11 24
eor r1, r1
3e: 2f 93
push r18
40: 8f 93
push r24
42: 9f 93
push r25
switch (direction) /* Note [3] */
44: 80 91 60 00 lds r24, 0x0060
48: 99 27
eor r25, r25
4a: 00 97
sbiw r24, 0x00 ; 0
4c: 19 f0
breq .+6
; 0x54
4e: 01 97
sbiw r24, 0x01 ; 1
50: 31 f5
brne .+76
; 0x9e
52: 14 c0
rjmp .+40
; 0x7c
{
case UP:
if (++pwm == 1023)
54: 80 91 61 00 lds r24, 0x0061
58: 90 91 62 00 lds r25, 0x0062
5c: 01 96
adiw r24, 0x01 ; 1
5e: 90 93 62 00 sts 0x0062, r25
62: 80 93 61 00 sts 0x0061, r24
66: 80 91 61 00 lds r24, 0x0061
6a: 90 91 62 00 lds r25, 0x0062
6e: 8f 5f
subi r24, 0xFF ; 255
70: 93 40
sbci r25, 0x03 ; 3
72: a9 f4
brne .+42
; 0x9e
direction = DOWN;
74: 81 e0
ldi r24, 0x01 ; 1
76: 80 93 60 00 sts 0x0060, r24
7a: 11 c0
rjmp .+34
; 0x9e
break;
7c:
80:
84:
86:
8a:
8e:
92:
96:
98:
9a:
142
<__SREG__+0x15>
<__SREG__+0x5f>
<__SREG__+0x3d>
<__SREG__+0x5f>
<__SREG__+0x5f>
case DOWN:
if (--pwm == 0)
80 91 61 00 lds r24, 0x0061
90 91 62 00 lds r25, 0x0062
01 97
sbiw r24, 0x01 ; 1
90 93 62 00 sts 0x0062, r25
80 93 61 00 sts 0x0061, r24
80 91 61 00 lds r24, 0x0061
90 91 62 00 lds r25, 0x0062
89 2b
or r24, r25
11 f4
brne .+4
; 0x9e <__SREG__+0x5f>
direction = UP;
10 92 60 00 sts 0x0060, r1
break;
}
OCR = pwm; /* Note [4] */
9e: 80 91 61 00 lds r24, 0x0061
a2: 90 91 62 00 lds r25, 0x0062
a6: 9b bd
out 0x2b, r25 ; 43
a8: 8a bd
out 0x2a, r24 ; 42
aa: 9f 91
pop r25
ac: 8f 91
pop r24
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5.28
ae:
b0:
b2:
b4:
b6:
b8:
A simple project
2f
0f
0f
0f
1f
18
91
90
be
90
90
95
143
pop r18
pop r0
out 0x3f, r0 ; 63
pop r0
pop r1
reti
000000ba <ioinit>:
}
void
ioinit (void) /* Note [5] */
{
/* tmr1 is 10-bit PWM */
TCCR1A = _BV (PWM10) | _BV (PWM11) | _BV (XCOM11);
ba: 83 e8
ldi r24, 0x83 ; 131
bc: 8f bd
out 0x2f, r24 ; 47
/* tmr1 running on full MCU clock */
TCCR1B = _BV (CS10);
be: 81 e0
ldi r24, 0x01 ; 1
c0: 8e bd
out 0x2e, r24 ; 46
/* set PWM value to 0 */
OCR = 0;
c2: 1b bc
out 0x2b, r1 ; 43
c4: 1a bc
out 0x2a, r1 ; 42
/* enable OC1 and PB2 as output */
DDROC = _BV (OC1);
c6: 82 e0
ldi r24, 0x02 ; 2
c8: 87 bb
out 0x17, r24 ; 23
/* enable interrupts */
TIMSK = _BV (TOIE1);
ca: 84 e0
ldi r24, 0x04 ; 4
cc: 89 bf
out 0x39, r24 ; 57
sei ();
ce: 78 94
sei
d0: 08 95
ret
000000d2 <main>:
}
int
main (void)
{
d2: cf e5
d4: d4 e0
d6: de bf
d8: cd bf
ioinit ();
da: ef df
dc: ff cf
ldi
ldi
out
out
r28, 0x5F
r29, 0x04
0x3e, r29
0x3d, r28
rcall .-34
rjmp .-2
000000de <__bad_interrupt>:
de: 90 cf
rjmp .-224
;
;
;
;
95
4
62
61
; 0xba <ioinit>
; 0xdc <main+0xa>
; 0x0 <__heap_end>
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5.28.5
144
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=at90s2313 -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)
.vectors
0x00000000
0xe0
0x00000000
0x00000000
0x00000000
0x00000026
0x26 /junk/AVR/avr-libc-1.4/avr/lib/avr4/atmega8/crtm8.o
__vectors
__vector_default
__ctors_start = .
The .text segment (where program instructions are stored) starts at location 0x0.
*(.fini2)
*(.fini1)
*(.fini0)
0x000000e0
.data
0x00800060
0x00800060
_etext = .
0x0 load address 0x000000e0
PROVIDE (__data_start, .)
*(.data)
*(.gnu.linkonce.d*)
0x00800060
0x00800060
0x00800060
.bss
*(.bss)
*(COMMON)
COMMON
.noinit
. = ALIGN (0x2)
_edata = .
PROVIDE (__data_end, .)
0x00800060
0x00800060
0x3
0x00800060
0x00800060
0x00800061
0x00800063
0x000000e0
0x000000e0
0x3 demo.o
direction
pwm
PROVIDE (__bss_end, .)
__data_load_start = LOADADDR (.data)
__data_load_end = (__data_load_start + SIZEOF (.data))
0x00800063
0x00800063
0x0
PROVIDE (__bss_start, .)
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PROVIDE (__noinit_start, .)
5.28
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145
*(.noinit*)
0x00800063
0x00800063
0x00800063
.eeprom
*(.eeprom*)
0x00810000
PROVIDE (__noinit_end, .)
_end = .
PROVIDE (__heap_start, .)
0x0
0x00810000
__eeprom_end = .
The last address in the .text segment is location 0xf2 ( denoted by _etext ), so the
instructions use up 242 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 a 2313 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.
5.28.6
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:
:1000000012C06DC06CC06BC06AC069C068C067C0F8
:1000100011C065C064C063C062C061C060C05FC021
:100020005EC05DC05CC011241FBECFE5D4E0DEBF62
:10003000CDBF4FC01F920F920FB60F9211242F9376
:100040008F939F93809160009927009719F00197F3
:1000500031F514C0809161009091620001969093F7
:1000600062008093610080916100909162008F5FD7
:100070009340A9F481E08093600011C080916100F9
:10008000909162000197909362008093610080914B
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146
:10009000610090916200892B11F4109260008091B0
:1000A0006100909162009BBD8ABD9F918F912F91BD
:1000B0000F900FBE0F901F90189583E88FBD81E0C1
:1000C0008EBD1BBC1ABC82E087BB84E089BF7894DC
:1000D0000895CFE5D4E0DEBFCDBFEFDFFFCF90CFF7
: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
The resulting demo_eeprom.hex file contains:
:00000001FF
which is an empty .hex file (which is expected, since we didn’t define any EEPROM
variables).
5.28.7
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
OPTIMIZE
=
=
=
=
DEFS
LIBS
=
=
demo
demo.o
atmega8
-O2
# 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
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A simple project
147
$(PRG).elf: $(OBJ)
$(CC) $(CFLAGS) $(LDFLAGS) -o [email protected] $^ $(LIBS)
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]
%_eeprom.srec: %.elf
$(OBJCOPY) -j .eeprom --change-section-lma .eeprom=0 -O srec $< [email protected]
%_eeprom.bin: %.elf
$(OBJCOPY) -j .eeprom --change-section-lma .eeprom=0 -O binary $< [email protected]
# 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
png: $(PRG).png
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pdf: $(PRG).pdf
%.eps: %.fig
$(FIG2DEV) -L eps $< [email protected]
%.pdf: %.fig
$(FIG2DEV) -L pdf $< [email protected]
%.png: %.fig
$(FIG2DEV) -L png $< [email protected]
5.29
Example using the two-wire interface (TWI)
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 the original Philips documentation, see
http://www.semiconductors.philips.com/buses/i2c/index.html
5.29.1
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.)
5.29.2
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
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149
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.
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.
5.29.3
The Source Code
/*
* ---------------------------------------------------------------------------* "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.
* ---------------------------------------------------------------------------*/
/* $Id: twitest.c,v 1.6 2005/11/05 22:32:46 joerg_wunsch Exp $ */
/*
* Simple demo program that talks to a 24Cxx IšC EEPROM using the
* builtin TWI interface of an ATmega device.
*/
#include <inttypes.h>
#include <stdio.h>
#include <stdlib.h>
#include <avr/io.h>
#include <util/twi.h>
/* Note [1] */
#define DEBUG 1
/*
* System clock in Hz.
*/
#define F_CPU 14745600UL
/* Note [2] */
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150
/*
* Compatibility defines. This should work on ATmega8, ATmega16,
* ATmega163, ATmega323 and ATmega128 (IOW: on all devices that
* provide a builtin TWI interface).
*
* On the 128, it defaults to USART 1.
*/
#ifndef UCSRB
# ifdef UCSR1A
/* ATmega128 */
# define UCSRA UCSR1A
# define UCSRB UCSR1B
# define UBRR UBRR1L
# define UDR UDR1
# else /* ATmega8 */
# define UCSRA USR
# define UCSRB UCR
# endif
#endif
#ifndef UBRR
# define UBRR UBRRL
#endif
/*
* Note [3]
* TWI address for 24Cxx EEPROM:
*
24C01/24C02
* 1 0 1 0 E2 E1 E0 R/~W
24C04
* 1 0 1 0 E2 E1 A8 R/~W
24C08
* 1 0 1 0 E2 A9 A8 R/~W
24C16
* 1 0 1 0 A10 A9 A8 R/~W
*/
#define TWI_SLA_24CXX
0xa0
/* E2 E1 E0 = 0 0 0 */
/*
* Maximal number of iterations to wait for a device to respond for a
* selection. Should be large enough to allow for a pending write to
* complete, but low enough to properly abort an infinite loop in case
* a slave is broken or not present at all. With 100 kHz TWI clock,
* transfering the start condition and SLA+R/W packet takes about 10
* ţs. The longest write period is supposed to not exceed ~ 10 ms.
* Thus, normal operation should not require more than 100 iterations
* to get the device to respond to a selection.
*/
#define MAX_ITER
200
/*
* Number of bytes that can be written in a row, see comments for
* ee24xx_write_page() below. Some vendor’s devices would accept 16,
* but 8 seems to be the lowest common denominator.
*
* Note that the page size must be a power of two, this simplifies the
* page boundary calculations below.
*/
#define PAGE_SIZE 8
/*
* Saved TWI status register, for error messages only.
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5.29
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151
* save it in a variable, since the datasheet only guarantees the TWSR
* register to have valid contents while the TWINT bit in TWCR is set.
*/
uint8_t twst;
/*
* Do all the startup-time peripheral initializations: UART (for our
* debug/test output), and TWI clock.
*/
void
ioinit(void)
{
#if F_CPU <= 1000000UL
/*
* Note [4]
* Slow system clock, double Baud rate to improve rate error.
*/
UCSRA = _BV(U2X);
UBRR = (F_CPU / (8 * 9600UL)) - 1; /* 9600 Bd */
#else
UBRR = (F_CPU / (16 * 9600UL)) - 1; /* 9600 Bd */
#endif
UCSRB = _BV(TXEN);
/* tx enable */
/* initialize TWI clock: 100 kHz clock, TWPS = 0 => prescaler = 1 */
#if defined(TWPS0)
/* has prescaler (mega128 & newer) */
TWSR = 0;
#endif
#if F_CPU < 3600000UL
TWBR = 10;
/* smallest TWBR value, see note [5] */
#else
TWBR = (F_CPU / 100000UL - 16) / 2;
#endif
}
/*
* Note [6]
* Send character c down the UART Tx, wait until tx holding register
* is empty.
*/
int
uart_putchar(char c, FILE *unused)
{
if (c == ’\n’)
uart_putchar(’\r’, 0);
loop_until_bit_is_set(UCSRA, UDRE);
UDR = c;
return 0;
}
/*
* Note [7]
*
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152
* Read "len" bytes from EEPROM starting at "eeaddr" into "buf".
*
* This requires two bus cycles: during the first cycle, the device
* will be selected (master transmitter mode), and the address
* transfered. Address bits exceeding 256 are transfered in the
* E2/E1/E0 bits (subaddress bits) of the device selector.
*
* The second bus cycle will reselect the device (repeated start
* condition, going into master receiver mode), and transfer the data
* from the device to the TWI master. Multiple bytes can be
* transfered by ACKing the client’s transfer. The last transfer will
* be NACKed, which the client will take as an indication to not
* initiate further transfers.
*/
int
ee24xx_read_bytes(uint16_t eeaddr, int len, uint8_t *buf)
{
uint8_t sla, twcr, n = 0;
int rv = 0;
/* patch high bits of EEPROM address into SLA */
sla = TWI_SLA_24CXX | (((eeaddr >> 8) & 0x07) << 1);
/*
* Note [8]
* First cycle: master transmitter mode
*/
restart:
if (n++ >= MAX_ITER)
return -1;
begin:
TWCR = _BV(TWINT) | _BV(TWSTA) | _BV(TWEN); /* send start condition */
while ((TWCR & _BV(TWINT)) == 0) ; /* wait for transmission */
switch ((twst = TW_STATUS))
{
case TW_REP_START:
/* OK, but should not happen */
case TW_START:
break;
case TW_MT_ARB_LOST:
goto begin;
default:
return -1;
/* Note [9] */
/* error: not in start condition */
/* NB: do /not/ send stop condition */
}
/* Note [10] */
/* send SLA+W */
TWDR = sla | TW_WRITE;
TWCR = _BV(TWINT) | _BV(TWEN); /* clear interrupt to start transmission */
while ((TWCR & _BV(TWINT)) == 0) ; /* wait for transmission */
switch ((twst = TW_STATUS))
{
case TW_MT_SLA_ACK:
break;
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case TW_MT_SLA_NACK:
153
/* nack during select: device busy writing */
/* Note [11] */
goto restart;
case TW_MT_ARB_LOST:
goto begin;
default:
goto error;
}
/* re-arbitrate */
/* must send stop condition */
TWDR = eeaddr;
/* low 8 bits of addr */
TWCR = _BV(TWINT) | _BV(TWEN); /* clear interrupt to start transmission */
while ((TWCR & _BV(TWINT)) == 0) ; /* wait for transmission */
switch ((twst = TW_STATUS))
{
case TW_MT_DATA_ACK:
break;
case TW_MT_DATA_NACK:
goto quit;
case TW_MT_ARB_LOST:
goto begin;
default:
goto error;
}
/* must send stop condition */
/*
* Note [12]
* Next cycle(s): master receiver mode
*/
TWCR = _BV(TWINT) | _BV(TWSTA) | _BV(TWEN); /* send (rep.) start condition */
while ((TWCR & _BV(TWINT)) == 0) ; /* wait for transmission */
switch ((twst = TW_STATUS))
{
case TW_START:
/* OK, but should not happen */
case TW_REP_START:
break;
case TW_MT_ARB_LOST:
goto begin;
default:
goto error;
}
/* send SLA+R */
TWDR = sla | TW_READ;
TWCR = _BV(TWINT) | _BV(TWEN); /* clear interrupt to start transmission */
while ((TWCR & _BV(TWINT)) == 0) ; /* wait for transmission */
switch ((twst = TW_STATUS))
{
case TW_MR_SLA_ACK:
break;
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154
case TW_MR_SLA_NACK:
goto quit;
case TW_MR_ARB_LOST:
goto begin;
default:
goto error;
}
for (twcr = _BV(TWINT) | _BV(TWEN) | _BV(TWEA) /* Note [13] */;
len > 0;
len--)
{
if (len == 1)
twcr = _BV(TWINT) | _BV(TWEN); /* send NAK this time */
TWCR = twcr;
/* clear int to start transmission */
while ((TWCR & _BV(TWINT)) == 0) ; /* wait for transmission */
switch ((twst = TW_STATUS))
{
case TW_MR_DATA_NACK:
len = 0;
/* force end of loop */
/* FALLTHROUGH */
case TW_MR_DATA_ACK:
*buf++ = TWDR;
rv++;
break;
default:
goto error;
}
}
quit:
/* Note [14] */
TWCR = _BV(TWINT) | _BV(TWSTO) | _BV(TWEN); /* send stop condition */
return rv;
error:
rv = -1;
goto quit;
}
/*
*
*
*
*
*
*
*
*
*
*
*
*
Write "len" bytes into EEPROM starting at "eeaddr" from "buf".
This is a bit simpler than the previous function since both, the
address and the data bytes will be transfered in master transmitter
mode, thus no reselection of the device is necessary. However, the
EEPROMs are only capable of writing one "page" simultaneously, so
care must be taken to not cross a page boundary within one write
cycle. The amount of data one page consists of varies from
manufacturer to manufacturer: some vendors only use 8-byte pages
for the smaller devices, and 16-byte pages for the larger devices,
while other vendors generally use 16-byte pages. We thus use the
smallest common denominator of 8 bytes per page, declared by the
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155
* macro PAGE_SIZE above.
*
* The function simply returns after writing one page, returning the
* actual number of data byte written. It is up to the caller to
* re-invoke it in order to write further data.
*/
int
ee24xx_write_page(uint16_t eeaddr, int len, uint8_t *buf)
{
uint8_t sla, n = 0;
int rv = 0;
uint16_t endaddr;
if (eeaddr + len < (eeaddr | (PAGE_SIZE - 1)))
endaddr = eeaddr + len;
else
endaddr = (eeaddr | (PAGE_SIZE - 1)) + 1;
len = endaddr - eeaddr;
/* patch high bits of EEPROM address into SLA */
sla = TWI_SLA_24CXX | (((eeaddr >> 8) & 0x07) << 1);
restart:
if (n++ >= MAX_ITER)
return -1;
begin:
/* Note [15] */
TWCR = _BV(TWINT) | _BV(TWSTA) | _BV(TWEN); /* send start condition */
while ((TWCR & _BV(TWINT)) == 0) ; /* wait for transmission */
switch ((twst = TW_STATUS))
{
case TW_REP_START:
/* OK, but should not happen */
case TW_START:
break;
case TW_MT_ARB_LOST:
goto begin;
default:
return -1;
/* error: not in start condition */
/* NB: do /not/ send stop condition */
}
/* send SLA+W */
TWDR = sla | TW_WRITE;
TWCR = _BV(TWINT) | _BV(TWEN); /* clear interrupt to start transmission */
while ((TWCR & _BV(TWINT)) == 0) ; /* wait for transmission */
switch ((twst = TW_STATUS))
{
case TW_MT_SLA_ACK:
break;
case TW_MT_SLA_NACK:
goto restart;
/* nack during select: device busy writing */
case TW_MT_ARB_LOST:
/* re-arbitrate */
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156
goto begin;
default:
goto error;
}
/* must send stop condition */
TWDR = eeaddr;
/* low 8 bits of addr */
TWCR = _BV(TWINT) | _BV(TWEN); /* clear interrupt to start transmission */
while ((TWCR & _BV(TWINT)) == 0) ; /* wait for transmission */
switch ((twst = TW_STATUS))
{
case TW_MT_DATA_ACK:
break;
case TW_MT_DATA_NACK:
goto quit;
case TW_MT_ARB_LOST:
goto begin;
default:
goto error;
}
/* must send stop condition */
for (; len > 0; len--)
{
TWDR = *buf++;
TWCR = _BV(TWINT) | _BV(TWEN); /* start transmission */
while ((TWCR & _BV(TWINT)) == 0) ; /* wait for transmission */
switch ((twst = TW_STATUS))
{
case TW_MT_DATA_NACK:
goto error;
/* device write protected -- Note [16] */
case TW_MT_DATA_ACK:
rv++;
break;
default:
goto error;
}
}
quit:
TWCR = _BV(TWINT) | _BV(TWSTO) | _BV(TWEN); /* send stop condition */
return rv;
error:
rv = -1;
goto quit;
}
/*
* Wrapper around ee24xx_write_page() that repeats calling this
* function until either an error has been returned, or all bytes
* have been written.
*/
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157
int
ee24xx_write_bytes(uint16_t eeaddr, int len, uint8_t *buf)
{
int rv, total;
total = 0;
do
{
#if DEBUG
printf("Calling ee24xx_write_page(%d, %d, %p)",
eeaddr, len, buf);
#endif
rv = ee24xx_write_page(eeaddr, len, buf);
#if DEBUG
printf(" => %d\n", rv);
#endif
if (rv == -1)
return -1;
eeaddr += rv;
len -= rv;
buf += rv;
total += rv;
}
while (len > 0);
return total;
}
void
error(void)
{
printf("error: TWI status %#x\n", twst);
exit(0);
}
FILE mystdout = FDEV_SETUP_STREAM(uart_putchar, NULL, _FDEV_SETUP_WRITE);
void
main(void)
{
uint16_t a;
int rv;
uint8_t b[16];
uint8_t x;
ioinit();
stdout = &mystdout;
for (a = 0; a < 256;)
{
printf("%#04x: ", a);
rv = ee24xx_read_bytes(a, 16, b);
if (rv <= 0)
error();
if (rv < 16)
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158
printf("warning: short read %d\n", rv);
a += rv;
for (x = 0; x < rv; x++)
printf("%02x ", b[x]);
putchar(’\n’);
}
#define EE_WRITE(addr, str) ee24xx_write_bytes(addr, sizeof(str)-1, str)
rv = EE_WRITE(55, "The quick brown fox jumps over the lazy dog.");
if (rv < 0)
error();
printf("Wrote %d bytes.\n", rv);
for (a = 0; a < 256;)
{
printf("%#04x: ", a);
rv = ee24xx_read_bytes(a, 16, b);
if (rv <= 0)
error();
if (rv < 16)
printf("warning: short read %d\n", rv);
a += rv;
for (x = 0; x < rv; x++)
printf("%02x ", b[x]);
putchar(’\n’);
}
printf("done.\n");
}
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)
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159
"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.
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]
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.
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160
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
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
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6 avr-libc Data Structure Documentation
161
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]
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.
6
avr-libc Data Structure Documentation
6.1
div_t Struct Reference
6.1.1
Detailed Description
Result type for function div().
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6.2
ldiv_t Struct Reference
Data Fields
• int quot
• int rem
6.1.2
Field Documentation
6.1.2.1
int div_t::quot
The Quotient.
6.1.2.2
int div_t::rem
The Remainder.
The documentation for this struct was generated from the following file:
• stdlib.h
6.2
ldiv_t Struct Reference
6.2.1
Detailed Description
Result type for function ldiv().
Data Fields
• long quot
• long rem
6.2.2
6.2.2.1
Field Documentation
long ldiv_t::quot
The Quotient.
6.2.2.2
long ldiv_t::rem
The Remainder.
The documentation for this struct was generated from the following file:
• stdlib.h
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162
7 avr-libc Page Documentation
7
7.1
163
avr-libc Page Documentation
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.
• 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 Opensource 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. ;-)
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7.2
avr-libc and assembler programs
7.2
avr-libc and assembler programs
7.2.1
Introduction
164
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.
• 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.
7.2.2
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.
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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
assembler-with-cpp option.
7.2.3
explicitly
be
specified
using
the
-x
Example program
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
_SFR_IO_ADDR(SREG), intsav
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; Note [6]
; Note [7]
; Note [8]
; Note [9]
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166
reti
ioinit:
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
out
work, 256 - tmconst
_SFR_IO_ADDR(TCNT0), work
CK/1
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]
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167
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
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.)
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168
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.
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.)
7.2.4
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)
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• .data switches to the .data section (initialized RAM variables)
• .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 AVRspecific 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.
7.3
Frequently Asked Questions
7.3.1
FAQ Index
1. My program doesn’t recognize a variable updated within an interrupt routine
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Frequently Asked Questions
170
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" messsage?
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?
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7.3
7.3.2
Frequently Asked Questions
171
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.
7.3.3
I get "undefined reference to..." for functions like "sin()"
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.
7.3.4
How to permanently bind a variable to a register?
This can be done with
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Frequently Asked Questions
172
register unsigned char counter asm("r3");
Typically, it should be possible to use r2 through r15 that way.
See C Names Used in Assembler Code for more details.
Back to FAQ Index.
7.3.5
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
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
preferrably be placed into section .init3 as the code in .init2 ensures the internal register __zero_reg__ is already cleared.
Back to FAQ Index.
7.3.6
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
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173
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. :-)
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.
7.3.7
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.)
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• 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.
7.3.8
Shouldn’t I initialize all my variables?
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
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175
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.
7.3.9
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.
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;
}
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176
Back to FAQ Index.
7.3.10
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)):);
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.
7.3.11
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 optimzation 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
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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.
7.3.12
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.
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
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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
rjmp
1:
ld
...
breq
...
inc
2:
cmp
brlo
1:
pop
pop
pop
pop
pop
ret
r16
r17
r18
YL
YH
r16, r16
; start loop
YL, lo8(sometable)
YH, hi8(sometable)
2f
; jump to loop test at end
r17, Y+
; loop continues here
1f
; return from myfunc prematurely
r16
r16, r18
1b
; jump back to top of loop
YH
YL
r18
r17
r16
Back to FAQ Index.
7.3.13
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
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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:
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
; 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;
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fa:
fc:
fe:
80 81
86 2b
80 83
ld
or
st
}
100:
08 95
ret
180
r24, Z
r24, r22
Z, r24
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 data sheet.
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
; 24
; 240
; 24
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.
7.3.14
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 the whole
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128K program memory space on the ATmega devices with > 64 KB of flash
ROM). 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.
• Fixed registers (r0, r1):
Never allocated by gcc for local data, but often used for fixed purposes:
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 caller
(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.
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182
Back to FAQ Index.
7.3.15
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]);
return 0;
}
The result is not want 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>:
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26:
28:
2e 00
2a 00
.word
.word
183
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
74:
6a 5d
subi
r22, 0xDA
76:
7f 4f
sbci
r23, 0xFF
78:
42 e0
ldi
r20, 0x02
7a:
50 e0
ldi
r21, 0x00
7c:
ce 01
movw
r24, r28
7e:
81 96
adiw
r24, 0x21
80:
08 d0
rcall
.+16
;
;
;
;
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 accomodate 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.
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7.3.16
184
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
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.
7.3.17
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 tradeoff. 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
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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
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.
7.3.18
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.
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7.3.19
186
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,
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.
7.3.20
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:
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#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)
{
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.
7.3.21
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:
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var &= (unsigned char)~mask;
Back to FAQ Index.
7.3.22
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).
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 avaialable 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 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.
7.3.23
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.
7.3.24
What is this "clock skew detected" messsage?
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
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189
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
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.
7.3.25
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
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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
TIFR = _BV(TOV0);
Back to FAQ Index.
7.3.26
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.
7.3.27
Which AVR-specific assembler operators are available?
See Pseudo-ops and operators.
Back to FAQ Index.
7.4
Inline Asm
AVR-GCC
Inline Assembler Cookbook
About this Document
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.
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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/.
7.4.1
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:
"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))
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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)));
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"::);
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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
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.
7.4.3
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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Constraint
a
b
d
e
G
I
J
K
L
l
M
N
O
P
q
r
t
w
x
y
z
194
Used for
Simple upper registers
Base pointer registers
pairs
Upper register
Pointer register pairs
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
Stack pointer register
Any register
Temporary register
Special upper register
pairs
Pointer register pair X
Pointer register pair Y
Pointer register pair Z
Range
r16 to r23
y, z
r16 to r31
x, y, z
0.0
0 to 63
-63 to 0
2
0
r0 to r15
0 to 255
-1
8, 16, 24
1
SPH:SPL
r0 to r31
r0
r24, r26, r28, r30
x (r27:r26)
y (r29:r28)
z (r31:r30)
These definitions seem not to fit properly to the AVR instruction set. The author’s assumption is, that this part of the compiler has never been really finished in this version,
but that assumption may be wrong. 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.
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
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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 (not supported by
inline assembler)
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
operation used in the assembler instructions.
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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
"mov
"mov
"mov
__tmp_reg__, %A0"
%A0, %D0"
%D0, __tmp_reg__"
__tmp_reg__, %B0"
"\n\t"
"\n\t"
"\n\t"
"\n\t"
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"mov %B0, %C0"
"\n\t"
"mov %C0, __tmp_reg__" "\n\t"
: "=r" (value)
: "0" (value)
);
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.
7.4.4
Clobbers
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.
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asm volatile(
"cli"
"ld r24, %a0"
"inc r24"
"st %a0, r24"
"sei"
:
: "e" (ptr)
: "r24"
);
198
"\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.
{
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"
}
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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.
7.4.5
Assembler Macros
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.
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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)
\
)
7.4.6
\
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"
"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)
);
}
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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.
7.4.7
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:
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
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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.
7.4.8
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/
7.5
Using malloc()
7.5.1
Introduction
On a simple device like a microcontroller, implementing dynamic memory allocation
is quite a challenge.
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.
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7.5
Using malloc()
203
.data
on−board RAM
!
.bss
variables variables
heap
external RAM
0xFFFF
0x10FF
0x1100
0x0100
Note:
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 2: RAM map of a device with internal RAM
Finally, there’s a challenge to make the memory allocator 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 since microcontrollers aren’t only often low on space, but 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.
7.5.2
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.
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7.5
7.5.3
Using malloc()
204
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
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,-Tdata=0x801100,--defsym=__heap_end=0x80ffff ...
stack
external RAM
.data
.bss
variables variables
SP
RAMEND
0xFFFF
on−board RAM
0x10FF
0x1100
0x0100
Note:
See explanation for offset 0x800000. See the chapter about using gcc for the -Wl
options.
heap
__malloc_heap_end == __heap_end
brkval
__malloc_heap_start == __heap_start
__bss_end
__data_end == __bss_start
__data_start
Figure 3: 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
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Using malloc()
205
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 ...
.bss
.data
variables variables
stack
0xFFFF
0x3FFF
on−board RAM
0x2000
0x10FF
0x1100
0x0100
external RAM
heap
SP
RAMEND
__bss_end
__data_end == __bss_start
__malloc_heap_end == __heap_end
brkval
__malloc_heap_start == __heap_start
__data_start
Figure 4: 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.
7.5.4
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.
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206
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.
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.
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.
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7.6
Release Numbering and Methodology
7.6
Release Numbering and Methodology
7.6.1
Release Version Numbering Scheme
207
7.6.1.1 Stable Versions A stable release will always have a minor number that is
an even number. This implies that you should be able to upgrade to a new version of
the library with the same major and minor numbers without fear that any of the APIs
have changed. The only changes that should be made to a stable branch are bug fixes
and under some circumstances, additional functionality (e.g. adding support for a new
device).
If major version number has changed, this implies that the required versions of gcc and
binutils have changed. Consult the README file in the toplevel directory of the AVR
Libc source for which versions are required.
7.6.1.2 Development Versions The major version number of a development series
is always the same as the last stable release.
The minor version number of a development series is always an odd number and is 1
more than the last stable release.
The patch version number of a development series is always 0 until a new branch is cut
at which point the patch number is changed to 90 to denote the branch is approaching
a release and the date appended to the version to denote that it is still in development.
All versions in development in cvs will also always have the date appended as a fourth
version number. The format of the date will be YYYYMMDD.
So, the development version number will look like this:
1.1.0.20030825
While a pre-release version number on a branch (destined to become either 1.2 or 2.0)
will look like this:
1.1.90.20030828
7.6.2
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 cvs 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.
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7.6
Release Numbering and Methodology
7.6.2.1
in cvs:
208
Creating a cvs branch The following steps should be taken to cut a branch
1. Check out a fresh source tree from cvs HEAD.
2. Update the NEWS file with pending release number and commit to cvs HEAD:
Change ”Changes since avr-libc-<last_release>:” to ”Changes in avr-libc<this_relelase>:”.
3. Set the branch-point tag (setting <major> and <minor> accordingly):
’cvs tag avr-libc-<major>_<minor>-branchpoint’
4. Create the branch:
’cvs tag -b avr-libc-<major>_<minor>-branch’
5. Update the package version in configure.ac and commit configure.ac to cvs
HEAD:
Change minor number to next odd value.
6. Update the NEWS file and commit to cvs HEAD:
Add ”Changes since avr-libc-<this_release>:”
7. Check out a new tree for the branch:
’cvs co -r avr-libc-<major>_<minor>-branch’
8. Update the package version in configure.ac and commit configure.ac to cvs
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. Announce the branch and the branch tag to the avr-libc-dev list so other developers can checkout the branch.
Note:
CVS tags do not allow the use of periods (’.’).
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Release Numbering and Methodology
209
7.6.2.2 Making a release A stable release will only be done on a branch, not from
the cvs HEAD.
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:
’cvs update -r avr-libc-<major>_<minor>-branch’
2. Update the package version in configure.in and commit it to cvs.
3. Update the gnu tool chain version requirements in the README and commit to
cvs.
4. Update the ChangeLog file to note the release and commit to cvs on the branch:
Add ”Released avr-libc-<this_release>.”
5. Update the NEWS file with pending release number and commit to cvs:
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:
’cvs tag avr-libc-<major>_<minor>_<patch>-release’
9. Upload the tarball to savannah.
10. Update the NEWS file, and commit to cvs:
Add ”Changes since avr-libc-<major>_<minor>_<patch>:”
11. Generate the latest documentation and upload to savannah.
12. Announce the release.
The following hypothetical diagram should help clarify version and branch relationships.
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7.7
Memory Sections
210
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 5: Release tree
7.7
Memory Sections
Remarks:
Need to list all the sections which are available to the avr.
Weak Bindings
FIXME: need to discuss the .weak directive.
The following describes the various sections available.
7.7.1
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.
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Memory Sections
211
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.
7.7.2
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.
7.7.3
The .bss Section
Uninitialized global or static variables end up in the .bss section.
7.7.4
The .eeprom Section
This is where eeprom variables are stored.
7.7.5
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")));
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Memory Sections
212
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.]
7.7.6
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.
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.
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7.7
Memory Sections
213
.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().
7.7.7
The .finiN Sections
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.
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Memory Sections
214
.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).
7.7.8
Using Sections in Assembler Code
Example:
#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.
7.7.9
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;
}
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Installing the GNU Tool Chain
215
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.
7.8
Installing the GNU Tool Chain
Note:
This discussion was taken directly from Rich Neswold’s document. (See Acknowledgments).
This discussion is Unix specific. [FIXME: troth/2002-08-13: we need a volunteer
to add windows specific notes to these instructions.]
This chapter shows how to build and install a complete development environment for
the AVR processors using the GNU toolset.
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.
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Installing the GNU Tool Chain
216
Note:
It is usually the best to use the latest released version of each of the tools.
7.8.1
Required Tools
• GNU Binutils
http://sources.redhat.com/binutils/
Installation
• GCC
http://gcc.gnu.org/
Installation
• AVR Libc
http://savannah.gnu.org/projects/avr-libc/
Installation
7.8.2
Optional Tools
You can develop programs for AVR devices without the following tools. They may or
may not be of use for you.
• uisp
http://savannah.gnu.org/projects/uisp/
Installation
• 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
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Installing the GNU Tool Chain
217
• AVaRice
http://avarice.sourceforge.net/
Installation
7.8.3
GNU Binutils for the AVR target
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
with the version of the package you downloaded.
Note:
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.
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Installing the GNU Tool Chain
218
$ 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.
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.
7.8.4
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 --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.
7.8.5
AVR Libc
Warning:
You must install avr-binutils, avr-gcc and make sure your path is set properly
before installing avr-libc.
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219
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 --build=‘./config.guess‘ --host=avr
make
make install
Note:
Other configure options might follow, notably –prefix in order to change the directory prefix for the installed files from its default /usr/local.
7.8.6
UISP
Uisp also uses the configure system, so to build and install:
$
$
$
$
$
$
$
gunzip -c uisp-<version>.tar.gz | tar xf cd uisp-<version>
mkdir obj-avr
cd obj-avr
../configure --prefix=$PREFIX
make
make install
7.8.7
Avrdude
Note:
It has been ported to windows (via cygwin) and linux. 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:
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7.8
$
$
$
$
$
$
$
Installing the GNU Tool Chain
220
gunzip -c avrdude-<version>.tar.gz | tar xf cd avrdude-<version>
mkdir obj-avr
cd obj-avr
../configure --prefix=$PREFIX
make
make install
7.8.8
GDB for the AVR target
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.
7.8.9
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.
7.8.10
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.
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221
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
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
7.9
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
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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
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
?
:
:
:
:
:
:
:
:
:
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
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quit
223
: quit
Use the ’part’ command to display valid memory types for use with the
’dump’ and ’write’ commands.
avrdude>
7.10
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.
7.10.1
Options for the C compiler avr-gcc
7.10.1.1 Machine-specific options for the AVR
options are recognized by the C compiler frontend.
The following machine-specific
• -mmcu=architecture
Compile code for architecture. Currently known architectures are
avr1
avr2
avr3
avr4
avr5
Simple CPU core, only assembler
support
"Classic" CPU core, up to 8 KB of
ROM
"Classic" CPU core, more than 8 KB of
ROM
"Enhanced" CPU core, up to 8 KB of
ROM
"Enhanced" CPU core, more than 8 KB
of ROM
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.
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Architecture
avr1
avr1
avr1
avr1
avr1
avr2
avr2
avr2
avr2
avr2
avr2
avr2
avr2
avr2
avr2
avr2
avr2
avr2
avr2
avr2
avr2
avr2
avr2
avr3
avr3
avr3
avr3
avr3
avr4
avr4
avr4
avr4
avr4
avr4
avr4
avr5
avr5
avr5
avr5
avr5
avr5
avr5
avr5
224
MCU name
at90s1200
attiny11
attiny12
attiny15
attiny28
at90s2313
at90s2323
at90s2333
at90s2343
attiny22
attiny25
attiny26
attiny45
attiny85
at90s4414
at90s4433
at90s4434
at90s8515
at90c8534
at90s8535
at86rf401
attiny13
attiny2313
atmega103
atmega603
at43usb320
at43usb355
at76c711
atmega48
atmega8
atmega8515
atmega8535
atmega88
at90pwm2
at90pwm3
at90can32
at90can64
at90can128
atmega128
atmega1280
atmega1281
atmega16
atmega161
Macro
__AVR_AT90S1200__
__AVR_ATtiny11__
__AVR_ATtiny12__
__AVR_ATtiny15__
__AVR_ATtiny28__
__AVR_AT90S2313__
__AVR_AT90S2323__
__AVR_AT90S2333__
__AVR_AT90S2343__
__AVR_ATtiny22__
__AVR_ATtiny25__
__AVR_ATtiny26__
__AVR_ATtiny45__
__AVR_ATtiny85__
__AVR_AT90S4414__
__AVR_AT90S4433__
__AVR_AT90S4434__
__AVR_AT90S8515__
__AVR_AT90C8534__
__AVR_AT90S8535__
__AVR_AT86RF401__
__AVR_ATtiny13__
__AVR_ATtiny2313__
__AVR_ATmega103__
__AVR_ATmega603__
__AVR_AT43USB320__
__AVR_AT43USB355__
__AVR_AT76C711__
__AVR_ATmega48__
__AVR_ATmega8__
__AVR_ATmega8515__
__AVR_ATmega8535__
__AVR_ATmega88__
__AVR_AT90PWM2__
__AVR_AT90PWM3__
__AVR_AT90CAN32__
__AVR_AT90CAN64__
__AVR_AT90CAN128__
__AVR_ATmega128__
__AVR_ATmega1280__
__AVR_ATmega1281__
__AVR_ATmega16__
__AVR_ATmega161__
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Architecture
avr5
avr5
avr5
avr5
avr5
avr5
avr5
avr5
avr5
avr5
avr5
avr5
avr5
avr5
avr5
avr5
avr5
avr5
avr5
avr5
avr5
225
MCU name
atmega162
atmega163
atmega164
atmega165
atmega168
atmega169
atmega32
atmega323
atmega324
atmega325
atmega3250
atmega329
atmega3290
atmega64
atmega640
atmega644
atmega645
atmega6450
atmega649
atmega6490
at94k
Macro
__AVR_ATmega162__
__AVR_ATmega163__
__AVR_ATmega164__
__AVR_ATmega165__
__AVR_ATmega168__
__AVR_ATmega169__
__AVR_ATmega32__
__AVR_ATmega323__
__AVR_ATmega324__
__AVR_ATmega325__
__AVR_ATmega3250__
__AVR_ATmega329__
__AVR_ATmega3290__
__AVR_ATmega64__
__AVR_ATmega640__
__AVR_ATmega644__
__AVR_ATmega645__
__AVR_ATmega6450__
__AVR_ATmega649__
__AVR_ATmega6490__
__AVR_AT94K__
• -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
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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.
• -mcall-prologues
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.
• -minit-stack=nnnn
Set the initial stack pointer to nnnn. By default, the stack pointer is initialized to the
symbol __stack, which is set to RAMEND by the run-time initialization code.
• -mtiny-stack
Change only the low 8 bits of the stack pointer.
• -mno-tablejump
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.
• -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
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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.
7.10.1.2 Selected general compiler options
might be of some interest to AVR users.
The following general gcc options
• -On
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()
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228
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.
• -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.
7.10.2
7.10.2.1
Options for the assembler avr-as
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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• -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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7.10.2.2 Examples for assembler options passed through the C compiler 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).
7.10.3
Controlling the linker avr-ld
7.10.3.1 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.
• -M
Print a linker map to stdout.
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• -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.
7.10.3.2 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
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
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232
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 unless a -minit-stack option has been given when compiling
the C source file that contains the function main(), 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.
7.11
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.
7.12
Deprecated List
Global enable_external_int(mask)
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7.12
Deprecated List
Global INTERRUPT(signame)
Global timer_enable_int(unsigned char ints)
Global inp(port)
Global outp(port, val)
Global sbi(port, bit)
Global cbi(port, bit)
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Index
$PATH, 214
$PREFIX, 214
–prefix, 214
<assert.h>: Diagnostics, 7
<avr/boot.h>: Bootloader Support Utilities, 8
<avr/eeprom.h>: EEPROM handling, 14
<avr/interrupt.h>: Interrupts, 118
<avr/io.h>: AVR device-specific IO definitions, 17
<avr/pgmspace.h>:
Program Space
String Utilities, 18
<avr/sfr_defs.h>: Special function registers, 131
<avr/sleep.h>: Power Management and
Sleep Modes, 27
<avr/version.h>:
avr-libc version
macros, 29
<avr/wdt.h>: Watchdog timer handling,
30
<compat/deprecated.h>:
Deprecated
items, 33
<compat/ina90.h>: Compatibility with
IAR EWB 3.x, 36
<ctype.h>: Character Operations, 37
<errno.h>: System Errors, 39
<inttypes.h>: Integer Type conversions,
40
<math.h>: Mathematics, 52
<setjmp.h>: Non-local goto, 56
<stdint.h>: Standard Integer Types, 58
<stdio.h>: Standard IO facilities, 70
<stdlib.h>: General utilities, 88
<string.h>: Strings, 99
<util/crc16.h>: CRC Computations, 108
<util/delay.h>: Busy-wait delay loops,
111
<util/parity.h>: Parity bit generation, 112
<util/twi.h>: TWI bit mask definitions,
113
_BV
avr_sfr, 133
_EEGET
avr_eeprom, 15
_EEPUT
avr_eeprom, 15
_FDEV_EOF
avr_stdio, 74
_FDEV_ERR
avr_stdio, 74
_FDEV_SETUP_READ
avr_stdio, 75
_FDEV_SETUP_RW
avr_stdio, 75
_FDEV_SETUP_WRITE
avr_stdio, 75
_FFS
avr_string, 100
__AVR_LIBC_DATE_
avr_version, 29
__AVR_LIBC_DATE_STRING__
avr_version, 29
__AVR_LIBC_MAJOR__
avr_version, 30
__AVR_LIBC_MINOR__
avr_version, 30
__AVR_LIBC_REVISION__
avr_version, 30
__AVR_LIBC_VERSION_STRING__
avr_version, 30
__AVR_LIBC_VERSION__
avr_version, 30
__EEPROM_REG_LOCATIONS__
avr_eeprom, 15
__compar_fn_t
avr_stdlib, 90
__malloc_heap_end
avr_stdlib, 99
__malloc_heap_start
avr_stdlib, 99
__malloc_margin
avr_stdlib, 99
_crc16_update
util_crc, 109
INDEX
_crc_ccitt_update
util_crc, 109
_crc_ibutton_update
util_crc, 109
_crc_xmodem_update
util_crc, 110
_delay_loop_1
util_delay, 112
_delay_loop_2
util_delay, 112
_delay_ms
util_delay, 112
_delay_us
util_delay, 112
A simple project, 135
abort
avr_stdlib, 90
abs
avr_stdlib, 90
acos
avr_math, 53
Additional notes from <avr/sfr_defs.h>,
26
asin
avr_math, 53
assert
avr_assert, 7
atan
avr_math, 53
atan2
avr_math, 53
atof
avr_stdlib, 91
atoi
avr_stdlib, 91
atol
avr_stdlib, 91
avr_assert
assert, 7
avr_boot
boot_is_spm_interrupt, 10
boot_lock_bits_set, 10
boot_lock_bits_set_safe, 10
boot_lock_fuse_bits_get, 10
boot_page_erase, 11
235
boot_page_erase_safe, 11
boot_page_fill, 11
boot_page_fill_safe, 12
boot_page_write, 12
boot_page_write_safe, 12
boot_rww_busy, 12
boot_rww_enable, 13
boot_rww_enable_safe, 13
boot_spm_busy, 13
boot_spm_busy_wait, 13
boot_spm_interrupt_disable, 13
boot_spm_interrupt_enable, 13
BOOTLOADER_SECTION, 13
GET_EXTENDED_FUSE_BITS,
13
GET_HIGH_FUSE_BITS, 14
GET_LOCK_BITS, 14
GET_LOW_FUSE_BITS, 14
avr_eeprom
_EEGET, 15
_EEPUT, 15
__EEPROM_REG_LOCATIONS__, 15
EEMEM, 16
eeprom_busy_wait, 16
eeprom_is_ready, 16
eeprom_read_block, 16
eeprom_read_byte, 16
eeprom_read_word, 16
eeprom_write_block, 16
eeprom_write_byte, 16
eeprom_write_word, 17
avr_errno
EDOM, 40
ERANGE, 40
avr_interrupts
EMPTY_INTERRUPT, 130
ISR, 130
SIGNAL, 131
avr_inttypes
int_farptr_t, 52
PRId16, 43
PRId32, 43
PRId8, 43
PRIdFAST16, 43
PRIdFAST32, 43
Generated on Sat Nov 19 23:00:48 2005 for avr-libc by Doxygen
INDEX
PRIdFAST8, 43
PRIdLEAST16, 43
PRIdLEAST32, 43
PRIdLEAST8, 44
PRIdPTR, 44
PRIi16, 44
PRIi32, 44
PRIi8, 44
PRIiFAST16, 44
PRIiFAST32, 44
PRIiFAST8, 44
PRIiLEAST16, 44
PRIiLEAST32, 44
PRIiLEAST8, 44
PRIiPTR, 45
PRIo16, 45
PRIo32, 45
PRIo8, 45
PRIoFAST16, 45
PRIoFAST32, 45
PRIoFAST8, 45
PRIoLEAST16, 45
PRIoLEAST32, 45
PRIoLEAST8, 45
PRIoPTR, 45
PRIu16, 46
PRIu32, 46
PRIu8, 46
PRIuFAST16, 46
PRIuFAST32, 46
PRIuFAST8, 46
PRIuLEAST16, 46
PRIuLEAST32, 46
PRIuLEAST8, 46
PRIuPTR, 46
PRIX16, 46
PRIx16, 47
PRIX32, 47
PRIx32, 47
PRIX8, 47
PRIx8, 47
PRIXFAST16, 47
PRIxFAST16, 47
PRIXFAST32, 47
PRIxFAST32, 47
PRIXFAST8, 47
236
PRIxFAST8, 47
PRIXLEAST16, 48
PRIxLEAST16, 48
PRIXLEAST32, 48
PRIxLEAST32, 48
PRIXLEAST8, 48
PRIxLEAST8, 48
PRIXPTR, 48
PRIxPTR, 48
SCNd16, 48
SCNd32, 48
SCNdFAST16, 48
SCNdFAST32, 49
SCNdLEAST16, 49
SCNdLEAST32, 49
SCNdPTR, 49
SCNi16, 49
SCNi32, 49
SCNiFAST16, 49
SCNiFAST32, 49
SCNiLEAST16, 49
SCNiLEAST32, 49
SCNiPTR, 49
SCNo16, 50
SCNo32, 50
SCNoFAST16, 50
SCNoFAST32, 50
SCNoLEAST16, 50
SCNoLEAST32, 50
SCNoPTR, 50
SCNu16, 50
SCNu32, 50
SCNuFAST16, 50
SCNuFAST32, 50
SCNuLEAST16, 51
SCNuLEAST32, 51
SCNuPTR, 51
SCNx16, 51
SCNx32, 51
SCNxFAST16, 51
SCNxFAST32, 51
SCNxLEAST16, 51
SCNxLEAST32, 51
SCNxPTR, 51
uint_farptr_t, 52
avr_math
Generated on Sat Nov 19 23:00:48 2005 for avr-libc by Doxygen
INDEX
acos, 53
asin, 53
atan, 53
atan2, 53
ceil, 54
cos, 54
cosh, 54
exp, 54
fabs, 54
floor, 54
fmod, 54
frexp, 54
isinf, 54
isnan, 55
ldexp, 55
log, 55
log10, 55
M_PI, 53
M_SQRT2, 53
modf, 55
pow, 55
sin, 55
sinh, 55
sqrt, 56
square, 56
tan, 56
tanh, 56
avr_pgmspace
memcpy_P, 23
PGM_P, 19
pgm_read_byte, 19
pgm_read_byte_far, 20
pgm_read_byte_near, 20
pgm_read_dword, 20
pgm_read_dword_far, 20
pgm_read_dword_near, 20
pgm_read_word, 21
pgm_read_word_far, 21
pgm_read_word_near, 21
PGM_VOID_P, 21
prog_char, 22
prog_int16_t, 22
prog_int32_t, 22
prog_int64_t, 22
prog_int8_t, 22
prog_uchar, 22
237
prog_uint16_t, 22
prog_uint32_t, 22
prog_uint64_t, 22
prog_uint8_t, 22
prog_void, 22
PROGMEM, 21
PSTR, 21
strcasecmp_P, 23
strcat_P, 23
strcmp_P, 23
strcpy_P, 23
strlcat_P, 24
strlcpy_P, 24
strlen_P, 24
strncasecmp_P, 24
strncat_P, 25
strncmp_P, 25
strncpy_P, 25
strnlen_P, 26
avr_sfr
_BV, 133
bit_is_clear, 133
bit_is_set, 133
loop_until_bit_is_clear, 134
loop_until_bit_is_set, 134
avr_sleep
set_sleep_mode, 29
sleep_mode, 29
SLEEP_MODE_ADC, 28
SLEEP_MODE_EXT_STANDBY,
28
SLEEP_MODE_IDLE, 28
SLEEP_MODE_PWR_DOWN, 28
SLEEP_MODE_PWR_SAVE, 28
SLEEP_MODE_STANDBY, 28
avr_stdint
INT16_C, 62
INT16_MAX, 62
INT16_MIN, 62
int16_t, 67
INT32_C, 62
INT32_MAX, 62
INT32_MIN, 62
int32_t, 67
INT64_C, 62
INT64_MAX, 62
Generated on Sat Nov 19 23:00:48 2005 for avr-libc by Doxygen
INDEX
INT64_MIN, 63
int64_t, 67
INT8_C, 63
INT8_MAX, 63
INT8_MIN, 63
int8_t, 67
INT_FAST16_MAX, 63
INT_FAST16_MIN, 63
int_fast16_t, 67
INT_FAST32_MAX, 63
INT_FAST32_MIN, 63
int_fast32_t, 67
INT_FAST64_MAX, 63
INT_FAST64_MIN, 63
int_fast64_t, 68
INT_FAST8_MAX, 63
INT_FAST8_MIN, 64
int_fast8_t, 68
INT_LEAST16_MAX, 64
INT_LEAST16_MIN, 64
int_least16_t, 68
INT_LEAST32_MAX, 64
INT_LEAST32_MIN, 64
int_least32_t, 68
INT_LEAST64_MAX, 64
INT_LEAST64_MIN, 64
int_least64_t, 68
INT_LEAST8_MAX, 64
INT_LEAST8_MIN, 64
int_least8_t, 68
INTMAX_C, 64
INTMAX_MAX, 64
INTMAX_MIN, 65
intmax_t, 68
INTPTR_MAX, 65
INTPTR_MIN, 65
intptr_t, 68
PTRDIFF_MAX, 65
PTRDIFF_MIN, 65
SIG_ATOMIC_MAX, 65
SIG_ATOMIC_MIN, 65
SIZE_MAX, 65
UINT16_C, 65
UINT16_MAX, 65
uint16_t, 68
UINT32_C, 65
238
UINT32_MAX, 66
uint32_t, 68
UINT64_C, 66
UINT64_MAX, 66
uint64_t, 68
UINT8_C, 66
UINT8_MAX, 66
uint8_t, 69
UINT_FAST16_MAX, 66
uint_fast16_t, 69
UINT_FAST32_MAX, 66
uint_fast32_t, 69
UINT_FAST64_MAX, 66
uint_fast64_t, 69
UINT_FAST8_MAX, 66
uint_fast8_t, 69
UINT_LEAST16_MAX, 66
uint_least16_t, 69
UINT_LEAST32_MAX, 66
uint_least32_t, 69
UINT_LEAST64_MAX, 67
uint_least64_t, 69
UINT_LEAST8_MAX, 67
uint_least8_t, 69
UINTMAX_C, 67
UINTMAX_MAX, 67
uintmax_t, 69
UINTPTR_MAX, 67
uintptr_t, 69
avr_stdio
_FDEV_EOF, 74
_FDEV_ERR, 74
_FDEV_SETUP_READ, 75
_FDEV_SETUP_RW, 75
_FDEV_SETUP_WRITE, 75
clearerr, 77
EOF, 75
fclose, 77
fdev_close, 75
fdev_get_udata, 75
fdev_set_udata, 75
FDEV_SETUP_STREAM, 75
fdev_setup_stream, 76
fdevopen, 78
feof, 78
ferror, 78
Generated on Sat Nov 19 23:00:48 2005 for avr-libc by Doxygen
INDEX
fflush, 78
fgetc, 79
fgets, 79
FILE, 76
fprintf, 79
fprintf_P, 79
fputc, 79
fputs, 79
fputs_P, 79
fread, 79
fscanf, 80
fscanf_P, 80
fwrite, 80
getc, 76
getchar, 76
gets, 80
printf, 80
printf_P, 80
putc, 76
putchar, 77
puts, 80
puts_P, 80
scanf, 81
scanf_P, 81
snprintf, 81
snprintf_P, 81
sprintf, 81
sprintf_P, 81
sscanf, 81
sscanf_P, 81
stderr, 77
stdin, 77
stdout, 77
ungetc, 81
vfprintf, 82
vfprintf_P, 84
vfscanf, 84
vfscanf_P, 87
vprintf, 87
vscanf, 87
vsnprintf, 87
vsnprintf_P, 87
vsprintf, 88
vsprintf_P, 88
avr_stdlib
__compar_fn_t, 90
239
__malloc_heap_end, 99
__malloc_heap_start, 99
__malloc_margin, 99
abort, 90
abs, 90
atof, 91
atoi, 91
atol, 91
bsearch, 91
calloc, 92
div, 92
DTOSTR_ALWAYS_SIGN, 90
DTOSTR_PLUS_SIGN, 90
DTOSTR_UPPERCASE, 90
dtostre, 92
dtostrf, 92
exit, 93
free, 93
itoa, 93
labs, 93
ldiv, 94
ltoa, 94
malloc, 94
qsort, 94
rand, 95
RAND_MAX, 90
rand_r, 95
random, 95
RANDOM_MAX, 90
random_r, 95
realloc, 95
srand, 96
srandom, 96
strtod, 96
strtol, 96
strtoul, 97
ultoa, 98
utoa, 98
avr_string
_FFS, 100
ffs, 100
ffsl, 101
ffsll, 101
memccpy, 101
memchr, 101
memcmp, 101
Generated on Sat Nov 19 23:00:48 2005 for avr-libc by Doxygen
INDEX
memcpy, 102
memmove, 102
memset, 102
strcasecmp, 102
strcat, 103
strchr, 103
strcmp, 103
strcpy, 103
strlcat, 104
strlcpy, 104
strlen, 104
strlwr, 104
strncasecmp, 105
strncat, 105
strncmp, 105
strncpy, 105
strnlen, 106
strrchr, 106
strrev, 106
strsep, 106
strstr, 107
strtok_r, 107
strupr, 107
avr_version
__AVR_LIBC_DATE_, 29
__AVR_LIBC_DATE_STRING__,
29
__AVR_LIBC_MAJOR__, 30
__AVR_LIBC_MINOR__, 30
__AVR_LIBC_REVISION__, 30
__AVR_LIBC_VERSION_STRING__, 30
__AVR_LIBC_VERSION__, 30
avr_watchdog
wdt_disable, 31
wdt_enable, 32
wdt_reset, 32
WDTO_120MS, 32
WDTO_15MS, 32
WDTO_1S, 32
WDTO_250MS, 33
WDTO_2S, 33
WDTO_30MS, 33
WDTO_4S, 33
WDTO_500MS, 33
WDTO_60MS, 33
240
WDTO_8S, 33
avrdude, usage, 220
avrprog, usage, 220
bit_is_clear
avr_sfr, 133
bit_is_set
avr_sfr, 133
boot_is_spm_interrupt
avr_boot, 10
boot_lock_bits_set
avr_boot, 10
boot_lock_bits_set_safe
avr_boot, 10
boot_lock_fuse_bits_get
avr_boot, 10
boot_page_erase
avr_boot, 11
boot_page_erase_safe
avr_boot, 11
boot_page_fill
avr_boot, 11
boot_page_fill_safe
avr_boot, 12
boot_page_write
avr_boot, 12
boot_page_write_safe
avr_boot, 12
boot_rww_busy
avr_boot, 12
boot_rww_enable
avr_boot, 13
boot_rww_enable_safe
avr_boot, 13
boot_spm_busy
avr_boot, 13
boot_spm_busy_wait
avr_boot, 13
boot_spm_interrupt_disable
avr_boot, 13
boot_spm_interrupt_enable
avr_boot, 13
BOOTLOADER_SECTION
avr_boot, 13
bsearch
avr_stdlib, 91
Generated on Sat Nov 19 23:00:48 2005 for avr-libc by Doxygen
INDEX
calloc
avr_stdlib, 92
cbi
deprecated_items, 35
ceil
avr_math, 54
clearerr
avr_stdio, 77
cos
avr_math, 54
cosh
avr_math, 54
ctype
isalnum, 37
isalpha, 37
isascii, 38
isblank, 38
iscntrl, 38
isdigit, 38
isgraph, 38
islower, 38
isprint, 38
ispunct, 38
isspace, 38
isupper, 38
isxdigit, 39
toascii, 39
tolower, 39
toupper, 39
Demo projects, 134
deprecated_items
cbi, 35
enable_external_int, 35
inp, 35
INTERRUPT, 35
outp, 36
sbi, 36
timer_enable_int, 36
disassembling, 139
div
avr_stdlib, 92
div_t, 160
quot, 161
rem, 161
DTOSTR_ALWAYS_SIGN
241
avr_stdlib, 90
DTOSTR_PLUS_SIGN
avr_stdlib, 90
DTOSTR_UPPERCASE
avr_stdlib, 90
dtostre
avr_stdlib, 92
dtostrf
avr_stdlib, 92
EDOM
avr_errno, 40
EEMEM
avr_eeprom, 16
eeprom_busy_wait
avr_eeprom, 16
eeprom_is_ready
avr_eeprom, 16
eeprom_read_block
avr_eeprom, 16
eeprom_read_byte
avr_eeprom, 16
eeprom_read_word
avr_eeprom, 16
eeprom_write_block
avr_eeprom, 16
eeprom_write_byte
avr_eeprom, 16
eeprom_write_word
avr_eeprom, 17
EMPTY_INTERRUPT
avr_interrupts, 130
enable_external_int
deprecated_items, 35
EOF
avr_stdio, 75
ERANGE
avr_errno, 40
Example using the two-wire interface
(TWI), 147
exit
avr_stdlib, 93
exp
avr_math, 54
fabs
Generated on Sat Nov 19 23:00:48 2005 for avr-libc by Doxygen
INDEX
avr_math, 54
FAQ, 168
fclose
avr_stdio, 77
fdev_close
avr_stdio, 75
fdev_get_udata
avr_stdio, 75
fdev_set_udata
avr_stdio, 75
FDEV_SETUP_STREAM
avr_stdio, 75
fdev_setup_stream
avr_stdio, 76
fdevopen
avr_stdio, 78
feof
avr_stdio, 78
ferror
avr_stdio, 78
fflush
avr_stdio, 78
ffs
avr_string, 100
ffsl
avr_string, 101
ffsll
avr_string, 101
fgetc
avr_stdio, 79
fgets
avr_stdio, 79
FILE
avr_stdio, 76
floor
avr_math, 54
fmod
avr_math, 54
fprintf
avr_stdio, 79
fprintf_P
avr_stdio, 79
fputc
avr_stdio, 79
fputs
avr_stdio, 79
242
fputs_P
avr_stdio, 79
fread
avr_stdio, 79
free
avr_stdlib, 93
frexp
avr_math, 54
fscanf
avr_stdio, 80
fscanf_P
avr_stdio, 80
fwrite
avr_stdio, 80
GET_EXTENDED_FUSE_BITS
avr_boot, 13
GET_HIGH_FUSE_BITS
avr_boot, 14
GET_LOCK_BITS
avr_boot, 14
GET_LOW_FUSE_BITS
avr_boot, 14
getc
avr_stdio, 76
getchar
avr_stdio, 76
gets
avr_stdio, 80
inp
deprecated_items, 35
installation, 214
installation, avarice, 219
installation, avr-libc, 217
installation, avrdude, 218
installation, avrprog, 218
installation, binutils, 216
installation, gcc, 217
Installation, gdb, 219
installation, simulavr, 219
installation, uisp, 218
INT16_C
avr_stdint, 62
INT16_MAX
avr_stdint, 62
Generated on Sat Nov 19 23:00:48 2005 for avr-libc by Doxygen
INDEX
INT16_MIN
avr_stdint, 62
int16_t
avr_stdint, 67
INT32_C
avr_stdint, 62
INT32_MAX
avr_stdint, 62
INT32_MIN
avr_stdint, 62
int32_t
avr_stdint, 67
INT64_C
avr_stdint, 62
INT64_MAX
avr_stdint, 62
INT64_MIN
avr_stdint, 63
int64_t
avr_stdint, 67
INT8_C
avr_stdint, 63
INT8_MAX
avr_stdint, 63
INT8_MIN
avr_stdint, 63
int8_t
avr_stdint, 67
int_farptr_t
avr_inttypes, 52
INT_FAST16_MAX
avr_stdint, 63
INT_FAST16_MIN
avr_stdint, 63
int_fast16_t
avr_stdint, 67
INT_FAST32_MAX
avr_stdint, 63
INT_FAST32_MIN
avr_stdint, 63
int_fast32_t
avr_stdint, 67
INT_FAST64_MAX
avr_stdint, 63
INT_FAST64_MIN
avr_stdint, 63
243
int_fast64_t
avr_stdint, 68
INT_FAST8_MAX
avr_stdint, 63
INT_FAST8_MIN
avr_stdint, 64
int_fast8_t
avr_stdint, 68
INT_LEAST16_MAX
avr_stdint, 64
INT_LEAST16_MIN
avr_stdint, 64
int_least16_t
avr_stdint, 68
INT_LEAST32_MAX
avr_stdint, 64
INT_LEAST32_MIN
avr_stdint, 64
int_least32_t
avr_stdint, 68
INT_LEAST64_MAX
avr_stdint, 64
INT_LEAST64_MIN
avr_stdint, 64
int_least64_t
avr_stdint, 68
INT_LEAST8_MAX
avr_stdint, 64
INT_LEAST8_MIN
avr_stdint, 64
int_least8_t
avr_stdint, 68
INTERRUPT
deprecated_items, 35
INTMAX_C
avr_stdint, 64
INTMAX_MAX
avr_stdint, 64
INTMAX_MIN
avr_stdint, 65
intmax_t
avr_stdint, 68
INTPTR_MAX
avr_stdint, 65
INTPTR_MIN
avr_stdint, 65
Generated on Sat Nov 19 23:00:48 2005 for avr-libc by Doxygen
INDEX
intptr_t
avr_stdint, 68
isalnum
ctype, 37
isalpha
ctype, 37
isascii
ctype, 38
isblank
ctype, 38
iscntrl
ctype, 38
isdigit
ctype, 38
isgraph
ctype, 38
isinf
avr_math, 54
islower
ctype, 38
isnan
avr_math, 55
isprint
ctype, 38
ispunct
ctype, 38
ISR
avr_interrupts, 130
isspace
ctype, 38
isupper
ctype, 38
isxdigit
ctype, 39
itoa
avr_stdlib, 93
244
log
avr_math, 55
log10
avr_math, 55
longjmp
setjmp, 57
loop_until_bit_is_clear
avr_sfr, 134
loop_until_bit_is_set
avr_sfr, 134
ltoa
avr_stdlib, 94
M_PI
avr_math, 53
M_SQRT2
avr_math, 53
malloc
avr_stdlib, 94
memccpy
avr_string, 101
memchr
avr_string, 101
memcmp
avr_string, 101
memcpy
avr_string, 102
memcpy_P
avr_pgmspace, 23
memmove
avr_string, 102
memset
avr_string, 102
modf
avr_math, 55
outp
deprecated_items, 36
labs
avr_stdlib, 93
ldexp
avr_math, 55
ldiv
avr_stdlib, 94
ldiv_t, 161
quot, 161
rem, 161
parity_even_bit
util_parity, 113
PGM_P
avr_pgmspace, 19
pgm_read_byte
avr_pgmspace, 19
pgm_read_byte_far
Generated on Sat Nov 19 23:00:48 2005 for avr-libc by Doxygen
INDEX
avr_pgmspace, 20
pgm_read_byte_near
avr_pgmspace, 20
pgm_read_dword
avr_pgmspace, 20
pgm_read_dword_far
avr_pgmspace, 20
pgm_read_dword_near
avr_pgmspace, 20
pgm_read_word
avr_pgmspace, 21
pgm_read_word_far
avr_pgmspace, 21
pgm_read_word_near
avr_pgmspace, 21
PGM_VOID_P
avr_pgmspace, 21
pow
avr_math, 55
PRId16
avr_inttypes, 43
PRId32
avr_inttypes, 43
PRId8
avr_inttypes, 43
PRIdFAST16
avr_inttypes, 43
PRIdFAST32
avr_inttypes, 43
PRIdFAST8
avr_inttypes, 43
PRIdLEAST16
avr_inttypes, 43
PRIdLEAST32
avr_inttypes, 43
PRIdLEAST8
avr_inttypes, 44
PRIdPTR
avr_inttypes, 44
PRIi16
avr_inttypes, 44
PRIi32
avr_inttypes, 44
PRIi8
avr_inttypes, 44
PRIiFAST16
245
avr_inttypes, 44
PRIiFAST32
avr_inttypes, 44
PRIiFAST8
avr_inttypes, 44
PRIiLEAST16
avr_inttypes, 44
PRIiLEAST32
avr_inttypes, 44
PRIiLEAST8
avr_inttypes, 44
PRIiPTR
avr_inttypes, 45
printf
avr_stdio, 80
printf_P
avr_stdio, 80
PRIo16
avr_inttypes, 45
PRIo32
avr_inttypes, 45
PRIo8
avr_inttypes, 45
PRIoFAST16
avr_inttypes, 45
PRIoFAST32
avr_inttypes, 45
PRIoFAST8
avr_inttypes, 45
PRIoLEAST16
avr_inttypes, 45
PRIoLEAST32
avr_inttypes, 45
PRIoLEAST8
avr_inttypes, 45
PRIoPTR
avr_inttypes, 45
PRIu16
avr_inttypes, 46
PRIu32
avr_inttypes, 46
PRIu8
avr_inttypes, 46
PRIuFAST16
avr_inttypes, 46
PRIuFAST32
Generated on Sat Nov 19 23:00:48 2005 for avr-libc by Doxygen
INDEX
avr_inttypes, 46
PRIuFAST8
avr_inttypes, 46
PRIuLEAST16
avr_inttypes, 46
PRIuLEAST32
avr_inttypes, 46
PRIuLEAST8
avr_inttypes, 46
PRIuPTR
avr_inttypes, 46
PRIX16
avr_inttypes, 46
PRIx16
avr_inttypes, 47
PRIX32
avr_inttypes, 47
PRIx32
avr_inttypes, 47
PRIX8
avr_inttypes, 47
PRIx8
avr_inttypes, 47
PRIXFAST16
avr_inttypes, 47
PRIxFAST16
avr_inttypes, 47
PRIXFAST32
avr_inttypes, 47
PRIxFAST32
avr_inttypes, 47
PRIXFAST8
avr_inttypes, 47
PRIxFAST8
avr_inttypes, 47
PRIXLEAST16
avr_inttypes, 48
PRIxLEAST16
avr_inttypes, 48
PRIXLEAST32
avr_inttypes, 48
PRIxLEAST32
avr_inttypes, 48
PRIXLEAST8
avr_inttypes, 48
PRIxLEAST8
246
avr_inttypes, 48
PRIXPTR
avr_inttypes, 48
PRIxPTR
avr_inttypes, 48
prog_char
avr_pgmspace, 22
prog_int16_t
avr_pgmspace, 22
prog_int32_t
avr_pgmspace, 22
prog_int64_t
avr_pgmspace, 22
prog_int8_t
avr_pgmspace, 22
prog_uchar
avr_pgmspace, 22
prog_uint16_t
avr_pgmspace, 22
prog_uint32_t
avr_pgmspace, 22
prog_uint64_t
avr_pgmspace, 22
prog_uint8_t
avr_pgmspace, 22
prog_void
avr_pgmspace, 22
PROGMEM
avr_pgmspace, 21
PSTR
avr_pgmspace, 21
PTRDIFF_MAX
avr_stdint, 65
PTRDIFF_MIN
avr_stdint, 65
putc
avr_stdio, 76
putchar
avr_stdio, 77
puts
avr_stdio, 80
puts_P
avr_stdio, 80
qsort
Generated on Sat Nov 19 23:00:48 2005 for avr-libc by Doxygen
avr_stdlib, 94
INDEX
quot
div_t, 161
ldiv_t, 161
rand
avr_stdlib, 95
RAND_MAX
avr_stdlib, 90
rand_r
avr_stdlib, 95
random
avr_stdlib, 95
RANDOM_MAX
avr_stdlib, 90
random_r
avr_stdlib, 95
realloc
avr_stdlib, 95
rem
div_t, 161
ldiv_t, 161
sbi
deprecated_items, 36
scanf
avr_stdio, 81
scanf_P
avr_stdio, 81
SCNd16
avr_inttypes, 48
SCNd32
avr_inttypes, 48
SCNdFAST16
avr_inttypes, 48
SCNdFAST32
avr_inttypes, 49
SCNdLEAST16
avr_inttypes, 49
SCNdLEAST32
avr_inttypes, 49
SCNdPTR
avr_inttypes, 49
SCNi16
avr_inttypes, 49
SCNi32
avr_inttypes, 49
247
SCNiFAST16
avr_inttypes, 49
SCNiFAST32
avr_inttypes, 49
SCNiLEAST16
avr_inttypes, 49
SCNiLEAST32
avr_inttypes, 49
SCNiPTR
avr_inttypes, 49
SCNo16
avr_inttypes, 50
SCNo32
avr_inttypes, 50
SCNoFAST16
avr_inttypes, 50
SCNoFAST32
avr_inttypes, 50
SCNoLEAST16
avr_inttypes, 50
SCNoLEAST32
avr_inttypes, 50
SCNoPTR
avr_inttypes, 50
SCNu16
avr_inttypes, 50
SCNu32
avr_inttypes, 50
SCNuFAST16
avr_inttypes, 50
SCNuFAST32
avr_inttypes, 50
SCNuLEAST16
avr_inttypes, 51
SCNuLEAST32
avr_inttypes, 51
SCNuPTR
avr_inttypes, 51
SCNx16
avr_inttypes, 51
SCNx32
avr_inttypes, 51
SCNxFAST16
avr_inttypes, 51
SCNxFAST32
avr_inttypes, 51
Generated on Sat Nov 19 23:00:48 2005 for avr-libc by Doxygen
INDEX
SCNxLEAST16
avr_inttypes, 51
SCNxLEAST32
avr_inttypes, 51
SCNxPTR
avr_inttypes, 51
set_sleep_mode
avr_sleep, 29
setjmp
longjmp, 57
setjmp, 58
SIG_ATOMIC_MAX
avr_stdint, 65
SIG_ATOMIC_MIN
avr_stdint, 65
SIGNAL
avr_interrupts, 131
sin
avr_math, 55
sinh
avr_math, 55
SIZE_MAX
avr_stdint, 65
sleep_mode
avr_sleep, 29
SLEEP_MODE_ADC
avr_sleep, 28
SLEEP_MODE_EXT_STANDBY
avr_sleep, 28
SLEEP_MODE_IDLE
avr_sleep, 28
SLEEP_MODE_PWR_DOWN
avr_sleep, 28
SLEEP_MODE_PWR_SAVE
avr_sleep, 28
SLEEP_MODE_STANDBY
avr_sleep, 28
snprintf
avr_stdio, 81
snprintf_P
avr_stdio, 81
sprintf
avr_stdio, 81
sprintf_P
avr_stdio, 81
sqrt
248
avr_math, 56
square
avr_math, 56
srand
avr_stdlib, 96
srandom
avr_stdlib, 96
sscanf
avr_stdio, 81
sscanf_P
avr_stdio, 81
stderr
avr_stdio, 77
stdin
avr_stdio, 77
stdout
avr_stdio, 77
strcasecmp
avr_string, 102
strcasecmp_P
avr_pgmspace, 23
strcat
avr_string, 103
strcat_P
avr_pgmspace, 23
strchr
avr_string, 103
strcmp
avr_string, 103
strcmp_P
avr_pgmspace, 23
strcpy
avr_string, 103
strcpy_P
avr_pgmspace, 23
strlcat
avr_string, 104
strlcat_P
avr_pgmspace, 24
strlcpy
avr_string, 104
strlcpy_P
avr_pgmspace, 24
strlen
avr_string, 104
strlen_P
Generated on Sat Nov 19 23:00:48 2005 for avr-libc by Doxygen
INDEX
avr_pgmspace, 24
strlwr
avr_string, 104
strncasecmp
avr_string, 105
strncasecmp_P
avr_pgmspace, 24
strncat
avr_string, 105
strncat_P
avr_pgmspace, 25
strncmp
avr_string, 105
strncmp_P
avr_pgmspace, 25
strncpy
avr_string, 105
strncpy_P
avr_pgmspace, 25
strnlen
avr_string, 106
strnlen_P
avr_pgmspace, 26
strrchr
avr_string, 106
strrev
avr_string, 106
strsep
avr_string, 106
strstr
avr_string, 107
strtod
avr_stdlib, 96
strtok_r
avr_string, 107
strtol
avr_stdlib, 96
strtoul
avr_stdlib, 97
strupr
avr_string, 107
supported devices, 2
tan
avr_math, 56
tanh
249
avr_math, 56
timer_enable_int
deprecated_items, 36
toascii
ctype, 39
tolower
ctype, 39
tools, optional, 215
tools, required, 215
toupper
ctype, 39
TW_BUS_ERROR
util_twi, 114
TW_MR_ARB_LOST
util_twi, 114
TW_MR_DATA_ACK
util_twi, 115
TW_MR_DATA_NACK
util_twi, 115
TW_MR_SLA_ACK
util_twi, 115
TW_MR_SLA_NACK
util_twi, 115
TW_MT_ARB_LOST
util_twi, 115
TW_MT_DATA_ACK
util_twi, 115
TW_MT_DATA_NACK
util_twi, 115
TW_MT_SLA_ACK
util_twi, 115
TW_MT_SLA_NACK
util_twi, 115
TW_NO_INFO
util_twi, 115
TW_READ
util_twi, 115
TW_REP_START
util_twi, 116
TW_SR_ARB_LOST_GCALL_ACK
util_twi, 116
TW_SR_ARB_LOST_SLA_ACK
util_twi, 116
TW_SR_DATA_ACK
util_twi, 116
TW_SR_DATA_NACK
Generated on Sat Nov 19 23:00:48 2005 for avr-libc by Doxygen
INDEX
util_twi, 116
TW_SR_GCALL_ACK
util_twi, 116
TW_SR_GCALL_DATA_ACK
util_twi, 116
TW_SR_GCALL_DATA_NACK
util_twi, 116
TW_SR_SLA_ACK
util_twi, 116
TW_SR_STOP
util_twi, 116
TW_ST_ARB_LOST_SLA_ACK
util_twi, 116
TW_ST_DATA_ACK
util_twi, 117
TW_ST_DATA_NACK
util_twi, 117
TW_ST_LAST_DATA
util_twi, 117
TW_ST_SLA_ACK
util_twi, 117
TW_START
util_twi, 117
TW_STATUS
util_twi, 117
TW_STATUS_MASK
util_twi, 117
TW_WRITE
util_twi, 117
UINT16_C
avr_stdint, 65
UINT16_MAX
avr_stdint, 65
uint16_t
avr_stdint, 68
UINT32_C
avr_stdint, 65
UINT32_MAX
avr_stdint, 66
uint32_t
avr_stdint, 68
UINT64_C
avr_stdint, 66
UINT64_MAX
avr_stdint, 66
250
uint64_t
avr_stdint, 68
UINT8_C
avr_stdint, 66
UINT8_MAX
avr_stdint, 66
uint8_t
avr_stdint, 69
uint_farptr_t
avr_inttypes, 52
UINT_FAST16_MAX
avr_stdint, 66
uint_fast16_t
avr_stdint, 69
UINT_FAST32_MAX
avr_stdint, 66
uint_fast32_t
avr_stdint, 69
UINT_FAST64_MAX
avr_stdint, 66
uint_fast64_t
avr_stdint, 69
UINT_FAST8_MAX
avr_stdint, 66
uint_fast8_t
avr_stdint, 69
UINT_LEAST16_MAX
avr_stdint, 66
uint_least16_t
avr_stdint, 69
UINT_LEAST32_MAX
avr_stdint, 66
uint_least32_t
avr_stdint, 69
UINT_LEAST64_MAX
avr_stdint, 67
uint_least64_t
avr_stdint, 69
UINT_LEAST8_MAX
avr_stdint, 67
uint_least8_t
avr_stdint, 69
UINTMAX_C
avr_stdint, 67
UINTMAX_MAX
avr_stdint, 67
Generated on Sat Nov 19 23:00:48 2005 for avr-libc by Doxygen
INDEX
uintmax_t
avr_stdint, 69
UINTPTR_MAX
avr_stdint, 67
uintptr_t
avr_stdint, 69
ultoa
avr_stdlib, 98
ungetc
avr_stdio, 81
util_crc
_crc16_update, 109
_crc_ccitt_update, 109
_crc_ibutton_update, 109
_crc_xmodem_update, 110
util_delay
_delay_loop_1, 112
_delay_loop_2, 112
_delay_ms, 112
_delay_us, 112
util_parity
parity_even_bit, 113
util_twi
TW_BUS_ERROR, 114
TW_MR_ARB_LOST, 114
TW_MR_DATA_ACK, 115
TW_MR_DATA_NACK, 115
TW_MR_SLA_ACK, 115
TW_MR_SLA_NACK, 115
TW_MT_ARB_LOST, 115
TW_MT_DATA_ACK, 115
TW_MT_DATA_NACK, 115
TW_MT_SLA_ACK, 115
TW_MT_SLA_NACK, 115
TW_NO_INFO, 115
TW_READ, 115
TW_REP_START, 116
TW_SR_ARB_LOST_GCALL_ACK, 116
TW_SR_ARB_LOST_SLA_ACK,
116
TW_SR_DATA_ACK, 116
TW_SR_DATA_NACK, 116
TW_SR_GCALL_ACK, 116
TW_SR_GCALL_DATA_ACK, 116
251
TW_SR_GCALL_DATA_NACK,
116
TW_SR_SLA_ACK, 116
TW_SR_STOP, 116
TW_ST_ARB_LOST_SLA_ACK,
116
TW_ST_DATA_ACK, 117
TW_ST_DATA_NACK, 117
TW_ST_LAST_DATA, 117
TW_ST_SLA_ACK, 117
TW_START, 117
TW_STATUS, 117
TW_STATUS_MASK, 117
TW_WRITE, 117
utoa
avr_stdlib, 98
vfprintf
avr_stdio, 82
vfprintf_P
avr_stdio, 84
vfscanf
avr_stdio, 84
vfscanf_P
avr_stdio, 87
vprintf
avr_stdio, 87
vscanf
avr_stdio, 87
vsnprintf
avr_stdio, 87
vsnprintf_P
avr_stdio, 87
vsprintf
avr_stdio, 88
vsprintf_P
avr_stdio, 88
wdt_disable
avr_watchdog, 31
wdt_enable
avr_watchdog, 32
wdt_reset
avr_watchdog, 32
WDTO_120MS
avr_watchdog, 32
Generated on Sat Nov 19 23:00:48 2005 for avr-libc by Doxygen
INDEX
WDTO_15MS
avr_watchdog, 32
WDTO_1S
avr_watchdog, 32
WDTO_250MS
avr_watchdog, 33
WDTO_2S
avr_watchdog, 33
WDTO_30MS
avr_watchdog, 33
WDTO_4S
avr_watchdog, 33
WDTO_500MS
avr_watchdog, 33
WDTO_60MS
avr_watchdog, 33
WDTO_8S
avr_watchdog, 33
Generated on Sat Nov 19 23:00:48 2005 for avr-libc by Doxygen
252
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