STM32 developer`s document

STM32 developer`s document

Embedding it better...

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Tasker Document

SMT32 Developer’s Document

uTaskerV1.4_Developers_Document/0.5 Copyright © 2012 M.J.Butcher Consulting

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Tasker – STM32 Developer’s Document

Table of Contents

1.

Introduction ....................................................................................................................3

2.

Preparing to work with the STM32 .................................................................................4

3.

First Steps with the STM32 .............................................................................................6

4.

Blinking an LED .............................................................................................................8

4.1.

F1 GPIOs ................................................................................................................9

4.2.

F2/F4 GPIOs ........................................................................................................ 11

4.3.

F4 System Clock .................................................................................................. 12

4.4.

F2 System Clock .................................................................................................. 13

4.5.

F1 System Clock .................................................................................................. 13

4.6.

Cortex M3/M4 peripherals .................................................................................. 15

5.

Using the STM32 UART .............................................................................................. 16

5.1.

F1 Peripheral Configuration ................................................................................ 16

5.2.

F2/F4 Peripheral Configuration .......................................................................... 17

6.

Ethernet ........................................................................................................................ 19

6.1.

STM3210C-EVAL ................................................................................................ 19

6.2.

STM3240G-EVAL ................................................................................................ 20

6.3.

Checksum Offloading .......................................................................................... 20

7.

FLASH ......................................................................................................................... 21

7.1.

F1 Flash ................................................................................................................ 21

7.2.

F2/F4 Flash .......................................................................................................... 21

8.

External Interrupts (EXTI) ............................................................................................ 23

9.

SPI FLASH .................................................................................................................. 23

10.

SD Card ..................................................................................................................... 24

11.

Flexible Static Memory Controller ............................................................................. 24

12.

USB Full-Speed Device ............................................................................................. 25

13.

Conclusion ................................................................................................................. 27

APPENDIX A - STM32F1, STM32L and STM32W ............................................................ 28

APPENDIX B – STM32F2xx ............................................................................................... 32

APPENDIX C – STM32F4xx ............................................................................................... 34

APPENDIX D – Building the µTasker Project in the µTasker Simulator and generating a cross-compiled Object for the HW Target ............................................................................. 35

APPENDIX E – Working with the µTasker Project and Rowely CrossWorks ....................... 39

APPENDIX F – Working with the µTasker Project and Atollic TrueSTUDIO ...................... 41

APPENDIX G – Working with the µTasker Project and IAR ............................................... 43

APPENDIX H – Working with the µTasker Project and Keil uVision .................................. 44

APPENDIX I – STM3240G-EVAL Modification to allow full Demo Functionality ............. 45 uTaskerV1.4_Developers_Document/0.5 2/46 22.02.2012

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Tasker – STM32 Developer’s Document

1. Introduction

This guide is a result of practical work during porting the µTasker project to the ST-

Micro STM32 family of devices and covers the SMT32F1xx, STM32F2xx and

STM32F4xx Cortex M3 and M4 based microcontrollers and their internal resources

(memory, peripherals etc.). The document explains many details which are possibly not immediately obvious from initial study of the extensive ST-Micro documentation, including data sheets and user’s manuals; however it isn’t intended to replace these sources of information.

Many details included explain the base of the implementation for the µTasker STM32 project, where readers can then better understand the choice of methods when working with the project or better build on the base for further study of the µTasker project code and methods.

The µTasker project intends to give support to developments based on the STM32 family of devices and includes various IDE projects so that users can efficiently work with their chosen tools - the following environments are included:

- GCC Make File build (without IDE for target debugging but useable together with the µTasker simulator as a post-build step)

- Rowley Crossworks

- Atollic TrueSTUDIO

- IAR

- Keil uVision

The µTasker project is supported in these environments, which means that the projects are verified as best as possible in all environments and experience with the tools is collected to allow help to be provided where possible.

Quick start guides to working with the µTasker project in these environments are included in the appendixes.

It is further to be noted that the µTasker project is designed to operate within all environments, meaning that there are not completely different projects for each cross-compiler. This also has advantages when evaluating IDEs to be used for project development since it is possible to have the project open in all possible development environments at the same time and any code changes to the project made in one will be valid for others too. Targets can be thus tested with multiple IDEs at the same time with the only restriction being that only one can actually be attached to the debugger at any time. uTaskerV1.4_Developers_Document/0.5 3/46 22.02.2012

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2. Preparing to work with the STM32

The STM32F1xx and STM32F2xx family of devices are based on the ARM Cortex

M3 and the STM32F4xx family on the ARM Cortex M4. The Cortex M4 can be considered to be a Cortex M3 with an increased instruction set, including additional

DSP like instructions and optional Floating Point Unit. This means that the Cortex M4 based parts can be more efficient in terms of execution speed of code and algorithms that can make use of the additional instructions; the programmer doesn’t however have to be fully aware of the differences when moving between Cortex M3 and

Cortex M4 based processors – code will essentially run on both without any changes, where the compiler will make decisions as to the best way to actually use the instruction set of the core available.

The STM32F4xx Cortex M4 based devices are however newer and thus contain many other optimisations in terms of bus structure, memory and peripherals and these details tend to be the most important differences in terms of actual project development; although core code is compatible between the devices the peripheral code can vary greatly.

In order to start work with the STM32 devices the following tools are required:

- A development/evaluation board with the processor so that code can be executed and internal/external peripherals controlled

- A development environment allowing code to be written and compiled to a format that can be loaded to the memory of the processor

- Preferably a debugging environment allowing the processor/boards’s memory to be viewed, and code execution to be manipulated (breakpoints, instruction viewer, stepping, etc.)

The µTasker simulator allows a great deal of the code to be tested and the device’s functionality to be verified without any of the tools above. It also allows increased development and debugging efficiency in many cases as a compliment to these tools.

At some point it will however be necessary to have basic capabilities as listed above to verify target operation in a real project.

The µTasker project supports essentially all STM32 device; F1, F2 and F4 families in all sizes and packages. The µTasker demonstration project can be built to run on, and simulate, any of these by configuring the processor/board in the file config.h.

//#define STM3210C_EVAL // evaluation board with STM32F107VCT

//#define STM3240G_EVAL // evaluation board with STM32F407IGH6

//#define ST_MB913C_DISCOVERY // discovery board with STM32F100RB

#define ST_MB997A_DISCOVERY // discovery board with STM32F407VGT6

Here four standard boards are shown, whereby one of them

(ST_MB997A_DISCOVERY) is activated for the build. Users can add their own boards to the list. uTaskerV1.4_Developers_Document/0.5 4/46 22.02.2012

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In the file app_hw_stm32.h the STM32 part is specified and additional details concerning the board and the exact hardware details of the project are configured.

The following shows the processor setup for the board above

#define CRYSTAL_FREQ 8000000

//#define DISABLE_PLL // run from clock source directly

//#define USE_HSI_CLOCK // use internal HSI clock source

#define PLL_INPUT_DIV 4 // 2..64 - should set the input to pll in

the range 1..2MHz (with preference near to 2MHz)

#define PLL_VCO_MUL 168 // 64 ..432 where VCO must be 64..432MHz

#define PLL_POST_DIVIDE 2 // post divide VCO by 2, 4, 6, or 8 to get the

system clock speed

#define PIN_COUNT PIN_COUNT_100_PIN

#define PACKAGE_TYPE PACKAGE_LQFP

#define _STM32F4XX

#define SIZE_OF_RAM (128 * 1024) // 128k SRAM

#define SIZE_OF_CCM (64 * 1024) // 64k Core Coupled Memory

#define SIZE_OF_FLASH (1024 * 1024) // 1M FLASH

#define SUPPLY_VOLTAGE SUPPLY_2_7__3_6 // power supply is in the range 2.7V..3.6V

#define PCLK1_DIVIDE 4

#define PCLK2_DIVIDE 2

The details allow the project to configure itself according to the chip, whereby the simulator knows which family type and package is being used and adapts itself to suit it. Details about the clock configuration details are given later in this document. uTaskerV1.4_Developers_Document/0.5 5/46 22.02.2012

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3. First Steps with the STM32

The first thing that needs to be known is how the STM32 starts, which means what the processor actually does when power is applied to the board and the reset line is negated. The exact behaviour is in fact STM32 family dependent since some devices include an internal boot loader which can start in this case and allow the user to load code to internal memory via certain peripherals; this is detailed later in the STM32 boot loader section.

In the case when no internal boot loader takes control of the processor at reset the core reads two long word locations from the start of Flash memory; the first long word location contains the initial stack pointer value and the second long work location contains the initial program counter value. This is in fact the same operation as performed by all Cortex M3/M4 based devices, as well as various other processor types like the M68000/Coldfire.

After loading these two registers with their initial values the processor starts executing the code at its initial program counter address location.

This means that the development environment must allow the programmer to put these two important initial values at the first two locations in internal Flash memory; how this is achieved can vary between development environments but the µTasker project avoids using assembler files and specifies the two values as follows: const RESET_VECTOR reset_vect

= {

(void *)(RAM_START_ADDRESS + SIZE_OF_RAM - 4), // stack pointer to top of RAM

(reserving one long word for random number)

(void (*)(void))START_CODE

};

In the case of the STM32 the value of RAM_START_ADDRESS is always 0x20000000 and the value of SIZE_OF_RAM is defined by the device used. The initial stack pointer is therefore set to the top of internal SRAM.

The value of START_CODE is compiler depended since some compilers require their start-up code to be executed to configure variables (initialised memory and zeroed memory); either it will cause the compiler’s initialisation routine to be called (which then jumps to µTasker’s main()) or else it directly starts at µTasker’s main()).

What is also needed to be known is where the Flash resides in the memory map so that the program code can be positional at the start of it. The start value is always the same FLASH_START_ADDRESS is equal to 0x08000000 and the size of the available Flash memory is device specific and is generally defined by

SIZE_OF_FLASH

.

For an overview of the sizes of Flash and SRAM in the STM32 devices see appendix

A, B and C. uTaskerV1.4_Developers_Document/0.5 6/46 22.02.2012

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When the processor starts it is driven from an internal RC oscillator (HSI) that runs at

8 MHz (F1 +/-1% at 25°C) or 16MHz (F2 and F4 +/-1% at 25°C). In some cases this oscillator can be used without the need for an external clock source or crystal, however in many cases a higher accuracy is preferred. This means that the processor will start even if there is no external oscillator available.

In most cases the speed of the HIS or the external oscillator/crystal is not used directly but instead the output of a PLL (phase locked loop) is used instead to drive the system clock. This allows much higher internal frequencies to be generated and one of the first operations after then code starts is usually to adjust the clocks settings so that the system is running at the required system frequency.

The following gives an overview of the clocks in the STM32, including some rules about their ranges:

The system clock is called SYSCLK. This can be driven from different clock sources:

- F1: HSI oscillator clock (internal 8MHz RC) – maximum system clock is

36MHz when this is used as input to the PLL. It is divided by 2 before use as

PLL input.

- F1 connectivity line devices can use the output of PLL2 as input to the main

PLL.

- F2/F4: HSI oscillator clock (internal 16MHz RC). It is divided by 2 before use as PLL input.

- HSE oscillator clock (external clock up to 25MHz [connectivity line up to

50MHz] or 4..16 MHz or crystal/ceramic resonator [connectivity line 3..25MHz,

F2/F4 4..26MHz]).

- PLL clock – this must be programmed to 48MHz or 72MHz when using USB.

The connectivity line has 3 PLLs and other F1 devices have 2 PLLs

F2 and F4 devices have 2 PLLs whereby the main PLL has 2 outputs.

The devices have two secondary clock sources:

- F1: 40kHz low speed internal RC oscillator (if the independent watchdog is enabled this is also automatically forced on)

- F2/F4: 32kHz low speed internal RC oscillator (if the independent watchdog is enabled this is also automatically forced on)

- 32.768kHz low speed external crystal

The system clock is used to generate various domain clocks with the following ranges:

- F1: AHB and APB2 up to 72MHz; APB1 up to 36MHz.

- F2: AHB up to 120MHz. APB2 up to 60MHz. APB1 up to 30MHz.

- F4: AHB up to 168MHz. APB2 up to 84MHz. APB1 up to 42MHz.

AHB must be at least 25MHz when using Ethernet. uTaskerV1.4_Developers_Document/0.5 7/46 22.02.2012

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The STM32 devices work from a supply voltage between 1.8V to 3.6 (F1 2.0V to

3.6V) and have an internal 1.8V regulator for the CPU.

4. Blinking an LED

A useful first step when starting with a new processor is to make a project that flashes an LED. The µTasker project does this when all major options are disabled* so that essentially only the watchdog task is active and toggles a chosen port output at a rate of 2.5Hz (periodically called with 200ms rate).

There are several things that need to be operational for this to take place:

- The processor must successfully start, initialize system variables and start the

µTasker scheduler.

- During initialization the system clock must be correctly configured (either from a direct clock source or from a PLL).

- The TICK interrupt needs to operate (interrupt configuration and interrupt handling). Hereby it is important to note that Cortex M3 and Cortex M4 processors have a dedicated SYSTICK periodic timer module which is always used for this and so have practically identical setups. Since the NVIC (nested vectored interrupt controller) is also integrated in the core the interrupt handling is virtually the same in each case.

- The port needs to have been correctly configured as an output and correctly toggled each time the watchdog task is executed.

This leads into the next topic of GPIOs since the blinking LED test can only be successful when the GPIO is correctly controlled. The next section thus introduces the port control as well as the differences between their implementation in the F1 and

F2/F3 devices.

*Disable USE_MAINTENANCE, SERIAL_INTERFACE, SDCARD_SUPPORT, ETH_INTERFACE and SUPPORT_GLCD in config.h to obtain a minimum project of this type. uTaskerV1.4_Developers_Document/0.5 8/46 22.02.2012

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4.1. F1 GPIOs

The ports can be multiplexed with various peripherals.

Ports are 16 bits wide and are named Port A to Port G; but not all ports and pins may be available in smaller packages. The port control registers are located on the APB2 peripheral bus and the port control block needs to be powered up on that bus before it can be used.

Most ports default to inputs with no pull-up/down (floating) but pull-ups/downs can be configured by software. Outputs can drive with push-pull outputs or open-drain outputs and can be configured to have maximum speeds of 2MHz, 10MHz or 50MHz.

The actual control of the GPIOs for simple input/output use is quite complicated due to the fact that the control registers for a 16 bit port are spread over two 32 bit registers with a number of configuration possibilities. To make the user interface as simple as possible macros have been devices (compatible or closely compatible with

the standard port macros in the uTasker project). The macros do all of the work necessary to achieve the configuration with the required characteristics. The macros are very efficient as long as the values passed are fixed values; the reason is that the work to calculate the values required is determined by the compiler and not at runtime. The macros should generally be avoided (or used carefully) when parameters are in variables. The reason is that the calculation of the configuration is quite complicated and so may require a large amount of instructions (inefficient) to be performed on a variable input.As example of the complexity involved, the macro to configure port pins as outputs is shown here. It first powers the port to be used in case it is still not clocked and calculates the configuration values required for each port bit to achieve the port output characteristic.

#define _CONFIG_PORT_OUTPUT(ref, pins, characteristics) RCC_APB2ENR |= (RCC_APB2ENR_IOP##ref##EN); \

GPIO##ref##_CRL = ((GPIO##ref##_CRL & \

~((0x0001 & pins) | ((0x0001 & pins) << 1) | ((0x0001 & pins) << 2) | ((0x0001 & pins) << 3) | \

(((0x0002 & pins) << 3) | ((0x0002 & pins) << 4) | ((0x0002 & pins) << 5) | ((0x0002 & pins) << 6)) | \

(((0x0004 & pins) << 6) | ((0x0004 & pins) << 7) | ((0x0004 & pins) << 8) | ((0x0004 & pins) << 9)) | \

(((0x0008 & pins) << 9) | ((0x0008 & pins) << 10) | ((0x0008 & pins) << 11) | ((0x0008 & pins) << 12)) | \

(((0x0010 & pins) << 12) | ((0x0010 & pins) << 13) | ((0x0010 & pins) << 14) | ((0x0010 & pins) << 15)) | \

(((0x0020 & pins) << 15) | ((0x0020 & pins) << 16) | ((0x0020 & pins) << 17) | ((0x0020 & pins) << 18)) | \

(((0x0040 & pins) << 18) | ((0x0040 & pins) << 19) | ((0x0040 & pins) << 20) | ((0x0040 & pins) << 21)) | \

(((0x0080 & pins) << 21) | ((0x0080 & pins) << 22) | ((0x0080 & pins) << 23) | ((0x0080 & pins) << 24))))| \

(((0x0001 & pins) | ((0x0001 & pins) << 1) | ((0x0001 & pins) << 2) | ((0x0001 & pins) << 3)) & (characteristics)) | \

((((0x0002 & pins) << 3) | ((0x0002 & pins) << 4) | ((0x0002 & pins) << 5) | ((0x0002 & pins) << 6)) & ((characteristics) << 4)) | \

((((0x0004 & pins) << 6) | ((0x0004 & pins) << 7) | ((0x0004 & pins) << 8) | ((0x0004 & pins) << 9)) & ((characteristics) << 8)) | \

((((0x0008 & pins) << 9) | ((0x0008 & pins) << 10) | ((0x0008 & pins) << 11) | ((0x0008 & pins) << 12)) & ((characteristics) << 12)) | \

((((0x0010 & pins) << 12)| ((0x0010 & pins) << 13) | ((0x0010 & pins) << 14) | ((0x0010 & pins) << 15)) & ((characteristics) << 16)) | \

((((0x0020 & pins) << 15)| ((0x0020 & pins) << 16) | ((0x0020 & pins) << 17) | ((0x0020 & pins) << 18)) & ((characteristics) << 20)) | \

((((0x0040 & pins) << 18)| ((0x0040 & pins) << 19) | ((0x0040 & pins) << 20) | ((0x0040 & pins) << 21)) & ((characteristics) << 24)) | \

((((0x0080 & pins) << 21)| ((0x0080 & pins) << 22) | ((0x0080 & pins) << 23) | ((0x0080 & pins) << 24)) & ((characteristics) << 28))); \

GPIO##ref##_CRH = ((GPIO##ref##_CRH & \

~(((0x0100 & pins) >> 8) | ((0x0100 & pins) >> 7) | ((0x0100 & pins) >> 6) | ((0x0100 & pins) >> 5) | \

(((0x0200 & pins) >> 5) | ((0x0200 & pins) >> 4) | ((0x0200 & pins) >> 3) | ((0x0200 & pins) >> 2)) | \

(((0x0400 & pins) >> 2) | ((0x0400 & pins) >> 1) | ((0x0400 & pins)) | ((0x0400 & pins) << 1)) | \

(((0x0800 & pins) << 1) | ((0x0800 & pins) << 2) | ((0x0800 & pins) << 3) | ((0x0800 & pins) << 4)) | \

(((0x1000 & pins) << 4) | ((0x1000 & pins) << 5) | ((0x1000 & pins) << 6) | ((0x1000 & pins) << 7)) | \

(((0x2000 & pins) << 7) | ((0x2000 & pins) << 8) | ((0x2000 & pins) << 9) | ((0x2000 & pins) << 10)) | \

(((0x4000 & pins) << 10) | ((0x4000 & pins) << 11) | ((0x4000 & pins) << 12) | ((0x4000 & pins) << 13)) | \

(((0x8000 & pins) << 13) | ((0x8000 & pins) << 14) | ((0x8000 & pins) << 15) | ((0x8000 & pins) << 16))))| \

((((0x0100 & pins) >> 8) | ((0x0100 & pins) >> 7) | ((0x0100 & pins) >> 6) | ((0x0100 & pins) >> 5)) & (characteristics)) | \

((((0x0200 & pins) >> 5) | ((0x0200 & pins) >> 4) | ((0x0200 & pins) >> 3) | ((0x0200 & pins) >> 2)) & ((characteristics) << 4)) | \

((((0x0400 & pins) >> 2) | ((0x0400 & pins) >> 1) | ((0x0400 & pins)) | ((0x0400 & pins) << 1)) & ((characteristics) << 8)) | \

((((0x0800 & pins) << 1) | ((0x0800 & pins) << 2) | ((0x0800 & pins) << 3) | ((0x0800 & pins) << 4)) & ((characteristics) << 12)) | \

((((0x1000 & pins) << 4) | ((0x1000 & pins) << 5) | ((0x1000 & pins) << 6) | ((0x1000 & pins) << 7)) & ((characteristics) << 16)) | \

((((0x2000 & pins) << 7) | ((0x2000 & pins) << 8) | ((0x2000 & pins) << 9) | ((0x2000 & pins) << 10)) & ((characteristics) << 20)) | \

((((0x4000 & pins) << 10)| ((0x4000 & pins) << 11) | ((0x4000 & pins) << 12) | ((0x4000 & pins) << 13)) & ((characteristics) << 24)) | \

((((0x8000 & pins) << 13)| ((0x8000 & pins) << 14) | ((0x8000 & pins) << 15) | ((0x8000 & pins) << 16)) & ((characteristics) << 28)));

_SIM_PORT_CHANGE

The user can however easily define a port to be configured as output using, for example:

_CONFIG_PORT_OUTPUT(D, PORTD_BIT4, (OUTPUT_SLOW | OUTPUT_PUSH_PULL)); uTaskerV1.4_Developers_Document/0.5 9/46 22.02.2012

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This configures pin 4 or port D as an output with push-pull output stage and slow slew-rate. Multiple pins of the same port can be configured at the same time as long as the same characteristics are required:

_CONFIG_PORT_OUTPUT(D, (PORTD_BIT4 | PORTD_BIT2), (OUTPUT_FAST |

OUTPUT_OPEN_DRAIN));

Special note concerning PC13, PC14 and PC15. These are supplied through the power switch and so can only be used at speeds up to 2MHz with 30pF load. Also only one of the three may be used as output at the same time! This warning is displayed in the uTasker simulator and the code will cause an exception if the user tries to configure something out of specification.

Most ports pins are 5V tolerant with the exception of :

PA0..PA7

PB5

PC0..PC3; PC13..PC15 uTaskerV1.4_Developers_Document/0.5 10/46 22.02.2012

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4.2. F2/F4 GPIOs

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The GPIO in the F2/F3 devices are controlled on the AHB1 bus and their configuration has been modified by a change in the control register set. Rather than a limited set of peripheral functions on a pin-by-pin basis the individual pins can be simply set to one of up to 15 peripheral functions when not used as a GPIO.

Ports are 16 bits wide and are named Port A to Port I; but not all ports and pins may be available in smaller packages.

Output port speeds can be configured for 2MHz, 25MHz, 50MHz or 100MHz.

The GPIO port macros for input/output configuration and control in the µTasker project allow the same operation in F2/F3 projects to be achieved as in F1 projects without needing to change code.

The JTAG pins have enabled pull-up/downs out of reset:

- PB4, PA13 and PA15 have pull-up enabled

- PA14 has pull-down enabled

Details about using GPIO pins as peripheral functions are given in a later chapter.

It is important to note that the debug pins reset to their debug function. These are:

• PA13 / JTMS / SWDIO

• PA14 / JTCK / SWCLK

• PA15 / JTDI

• PB3 / JTDO

• PB4 / NJRTS

If these are required for other functions; either general purpose input/output or alternative peripheral functions they can be reconfigured by code to achieve this.

However this may lose some debug capabilities since the full JTAG supports will no longer be possible if the function is modified. In the case of using a debugger in SWD mode (like the STLINK) three of the lines can still be modified without losing the debugging ability.

The LED blinking speed is determined by the system frequency and the configuration of the SYSTICK in the ARM Cortex M3/M4 core. The faster the system frequency, the higher the SYSTICK overflow value to result in the same TICK speed (and blinking LED speed). Therefore the same flashing frequency can be obtained from and system frequency, as long as the system frequency is accurately configured.

This leads to the topic of configuring the system speed based on the clock source and PLL settings, when the PLL is used. uTaskerV1.4_Developers_Document/0.5 11/46 22.02.2012

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4.3. F4 System Clock

The system clock frequency configuration is very simple in the µTasker project. The user has choices of clocking directly from the HSI clock (the internal high speed RC oscillator) or directly from the external oscillator/crystal (HSE), as well as using either of these inputs as input to the main PLL to generate a high speed system clock.

There are three main settings that can be chosen to select the basic mode:

#define CRYSTAL_FREQ 8000000

//#define DISABLE_PLL // run from clock source directly

//#define USE_HSI_CLOCK // use internal HSI clock source

When an external oscillator/crystal is used its frequency must be specified. The use of HSI as clock rather than HSE is enabled by activating USE_HSI_CLOCK. If either of the clock sources is to be used directly DISABLE_PLL can be enabled.

When the PLL is not disabled either clock sources can be used as input to the PLL

(when the HSI source is used the input frequency is half of the HSI oscillator

frequency).

In order to configure the system frequency the PLL parameters must then be configured as the following example illustrates:

#define PLL_INPUT_DIV 4 // 2..64 - should set the input to pll in the range 1..2MHz

(with preference near to 2MHz)

#define PLL_VCO_MUL 168 // 64 ..432 where VCO must be 64..432MHz

#define PLL_POST_DIVIDE 2 // post divide VCO by 2, 4, 6, or 8 to get the system clock

speed

The calculation of the system frequency is very simple for this processor. The input to the PLL must be within the range 1MHz..2MHz (2MHz is preferred due to less jitter) and so by dividing the input (8MHz assumed) by 4 results in the optimal value.

To generate 168MHz (the maximum speed of the F4) the PLL input of 2MHz is multiplied by 168 times to get a VCO frequency of 336MHz, which is within its valid range. The system clock is then equal to the VCO frequency divided by the postdivide block of either 2 (minimum), 4, 6 or 8.

The PLL macros used to configure the PLL in the µTasker initialization code uses these values to set the corresponding PLL registers. If the user makes an error in the use of any parameters or an intermediate frequency is out of range a compiler error is generated informing of the violation so that the value can be corrected accordingly.

The system speed obtained with the settings is also shown in the µTasker simulator when it is running.

It is worth noting that the initialization also configures the wait states used with internal Flash according to the system operating speed in order to optimize its timing. uTaskerV1.4_Developers_Document/0.5 12/46 22.02.2012

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A final user setting informs the compiler of the voltage range that the STM32 is to be operated in.

#define SUPPLY_VOLTAGE SUPPLY_2_7__3_6 // power supply is in the range 2.7V..3.6V

Other valid ranges are SUPPLY_2_4__2_7, SUPPLY_2_1__2_4 and

SUPPLY_1_8__2_1

, (in the case of larger anticipated operating range the lowest

should be selected) whereby it is to be noted that the maximum system speed is limited when a lower supply range is used. As an example, operating in the supply range below 2.1V reduces the maximum system frequency from 168MHz to 128MHz and also requires more wait states to be configured in the Flash interface for a given speed. These details, and also system limitation checks, are controlled by the macros used in the µTasker initialization code to automatically configure the values or generate compiler errors in case the user attempts to configure the system outside of its specified range.

4.4. F2 System Clock

The F2 devices use the same technique as the F4 devices but the limits are different.

For example the highest system frequency is 120MHz rather than 168MHz and the

PLL VCO range is less wide. The details are checked at compilation time in the

µTasker project and so the user is warned in case of configuration errors.

4.5. F1 System Clock

The F1 device user has choices of clocking directly from the HSI clock (the internal high speed RC oscillator) or directly from the external oscillator/crystal (HSE), as well as using either of these inputs as input to the main PLL to generate a high speed system clock.

Connectivity line users have a further option to use PLL2 as input to the main PLL and so derive system optimal system frequencies and respect requirements for peripherals such as the Ethernet module.

There are four main settings that can be chosen to select the basic mode, whereby the option USE_PLL2_CLOCK is only used in connectivity line projects :

#define CRYSTAL_FREQ 25000000

//#define DISABLE_PLL // run from clock source directly

//#define USE_HSI_CLOCK // use internal HSI clock source

#define USE_PLL2_CLOCK // use the PLL2 output as PLL input

(don't use USE_HSI_CLOCK in this configuration)

When an external oscillator/crystal is used its frequency must be specified. The use of HSI as clock rather than HSE is enabled by activating USE_HSI_CLOCK. If either of the clock sources is to be used directly DISABLE_PLL can be enabled.

When the PLL is not disabled either clock sources can be used as input to the PLL

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frequency). When USE_PLL2_CLOCK is selected in connectivity line projects the input of the main PLL is taken from the output of PLL, which has its own configuration as shown below.

In order to configure the system frequency the PLL parameters must then be configured as the following examples illustrates:

The first example is from an access line F1 project:

#define PLL_INPUT_DIV 2 // 1..16 - should set the input to pll in the range 1..24MHz

(with preference near to 8MHz) - not valid for HSI clock source

#define PLL_VCO_MUL 6 // 2 ..16 where PLL out must be 16..24MHz

The F1 doesn’t have a post divider after the PLL and so is less flexible than the PLL in the F2/F4. The value ranges are limited as in the code comments and the PLL macros used to configure the PLL in the µTasker initialization code uses these values to set the corresponding PLL registers. If the user makes an error in the use of any parameters or an intermediate frequency is out of range a compiler error is generated informing of the violation so that the value can be corrected accordingly. The system speed obtained with the settings is also shown in the µTasker simulator when it is running.

The second example is from a connectivity line F1 project whereby PLL2 is used as input (when PLL2 is not used it is otherwise equivalent to the first example):

#define PLL2_INPUT_DIV 5 // clock input is divided by 5 to give 5MHz to the PLL2

input (range 1..16)

#define PLL2_VCO_MUL 8 // the pll2 frequency is multiplied by 8 to 40MHz

(range 8..14 or 16 or 20)

#define PLL_INPUT_DIV 5 // 1..16 - should set the input to pll in the range

3..12MHz - not valid for HSI clock source

#define PLL_VCO_MUL 9 // 4..9 where PLL out must be 18..72MHz. Also 65 is

accepted as x6.5 (special case)

In addition to the PLL configuration values a set of PLL2 configuration values (and range limits) are shown. In this particular case PLL2 is used to multiply the 25MHz input crystal frequency (PLL2 always uses this clock input) to 40MHz (by dividing first by 5 and then multiplying by 8). This frequency allows the main PLL to multiply it

(divide by 5 and then multiply by 9) up to the maximum system frequency of 72MHz for this device.

It is worth noting that the initialization also configures the wait states used with

internal Flash according to the system operating speed in order to optimize its timing. uTaskerV1.4_Developers_Document/0.5 14/46 22.02.2012

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4.6. Cortex M3/M4 peripherals

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Since the SYSTICK and NVIC are used in the blinking LED test the following details are appropriate to be mentioned here:

• Cortex M3/M4 peripherals consist of the NVIC (Nested Vectored Interrupt

Controller), SCB (System Control Block) and SYSTICK (System timer). The

Cortex M3/M4 processor uses the Cortex Microcontroller software interface standard (CMSIS) in order to ensure a high level of software compatibility.

• In the STM32 NVIC 16 levels of priorities are supported (0..15) whereby 0 is the highest level and 15 is the lowest level. The priority of each interrupt needs to be set in the corresponding NVIC_IPR register using the bits 7:4 – bits 3:0 are read always as 0 and cannot be written. Priorities values are thus effectively 0x10:0xf0. In order to keep compatibility 0..15 are defined by the user but these values are shifted by 4 places when programmed. uTaskerV1.4_Developers_Document/0.5 15/46 22.02.2012

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5. Using the STM32 UART

The STM32 has up to 6 asynchronous interfaces. Up to four of these are known as

USARTs and two as UARTs – the USARTs have increased functionality, including synchronous modes.

USART1 and USART6 are clocked from PCLK2 and the other interfaces are clocked from PCLK.

After successfully completing the requirements for the blinking LED the next step in porting the µTasker project to the STM32 is to enable the UART operation.

This step requires the configuration of peripherals pins and also the handling of peripheral interrupts; whereas the blinking LED exercise uses a system interrupt which is not specific to the STM32’s own peripherals the UART requires the use of a processor-specific interrupt.

This brings us to the topic of setting up the pins for peripheral use, which is different when using F1 or F2/F4 parts as discussed below:

5.1. F1 Peripheral Configuration

When configuring ports for peripheral use the ports need to be configured as

(floating) input when the peripheral function is an input and as alternative output (with the desired characteristics) when the peripheral function is an output. Peripheral inputs are always connected in parallel but output peripherals need to be specially selected.

Note that this makes simulation of input peripherals more complicated due to the fact that there is no information in the GPIO block informing of the fact that a peripheral is operating on the input – only the fact that the peripheral is enabled can be used to determine this. In the case of outputs the alternative output information indicates that

it is in use.

There is nothing to stop multiple peripherals from being connected to the same port line – it is therefore up to the user to be careful with their configuration. The µTasker simulator performs additional checks and errors in the use (peripheral collisions) lead to exceptions being indicated.

Peripherals often have remapping capability so that a group of signals can be positioned on a different set of port pins. This is controlled by the AFIO_MAPR register. The alternative I/O module has its own power supply which is activated in case remapping is required. uTaskerV1.4_Developers_Document/0.5 16/46 22.02.2012

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5.2. F2/F4 Peripheral Configuration

F2/F4 peripheral pins are controlled differently to the F1. Each pin can be set to an alternate function mode and has the ability to be connected to one of up to 16 different peripherals. Inputs are thus also connected independently and not in parallel to GPIO inputs as is the case with the F1 parts.

There is no remapping modes since the alternative function switching in the GPIO block itself can control multiple pin functions.

Since the peripheral control is different depending on the STM32 family used the

µTasker port macros use two functions which are effectively compatible for all families.

_CONFIG_PERIPHERAL_OUTPUT(B, (PERIPHERAL_USART1_2_3), (PORTB_BIT6),

(OUTPUT_MEDIUM | OUTPUT_PUSH_PULL));

This shows how port B-6 is configured as USART peripheral output (this is in fact

USART1_TX

which occupies the same location in F1/F2 and F3 devices). This will configure the alternative function in the F1, whereby it doesn’t actually use the peripheral selection value PERIPHERAL_USART1_2_3 in that case since it only has this function on that pin. The output is set to medium speed, push-pull mode.

The macro used when F2/F4 parts are in operation performs all configuration necessary to do the same thing, whereby also the exact peripheral function for this pin (it supports various different peripheral functions) is set. As long as the

_CONFIG_PERIPHERAL_OUTPUT()

macro is used the code is then operational on all device types.

For peripheral input types the following macro ensures compatibility in an equivalent manner (USART1_RX):

_CONFIG_PERIPHERAL_INPUT(B, (PERIPHERAL_USART1_2_3), (PORTD_BIT8), (FLOATING_INPUT)); uTaskerV1.4_Developers_Document/0.5 17/46 22.02.2012

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The USART and UART interfaces consist of Tx, Rx, RTS and CTS lines for each interface. The USARTS have also a clock line. The location of the peripherals are consistent across the range of parts as illustrated from the following table which shows the default (not-remapped) and remapped locations for all signals.

USART1

USART2

UART1_TXD UART1_RXD UART1_RTS UART1_CTS

default Port A9 Port A10 Port A12 Port A11

USART1_REMAP Port B6 Port B7 - -

UART2_TXD UART2_RXD UART2_RTS UART2_CTS

default Port A2

USART2_REMAP

Port D5

Port A3

Port D6

Port A0

Port D3

Port A1

Port D4

USART3 UART3_TXD UART3_RXD UART3_RTS UART3_CTS

Default Port B10 Port B11 Port B14 Port B13

USART3_PARTIAL_REMAP

Port C10

USART3_FULLY_REMAPPED

Port D8

Port C11

Port D9

Port B14

Port D12

Port B13

Port D11

UART4 UART4_TXD

default Port C10

UART4_RXD UART4_RTS UART4_CTS

Port C11 - -

UART5

USART6

UART5_TXD UART5_RXD UART5_RTS UART5_CTS

default Port C12 Port D2 - -

UART6_TXD UART6_RXD UART6_RTS UART6_CTS

default Port C6

USART6_REMAP

Port G14

Port C7

Port G9

Port G8

Port G12

Port G13

Port G15

Note that not all pins and UARTs/USARTs are available on all devices

The µTasker UART driver supports 6 channels and defaults to the pin-outs as shown in the “default” rows. By activating the alternative defines, for UARTs with multiple positions, the set of combinations can be configured accordingly.

On the STM3210C-EVAL board USART2 is connected to the single DSUB-9 connector. A cross-over RS232 cable is required to connect the board to a PC.

The µTasker command line demo uses this USART at 115k Baud with 1 stop bit

(XON/XOFF protocol) by default as command line menu control. The user can configure various settings using this interface, including Ethernet IP settings, which can then be saved to the parameter system.

When an SD card in is use the menu also contains a DOS-like interface for the

FAT32 (µtFAT) file system.

The use of UARTs in the µTasker project are discussed in more detail in the “UART

User’s Guide”: http://www.utasker.com/docs/uTasker/uTaskerUART.PDF uTaskerV1.4_Developers_Document/0.5 18/46 22.02.2012

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6. Ethernet

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Some of the STM32 devices include an Ethernet MAC supporting 10/100M operation with either MII or RMII interface to an external PHY.

The MAC contains support for PTP (Precision Time protocol according to IEEE1588) and also some off-loading check sum support for IPv4 and IPv6 datagrams.

When Ethernet is used the AHB clock must be at least 25MHz.

Note that it is possible to configure the port MCO to drive various clock signals, including 25MHz. This could be used to drive the PHY clock, for instance!

6.1. STM3210C-EVAL

The STM3210C-EVAL board uses a DP83848 as external PHY. Although it could be configured to work in RMII mode there is no 50MHz oscillator on the board as standard and so the MII mode is used.

Problem with ETH_DMABMR

According to the user’s manual this register resets to the value 0x2101. When working with the debugger it was found to default to 0x20101 as soon as the module’s clocks are enabled. The bit 0x00000001 (SR) is a module reset which means that it starts in the reset state and the user should wait for this to return to 0 before continuing. After a power on reset this tended to hang in this wait loop forever but when stepping the code the bit would return to zero and the board would then start correctly.

If the reset bit could be cleared (which rarely, but sometimes happens) the value in the register after a warm reset is 0x20100 and it doesn’t hang any more during the initialization.

The reason for this difficulty was identified as being due to a missing clock. The jumper JP4 was set to supply the 25MHz clock to the PHY via the MCO output but this was not driven. By setting the jumper to the position allowing the PHYs external

25MHz crystal to be used was found to solve the issue.

Since it is interesting to be able to save the PHYs external crystal a setting was made to configure the MCO output with a 25MHz signal:

#define ETHERNET_DRIVE_PHY_25MHZ

.

The PHY interrupt is connected to an IO expander input (EXP_IO8) on the

STM3210C-EVAL board. This is quite a complicated method since it requires the I

2

C driver to be used to configure the IO expander (STMPE811 Address 0x88) and its interrupt line on PB14 to be used to detect the input change. Since a second IO expander (I

2

C address 0x82) is used for touch screen operation this means that any interrupt requires reading both chips to determine which one is requesting the interrupt and then handling either the touch screen interrupt or the PHY interrupt.

Rather than mixing the touch screen interrupt handler with the Ethernet PHY interrupt handler the PHY interrupt was connected in addition to PC13 (removing JP1 completely). uTaskerV1.4_Developers_Document/0.5 19/46 22.02.2012

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6.2. STM3240G-EVAL

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The Ethernet interface on this board is equivalent to that on the STM3210C-EVAL board. It has the PHY’s interrupt line directly connected to the processor port B-14.

6.3. Checksum Offloading

Probably the most interesting feature of the Ethernet controller in the STM32 is its capability to perform checksum offloading. By implementing IPv4 and IPv6 payload and header checksum calculation in hardware this calculation overhead can be removed from software, resulting in greatly improved performance, especially when large payload lengths would otherwise need to be calculated.

#define IP_RX_CHECKSUM_OFFLOAD

- When this is defined the IPv4/v6 reception calculation is enabled. If an IPv4/IPv6 protcol frame is received it will be immediately discarded if the EMAC flags that there was either a payload or header checksum error. This saves the TCP/IP stack from needing to handle frames that will obviously fail.

Furthermore the check sum calculation is removed from the IPv4, IPv6, UDP, ICMP and TCP reception handling. Since no frames will arrive which are corrupted there is no need to perform these checks, resulting in much fast reception frame handling.

#define IP_TX_CHECKSUM_OFFLOAD

- When this is defined the EMAC transmitter automatically inserts the IPv4/IPv6 header checksum. This means that the IP transmission code doesn’t need to calculate the value and insert it – it can just leave a random value at the checksum position in the buffer.

IP_TX_PAYLOAD_CHECKSUM_OFFLOAD –

When this is defined also the ICMP,

UDP,and TCP checksums and pseudo headers are automatically inserted. In this case the checksum location must be set to the value 0x0000 since it is also used as input to the calculation. Furthermore the transmitter operation must be set to storeand-forward mode with adequate FIO length!

This option overrides the IP_TX_CHECKSUM_OFFLOAD option and both are active.

Additional software calculation can be saved when the option is enabled.

When frames of less than 60 bytes length are transmitted the Ethernet transmitter automatically pads them with zeros. uTaskerV1.4_Developers_Document/0.5 20/46 22.02.2012

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7. FLASH

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7.1. F1 Flash

The connectivity line devices have 2k page sizes and devices with less than 256k

Flash have 1k page sizes. When reading program code the pre-fetch buffer (2 x 64 bytes) achieves fast instruction operation since a single pre-fetch then holds multiple instructions. The pre-fetch buffer is enabled by default.

Programming of the FLASH takes place on half-word (16 bits). Page or full FLASH

(not information block) deletion is possible with erase time of maximum 40ms in each case. Half-word programming takes place in max. 70us.

The STM32 user’s manual doesn’t contain programming information so this needs to be studied in the “STM32F10xxx Flash Programming Manuals”.

After a reset the FLASH programming interface is protected and can only be accessed after performing an unlocking sequence. This consists of the writing of a two key sequence:

0x45670123

followed by 0xcdef89ab to the FLASH_KEYR register.

All FLASH operation is self-timed using a dedicated internal clock which has a fixed frequency and thus avoids the need for configuration and risk of false programming times being used.

Each half-word write includes a check of the present half-word content value. A halfword value must be 0xffff (deleted) for a half-word write to be accepted. This means that accumulative writes to half-words is not possible.

The FLASH driver can operate from FLASH meaning that pages can be erased and half-works written in other pages when code is running from the same FLASH module. This also means that interrupts don’t need to be blocked when FLASH operations are performed.

7.2. F2/F4 Flash

These parts have Flash section sizes that vary in size. There are 4 initial sections of

16k size followed by a single section of 64k size and then several sections of 128k in size, depending on the size of Flash memory in the device.

Unlike the F1 Flash the F2/F4 Flash can be programmed as bytes, half-words, long works or 64 bit long words. However this possibility is also dependent on the power supply used since there is a limit to the number of bits in the programming element that can be programmed to 0 at each operation. 64 bit programming is, for example, only possible when an external voltage of 8..9V is applied externally on the Vpp pin and this option is therefore generally reserved for production programming rather than in-application programming. Below 2.1V only 8 bit programming is possible.

Below 2.7V 16 or 8 bit programming is possible. 32 bit programming is only possible when the supply range is above 2.7V. uTaskerV1.4_Developers_Document/0.5 21/46 22.02.2012

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It is also to be noted that all write operations must be correctly aligned and fit within a

128 bit (16 byte) line boundary. Should any of these rules not be respected the Flash controller will signal an error.

The operation of the Flash controller is not compatible between the F1 and F2/F4 parts and some of the registers and their contents are also different.

The cpu clock frequency (HCLK) must be at least 1MHz in order to program the internal Flash.

Programming a byte, short word or long word takes typically 16us and maximum

100us (in worst case after 100’000 programming cycles). The sector delete durations depend on the sector size with the 16k blocks erased in typically 300ms, the 64k block in 700ms and the 128k blocks in 1.3s each. These values are also dependent on the supply voltage whereby the average and maximum delete times increase with lower voltage and a worst case of 4s for a 128k block results at the lowest operation voltage.

The Flash driver in the µTasker STM32 project uses the project configuration to know which parts are used and also which voltage range the design is operating in.

Therefore it adapts the programming interface accordingly without the user having to know all details and restrictions; for example, if a low voltage configuration is being used programming will automatically take place on a byte basis rather than on a wider operation basis when a higher supply voltage is present and the access allows it.

When programming memory it will do it using the widest write widths possible depending on the power supply available (eg. When limited supply range used the widest accesses will not be made since they are not allowed), the amount of data to be written and the alignment of the accesses. When the STM32F2/F4 parts are used byte writes are allowed, although they are only used when needed in preference of wider accesses, whereas only short word writes are possible when the STM32F1xx are used. This allows increased efficiency where the capability to write bytes allows this – see the define NO_ACCUMULATIVE_WORDS in the µFileSystem to see an example of its implications which is set when the STM32F1xx is used but not when the F2/F4 parts are specified.

Due to the large flash granularity in the F2/F4 parts it is advised to use

SUB_FILE_SIZE option so that the µFileSystem can store multiple files in a single sector. This operation is discussed in the document http://www.utasker.com/docs/STR91XF/FileSystemSTR91X.PDF

It is further recommended to position parameter blocks as used by the

µParameterSystem in the smaller sectors at the start of the flash. Typically the second and third sectors (each 16k) are used as parameter swap blocks since the user of larger ones would be very inefficient in terms of memory utilisation. The first sector is used for reset vectors and possibly a boot loader and the application code can be located to start in the fourth boot sector (0x0000c000). uTaskerV1.4_Developers_Document/0.5 22/46 22.02.2012

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8. External Interrupts (EXTI)

The external interrupt controller consists of a group of 16 edge detectors for port interrupts. These can be connected to various GPIOs (EXTI0 can be connected to one of PA0, PB0, …PG0, etc.; EXTI1 can be connected to one of PA1, PB1, …PG1, etc.; … EXTI15 can be connected to one of PA15, PB15, …PG15, etc.;

Additional EXTI lines (16..19 in connectivity line devices or 16..18 in others) are connected to PVD output, RTC alarm, USB wakeup and Ethernet wakeup respectively in the STM32F1xx parts and additionally to high-speed USB and RTC tamper and RTC wakeup when available.

This means that there is one EXTI for each possible port bit (0..15) but each port needs to use a different bit as they are not all available together.

EXTI0..4 have their own dedicated interrupt vectors.

EXTI5..9 and EXT10..15 share vectors for several inputs

Each interrupt input can generate falling and/or rising edge interrupts – they cannot generate level sensitive interrupts.

A difference between the control of the connection between the port input and the

EXTI edge detector between the STM32F1xx and STM32F2/4 parts is that the F1 controls this in the alternate-function I/O block and the F2/F4 in the system configuration controller. In both cases the corresponding block also needs to be powered on for the operation to be successful.

9. SPI FLASH

Supported – discussion to be added… uTaskerV1.4_Developers_Document/0.5 23/46 22.02.2012

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10. SD Card

SC cards and micro SD cards can usually be operated in SPI or SDIO modes.

Some of the STM32 devices have SDIO controllers allowing the faster 4 bit data mode to be used.

When the utFAT module is used in the µTasker project on the STM3210C-EVAL board, with STM32F107 it uses the SPI mode of operation since this device has only

SPI interfaces.

When the utFAT module is used in the µTasker project on the STM3240G-

EVALboard, with STM32F407 it uses the SDIO mode of operation since the micro SD card on the board is connected to this interface. Often the SDIO pin layout of the processors are overlaid with the corresponding SPI lines so that either SDIO or SPI can be used. In the case of the STM32F4 this is not the case since the SDIO pins are not multiplexed with corresponding SPI pins.

F4:

The SDIO module uses the APB2 clock for its register, interrupt and DMA operation.

The SDIO interface is clocked form the ring clock (the second output from the main

PLL). When USB FS is used this clock will be set to exactly 48MHz, otherwise its speed can be set lower.

11. Flexible Static Memory Controller

F4:

The FSMC can interface with various memory types in 8 or 16 bit modes. The memory types supported are SRAM, ROM NOR Flash/OneNAND Flash and PSRAM.

Also two banks for NAND flash are supported with ECC hardware.

The memory types are supported in 4 different banks of 256 MByte size each:

Bank 1 is split into 4 NOR/PSRAM regions, whereby each has its own chip select line

[0x60000000..0x6fffffff].

Banks 2 and 3 can each address one NAND Flash device each

[0x70000000..0x7fffffff and 0x80000000..0x8fffffff].

Bank 4 can be used to address a PC card device [0x90000000..0x9fffffff]. uTaskerV1.4_Developers_Document/0.5 24/46 22.02.2012

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12. USB Full-Speed Device

The OTG (On-The-Go) FS (Full-speed) USB controller available on most STM32 processors supports OTG, Host and Device modes of operation.

This section discusses the device mode of operation since this is a popular mode often used in projects where a connection via USB to a PC is required.

The USB controller is USB-IF certified to USB specification revision 2.0 and the

STM32 includes a physical, meaning that only 2 pins are required for the minimal device mode operation. These are the OTG_FS_DP and OTG_FS_DM pins.

The USB device mode of the STM32 has been integrated into the µTasker USB module, taking advantage of the generic USB software layers. The following technical details are useful to be aware of since they are hardware specific to the STM32 lowlevel driver:

• USB data is coordinated in 1.25k of dedicated RAM with advanced FIFO control, where each FIFO can hold multiple packets waiting to be transferred or treated by the processor. The allocation of the space to the various USB endpoints for reception and transmission use is very flexible so that this can be dimensioned optimally for a particular use.

• In device mode there is one bi-directional control endpoint 0 and up to three IN and OUT endpoints, supporting bulk, interrupt or isochronous transfers.

• There is a shared Rx FIFO and a Tx-OUT FIFO, as well as up to four dedicated Tx-IN FIFOs (allowing one for each of the four possible IN endpoints).

• The device can only operate in full-speed mode and not in low-speed mode.

• The required 48MHz +/- 0.25% clock for the USB controller core is derived from the power and clock control module from a second output from the main

PLL, known as PLL48CLK. When USB is active the PLL VCO frequency must be a multiple of 48MHz to allow the correct USB frequency to be achieved.

The configuration value for the PLL’s second output is calculated automatically and an error is issued when the project is compiled when either the divide value is not allowed or when the USB clock frequency of 48MHz is not exact.

It is to be noted that the AHB frequency (HCLK) should be greater than 14.2MHz for correct USB device operation. If the µTasker project is configured for USB device operation a compiler error results if this constraint is not fulfilled.

It is to be further noted that the STM32F4 supports a USB based boot loader on the

OTG_FS USB controller. In order for this to be able to operate an external clock

(HSE) needs to be available with a frequency between 4MHz and 26MHz (dividable by 1MHz).

• When the USB controller is enabled as a device it automatically connects a pull-up resistor to the OTG_FS_DP line. uTaskerV1.4_Developers_Document/0.5 25/46 22.02.2012

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The following details are the result of practical work with the FS USB device in the

STM32F4:

• The first interrupt occurs when the USB cable is connected and the host performs a USB reset. This is signaled by the OTG_FS_GINTSTS_USBRST flag in the core interrupt register OTG_FS_GINTSTS. The reset clears all

FIFOs and prepares for the enumeration sequence.

• The following figure shows the process involved when a SETUP frame is received. The first such SETUP occurs after the USB reset in form of a

GetDescriptor (Device)

• The USB host sends the first SETUP token, which results in an interrupt since the Rx FIFO on the control end point is no longer empty. The interrupt can be reset before reading the FIFO content.

• The status popped from the receive FIFO show the value 0x01AC0080, which means that 8 bytes are available and the frame is a SETUP token. The 8 bytes of data correspond to a request for the standard device descriptor.

To complete… uTaskerV1.4_Developers_Document/0.5 26/46 22.02.2012

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13. Conclusion

The purpose of this document was to give an introduction to working with the STM32 family of Cortex M3/M4 processors by introducing their basic operation and detailing how the µTasker project makes it simple to work with them as well as move the project between different families.

In addition to giving various information useful for practical developments quick start guides are available in appendixes for working with the µTasker project together with various development environments and tools.

Where appropriate, advanced chapters give insight into complex peripherals to help better understand their practical operation and how their use is simplified by the

µTasker project and its simulator.

V0.4 17.12.2011 Provisional – in development – added Ethernet, external interrupts and internal Flash descriptions

V0.5 22.02.2012: Added SD card, Flexible Static Memory Controller, USB-FS-

Device, STM32F407-EVAL board modification (Appendix I).

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APPENDIX A - STM32F1, STM32L and STM32W

The STM32 from ST-Micro is a Cortex M3/M4 based single-chip processor family.

• STM32F1 – ARM Cortex M3

• STM32L - ultra low power

• STM32W – ARM Cortex RF

The device members are referred to as low, medium, high and XL density devices depending on the amount of internal FLASH that they have. Low density devices have 16k to 32k of internal FLASH, medium density devices 64k or 128k, highdensity devices 256k or 512k and XL-density 768k to 1Meg.

The internal FLASH is located at 0x08000000. Its Flash granularity (section size that can be independently deleted) can be taken from the following table:

Flash size range Flash granularity

Low-density

Medium-density

High-density

16k..32k

64k..128k

256k..512k

1k page size

1k page size

2k page size

XL-density 768k.1M 2k page size

The internal FLASH contains also an information block and option bytes. The information block (0x1ffff000) is usually 2k in size and there are 16 option bytes

(0x1ffff800).

Connectivity line devices have an 18k information block at 0x1fffb000 and the XLdensity types 6k at 0x1fffe000.

Internally the FLASH is 128 bits wide. It can be accessed at up to 24MHz with zero wait states. One wait state is required up to 48MHz and two wait states up to the maximum operating speed of 72 MHz. SYSCLK should be equal to HCLK.

The STM32 F1 series is divided into 5 different product lines:

STM32F100xx

STM32F101xx

STM32F102xx

STM32F103xx

Value line (up to 24MHz)

Access line (up to 36MHz)

Access line (with USB) (up to 48MHz)

Performance line (up to 72MHz)

STM32F105xx/STM32F107xx Connectivity line (up to 72MHz)

The internal SRAM is located at 0x20000000. Its size can be taken from the table of available devices: uTaskerV1.4_Developers_Document/0.5 28/46 22.02.2012

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Available F1 devices

Type Housing Speed FLASH size

SRAM size

Remarks

STM32F105R8 LQFP 64

STM32F105RB LQFP 64

STM32F105RC LQFP 64

72MHz 64k

72MHz 128k

72MHz 256k

STM32F105V8 LQFP 100 72MHz 64k

20k

32k

64k

20k

Connectivity USB

Connectivity USB

Connectivity USB

Connectivity USB

STM32F105VBT LQFP 100 72MHz 128k 32k

STM32F105VBH BGA 100 72MHz 128k 32k

STM32F105VC LQFP 100 72MHz 256k 64k

STM32F107RB LQFP 64 72MHz 128k 48k

STM32F107RC

STM32F107VB

LQFP 64

LQFP 100

STM32F107VCT LQFP 100

STM32F107VCH BGA 100

72MHz 256k

72MHz 128k

72MHz 256k

72MHz 256k

64k

48k

64k

64k

Connectivity USB

Connectivity USB

Connectivity USB

Connectivity USB +

Ethernet

Connectivity USB +

Ethernet

Connectivity USB +

Ethernet

Connectivity USB +

Ethernet

Connectivity USB +

Ethernet

STM32F103ZET LQFP 144 72MHz 512k 64k

STM32F103ZEH BGA 144 72MHz 512k 64k

STM32F103ZDT LQFP 144 72MHz 384k 64k

STM32F103ZDH BGA 144 72MHz 384k 64k

STM32F103ZCT LQFP 144 72MHz 256k 48k

STM32F103ZCH BGA 144 72MHz 256k 48k

STM32F103VET LQFP 100 72MHz 512k 64k

STM32F103VEH BGA 100 72MHz 512k 64k

STM32F103VDT LQFP 100 72MHz 384k 64k

STM32F103VDH BGA 100 72MHz 384k 64k

STM32F103VCT LQFP 100 72MHz 256k 48k

STM32F103VCH BGA 100 72MHz 256k 48k

STM32F103VBT LQFP 100 72MHz 128k 20k

STM32F103VBH BGA 100 72MHz 128k 20k

Performance line

Performance line

Performance line

Performance line

Performance line

Performance line

Performance line

Performance line

Performance line

Performance line

Performance line

Performance line

Performance line

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STM32F103V8T LQFP 100 72MHz 64k 20k Performance line

STM32F103V8H BGA 100 72MHz 64k 20k Performance line

STM32F103TB VFQFPN 36 72MHz 128k 20k

STM32F103T8 VFQFPN 36 72MHz 64k

STM32F103T6 VFQFPN 36 72MHz 32k

20k

10k

Performance line

Performance line

Performance line

STM32F103T4 VFQFPN 36 72MHz 16k

STM32F103RE LQFP 64 72MHz 512k

6k

64k

STM32F103RD LQFP 64 72MHz 384k 64k

STM32F103RC LQFP 64

STM32F103RB LQFP 64

STM32F103R8 LQFP 64

72MHz 256k

72MHz 128k

72MHz 64k

48k

20k

20k

Performance line

Performance line

Performance line

Performance line

Performance line

Performance line

STM32F103R6 LQFP 64

STM32F103R4 LQFP 64

STM32F103CB LQFP 48

STM32F103C8 LQFP 48

STM32F103C6 LQFP 48

STM32F103C4 LQFP 48

STM32F102RB LQFP 64

STM32F102R8 LQFP 64

72MHz 32k

72MHz 16k

10k

6k

72MHz 128k 20k

72MHz 64k 20k

72MHz 32k 10k

72MHz 16k 6k

48MHz 128k 16k

48MHz 64k 10k

STM32F102R6 LQFP 64

STM32F102R4 LQFP 64

STM32F102CB LQFP 48

STM32F102C8 LQFP 48

STM32F102C6 LQFP 48

48MHz 32k

48MHz 16k

6k

4k

48MHz 128k 16k

48MHz 64k 10k

48MHz 32k 6k

STM32F102C4 LQFP 48 48MHz 16k 4k

STM32F101ZE LQFP 144 36MHz 512k 48k

STM32F101ZD LQFP 144 36MHz 384k 48k

STM32F101ZC LQFP 144 36MHz 256k 32k

STM32F101VE LQFP 100 36MHz 512k 48k

STM32F101VD LQFP 100 36MHz 384k 48k

STM32F101VC LQFP 100 36MHz 256k 32k

STM32F101VB LQFP 100 36MHz 128k 16k

STM32F101V8 LQFP 100 36MHz 64k 10k

STM32F101TB VFQFPN 36 36MHz 128k 16k

Access line

Access line

Access line

Access line

Access line

Access line

Access line

Performance line

Performance line

Performance line

Performance line

Performance line

Performance line

Access line with USB

Access line with USB

Access line with USB

Access line with USB

Access line with USB

Access line with USB

Access line with USB

Access line with USB

Access line

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STM32F101T8 VFQFPN 36 36MHz 64k 10k Access line

STM32F101T6 VFQFPN 36 36MHz 32k 6k Access line

STM32F101T4 VFQFPN 36 36MHz 16k

STM32F101RE LQFP 64

STM32F101RD LQFP 64

36MHz 512k

36MHz 384k

4k

48k

48k

Access line

Access line

Access line

STM32F101RC LQFP 64

STM32F101RB LQFP 64

STM32F101R8 LQFP 64

STM32F101R6 LQFP 64

STM32F101R4 LQFP 64

STM32F101CB LQFP 48

36MHz 256k 32k

36MHz 128k 16k

36MHz 64k

36MHz 32k

36MHz 16k

10k

6k

4k

36MHz 128k 16k

Access line

Access line

Access line

Access line

Access line

Access line

STM32F101C8 LQFP 48

STM32F101C6 LQFP 48

36MHz 64k

36MHz 32k

10k

6k

STM32F101C4 LQFP 48 36MHz 16k 4k

STM32F100VB LQFP 100 24MHz 128k 8k

STM32F100V8 LQFP 100 24MHz 64k 8k

STM32F100RB LQFP 64

STM32F100R8 LQFP 64

STM32F100R6 LQFP 64

24MHz 128k

24MHz 64k

24MHz 32k

8k

8k

4k

STM32F100R4

STM32F100CB

STM32F100C8

STM32F100C6

STM32F100C4

LQFP 64

LQFP 48

LQFP 48

LQFP 48

LQFP 48

24MHz 16k 4k

24MHz 128k 8k

24MHz 64k

24MHz 32k

24MHz 16k

8k

4k

4k

Access line

Access line

Access line

Value line

Value line

Value line

Value line

Value line

Value line

Value line

Value line

Value line

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APPENDIX B – STM32F2xx

Available F2 devices – Cortex M3

Type

STM32F205RB

STM32F205RC

Housing

LQFP 64

LQFP 64

STM32F205RE LQFP 64

STM32F205RF LQFP 64

STM32F205RG LQFP 64

Speed FLASH size

SRAM size

120MHz 128k 64k

Remarks

120MHz 256k 96k

USB

USB

120MHz 512k 128k USB

120MHz 768k 128k USB

120MHz 1M 128k USB

STM32F205VB LQFP 100 120MHz 128k 64k

STM32F205VC LQFP 100 120MHz 256k 96k

USB

USB

STM32F205VE LQFP 100 120MHz 512k 128k USB

STM32F205VF LQFP 100 120MHz 768k 128k USB

STM32F205VG LQFP 100 120MHz 1M 128k USB

STM32F205ZC LQFP 144 120MHz 256k 96k USB

STM32F205ZE LQFP 144 120MHz 512k 128k USB

STM32F205ZF LQFP 144 120MHz 768k 128k USB

STM32F205ZG LQFP 144 120MHz 1M

STM32F207IC BGA 176 120MHz 256k

128k

96k

USB

Ethernet + 2 xUSB

STM32F207IE BGA 176

STM32F207IF BGA 176

STM32F207IG BGA 176

120MHz 512k

120MHz 768k

120MHz 1M

128k

128k

128k

Ethernet + 2 xUSB

Ethernet + 2 xUSB

Ethernet + 2 xUSB

STM32F207VC LQFP 100 120MHz 256k 128k Ethernet + 2 xUSB

STM32F207VE LQFP 100 120MHz 512k 128k Ethernet + 2 xUSB

STM32F207VF LQFP 100 120MHz 768k 128k Ethernet + 2 xUSB

STM32F207VG LQFP 100 120MHz 1M 128k Ethernet + 2 xUSB

STM32F207ZC LQFP 144 120MHz 256k 128k Ethernet + 2 xUSB

STM32F207ZE LQFP 144 120MHz 512k 128k Ethernet + 2 xUSB

STM32F207ZF LQFP 144 120MHz 768k 128k Ethernet + 2 xUSB

STM32F207ZG LQFP 144 120MHz 1M 128k Ethernet + 2 xUSB

STM32F215RE LQFP 64

STM32F215RG LQFP 64

120MHz 512k

120MHz 1M

128k

128k

USB

USB

STM32F215VE LQFP 100 120MHz 512k 128k USB uTaskerV1.4_Developers_Document/0.5 32/46 22.02.2012

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STM32F215VG LQFP 100 120MHz 1M 128k USB

STM32F217IE BGA 176 120MHz 512k 128k Ethernet + 2 x USB

STM32F217IG BGA 176 120MHz 1M 128k Ethernet + 2 x USB

STM32F217VE LQFP 100 120MHz 512k 128k Ethernet + 2 x USB

STM32F217VG LQFP 100 120MHz 1M 128k Ethernet + 2 x USB

STM32F217ZE LQFP 144 120MHz 512k 128k Ethernet + 2 x USB

STM32F217ZG LQFP 144 120MHz 1M 128k Ethernet + 2 x USB uTaskerV1.4_Developers_Document/0.5 33/46 22.02.2012

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APPENDIX C – STM32F4xx

Available F4 devices (active at time of writing) – Cortex M4

Type Housing Speed FLASH size

SRAM size

168MHz 1M 192k

Remarks

STM32F405RG LQFP 64

STM32F407IG BGA 176 168MHz 1M 192k

STM32F407VE LQFP 100 168MHz 512k 192k

STM32F407VG LQFP 100 168MHz 1M 192k

STM32F407ZG LQFP 144 168MHz 1M 192k

STM32F415RG LQFP 64

STM32F417IG BGA 176

168MHz 1M

168MHz 1M

STM32F417VG LQFP 100 168MHz 1M

STM32F417ZG LQFP 144 168MHz 1M

192k

192k

192k

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APPENDIX D – Building the µTasker Project in the µTasker

Simulator and generating a cross-compiled Object for the HW

Target

The µTasker project contains VisualStudio 6.0 and VisualStudio 2010 projects in the folder \Applications\uTaskerV1.4\Simulator.

This allows the project to be build and executed with the µTasker simulator – this is

detailed in the µTasker tutorial to the STM32 devices. When the simulator runs the same project code is executed that will later be operating on the HW target but the simulation environment gives powerful capabilities enabling development, testing and debugging of the majority of project code (including peripheral use) without needing to leave the PC environment. The following screen short is an example of an STM32 device being simulated, showing the present use of ports and peripherals. uTaskerV1.4_Developers_Document/0.5 35/46 22.02.2012

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For users of the GCC tool chain who don’t need to work in an DIE for the target processor the project can be built with the cross-compiler by selecting the

VisualStudio target „Win32 uTasker STM32 plus GNU build“.

When the VisualStudio successfully builds the bat file

\Applications\uTaskerV1.4\GNU_STM32\Build_STM32.bat

is executed as a post-build step. This creates binare and hex outputs for stand-alone and boot loadable targets based on the make file make_uTaskerV1.4_GNU_STM32 in the same folder.

The linker script file for the stand-alone target is uTaskerSTM32.ld, which is configured for a processor with 1M internal Flash and 192k internal SRAM. This file can generally be used without changes since the actual project details are controlled in the initialisation code of the µTasker project which automatically configures the initial stack pointer to suit. The linker script’s memory dimensions simply inform the linker how much maximum resources are available. If the user desires a warning from the linker when too much code or variables are generated to fit into the physical limits imposed by the chip the SRAM and Flash sizes in the linker script file can simply be reduced to match.

The VisualStudio console window shows the result fo the build as illustrated in the following example (only one C-file compile step is shown to save space):

... arm-none-eabi-gcc -mcpu=cortex-m4 -mfpu=fpv4-sp-d16 -mlittle-endian -mthumb -Wall -

Wstrict-prototypes -I../../uTaskerV1.4 -D _GNU -D _STM32 -g -c -Os

../../../stack/zero_config.c -o Build/zero_config.o arm-none-eabi-gcc -mcpu=cortex-m4 -mfpu=fpv4-sp-d16 -mlittle-endian -mthumb -Wall -

Wstrict-prototypes -I../../uTaskerV1.4 -D _GNU -D _STM32 -g -Os -Wl,-

Map=uTaskerV1.4.map --no-gc-sections -nostartfiles -TuTaskerSTM32.ld -o uTaskerV1.4.elf Build/app lication.o Build/debug.o Build/webInterface.o Build/KeyScan.o

Build/NetworkIndicator.o Build/usb_application.o Build/STM32.o Build/MODBUS.o

Build/modbus_app.o Build/mass_storage.o Build/GLCD.o Build/LCD.o Build/eth_drv.o

Build/Driver.o Build/uMalloc

.o Build/uTasker.o Build/Tty_drv.o Build/iic_drv.o Build/USB_drv.o Build/uFile.o

Build/Watchdog.o Build/GlobalTimer.o Build/low_power.o Build/Ethernet.o Build/arp.o

Build/dhcp.o Build/dns.o Build/ftp.o Build/http.o Build/icmp.o Build/ip_utils.o

Buil d/ip.o Build/pop3.o Build/smtp.o Build/snmp.o Build/tcp.o Build/telnet.o

Build/tftp.o Build/udp.o Build/webutils.o Build/NetBIOS.o Build/zero_config.o arm-none-eabi-gcc -mcpu=cortex-m4 -mfpu=fpv4-sp-d16 -mlittle-endian -mthumb -Wall -

Wstrict-prototypes -I../../uTaskerV1.4 -D _GNU -D _STM32 -g -Os -Wl,-

Map=uTaskerV1.4_BM.map --no-gc-sections -nostartfiles -TuTaskerSTM32_BM.ld -o uTaskerV1.4_BM.elf

Build/application.o Build/debug.o Build/webInterface.o Build/KeyScan.o

Build/NetworkIndicator.o Build/usb_application.o Build/STM32.o Build/MODBUS.o

Build/modbus_app.o Build/mass_storage.o Build/GLCD.o Build/LCD.o Build/eth_drv.o

Build/Driver.o Buil d/uMalloc.o Build/uTasker.o Build/Tty_drv.o Build/iic_drv.o Build/USB_drv.o

Build/uFile.o Build/Watchdog.o Build/GlobalTimer.o Build/low_power.o

Build/Ethernet.o Build/arp.o Build/dhcp.o Build/dns.o Build/ftp.o Build/http.o

Build/icmp.o Build/ip_uti ls.o Build/ip.o Build/pop3.o Build/smtp.o Build/snmp.o Build/tcp.o Build/telnet.o

Build/tftp.o Build/udp.o Build/webutils.o Build/NetBIOS.o Build/zero_config.o arm-none-eabi-objcopy --only-section=.data --only-section=.init --onlysection=.text --only-section=.rodata --only-section=.vectors --output-target=ihex uTaskerV1.4.elf uTaskerV1.4.hex arm-none-eabi-objcopy --only-section=.data --only-section=.init --onlysection=.text --only-section=.rodata --only-section=.vectors --output-target=binary uTaskerV1.4.elf uTaskerV1.4.bin uTaskerV1.4_Developers_Document/0.5 36/46 22.02.2012

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arm-none-eabi-objcopy --only-section=.data --only-section=.init --onlysection=.text --only-section=.rodata --only-section=.vectors --output-target=binary uTaskerV1.4_BM.elf uTaskerV1.4_BM.bin arm-none-eabi-size uTaskerV1.4.elf

text data bss dec hex filename

23501 81 432 24014 5dce uTaskerV1.4.elf arm-none-eabi-gcc -v

Using built-in specs.

Target: arm-none-eabi

Configured with: /scratch/julian/2010q1-release-eabi-lite/src/gcc-4.4-

2010q1/configure --build=i686-pc-linux-gnu --host=i686-mingw32 --target=arm-noneeabi --enable-threads --disable-libmudflap --disable-libssp --disable-libstdcxx-pch

--enable-extra

-sgxxlite-multilibs --with-gnu-as --with-gnu-ld --with-specs='%{O2:%{!fno-removelocal-statics: -fremove-local-statics}} %{O*:%{O|O0|O1|O2|Os:;:%{!fno-remove-localstatics: -fremove-local-statics}}}' --enable-languages=c,c++ --disable-shared -disab le-lto --with-newlib --with-pkgversion='Sourcery G++ Lite 2010q1-188' --withbugurl=https://support.codesourcery.com/GNUToolchain/ --disable-nls -prefix=/opt/codesourcery --with-headers=yes --with-sysroot=/opt/codesourcery/armnone-eabi --with-buil d-sysroot=/scratch/julian/2010q1-release-eabi-lite/install/host-i686-mingw32/armnone-eabi --with-libiconv-prefix=/scratch/julian/2010q1-release-eabi-lite/obj/hostlibs-2010q1-188-arm-none-eabi-i686-mingw32/usr --with-gmp=/scratch/julian/2010q1rele ase-eabi-lite/obj/host-libs-2010q1-188-arm-none-eabi-i686-mingw32/usr --withmpfr=/scratch/julian/2010q1-release-eabi-lite/obj/host-libs-2010q1-188-arm-noneeabi-i686-mingw32/usr --with-ppl=/scratch/julian/2010q1-release-eabi-lite/obj/hostlibs-2010 q1-188-arm-none-eabi-i686-mingw32/usr --with-host-libstdcxx='-static-libgcc -Wl,-

Bstatic,-lstdc++,-Bdynamic -lm' --with-cloog=/scratch/julian/2010q1-release-eabilite/obj/host-libs-2010q1-188-arm-none-eabi-i686-mingw32/usr --disable-libgomp -enable

-poison-system-directories --with-build-time-tools=/scratch/julian/2010q1-releaseeabi-lite/obj/tools-i686-pc-linux-gnu-2010q1-188-arm-none-eabi-i686-mingw32/armnone-eabi/bin --with-build-time-tools=/scratch/julian/2010q1-release-eabilite/obj/tool s-i686-pc-linux-gnu-2010q1-188-arm-none-eabi-i686-mingw32/arm-none-eabi/bin

Thread model: single gcc version 4.4.1 (Sourcery G++ Lite 2010q1-188)

As can be seen, the size of the generated file as well as details about the compiler version used are displayed. In the compiler flags it is also visible that the target is being built for a Cortex M4 with FPU support (-mcpu=cortex-m4 -mfpu=fpv4sp-d16

). This detail is in the make file and so the user should first ensure that the correct target is being used by commenting the correct one in the file:

# C_FLAGS = -mcpu=cortex-m3 -mlittle-endian -mthumb -Wall -Wstrict-prototypes

C_FLAGS = -mcpu=cortex-m4 -mfpu=fpv4-sp-d16 -mlittle-endian -mthumb -Wall -Wstrictprototypes

The project will be built with maximum optimisation for size. In case the user wishes to use different settings these can be adapted accordingly by editing the compiler flag settings in the same make file.

OPTS = -D _GNU -D _STM32 -g -c –Os

The resulting standalone object files uTaskerV1.4.bin and uTaskerV1.4.hex, which are located in the GNU_STM32 directory can then be loaded to the STM32 Flash uTaskerV1.4_Developers_Document/0.5 37/46 22.02.2012

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either using a boot loader (depending on the chip type) of using and STLINK with the

ST-Micro “STM32 ST-LINK utility”.

The object files generated during the build process are located in

\Applications\uTaskerV1.4\GNU_STM32\Build

. This directory must be present to avoid build errors and its content can be simply deleted to cause the make file to rebuild all files again.

The following software is available from the ST-Micro web site for working with the

ST-LINK; this is either a low cost JTAG/SWD adapter from ST-Micro or is a built in interface in the discovery board.

• ST-LINK USB driver for Windows XP (this is the driver DLL used by the various IDEs to communicate with the ST-LINK).

• ST-LINK firmware upgrade (this allows ST-LINK firmware updates to be made or for checking the installed firmware version in the ST-LINK).

• STM32 ST-LINK utility (program allowing connecting to the device via ST-

LINK, viewing memory, erasing memory and programming binary files to the target).

To program the binary file generated by the simulator post-build step (or from simply executing Build_STM32.bat) the STM32 ST-LINK utility can be opened.

• With the target connected to the PC via the ST-LINK cable a connection is established to the board by clicking on the “Connect to the target” button. A portion of the present memory content will then be displayed.

• The code in the STM32 flash can be erased by clicking the “Full chip erase

” button, after which the display will show all 0xff content at the start fo

Flash memory. (There is also an option to erase just certain sectors of the chip in the “Target” menu).

• Open the uTaskerV1.4.bin file in the STM32 ST-LINK utility and then

“Program verify”. (This download dialog is usually opened automatically

when the binary file is opened in the program – note that the default

programming address 0x08000000 can be used).

• Once the download has successfully completed the new program can be started by resetting the board or by commanding a system reset in the menu

“Target | MCU Core…”.

• Once experienced with the tool it can be customised in the “Target |

Automatic mode…

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APPENDIX E – Working with the µTasker Project and Rowely

CrossWorks

Rowley CrossWorks for ARM from Rowley Associates (http://www.rowley.co.uk/) is a modern IDE based on the GCC compiler with replacement optimised libraries. It supports the STM32 and can be used with a large number of JTAG debuggers, including ST-LINK and ST-LINK/V2 as well as the well-known Segger JTAG debugger and Olimex-ARM-OCD. It is available with different licensing starting with a

Personal edition, through educational up to Commercial. Also MAC (x86), Linux (x86) and Solaris (x86) versions are available!

The CrossWorks project is called uTaskerV14.hzp and is located in the directory

\Applications\uTaskerV1.4\Rowley_STM32

. It can be opened by simply double-clicking on this file or else from the IDE by selecting “Open Solution” and browsing to the file.

The project has two targets: THUMB Flash Debug and THUMB Flash Release.

Both of these can be loaded to Flash and debugged but the release version is configured for highest size optimisation and the debug version with disabled optimisation. If possible it is recommended to work with the release version since it also includes debug information for source-level debugging, but in case of debug difficulties the debug version can be used (GCC debugging can be more complicated

with high optimisation level enabled since the code doesn’t always match well to the

source file).

To build the project, simply execute the “Build | Build Solution” command.

The code can be loaded to the target by clicking on the “Start execution” button

(or F5), and the IDE offers powerful debug support including monitoring registers while the target is operating as well as setting break points without needing to halt the operation. In addition it is possible to connect to a running target and start debugging (“Target | Attach Debugger”) without needing to restart the processor’s operation.

The linker script file for the stand-alone target is uTaskerSTM32.ld, which is configured for a processor with 1M internal Flash and 192k internal SRAM. This file can generally be used without changes since the actual project details are controlled in the initialisation code of the µTasker project which automatically configures the initial stack pointer to suit. The linker script’s memory dimensions simply inform the linker how much maximum resources are available. If the user desires a warning from the linker when too much code or variables are generated to fit into the physical limits imposed by the chip, the SRAM and Flash sizes in the linker script file can simply be reduced to match.

It is possible to load the code to RAM instead by selecting the RAM placement rather than Flash placement [Click on the project in the project explorer and use the context menu – right click – to select “Placement | RAM”].

The SRAM target is possible only when there is enough SRAM to hold the code, variables, heap and stack required for the project to run. uTaskerV1.4_Developers_Document/0.5 39/46 22.02.2012

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When working with the STM32F2xx or STM32F4xx the arm-unknown-eabi tool chain should be used instead of the arm-unknown-elf tool chain. This is configured in the target properties under “Code Generation Options | GCC target

- arm-unknown.elf is used for STM32F1xx

- arm-unknown-eabi is used for STM32F2xx/STM32F4xx

Crossworks can connect using ST-LINK or ST-LINK/V2 (ST-LINK can actually connect to both types but ST-LINK/V2 can only connect to V2 versions of the ST-

LINK). Beware that the JTAG properties of these targets can be set to either

JTAG or SWD; when using the discovery board with SWD this option must be

set accordingly.

Note that the USB driver for the ST-LINK is not included in the Crossworks setup and should be installed separately. This can be obtained from the ST-Micro web site and is called “ST-LINK USB driver for Windows XP”. The location of

STLinkUSBDriver.dll

needs to be entered in the properties of the STLINK target under ST-LINK DLL File.

Finally, the target processor should match the one used in the hardware, which can be set by clicking on the project in the project explorer and using the context menu – right click – to select “Target Processor” from the drop down list that appears. uTaskerV1.4_Developers_Document/0.5 40/46 22.02.2012

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APPENDIX F – Working with the µTasker Project and Atollic

TrueSTUDIO

Atollic TrueSTUDIO is an Eclipe based IDE using the GCC compiler. It has various plug-ins that can be added to it to extend the functionality of the environment for professional users – see http://www.atollic.com/ Atollic TrueStudio is available as a version for the ST Microprocessors or as a general version for ARM. A LITE version allows users to experiment with real projects before upgrading to the professional version with extended features and support. The professional version support a large range of debuggers but the LITE version is restricted to the ST-LINK and Segger J-

Link.

The µTasker project includes an Atollic project that can be simply imported into the

Atollic IDE and immediately used real work:

1) Start Atollic TrueSTUDIO and go to the C/C++ perspective (a new or existing

workspace can be selected if asked for).

2) If no other projects have been created or imported the Project Explorer will be empty. With the mouse in the Project Explorer area open the content menu

(right mouse click) and select “Import…”. When the dialog appears expand the “General” folder by clicking the arrow just before it and then select

“Existing projects into Workspace” and click on the “Next>” button at the bottom of the dialog.

3) In the next dialog step enter the path to the µTasker project on the PC next to

“Select root directory:”. This can be performed by using the

“Browser” button and searching for the location. When selected, the location will appear in the “Projects” window in the dialog with a tick in front of it, indicating that it is a valid project.

Note that there is a check box below the project window with the title “Copy

Projects into workspace

”. This can be left unchecked so that the project files are not physically copied into the workspace.

Finally click on the “Finish” button at the bottom of the dialog.

4) The uTaskerV1.4 project will now be visible as a folder in the Project Explorer.

It has a small ‘c’ on the folder indicating that it is an active project. Atollic

TrueSTUDIO will immediately build the new project, which can be seen if the

“Console” window is activated.

By expanding the project directory in the Project Explorer window the complete project structure can be seen and files edited after opening them with a double click on them.

Under “Project | Properties” the settings can be viewed whereby the target is fixed for the STM32F2xx/STMF4xx if the LITE version is used.

The linker script file for the stand-alone target is stm32_flash.ld (located in

\Applications\uTaskerV1.4\Atollic

), which is configured for a processor with 1M internal Flash and 192k internal SRAM. This file can generally be used without changes since the actual project details are controlled in the initialisation uTaskerV1.4_Developers_Document/0.5 41/46 22.02.2012

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code of the µTasker project which automatically configures the initial stack pointer to suit. The linker script’s memory dimensions simply inform the linker how much maximum resources are available. If the user desires a warning from the linker when too much code or variables are generated to fit into the physical limits imposed by the chip, the SRAM and Flash sizes in the linker script file can simply be reduced to match.

The generated object file can be loaded to the HW target by clicking on the “Debug uTaskerV1.4

” button (green beetle picture). To ensure that the debugger is correctly setup to match the one used before doing this click on the µTasker project folder in the Project Explorer and open the context menu (right mouse click) and select “Debug As | Debug Configurations”. In the dialog window that opens select the JTAG Probe from the drop-down list that appears. When doing this also check that the Interface is correctly set to either SWD or JTAG depending on the board used (Discovery boards use SWD). Accept the changes and click on the

“Debug” button at the bottom of the dialog to start the debug session; the code will be loaded to the board and the Debug perspective opens.

After changes have been made to the code the project can be built by executing

“Project | Build Project” or clicking on the button with the picture of a hammer. uTaskerV1.4_Developers_Document/0.5 42/46 22.02.2012

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APPENDIX G – Working with the µTasker Project and IAR

IAR Embedded Workbench for ARM is a well know IDE. It supports a large amount of

ARM chip manufacturers and device families and also a wide range of JTAG debuggers. Its ARM compiler usually generates better code densities that most other

ARM compilers.

The IAR project workspace is called uTaskerV1.4.eww

and is located in the directory \Applications\uTaskerV1.4\IAR6_STM32. IAR Embedded

Workbench can be started by double clicking on the workspace file or by opening the workspace in the IDE itself.

There are two build targets: uTaskerV1.4 - Debug STM32 and uTaskerV1.4 –

Release STM32

. Both are compiled with highest optimisation for size; the release target runs from Flash and the debug target from SRAM. The SRAM target is

possible only when there is enough SRAM to hold the code, variables, heap and

stack required for the project to run. Generally it is not necessary to work with reduced optimisation levels when debugging in IAR since the code can usually still be stepped at the source level with little difficulty.

The linker script file for the stand-alone target is STM32_Flash.icf, which is configured for a processor with 1M internal Flash and 192k internal SRAM. This file can generally be used without changes since the actual project details are controlled in the initialisation code of the µTasker project which automatically configures the initial stack pointer to suit. The linker script’s memory dimensions simply inform the linker how much maximum resources are available. If the user desires a warning from the linker when too much code or variables are generated to fit into the physical limits imposed by the chip the SRAM and Flash sizes in the linker script file can simply be reduced to match. When working from SRAM the linker script file used is

STM32_RAM.icf

; both linker script files are located in the directory

\Applications\uTaskerV1.4\IAR6_STM32\settings

.

The project is built by clicking on the “make” button and the code is loaded to the target by clicking on the “Download and Debug” button. When the project to be debugged is already loaded into Flash the “Debug without Downloading” is a practical way to debug it without needing to load the code.

When the target processor is changed the new processor type can be selected by clicking on the µTasker project displayed in the Workspace (file explorer in IAR

Embedded Workbench) and selecting the context menu with right mouse click. Then the project’s options are opened by executing “Options…”. In the “General

Options

” category, the device type can be selected from the drop down list to suit and the FPU option enabled if the device has an FPU.

When selecting the debugger make sure that the debugger’s option is correctly set between JTAG and SWD – the Discovery boards require SWD. uTaskerV1.4_Developers_Document/0.5 43/46 22.02.2012

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APPENDIX H – Working with the µTasker Project and Keil uVision

Keil is an ARM-owned company and the uVision IDE a well-known development environment supporting a wide range of ARM manufacturers and device families as well as various JTAG debuggers.

The uVision project is called uTaskerV1.4.uvproj and is located in the directory

\Applications\uTaskerV1.4\uVision_STM32

. The uVision project can be opened by double clicking on this file or else by opening the project file in the IDE itself.

The project is built by clicking on the “Build” button (or using F7) and the code is loaded to the target using the “Start/Stop Debug Session” button (or Ctrl + F5).

The Keil project doesn’t contain a linker script file since the memory settings are taken from the target dialog, which means that the exact device selected automatically selects the internal memory range used. The user should however ensure that the start of the SRAM is set to 0x20000200 rather than 0x200000000 since the µTasker project uses the start of SRAM for interrupt vectors.

When changing the settings to build for different STM32 parts there are three things that need to be adjusted appropriately (the options dialog can be opened by using

ALT + F7

):

- Select the device that is to be used in the “Device” register.

- Move then to the Target register and adjust the “Xtal (MHz)“ setting to match the board’s clock (this is however optional).

- In the “Read/Write memory areas“ set the start of SRAM (IRAM1) to

0x20000200

as described above. uTaskerV1.4_Developers_Document/0.5 44/46 22.02.2012

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APPENDIX I – STM3240G-EVAL Modification to allow full Demo

Functionality

Due to conflicts between peripherals and some missing connections it can be useful to perform some small modifications to this evaluation board as discussed in this section. The modifications allow a single project using the TFT display with backlight intensity control together with UART, Ethernet, USB and SD card, which is otherwise not possible.

The first problem is that the SC card cannot be used at the same time as the original

UART. This is because the board supports only one UART on USART4 with RS232 transceiver and DSUB connector. The RxD line of the UASRT is multiplexed with the

D3 line of the SD card and TxD with D2 of the SD card. When the SD card is used alone it is possible to remove JP22 so that the output of the RS232 transceiver doesn’t disturb the SD card data bus, but to use a serial output and the SC card together the following modification is recommended:

1) Remove JP22

2) Connect the centre pin of JP22 with pin 33 of CN2 (USART3_RXD PB-11).

This can be performed with a plug-wire between the connector pins.

3) Break the PC track to pin 13 of U17 (RS232 transceiver output) and carefully solder a short wire from pin 13 to JP32 pin connected to the diode D2. Also remove D2. Now connect the same JP32 pin to pin 32 of CN2 (USART3_TXD

PB-10). This can be performed with a plug-wire between the connector pins.

USART3 (default pins) can now be used for the serial connection without disturbing

SD card, Ethernet or TFT display operation.

The TFT module is equipped with a backlight driver which can control the backlight intensity. On the processor board this is attached to +5V, which means that the backlight intensity is maximum and cannot be controlled.

To enable the backlight control pin 23 of the TFT module connector can be removed so that it doesn’t connect to the main board (the input will float and the backlight will be undefined). Adding a connection from the CN3 pin 21 (PC-6) to the TFT board

(pin 23) allows the intensity to be controlled, as well as the backlight to be disabled to turn the LCD off when not needed.

When the signal is set to ‘0’ the backlight is off and the display is dark.

When the signal is set to ‘1’ the backlight is on and the display has maximum intensity.

Since the pin PC-3 can be multiplexed with timer 3 output (TIMER_3_FULL_REMAP) the intensity can also be controlled with intermediate levels by setting the PWM output of the timer. The µTasker project controls this signal by initialising it to GPIO output with logic level ‘0’ so that the display is initially dark. Once the display has been initialised the backlight intensity is set with a PWM value stored as parameter

(default is 95%, which is virtually full intensity). The PWM frequency is about 1.3kHz so that there is no flickering. It is also useful to replace the capacitor C1 on the TFT module with an equivalent leaded capacitor (or else solder just one of the SMD ends to the board, stand the capacitor on its end and connect the second terminal with a short piece of wire. This stops the capacitor from “buzzing” at the switching uTaskerV1.4_Developers_Document/0.5 45/46 22.02.2012

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frequency. Higher frequencies are not advisable since the backlight controller will otherwise no longer operate linearly due to its speed constraints. uTaskerV1.4_Developers_Document/0.5 46/46 22.02.2012

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