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Pull CMSIS headers from github
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‎README.md

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@@ -1315,26 +1315,23 @@ CMSIS is an ARM standard, and since CMSIS headers are supplied by the MCU
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vendor, they are the source of authority. Therefore, using vendor
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headers is a preferred way, rather than writing definitions manually.
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In this section, we will replace our API functions in the `mcu.h` by the
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CMSIS vendor header, and leave the rest of the firmware intact.
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STM32 CMSIS headers for F4 family can be found at
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https://github.com/STMicroelectronics/cmsis_device_f4 repo. From there,
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copy the following files into our firmware directory,
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[step-5-cmsis](step-5-cmsis):
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- [stm32f429xx.h](https://raw.githubusercontent.com/STMicroelectronics/cmsis_device_f4/master/Include/stm32f429xx.h)
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- [system_stm32f4xx.h](https://raw.githubusercontent.com/STMicroelectronics/cmsis_device_f4/master/Include/system_stm32f4xx.h)
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Those two files depend on a standard ARM CMSIS includes, download them too:
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- [core_cm4.h](https://raw.githubusercontent.com/STMicroelectronics/STM32CubeF4/master/Drivers/CMSIS/Core/Include/core_cm4.h)
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- [cmsis_gcc.h](https://raw.githubusercontent.com/STMicroelectronics/STM32CubeF4/master/Drivers/CMSIS/Core/Include/cmsis_gcc.h)
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- [cmsis_version.h](https://raw.githubusercontent.com/STMicroelectronics/STM32CubeF4/master/Drivers/CMSIS/Core/Include/cmsis_version.h)
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- [cmsis_compiler.h](https://raw.githubusercontent.com/STMicroelectronics/STM32CubeF4/master/Drivers/CMSIS/Core/Include/cmsis_compiler.h)
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- [mpu_armv7.h](https://raw.githubusercontent.com/STMicroelectronics/STM32CubeF4/master/Drivers/CMSIS/Core/Include/mpu_armv7.h)
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From the `mcu.h`, remove all peripheral API and definitions, and leave only
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standard C inludes, vendor CMSIS include, defines to PIN, BIT, FREQ, and
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`timer_expired()` helper function:
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There are two sets of CMSIS headers:
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- First, there are ARM Core CMSIS headers. They describe ARM core,
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and published by ARM on github: https://github.com/ARM-software/CMSIS_5
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- Second, there are MCU vendor CMSIS headers. They describe MCU peripherals,
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and published by the MCU vendor. In our case, ST publishes them at
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https://github.com/STMicroelectronics/cmsis_device_f4
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We can pull those headers by a simple Makefile snippet:
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The ST CMSIS package also provides startup files for all their MCUs. We
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can use those instead of hand-writing the startup.c. The ST-provided startup
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file calls `SystemInit()` function, so we define it in the `main.c`.
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Now, let's replace our API functions in the `mcu.h` using CMSIS definitions,
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and leave the rest of the firmware intact. From the `mcu.h`, remove all
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peripheral API and definitions, and leave only standard C inludes, vendor CMSIS
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include, defines to PIN, BIT, FREQ, and `timer_expired()` helper function:
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```c
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#pragma once
@@ -1366,38 +1363,12 @@ If we try to rebuild the firmware - `make clean build`, then GCC will fail
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complaining about missing `systick_init()`, `GPIO_MODE_OUTPUT`, `uart_init()`,
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and `UART3`. Let's add those using STM32 CMSIS files.
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Let's start from `systick_init()`. The `core_cm4.h` header defines
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`SysTick_Type` structure which is identical to our `struct systick`, and has
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an appropriate #define for `SysTick` peripheral. Also, `stm32f429xx.h` has
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a `RCC_TypeDef` structure and appropriate #define for the `RCC`. Therefore
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our `systick_init()` function remains almost unchanged: we only have to replace
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`SYSTICK` with `SysTick`:
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```c
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static inline void systick_init(uint32_t ticks) {
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if ((ticks - 1) > 0xffffff) return; // Systick timer is 24 bit
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SysTick->LOAD = ticks - 1;
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SysTick->VAL = 0;
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SysTick->CTRL = BIT(0) | BIT(1) | BIT(2); // Enable systick
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RCC->APB2ENR |= BIT(14); // Enable SYSCFG
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}
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```
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Let's start from `systick_init()`. ARM core CMSIS headers provide a
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`SysTick_Config()` function that does the same - so we'll use it.
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Next goes `gpio_set_mode()` function. The `stm32f429xx.h` header has
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`GPIO_TypeDef` structure, identical to our `struct gpio`. Let's use it:
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```c
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#define GPIO(bank) ((GPIO_TypeDef *) (GPIOA_BASE + 0x400 * (bank)))
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enum { GPIO_MODE_INPUT, GPIO_MODE_OUTPUT, GPIO_MODE_AF, GPIO_MODE_ANALOG };
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static inline void gpio_set_mode(uint16_t pin, uint8_t mode) {
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GPIO_TypeDef *gpio = GPIO(PINBANK(pin)); // GPIO bank
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int n = PINNO(pin); // Pin number
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RCC->AHB1ENR |= BIT(PINBANK(pin)); // Enable GPIO clock
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gpio->MODER &= ~(3U << (n * 2)); // Clear existing setting
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gpio->MODER |= (mode & 3) << (n * 2); // Set new mode
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}
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```
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https://github.com/cpq/bare-metal-programming-guide/blob/2a61ea23e44c4531b66f6508238cfc43ca7c2634/step-5-cmsis/mcu.h#L32-L41
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The `gpio_set_af()` and `gpio_write()` functions is also trivial -
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simply replace `struct gpio` with `GPIO_TypeDef`, and that's all.
@@ -1419,15 +1390,11 @@ shows the output. Congratulations, we have adopted our firmware code to
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use vendor CMSIS header files. Now let's reorganise the repository a bit
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by moving all standard files into `include` directory and updating Makefile
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to let GCC know about it:
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https://github.com/cpq/bare-metal-programming-guide/blob/2a61ea23e44c4531b66f6508238cfc43ca7c2634/step-5-cmsis/Makefile#L3
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```make
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...
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-g3 -Os -ffunction-sections -fdata-sections -I. -Iinclude \
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```
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We have left with
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a project template that can be reused for the future projects.
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A complete project source code you can find in [step-5-cmsis](step-5-cmsis)
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We have left with a project template that can be reused for the future
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projects. A complete project source code you can find in
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[step-5-cmsis](step-5-cmsis)
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## Setting up clocks

‎step-5-cmsis/Makefile

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@@ -1,26 +1,34 @@
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CFLAGS ?= -W -Wall -Wextra -Werror -Wundef -Wshadow -Wdouble-promotion \
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-Wformat-truncation -fno-common -Wconversion \
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-g3 -Os -ffunction-sections -fdata-sections -I. -Iinclude \
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-g3 -Os -ffunction-sections -fdata-sections \
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-I. -Iinclude -Icmsis_core/CMSIS/Core/Include -Icmsis_f4/Include \
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-mcpu=cortex-m4 -mthumb -mfloat-abi=hard -mfpu=fpv4-sp-d16 $(EXTRA_CFLAGS)
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LDFLAGS ?= -Tlink.ld -nostartfiles -nostdlib --specs nano.specs -lc -lgcc -Wl,--gc-sections -Wl,-Map=$@.map
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SOURCES = main.c startup.c syscalls.c
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SOURCES = main.c syscalls.c
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SOURCES += cmsis_f4/Source/Templates/gcc/startup_stm32f429xx.s # ST startup file. Compiler-dependent!
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ifeq ($(OS),Windows_NT)
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RM = cmd /C del /Q /F
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else
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RM = rm -f
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RM = rm -rf
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endif
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build: firmware.bin
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firmware.elf: $(SOURCES)
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arm-none-eabi-gcc $(SOURCES) $(CFLAGS) $(LDFLAGS) -o $@
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firmware.elf: cmsis_core cmsis_f4 mcu.h link.ld Makefile $(SOURCES)
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arm-none-eabi-gcc $(SOURCES) $(CFLAGS) $(CFLAGS_EXTRA) $(LDFLAGS) -o $@
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firmware.bin: firmware.elf
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arm-none-eabi-objcopy -O binary $< $@
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flash: firmware.bin
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st-flash --reset write $< 0x8000000
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cmsis_core:
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git clone --depth 1 -b 5.9.0 https://github.com/ARM-software/CMSIS_5 $@
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cmsis_f4:
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git clone --depth 1 -b v2.6.8 https://github.com/STMicroelectronics/cmsis_device_f4 $@
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clean:
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$(RM) firmware.*
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$(RM) firmware.* cmsis_*

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