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How to port Zephy to STM32?

#zephy #stm32 #stm32f4 #stm32h7

Porting Zephyr RTOS to an STM32 microcontroller involves setting up the development environment, configuring the board support package (BSP), and building/flashing a sample application. Below is a step-by-step guide:

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1. Prerequisites
Hardware:

STM32 development board (e.g., STM32F4 Discovery, Nucleo-144).

Software:

  • Zephyr SDK (Toolchain for ARM Cortex-M).
  • Python 3.8+ (for west tool).
  • Git (to fetch Zephyr source).
  • STM32CubeProgrammer (for flashing).

2. Install Zephyr Development Environment
A. Install Dependencies (Linux/macOS/WSL)

bash # Install Python and pip sudo apt update && sudo apt install -y git cmake ninja-build gperf \ python3 python3-pip # Install west (Zephyr meta-tool) pip3 install west # Install Zephyr SDK (ARM toolchain) wget https://github.com/zephyrproject-rtos/sdk-ng/releases/download/v0.16.0/zephyr-sdk-0.16.0_linux-x86_64.tar.gz tar xvf zephyr-sdk-0.16.0_linux-x86_64.tar.gz cd zephyr-sdk-0.16.0 ./setup.sh
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B. Fetch Zephyr Source

bash west init ~/zephyrproject cd ~/zephyrproject west update
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C. Set Environment Variables

bash export ZEPHYR_BASE=~/zephyrproject/zephyr source $ZEPHYR_BASE/zephyr-env.sh
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3. Check STM32 Board Support
Zephyr supports many STM32 boards out-of-the-box. Check compatibility:

bash ls $ZEPHYR_BASE/boards/arm | grep stm32
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Example supported boards:

  • nucleo_f401re (STM32F4)
  • nucleo_h743zi (STM32H7)
  • stm32f4_disco (STM32F4 Discovery)

4. Build and Flash a Sample Application
A. Build "Hello World" for STM32

bash west build -p auto -b nucleo_f401re $ZEPHYR_BASE/samples/hello_world
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  • -p auto: Auto-detects available cores.
  • -b nucleo_f401re: Specifies the board.

B. Flash the Binary
Option 1: Using OpenOCD (via ST-Link)

bash west flash
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Requires ST-Link debugger (built into Nucleo boards).

Option 2: Manual Flashing (STM32CubeProgrammer)

  1. Locate the .hex or .bin file: 
bash ls build/zephyr/zephyr.hex
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  1. Flash using STM32CubeProgrammer GUI or CLI: 
bash STM32_Programmer_CLI -c port=SWD -w build/zephyr/zephyr.hex 0x08000000
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5. Customizing for a New STM32 Board
If your board isn’t officially supported, follow these steps:

A. Create a Custom Board Directory

bash cd $ZEPHYR_BASE/boards/arm mkdir my_stm32_board cd my_stm32_board
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B. Required Files

  1. board.cmake (Specifies CPU/flash settings): 
cmake set(CPU_TYPE cortex-m4) # e.g., M4 for STM32F4 set(FLASH_SIZE 512K) set(RAM_SIZE 128K)
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  1. Kconfig.board (Board-specific options): 
config BOARD_MY_STM32_BOARD bool "My Custom STM32 Board" depends on SOC_STM32F401XE
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  1. .dts (Device Tree for peripherals): 
dts / { model = "My STM32 Board"; compatible = "st,stm32f401"; chosen { zephyr,console = &usart2; }; };
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  1. _defconfig (Default Zephyr config): 
CONFIG_SERIAL=y CONFIG_UART_INTERRUPT_DRIVEN=y
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C. Build and Test

bash west build -b my_stm32_board samples/hello_world west flash
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6. Debugging
A. Serial Output (UART)
Connect to the STM32’s UART (e.g., /dev/ttyACM0):

bash picocom -b 115200 /dev/ttyACM0
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Should show:

*** Booting Zephyr OS build v3.4.0 *** Hello World! my_stm32_board
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B. GDB Debugging

bash west build -b nucleo_f401re -- -DCMAKE_EXPORT_COMPILE_COMMANDS=ON arm-none-eabi-gdb build/zephyr/zephyr.elf (gdb) target remote :3333 # Connect to OpenOCD (gdb) monitor reset halt (gdb) continue
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7. Adding Peripheral Drivers
To enable I2C, SPI, or GPIO:

  1. Edit prj.conf: 
CONFIG_I2C=y CONFIG_SPI=y CONFIG_GPIO=y
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  1. Use Zephyr’s Device Tree (DTS) to map pins: 
dts &i2c1 { status = "okay"; sda-pin = <&gpiob 7>; scl-pin = <&gpiob 6>; };
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8. Troubleshooting

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  1. Next Steps ✔ Explore Zephyr’s sensor drivers (e.g., BME280 over I2C). ✔ Implement multi-threading with Zephyr’s kernel API. ✔ Integrate RTOS features (message queues, timers).

For advanced use, refer to:

  • Zephyr STM32 Documentation
  • Zephyr Device Tree Guide

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