Setting Up Embededd Development Environment

To develop STM32 applications on Linux, configure the ARM GNU toolchain for cross-compilation. Download the latest ARM GNU Toolchain from Arm Developer and extract it to /opt/gcc-arm-none-eabi. Add the binary path to your shell configuration:

export PATH=$PATH:/opt/gcc-arm-none-eabi/bin

Install required dependencies:

sudo apt install -y libncursesw5 python3.8

Verify installation with:

arm-none-eabi-gcc --version

Hardware Connnectivity Seetup

Use USBIPD to access Windows-connected USB devices from WSL. Follow Microsoft's USBIPD documentation to share STM32 debugger interfaces with the Linux environment.

Embedded Debugging Tools

Install OpenOCD for programming and debugging:

sudo apt install openocd

This provides JTAG/SWD communication with STM32 chips through interfaces like ST-Link.

Assembly Implementation

Modify the Reset_Handler in the startup file (startup_stm32f10x_md.s) to initialize GPIO and control LED blinking:

Reset_Handler:
    bl init_led
    b lights_loop

init_led:
    ldr r0, =0x40021018   @ RCC_APB2ENR
    ldr r1, [r0]
    orr r1, r1, #0x10     @ Enable GPIOC clock
    str r1, [r0]

    ldr r0, =0x40011004   @ GPIOC_CRH
    ldr r1, [r0]
    orr r1, r1, #0x100000 @ Configure PC13 as output
    str r1, [r0]
    bx lr

lights_loop:
    bl led_on
    bl delay
    bl led_off
    bl delay
    b lights_loop

led_on:
    ldr r0, =0x4001100C   @ GPIOC_ODR
    ldr r1, [r0]
    bic r1, r1, #(1<<13)  @ Set PC13 low
    str r1, [r0]
    bx lr

delay:
    mov r2, #0x100000
delay_loop:
    subs r2, r2, #1
    bne delay_loop
    bx lr

Linker Script Configuration

Create a linker script (STM32F103RETx_FLASH.ld) to manage memory allocation:

MEMORY {
    FLASH (rx) : ORIGIN = 0x08000000, LENGTH = 512K
    RAM (xrw)  : ORIGIN = 0x20000000, LENGTH = 64K
}

ENTRY(Reset_Handler)

SECTIONS {
    .text : {
        *startup_stm32f10x_md.o (.text)
    } > FLASH
}

Compilation and Flashing

Compile the assembly to object file:

arm-none-eabi-gcc -c -mthumb -mcpu=cortex-m3 -o startup.o startup_stm32f10x_md.s

Link objects into ELF executable:

arm-none-eabi-gcc -o firmware.elf startup.o -T STM32F103RETx_FLASH.ld

Generate binary file:

arm-none-eabi-objcopy -O binary firmware.elf firmware.bin

Flash using OpenOCD:

openocd -f interface/stlink.cfg -f target/stm32f1x.cfg -c "program firmware.bin verify reset exit"