Bare minimum STM32 Blink without IDE

1. Install GCC ARM toolchain.
2. Write bare-metal or HAL-based C code.
3. Create a linker script.
4. Compile using arm-none-eabi-gcc.
5. Convert to binary with arm-none-eabi-objcopy.
6. Flash using st-flash or OpenOCD.
7. Debug with GDB (optional).

1. Set Up the Toolchain

To compile code for STM32, you need an ARM GCC toolchain:

• Download ARM GCC (GNU Arm Embedded Toolchain):
  https://developer.arm.com/downloads/-/gnu-rm
  Extract and add the bin folder to your system PATH.

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2. Write Your Code (Bare-metal or HAL)

Create a main.c file with your STM32 application logic. Example:

#include "stm32f4xx.h"

void delay(volatile uint32_t s) {
    for (; s > 0; s--);
}

int main(void) {
    RCC->AHB1ENR |= (1 << 3);  // Enable GPIOD clock
    GPIOD->MODER |= (1 << 26); // Set PD13 as output

    while (1) {
        GPIOD->ODR ^= (1 << 13); // Toggle LED
        delay(1000000);
    }
}

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3. Create a Linker Script (STM32F4.ld)

Define memory sections for your STM32 chip:

ld

MEMORY
{
    FLASH (rx) : ORIGIN = 0x08000000, LENGTH = 512K
    SRAM (rwx) : ORIGIN = 0x20000000, LENGTH = 128K
}

SECTIONS
{
    .text : {
        *(.isr_vector)
        *(.text)
        *(.rodata)
        . = ALIGN(4);
    } > FLASH

    .data : {
        *(.data)
        . = ALIGN(4);
    } > SRAM AT > FLASH

    .bss : {
        *(.bss)
        . = ALIGN(4);
    } > SRAM
}

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4. Compile Using GCC

Run the following command to compile your main.c file:

sh

arm-none-eabi-gcc -mcpu=cortex-m4 -mthumb -O2 -T STM32F4.ld -o main.elf main.c -nostartfiles

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5. Convert ELF to Binary

To flash the STM32, convert the ELF file to a binary format:

sh

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

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6. Flash the Code

You can use st-flash (from stlink) to upload the binary to your STM32 via ST-Link:

sh

st-flash write main.bin 0x08000000

Alternatively, use OpenOCD:

sh

openocd -f interface/stlink.cfg -f target/stm32f4x.cfg -c "program main.elf verify reset exit"

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7. Debugging (Optional)

If you want to debug without an IDE, use GDB with OpenOCD:

sh

openocd -f interface/stlink.cfg -f target/stm32f4x.cfg

Then, in another terminal:

sh

arm-none-eabi-gdb main.elf (gdb) target remote localhost:3333 (gdb) monitor reset halt (gdb) load (gdb) continue

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