Zig STM32 Blink

Make LEDs blink on an STM32F4 Discovery board using only Zig (and a linker script).

See my blogpost for a more thorough explanation of
what’s going on.

Build

The code was tested with Zig 0.9.0.

To build the ELF file just run:

zig build

Flashing

The easiest way to flash the board is to install stlink
tools. Most Linux distributions should have them in their
repos, the build system will try to use the st-flash program.

The command to flash the board is:

zig build flash

After flashing the board you should see the 4 LEDs blinking in an alternating pattern.

Debugging

It’s possible to use openocd and gdb-multiarch to debug the firmware
directly on the board.

In a terminal run:

openocd -f board/stm32f4discovery.cfg

Then from another terminal navigate to the directory containing the ELF output (i.e.
zig-out/bin) and run:

gdb-multiarch zig-stm32-blink.elf -ex "target remote :3333"

You can also manually flash the firmware inside gdb with:

load

Emulation using qemu

If you don’t have an STM32F4 Discovery board or you just want to test the code locally, you can use
xPack QEMU Arm.

Note: you have to comment out this
line to make the code work
in QEMU since it doesn’t support the FPU coprocessor yet.

After that, you can emulate the board with:

qemu-system-gnuarmeclipse -machine STM32F4-Discovery -mcu STM32F407VG \
  -kernel zig-out/bin/zig-stm32-blink.elf -gdb tcp::3333

You should see the blinking LEDs on the board image, and you can connect a gdb instance to it (see
the previous section).