Blink the built-in status light.
To generate the target description avr-atmega328p.json:
rustc +nightly --print target-spec-json -Z unstable-options --target avr-unknown-gnu-atmega328 > avr-atmega328p.json
then remove is-builtin and change cpu and -mmcu to atmega328p (add the
p).
Then, to build:
AVR_CPU_FREQUENCY_HZ=16000000 cargo +nightly build -Z build-std=core --target avr-atmega328p.json --release
CPU is 16MHz, hence the value for AVR_CPU_FREQUENCY_HZ.
On WSL2, it appears that COMX is available at /dev/ttySX, e.g.
COM3
/dev/ttyS3
To flash after building the .elf:
avrdude -patmega328p -carduino -P/dev/ttyS3 -b115200 -D -Uflash:w:target/avr-atmega328p/release/blink.elf:e
Since USB support on WSL2 is currently lacking,
the easiest solution to flash on Windows is to install avrdude for Windows,
build the .elf on WSL, then flash from Windows (you can reference the Windows
.exe directly).
/mnt/../avrdude.exe -patmega328p -carduino -PCOM3 -b115200 -D -Uflash:w:target/avr-atmega328p/release/blink.elf:e