I've been writing one with my little brother: https://github.com/splicer/arduin_os https://github.com/splicer/arduin_os It still has a ways to go, but it's abl

I've been writing one with my little brother: https://github.com/splicer/arduin_os https://github.com/splicer/arduin_os It still has a ways to go, but it's able to context-switch between threads. Feel free to fork it if you want to contribute.