[HeyLaughingBoy]

be a thing to do in an evening or a week, not three months. As someone who wrote an AVR RTOS kernel for a class in Realtime systems I agree, but you're comparing apples to oranges. I can write, and have written, a real-time control system (RTCS) for a set of peripherals in an evening or a few days, but that's not the same thing as an RTOS. The RTCS is a specific case, the RTOS is the general one and as a result it's much more complex because it has a more open-ended specification. My RTOS took me about 4 weeks or so before it was usable.