I’ve been building a small, modular Real-Time Operating System (RTOS) for ARM Cortex‑M, focusing on clarity, portability, and hackability.

It started as an experiment to see how small an RTOS kernel could be — the first version was about 400 lines, implementing memory management and a simple multithreaded scheduler. I later expanded it into a complete, readable system and wrote an English tutorial series along the way.

The project includes tutorials covering:

• memory management • ARM exception model • context switching • scheduler design • IPC and synchronization

Everything is implemented from scratch with readability in mind, and each subsystem is explained step by step.