I built a real-time operating system from scratch

I built a small real‑time operating system for ARM Cortex‑M as a step‑by‑step guide to teach how an RTOS is built from scratch. The kernel starts from a few hundred lines and grows through context switching, scheduling, interrupts, and simple IPC — all explained in a minimal, readable way.

If you want a practical, tiny example that shows exactly how to write an operating system for microcontrollers, this project is designed for that.