ChibiOS/NIL  3.2.2
Giovanni Di Sirio (

Why Nil?

Of course because it is so small that it is almost nil. I wrote Nil because I wanted to experiment with an idea I had regarding a minimal RTOS. Basically I wanted to verify how small could be an RTOS while retaining useful features.


  • Free software, GPL3 licensed. Stable releases include a exception clause to the GPL.
  • Designed for realtime applications.
  • Easily portable.
  • Preemptive scheduling.
  • Each thread has its own priority level.
  • Offers tasks, time, semaphores, event flags, timeouts.
  • Fully static.
  • Minimal system requirements: about 700 bytes ROM with all options enabled.
  • Almost totally written in C with little ASM code required for ports.
  • Compatible with ChibiOS/HAL.
  • API compatible with ChibiOS/RT of which, ChibiOS/NIL, is functionally a subset.