Atomthreads is a compact open-source RTOS that targets microcontroller platforms that need task scheduling but not higher-level services such as Internet Protocol (IP) network stacks or file systems. It has a preemptive and round robin scheduler. Also, it provides interprocess communication services such as queues and semaphores. The ANSI C source code isn’t tied to a particular compiler. The first power was for Atmel’s 8-bit AVR microcontroller family. Atomthreads is available under a BSD license.