RIOS: a lightweight task scheduler for embedded systems

Abstract

RIOS (Riverside-Irvine Operating System) is a lightweight portable task scheduler written entirely in C. The scheduler consists of just a few dozens lines of code, intended to be understandable by students learning embedded systems programming. Non-preemptive and preemptive scheduler versions exist. Compared to the existing open-source solutions FreeRTOS and AtomThreads, RIOS on average has 95% fewer lines of total C code for a sample multitasking application, a 71% smaller executable, and 70% less scheduler time overhead. RIOS source code and examples are available for free at http://www.riosscheduler.org. RIOS is useful for education and as a stepping stone to understanding real-time operating system behavior. Additionally, RIOS is a sufficient real-time scheduling solution for various commercial applications.