There are hundreds of Real Time Operation System in the market, some are very expensive and some others are for free but with small features. We have done an extensive study an evaluation of the best options, with a special consideration to these under the license of GNU GPL and royalties free licenses.

For RTOS with the smallest footprint, intended for the deeply embedded applications, our favorite is ChibiOS/RT. ChibiOS/RT is designed for deeply embedded real time applications where execution efficiency and compact code are important requirements. This RTOS is characterized by its high portability, compact size and, mainly, by its architecture optimized for extremely efficient context switching.

We have a wide experience in the integration and utilization of Micrium µC/OS-II, an excellent property Real Time Operation System.

Some say that µC/OS-II is simple enough for use by a hobbyist, the fact is that Micrium's strict standards were instrumental in creating a Validation Suite for µC/OS-II. As a result, it is successfully implemented in some of the highest level safety-critical devices, including those certified for avionics DO-178B Level A, and EUROCAE ED-12B, medical FDA pre-market notification (510(k)), and pre-market approval (PMA), and SIL 3/SiL4 IEC for transportation and nuclear systems.