PRTOS is an open-source preemptive real time operating system kernel for embedded applications. It presently supports the AVR and MSP430 architectures.
The advantages of PRTOS are:
It has the smallest footprint of any true preemptive system: 1.9kB for basic scheduling and task control, 5.1kB with all the features below (AVR '328 / gcc -Os);
Only 950 lines of code implement all of the RTOS features (SLOC-L);
The system is well documented with a comprehensive manual,...