FreeRTOS

The free real-time operating System FreeRTOS for embedded systems is based on a microkernel architecture. Thus said, FreeRTOS provides mechanisms like low-level address space management, task management, inter-process communication and the applications can access the hardware more or less independent of the kernel. FreeRTOS is a scalable real-time kernel designed specifically for small embedded systems. Besides that, it is open source with GPL and royality-free, it has features like:

• FreeRTOS scheduler - preemptive, cooperative and hybrid configuration options, with optional time slicing.
• RTOS objects (tasks, queues, semaphores, software timers, mutexes and event groups) can be created using either dynamically or statically allocated RAM.
• FreeRTOS-MPU supports the ARM Cortex-M3 Memory Protection Unit (MPU).
• Designed to be small, simple, and easy to use. Typically, a RTOS kernel binary image will be in the region of 4K to 9K bytes.
• Mutexes with priority inheritance.
• Efficient software timers.
• Powerful execution trace functionality.
• Stack overflow detection options.