NuttX

Apache NuttX is a free and open-source real-time operating system (RTOS) with an emphasis on technical standards compliance and on having a small footprint. It is scalable from 8-bit to 64-bit microcontroller environments. The main governing standards in NuttX are from the Portable Operating System Interface (POSIX) and the American National Standards Institute (ANSI). Further standard application programming interfaces (APIs) from Unix and other common RTOSes are adopted for functions unavailable under these standards, or inappropriate for deeply embedded environments, such as the fork system