Adding an RTOS to an existing bare-metal STM32 project doesn't require rebuilding from scratch. Using PX5 RTOS with its POSIX pthreads interface, the integration involves just five steps: adding two source files and an include path, calling px5_pthread_start() in main(), connecting PendSV and SysTick handlers, verifying behavior, and optionally enabling dynamic memory or PDV features. The existing application, build system, and project structure remain intact. The scheduler runs underneath the existing code, and threads can be introduced incrementally. A comparison with Zephyr highlights that PX5 is a minimal scheduler addition while Zephyr is a full embedded platform — neither is universally better, but PX5 suits teams wanting to add multithreading without adopting an entire ecosystem.
