Apache NuttX vs PX5 RTOS

Apache NuttX is a real-time operating system for embedded systems, designed for a small footprint and standards-oriented development. It scales across 8-bit to 64-bit microcontroller environments and supports more than 15 CPU architectures, including ARM, RISC-V, x86, and Xtensa. The project lists support for more than 300 hardware boards and over 1,500 configuration templates for prototyping and production. NuttX uses POSIX and ANSI as its main standards, with POSIX serving as a development guideline rather than a licensed trademark claim. Optional filesystem support includes VFAT, ROMFS, littlefs, and NFS version 3 over UDP, and networking includes a BSD-compatible socket interface. It is free and open-source software, with separate release artifacts for the OS and integrated Apps. The configurable build system targets physical boards and devices as well as documented simulator targets. Its pseudo root filesystem can work without physical storage; mounting a true filesystem requires the relevant drivers and filesystem support. The project lists a main mailing list and Discord as community channels and is maintained by volunteers.

PX5 RTOS is a hard real-time operating system for resource-constrained embedded applications, with a native POSIX pthreads API. It is presented for safety-critical work in automotive, industrial, medical, rail, and other demanding settings. The maker says a minimal setup on typical 32-bit microcontrollers can use as little as 1KB of flash and 1KB of RAM. At 80MHz, most API calls and context switches are stated to take less than one microsecond; processing is described as predictable and independent of the number of active threads. Stated certifications include IEC 61508 SIL 4, IEC 62304 Class C, ISO 26262 ASIL D, and EN 50128 SW-SIL 4. Run-time checks cover function pointers, system objects, buffers, and stacks. Supported architectures include Arm Cortex-M, Cortex-R and Cortex-A, RISC-V, Renesas RX, AMD MicroBlaze, and Infineon TriCore. Listed tools include IAR, Eclipse/GCC, Arm DS, and Arm Keil. Pricing is on request; listed packages start at 5000.00 USD as a one-time fee or $5,000 a year for a subscription. Free evaluation kits are available with a free PX5 Community login.