Open Source Real-Time Operating Systems

Neptune OS is a microkernel-based operating system that implements a Windows NT personality on top of the seL4 microkernel. It executes the NT Executive as a userspace root task, providing a faithful implementation of the NT Native API and a driver model where device drivers run in isolated processes while communicating via seL4 IPC.

TizenRT is a lightweight, RTOS-based platform designed for low-end IoT devices with limited resources, typically equipped with ARM Cortex-M/R processors and less than 2MB of RAM. It extends the NuttX kernel with a comprehensive ecosystem including Linux-style development environments, advanced networking stacks, and support for high-level languages like JavaScript to bridge the gap between RTOS efficiency and Linux-like developer experience.

ChibiOS is a modular, high-performance development environment for embedded systems, featuring a dual-kernel architecture with the full-featured RT kernel and the ultra-compact NIL kernel. It provides a comprehensive Hardware Abstraction Layer (HAL), a Virtual File System (VFS), and advanced sandboxing capabilities, making it highly suitable for functional safety and multicore ARM Cortex-M applications.

Embox is a highly modular and configurable real-time operating system designed to execute Linux-compatible software on resource-constrained embedded systems and microcontrollers. It provides a POSIX-compliant environment, allowing developers to port complex desktop-grade libraries and applications like Qt, OpenCV, and PJSIP to platforms with limited RAM and ROM.

RT-Thread is a modular, object-oriented real-time operating system (RTOS) designed for both resource-constrained microcontrollers and high-performance IoT devices. It provides a scalable architecture ranging from a 3KB footprint kernel to a comprehensive IoT OS featuring a vast ecosystem of over 450 software packages and standardized interfaces like POSIX and CMSIS.

Tock is a secure, concurrent embedded operating system designed for ARM Cortex-M and RISC-V microcontrollers, prioritizing isolation between the kernel, device drivers, and applications. It leverages Rust's memory safety for its kernel and hardware Memory Protection Units (MPUs) to run multiple mutually distrustful applications on resource-constrained hardware with as little as 64kB of RAM.

Mongoose OS is a modular IoT firmware development framework designed for microcontrollers, enabling rapid development in both C/C++ and JavaScript. It provides a comprehensive environment for connected devices with built-in support for secure OTA updates, remote management via a robust RPC mechanism, and native integration with major cloud providers like AWS IoT and Google IoT Core.

RIOT is a modular, open-source real-time operating system specifically engineered for the Internet of Things (IoT), supporting a wide range of 8-bit, 16-bit, and 32-bit microcontrollers. It features a micro-kernel architecture with a preemptive, tickless scheduler and provides a uniform API with partial POSIX compliance to simplify cross-platform development and code reuse.