Open Source Real-Time Operating Systems

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.

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.

F9 microkernel is a microkernel-based (L4-style) kernel to support running real-time and time-sharing applications (for example, wireless communications) for ARM Cortex-M series microprocessors with efficiency (performance + power consumption) and security (memory protection + isolated execution) in mind.

Linmo is a lightweight, preemptive multi-tasking RTOS kernel designed as an educational showcase for resource-constrained systems. It features a shared address space model and a priority-based round-robin scheduler, specifically targeting the RISC-V architecture and QEMU emulation.

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.

seL4 is a high-assurance, high-performance microkernel that is the first of its kind to be formally verified for functional correctness and security properties. It serves as a minimal core for building secure and reliable operating systems by enforcing strict isolation through a capability-based access control system.

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.