ChibiOS/RT

Features

• Dual-kernel architecture offering the full-featured RT kernel and the ultra-compact NIL kernel for varying resource constraints.

• Comprehensive Hardware Abstraction Layer (HAL) providing a unified interface for MCU peripherals across multiple vendors.

• Dedicated functional safety module (SFT) implementing system and list integrity checks for high-reliability applications.

• Support for multicore and NUMA architectures using specialized memory class modifiers to handle non-coherent caches.

• Advanced sandboxing capabilities including para-virtualized ports, virtual IRQ mechanisms, and memory protection.

• Virtual File System (VFS) integration supporting LittleFS and FatFS with per-sandbox instance visibility.

• Optimized context switching for ARM Cortex-M that avoids FPU register saving for threads not utilizing the floating-point unit.

• Dynamic thread management featuring a thread registry garbage collector and customizable dispose functions.

• Managed Flash Storage (MFS) driver with flash-level mutual exclusion and wear-leveling support.

• POSIX-compatible mini shell (msh) and enhanced XShell for command-line interaction and sub-app execution.

• Support for loading and executing ELF files within isolated sandboxed environments.

• Static MPU initialization for ARMv7-M and ARMv8-M architectures to enforce memory boundaries at boot.

• Virtual timers with runtime delta recalculation for high-precision timing and reduced jitter.

• Object-oriented framework (OOP) in C for structured and modular OS module development.

• Support for CMSIS-RTOS and NASA OSAL emulation layers for legacy code compatibility.

• Extensive test suite including kernel tests, HAL integration tests, and MISRA-C compliance checks.

Architecture

ChibiOS is designed with a highly modular and layered architecture that centers around its unique dual-kernel approach. The system provides two distinct kernels: the RT (Real-Time) kernel, which is a full-featured, high-performance preemptive RTOS, and the NIL kernel, which is an ultra-compact implementation designed for extremely resource-constrained microcontrollers. Both kernels share a common API philosophy and can utilize the same high-level OS libraries (OSLIB), allowing developers to scale their applications based on hardware capabilities without rewriting core logic.

Beyond the kernels, the architecture includes a robust Hardware Abstraction Layer (HAL) that provides a standardized interface for peripherals like GPIO, UART, I2C, and SPI across different MCU families. A specialized Virtual File System (VFS) layer abstracts storage devices, while the Sandbox (SB) component enables application isolation through memory protection and para-virtualization. The system also incorporates an object-oriented framework (OOP) written in C, which facilitates the development of structured and maintainable OS modules.

Use Cases

This RTOS is ideal for:

• Industrial Automation: High-performance real-time control using the RT kernel’s low-latency context switching and deterministic scheduling.
• Functional Safety: Applications requiring high reliability, leveraging the dedicated SFT module for runtime integrity checks and MISRA-C compliance.
• Resource-Constrained IoT: Deploying the NIL kernel on small microcontrollers to minimize RAM and Flash footprint while maintaining RTOS capabilities.
• Secure Edge Computing: Utilizing sandboxing and MPU-based isolation to run untrusted or third-party applications securely.
• Automotive Systems: Leveraging multicore and NUMA support for complex Electronic Control Unit (ECU) development on modern ARM architectures.
• Embedded Storage Solutions: Implementing robust data logging using the Managed Flash Storage (MFS) and VFS with LittleFS or FatFS.

Getting Started

ChibiOS is organized into a clear directory structure where the os/ folder contains the core components and demos/ provides platform-specific examples for various evaluation boards. To begin development, it is recommended to select a demo project that matches your hardware target; these demos typically include pre-configured Makefiles and project files for ChibiStudio or other GCC-based toolchains.

Key configuration is handled through header files: chconf.h for kernel settings, halconf.h for peripheral driver selection, and mcuconf.h for clock and DMA configurations. The root directory contains a documentation.html file which serves as the primary entry point for the Doxygen-generated API reference. Developers can also find extensive test suites in the test/ directory to verify kernel and HAL integrity on their specific hardware ports.