IsixRTOS Open Source
- Project Open Source Free Realtime operating system
- Technologies TCP/IP stack (LWIP), USB host and device stack, PPP driver
- Languages ANSI C, C++
The challenge
Developers of embedded systems often face limitations with existing real-time operating systems: restricted task management, lack of flexibility, minimal C++ support, or poor integration with networking and peripheral interfaces. For resource-constrained microcontrollers, the need for a lightweight, flexible, and fully-featured RTOS is especially critical — without sacrificing performance, portability, or developer ergonomics.
The solution
We created IsixRTOS – a free and open-source real-time operating system designed specifically for embedded microcontroller environments. Developed entirely in ANSI C, with full support for C++ (including exceptions and STL containers), IsixRTOS offers a compact yet powerful kernel and complete development environment.
Key features include:
🧠 Kernel & Core
Tiny footprint: ~8 kB Flash / 256 B + 128 B RAM per task (ARMv7-M)
Unlimited number of tasks/priorities, limited only by memory
Standard RTOS primitives: tasks, queues, semaphores, mutexes, events
Fully portable, architecture-agnostic design
Custom GCC-based toolchain for optimized builds
🌐 Connectivity & Drivers
Integrated TCP/IP stack (LWIP) + TLS/SSL (mbedTLS)
Drivers: Ethernet, PPP (GSM), USB Host/Device, SDIO/SPI, I2C, SPI, UART, I2S
SD card support for storage and logging
🧩 C++ Middleware
MicroGUI: minimalist GUI framework for embedded displays
FsEnv: flash-resident config file system
EmeterLib: 3-phase, full-quadrant energy metering library
DSPLib: essential signal processing tools (FFT, filters, etc.)
The result
IsixRTOS empowers developers with a modern, modular, and deeply configurable RTOS for real-world embedded projects — from IoT to industrial automation. It combines the determinism of a classic RTOS with the flexibility and power of C++, making it suitable for both rapid prototyping and production-grade firmware. With a rich driver ecosystem and integrated networking, **IsixRTOS simplifies embedded software design without locking developers into proprietary tools or heavyweight frameworks.