FreeRTOS
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| Developer | Real Time Engineers Ltd. |
|---|---|
| OS family | Real-time operating systems |
| Working state | Current |
| Source model | Source available |
| Latest release | 9.0.0 / August 16th, 2016 |
| Marketing target | Embedded devices |
| Platforms | ARM (ARM7, ARM9, Cortex-M3, Cortex-M4, Cortex-A), Atmel AVR, AVR32, HCS12, MicroBlaze, Cortus (APS1, APS3, APS3R, APS5, FPF3, FPS6, FPS8), MSP430, PIC, Renesas H8/S, SuperH, RX, x86, 8052, Coldfire, V850, 78K0R, Fujitsu MB91460 series, Fujitsu MB96340 series, Nios II, Cortex-R4, TMS570, RM4x |
| Kernel type | Microkernel |
| License | Modified GPL |
| Official website | www |
FreeRTOS is a popularreal-time operating system kernel for embedded devices, that has been ported to 35 microcontrollers. It is distributed under the GPL with an additional restriction and optional exception. The restriction forbids benchmarking while the exception permits users' proprietary code to remain closed source while maintaining the kernel itself as open source, thereby facilitating the use of FreeRTOS in proprietary applications.
FreeRTOS has been used in space.
FreeRTOS is designed to be small and simple. The kernel itself consists of only three C files. To make the code readable, easy to port, and maintainable, it is written mostly in C, but there are a few assembly functions included where needed (mostly in architecture-specific scheduler routines).
FreeRTOS provides methods for multiple threads or tasks, mutexes, semaphores and software timers. A tick-less mode is provided for low power applications. Thread priorities are supported. FreeRTOS applications can be completely statically allocated. Alternatively RTOS objects can be dynamically allocated with five schemes of memory allocation provided:
There are none of the more advanced features typically found in operating systems like Linux or Microsoft Windows, such as device drivers, advanced memory management, user accounts, and networking. The emphasis is on compactness and speed of execution. FreeRTOS can be thought of as a 'thread library' rather than an 'operating system', although command line interface and POSIX-like I/O abstraction add-ons are available.
FreeRTOS implements multiple threads by having the host program call a thread tick method at regular short intervals. The thread tick method switches tasks depending on priority and a round-robin scheduling scheme. The usual interval is 1/1000 of a second to 1/100 of a second, via an interrupt from a hardware timer, but this interval is often changed to suit a particular application.
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