If operating systems weren’t so useful, we would not be running them on every single of our desktop systems. In the same vein, embedded operating systems provide similar functionality as these desktop OSes, while targeting a more specialized market. Some of these are adapted versions of desktop OSes (e.g. Yocto Linux), whereas others are built up from the ground up for embedded applications, like VxWorks and QNX. Few of those OSes can run on a microcontroller (MCU), however. When you need to run an OS on something like an 8-bit AVR or 32-bit Cortex-M MCU, you need something smaller.
Something like ChibiOS (‘Chibi’ meaning ‘small’ in Japanese), or FreeRTOS (here no points for originality). Perhaps more accurately, FreeRTOS could be summarized as a multi-threading framework targeting low-powered systems, whereas ChibiOS is more of a full-featured OS, including a hardware abstraction layer (HAL) and other niceties.
In this article we’ll take a more in-depth look at these two OSes, to see what benefits they bring.
Basic feature set
FreeRTOS supports a few dozen microcontroller platforms, the most noticeable probably being AVR, x86 and ARM (Cortex-M & Cortex-A). In contrast, ChibiOS/RT runs on perhaps fewer platforms, but comes with a HAL that abstracts away hardware devices including I2C, CAN, ADC, RTC, SPI and USB peripherals. Both of them offer a preemptive multi-tasking scheduler with priority levels and multi-threading primitives, including mutexes, condition variables and semaphores.
The corollary of this comparison then seems to be that FreeRTOS is good for basic multi-threading features, whereas Chib ..
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