This white paper provides a comparative analysis of two real-time operating systems (RTOS) for embedded systems: FreeRTOS and the Zephyr project. FreeRTOS is characterized as a minimalistic RTOS, which is easier to learn and suitable for highly resource-constrained devices. The Zephyr project, while still appropriate for resource-constrained environments, offers a more feature-rich platform with advantages such as modularity, integrated device drivers, a comprehensive networking stack, and support for various subsystems and scheduling types.
A quick reference table is presented to map common FreeRTOS features to their Zephyr equivalents, highlighting differences such as the default support in the Zephyr project for recursive mutexes and counting semaphores. The Zephyr project also uses a different configuration system, Kconfig, which provides an interactive interface for customization as opposed to a FreeRTOS FreeRTOSConfig.h file.
The white paper concludes with an example of porting an application from FreeRTOS to the Zephyr project, highlighting key differences along the way. The example includes code snippets for initializing tasks, timers, and queues, as well as the main function, which highlights differences in thread priorities, debugging, and scheduler initiation between the two operating systems.