Scheduler without OS

Question

Do you know if there is any open source task scheduler without the OS support?

Basically, we are looking for a lean scheduler that can schedule and preempt the tasks on our AM335X TI chipset based boards, which don't have any RTOS running on them.

Answer 1

There are no "portable" schedulers at that level, because the context switch functions are hardware-dependent. Therefore, you need a scheduler for your specific hardware (e.g., provided by TI in their development environments) or a very minimal RTOS.

There are RTOSs that are very minimal (a few KB of footprint) and can contain only the scheduler. Have a look for example at http://erika.tuxfamily.org. However, I'm afraid that your specific microcontroller is not supported.

Answer 2

Most simple RTOS kernels provide at least scheduling, synchronisation, and IPC. However since they are also provided as static libraries, what you don't use will not be included in your product. That said I find it difficult to think of a system where synchronisation, IPC and timer services would not be required or at least beneficial.

There are numerous such RTOS libraries including Segger embOS for example.

Answer 3

The only portable, hardware independent solution I know is Protothreads by Adam Dunkels. But it is not true multitasking anyway, just a nice syntax sugar on concurrent state machines. However it may help you in your task.