This is the first approach at the Real Time Operative Systems for microcontrollers and I don't know which are the specified functions that an RTOS must develop.
For this reason I would like to know if the RTOS (Micrium, FreeRTOS, DSPnano, and so on) integrate the api/library/driver of the internal microcontroller peripheral (such as adc, timer counter, serial interface and so on) or if the user must develop your peripheral driver and than he must add this library in his project.
In the same articles that I have read in this day, we can acquire information about the specified function of the RTOS, but there aren't information about the peripheral drivers.
Your question is kind of broad, I would suggest checking out FreeRTOS's website as they have an adequate description of their real time operating system.
If you are still searching for information or are wanting to dig further into RTOS, I would suggest checking out the microC book by Micrium. It is dependent upon what MCU family you are running.
Hope this helps out,
The RTOS you pick will likely have very little in the way of peripheral drivers libraries. Porting to a platform when discussing an RTOS usually means that there's a timer and some serial I/O implemented.
The Renesas RPDL has been used with FreeRTOS and Micrium for code examples that ship with our kits. This means that the RTOS works along side the drivers you need, but the drivers are generated by the RPDL package.