I have never found, in 20 years of doing embedded designs, the need of a formal RTOS in a project that has been coded by one person. A main loop function dispatcher is simple to code and can make the most efficient use of the microcontroller resources.

An RTOS can be useful if there are multiple programmers because it offers a pre-documented task level interface whereby it is easy to gain a springboard for several people to go off and work independently.

Michael Karas