It better to use "SimpleTimerWP.c", more easier and flexible to use, but mayb lil bit complicated to understand (look the simpler code on "OldVersion/SimpleTimer.c").
Not RTOS required. Just config some timers of any microcontroller to ticking as a reference for and use this lib.
You can launch the console app to see what happens on this example application. To do it: go to the folder "DemoAppl/" and open "TimerWithCBdemo.exe" Download this demo "*.exe" by clicking "Download raw file" and run it.
!!! PROJECT'S STATUS !!! Completed.