@Nigel31 Thank you, I will try to write some code and test it. It can take a few weeks as I have to do it in my spare time (like most of us).

@mfalkvidd Thank you!

I'm using the sleepRemainingMs function for that and it works if accuracy is not important

Yes, the pin change intgerrupt gives me what I want. The sleep call also wakes up on this interrupt, I thought it would only wake up in INT0 or INT1. So for now my experiments with FreeRTOS end. @electrik thanks for the hint!

Thanks @cvdenzen Adding reference link in case someone needs to check it later: https://github.com/mysensors/MySensors/commit/98355b2d0b68190a87c3ac76698014adb58fc882#diff-407bf395289c3cbd3d7728909c25b3adR186