PetrOsipov:
Thanks! I will try the simple one today. Will also check which resistor is the maximum - will breadboard 1k resistor and a 10k potentiometer in series, and see how far I can turn the potentiometer until the comm breaks up.
Then your final design should have no more than half that value - you don't want to start losing bits in the heat of battle!
Is there a guide how to program ATTiny with Arduino?