When the APM is powered from the RC equipment what is the acceptable voltage range? I know it's ~ 5 volts, but 5 volts +/- what?
Typical RC servo/radio power is anywhere from 4.5 to 6 volts. Will 6 volts be too much? What about 5.5 volts?
Typically a ~5 volt component will be rated for something like 5 volts, +/- 5% or +/- 10% like the Amtel 2560 chip. A bit more is usually OK, but strange/intermittent things can happen as the limits are pushed.