A number of changes:
- don't enable interrupts, since they often cause hangs (not sure why)
- remove GND measurement
- wait 100 us between AMUX setup and start of conversion, to let input
settle
- reduce delay between line setup and samping from 100 ms to 50 ms,
for this is already sufficient
The RF communicaion improvements:
- separate ACK handling from packet(),
- pass ACK payload to caller,
- take reception timeout from callers,
- -d also dumps received packets.
