continue refactoring of sensors using multiple read entities
allow to have separate readings in either form
- global voltage & frequency only
- global & channel a only
- global & channel b only
- global & channel a & channel b (default)
still, prone to ordering errors. driver code might need a separate loop
to allow more flexible processing, outside of 'sensor' method constraints
(also note that I have no idea if it actually works on a real device)