low power reading of NC switch with mcu
You are already using a 1M pull-up... how low current do you want to go?

That is also a wonderful antenna you have which is why I assume you have that 10nF cap in there. 

You are aware the charge up RC time is 10mS right. 

You need to do the math and see if the current drop you gain by switching outweighs the current you lose by staying awake long enough to let that settle. Which I doubt.

As for the floating part, since you protected it with diodes you should be ok though providing a discharge path for the cap would be prudent. 

Personally I think something more on these lines would be more prudent. Use the output pin to drive the line directly and sense with the other. Also adds the benefit that you can modulate the output if need be to detect it is really the wire and not a short somewhere.







simulate this circuit &ndash; Schematic created using CircuitLab