adc help

[BigWumpus]

It is not possible to read this voltages by a digital input.
You have to use a lot of analog-inputs or design another keyboard !

[mpardinho]

i use 16f872 and adc input A0, ...
I use 4 pin for test 2 row and 2 col,
if i read with 4 pins....i'll be change the pic 16f877 or other 40píns

[ErnieM]

I'm not sure what your input is, are you saying with no key pressed you have between 0,5 and 4 volts, but with key pressed you get a solid 0V?

If so, then you need to use the analog to digital input feature. Unfortunately, the 16f872 only has 5 such inputs, and you need 7 inputs.