Inconsistant A2D readings

[HenrikOlsson]

Hi,
The recommended source impedance for the ADC on the 45K22 is 3k, you have 30k - that might play a role in your results (see table 27-22 in the datasheet).

Since you have the acquisition time set to manual and such large source impedance perhaps you could try increasing the Pause 5 and see if that helps (or try reducing your source impedance to meet the recommended value of 3k). I'd probably also disconnect the signal from the second PIC until you get stable readings on the firts one.

/Henrik.

[Luckyborg]

I tried cutting the trace to the second pic and it didn't seem to have any effect. I adjusted the pause to Pauseus 10, pauseus 50 and pause 5. None seemed to help any. The resistors are surface mount, but I think I will try putting a 1k in parallel with the 30k and see if it at least stabilizes

Thanks

[Luckyborg]

I found the problem. I had two similar net names "Display Type" and "DisplayType" which should have been connected and weren't, so the microchip pin was effectively floating. I found it will playing with resistor values, so thanks Henrik for the help.