> From: Andy Kunz <mtdesign@FAST.NET>
> snip
> Question is, do the ADC inputs have diode protection like the digital
> inputs?  Will my scheme work properly?

I think the analog inputs has protection diodes in it.  It is stated in
the datasheet that RA0:RA5 had it, so your scheme may not work because
the point between R1 and R2 (AN0) will stay at 5.7V.

How about this:

3-30V ---+-R1-+-->AN0
         |    |
         |    R2
         |    |
         |    *
         |
         +-R3-+-->AN1
         |    |
         |    R4
         |    |
         |    *
         |
         .
         .
         .
         |
         +-R?-+-->ANx
              |
              R?
              |
              *

This may work if the impedance of 3-30V output is low enough.
If not, an op-amp buffer or setting R1, R3 (resistors in
series) to a high value may help. But this solution uses 2X
resistors than your previous concept.


Rgds,

Reggie