Pete,
You are right,
If you leave channels unconnected, or in a very high impedance state,
the PIC's internal  multiplexer will tend to pass the strongest signals
around to these ports also is you are cycling them fast. Motorola
68HC11s also do this. Quick way out is to put a very small capacitor
between each A2D pin and ground (unless on low impedance input.)
regards,
Graham


PIC development wrote:
>
> Has anyone who has used the example code for the A/D convertor
> on the 16c74A noticed "leakage" between channels?
>
> I don't know if it's because I'm not waiting long enough
> for the internal capacitor to settle or what, but I seem
> to get slightly different values read from AN2, depending
> on the voltage on AN1.
> ..............................................................................
> . Never trust a man who, when left alone in ....... Pete Lynch               .
> . a room with a tea cosy, doesn't try it on ....... Marlow, England          .
> ..........Billy Connolly. ......................... pic@beowulf.demon.co.uk ..