. . . Disclaimer . . .  I have never even read the F877 data sheet

Are you maybe having trouble charging the input capacitance of the ADC
through 50k?  I kind of remember a 5k recommended maximum on the data
sheets for some of the other PICs with analog inputs.

Lyle


> -----Original Message-----
> From: pic microcontroller discussion list
> [mailto:PICLIST@MITVMA.MIT.EDU] On Behalf Of Micro Eng
> Sent: June 11, 2002 9:15 AM
> To: PICLIST@MITVMA.MIT.EDU
> Subject: [PIC]:strange analog in problem
>
>
> Using the F877, I have PortA configured for analog inputs,
> and had 10K pots. Seemed to work ok, I had a watch window set
> up, and a breakpoint right after the read sequences (for 4 pots).
>
> I've changed the pots to 50K now, and upped the aquisition
> time, but the values seem to be way off now, and are affected
> by each other.
>
> ie...
>
> if I read just one, it is close...but not exact.  If I put
> the second pot in the loop to read, the first one goes way
> off scale.  I've read the actual voltages on the pins, and
> they are not changing. Anyone ever seen where just reading a
> second port affects the value of the first one?
>
>
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