You must:
1) Switch to the first analog input
2) WAIT long enough for the circuitry to settle
3) Initiate a conversion cycle
4) Wait for end of conversion
5) Read the first analog input.
1') Switch to the second analog input
2') WAIT long enough for the circuitry to settle
3') Initiate a conversion cycle
4') Wait for end of conversion
5') Read the second analog input

Step 2 is the one that most people leave out, and it
cause the readings to be way out of whack.

Fr. Thomas McGahee

----- Original Message -----
From: "Micro Eng" <micro_eng@HOTMAIL.COM>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Tuesday, June 11, 2002 12:14 PM
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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