I know its something that you have already looked at, but just what is in
the TRISB register.  Just for the heck of it, why not add a couple of lines
just before Read_Function:

         movlw   b'xxxxxxxx'     ;set bits accordingly . . .
         tris    PORTB

Lets just make sure that the DDR is what you think it is.

dwayne

At 09:50 PM 12/31/00 -0500, David VanHorn wrote:
>I'm having trouble with an I/O function.
>
>I have a capacitor, connected through three resistors, to three I/O pins.
>The Capsense pin connects to the cap through a 1k resistor.
>The other two pins are varying resistance.
>If I set them as inputs, then the resistances don't matter.
>If I set either one as output, then it charges or discharges the cap at a
>rate determined by it's resistor.
>
>The basic idea is to read the cap RC time constant, as a form of A/D
>converter.
>
>Everything's fine, till I get to the point where I want to watch the cap
>discharge, until it's low, before taking one of the other pins to output high.
>
>Read_Function:
>        btfsc   PORTB,Capsense          ;loop here till low on cap sense pin
>        goto    Read_Function           ;
>
>The Capsense pin is set as an input, as is one of the other two pins
>The third is an output, and I can see that it is low, and that the voltage
>on the capsense pin is also low, but the code loops here forever,
>indicating that it's seeing a high input.
>
>I've walked through all the banking, and I believe that I'm in the right
>banks when I'm talking to PORTB and TRISB.
>
>I've disabled all peripherals that would otherwise use portb pins.
>
>So, how could I get stuck here, given a low on the Capsense pin of portb?



Dwayne Reid   <dwayner@planet.eon.net>
Trinity Electronics Systems Ltd    Edmonton, AB, CANADA
(780) 489-3199 voice          (780) 487-6397 fax

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