Mike,

Try initializing CMCON, then ANSEL, then TRISIO, and then enable WPU.
Check the datasheet too. I think there is note someplace in there that
talks about the sequence in which they should be initialized.

Shahid.

-----Original Message-----
From: Mike Hord [mailto:gaidinmd@HOTMAIL.COM]=20
Posted At: Thursday, February 19, 2004 2:47 AM
Subject: [PIC:] 12F675 GPIO won't pullup


Sometimes the pull-ups work, sometimes not.  I've
changed pins, to check if it is a bad pin, and I've
changed PICs, to see if it's a bad PIC, but I still have
the problem that sometimes GPIO.0 (or GPIO.1, if
I rewrite the code with that pin as the input) just
doesn't pull itself high.  I've been staring at this off
and on for two days.  What am I missing?

I'm leaving out the interrupt handler, because all it
does is strobe a pin, and the timing functions,
because all they do is control the rate at which the
pin strobes.  After the code included here, the only
special function registers that get touched are GPIO
and INTCON.  The program is a simple IR remote
control intended to turn on and off a device for
which the remote is prohibitively expensive.

Mike H.

__CONFIG   _CP_OFF & _CPD_OFF & _BODEN_OFF & _MCLRE_OFF & _WDT_OFF &
_PWRTE_ON & _XT_OSC

        calls   EQU     0x20    ; temp to hold calls during wait loops
        codel   EQU     0x21    ; low of the pertinent code
        codeh   EQU 0x22                ; high of the pertinent code
        timeleft        EQU     0x23    ; time left to add to make
period 45 mS

        #DEFINE pwrbtn GPIO,0           ; alias to the button for power
code
        #DEFINE led GPIO,1                      ; alias to the IR led
        #DEFINE inpbtn GPIO,2           ; alias to the button for input
code
        #DEFINE mutebtn GPIO,3          ; alias to the button for mute
code

        CONSTANT        ONECALLS=3D47             ; number of calls to
encode a one
        CONSTANT        ZEROCALLS=3D23            ; number of calls to
encode a zero
        CONSTANT        HEADERCALLS=3D95          ; number of calls to
encode header
        CONSTANT        PAUSECALLS=3D25           ; number of calls to
wait between bits

;**********************************************************************
ORG     0x000             ; processor reset vector
        goto    main              ; go to beginning of program

main
        bsf     STATUS,RP0      ; start initializing the registers in
bank 1
        clrf    OPTION_REG      ; turn on pull-ups, other funcs not
important
        movlw   b'00111101'     ; mostly inputs, except GPI01, which is
LED
        movwf   TRISIO
        movwf   WPU             ; turn on pull-ups for each input
channel
        movwf   IOC             ; turn on interrupt-on-change for each
input
        clrf    ANSEL           ; needed for prototyping on 675
        bcf     STATUS,RP0      ; done initializing the bank 1 registers
        movlw   b'10001000'     ; turn GIE on, and GPIE on
        movwf   INTCON
        movlw   7               ; turn comparator off
        movwf   CMCON
naptime
        sleep                   ; sleep while waiting for a button to be
pressed
        goto    $+1             ; give interrupt a moment to vector
        goto    naptime         ; go back to sleep

                END                       ; directive 'end of program'

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