Internal pullups not working on PIC12F675

[Yobortsa]

Hi all,

Does anybody have any idea why internal pullups might be working on GPIO5 but not GPIO4 on a PIC12F675?

RESET	clrf	STATUS			;
		clrf	GPIO			; Init GPIO
		movlw	b'00000111'		;
		movwf	CMCON			; comparator off, digital I/O
		bsf     STATUS,RP0      ; bank 1                          |B1
        call    h'3FF'          ; get factory calibration value   |B1
        movwf   OSCCAL          ; set OSCCAL calibration value    |B1
		movlw   b'00111000'     ; Set 0,1,2 to outputs; 3,4,5 to inputs (switches)
        movwf   TRISIO          ; 
		movlw	b'00110000'		; Enable port 4,5 pullups
		movwf	WPU				; Set Weak Pull Up register
  		bcf     OPTION_REG, 7	;  Enable Pull Ups
        bcf     STATUS,RP0      ; bank 0                          |B0

I have tried programming with PICKit1 and PICKit2 and on test boards with connections going nowhere GPIO5 works fine (5V) but GPIO4 has varying voltage below 1.3V. I have tried with 3 PIC chips. Have also tried in my circuit which has GPIO4 and GPIO5 going to ground via microswitches. I never get GPIO4 held high with internal pullup. Do I need to disable the Analog port somehow perhaps?

Regards,

David

 

[geko]

Yes you need to clear the bit in the ANSEL register to set the port bit to digital mode. Check the datasheet for more info.

 

[Yobortsa]

Yep, worked - thankyou so much

clrf ANSEL