Internal pullups not working on PIC12F675 - Electronic Circuits Projects Diagrams Free

Yobortsa · 14th November 2009, 11:55 AM

Hi all,

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

Code:

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 · 14th November 2009, 12:31 PM

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 · 14th November 2009, 12:44 PM

Yep, worked - thankyou so much

Code:

clrf ANSEL

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14th November 2009, 11:55 AM	#1
Yobortsa	Internal pullups not working on PIC12F675 Hi all, Does anybody have any idea why internal pullups might be working on GPIO5 but not GPIO4 on a PIC12F675? Code: 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

14th November 2009, 12:31 PM	#2
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. __________________ Pete picprojects.org.uk

14th November 2009, 12:44 PM	#3
Yobortsa	Yep, worked - thankyou so much Code: clrf ANSEL