Hi,
 
I have been trying to get the ADC working on a PIC 12F683, but I can only
read the upper byte successfully (I vary a potentiometer and output a
flashing LED when a particular bit gets set). All of the bits in the lower
byte (from ADRESL) read as zero despite the fact that the code for the lower
byte is almost identical to the upper byte. I am using the *internal*
oscillator running at 1 MHz. Any help would be great as I have reached a
dedend! The code fragments are:
 
 LIST P=12F683
 INCLUDE "p12f683.inc"
 __config 30C4H  ; used for 12f683  Power up timer, Int RC/No clockout
 
#DEFINE LED_ON      BSF     GPIO,2          ; switch LED on
#DEFINE LED_OFF    BCF     GPIO,2          ; switch LED off
#DEFINE BANK0        BCF     STATUS,RP0 ; Select BANK 0
#DEFINE BANK1        BSF     STATUS,RP0 ; Select BANK 1

; variables defined here from 20H onwards
 
         ORG  00H    ; reset vector
        
         GOTO    MAIN
 
         ORG 005H
 
ADC_10BIT
         CLRF         ADC_LO
         CLRF         ADC_HI
 
         BANK1
         MOVLW     B'01110001'      ; RC, GP0 analog, rest digital I/O
         MOVWF     ANSEL
 
         BSF           TRISIO,0          ; set GP0 to i/p
         BANK0
 
         MOVLW     B'10000001'     ; right justified, Vdd as ref, AN0
         MOVWF     ADCON0

         CALL         ONE_MS        ; my delay
 
         BSF          ADCON0, GO  ; start conversion
LP3   BTFSC      ADCON0, GO
         GOTO       LP3                 ; poll to see if conversion complete
 
         MOVF       ADRESH, W
         MOVWF    ADC_HI
         BANK1
         MOVF       ADRESL, W
         MOVWF    ADC_LO
         BANK0
 RETURN  
 
INIT_PORTS_OP
         CLRF         GPIO
         MOVLW     07H
         MOVWF     CMCON0    ; set GP0, GP1 and GP2 as digital I/O 
         BANK1
         CLRF         ANSEL
         MOVLW     B'0001011'  
         MOVWF     TRISIO
         BANK0
 RETURN
 
MAIN
         BANK1
         MOVLW      040H
         MOVWF     OSCCON
         BANK0
         CALL          INIT_PORT_OP
 
SAMPX 
         CALL         ADC_10BIT
         CALL         ONE_MS
 
         BTFSC      ADC_LO, 4            ; I am checking that this bit
changes as I vary the pot.
         GOTO       NO_LED
 
         LED_ON
         CALL         MY_DELAY
         LED_OFF
         CALL         MY_DELAY
 
NO_LED 
         GOTO SAMPX 
 
 
Many thanks,      Steve
 
 
 
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