This is a piece of trial ADC code from something I'm
working on at the moment. It shows 0000 to 1024 on
an LCD - the position of a 5k pot. I can't suggest a
reason for your adresl always containing 00. Unless
you've a typo that I've missed, the banking and code
looks very similar

bank0 macro
         bcf     status,rp0
         bcf     status,rp1
         bcf     status,irp
         endm

bank1   macro
         bsf     status,rp0
         bcf     status,rp1
         bcf     status,irp
         endm

adch0  macro
         bcf    adcon0,chs0
         bcf    adcon0,chs1
         bcf    adcon0,chs2
         endm

         bank1
         movlw   b'11111111'    ;RA0 - RA7 analogue inputs
         movwf   trisa
         clrf    adcon0
         movlw   b'00000000'    ;set PortA I/O to all A2D
         movwf   adcon1

         bank0
         call    lcd_init     ;initialise LCD screen

         clrf    adcon0
         bsf     adcon0,adcs1   ;select Fosc/32 @ 18.432MHz
         bank1
         bsf     adcon1,adfm    ;right-justify result
         bank0
         bsf     adcon0,adon    ;turn A/D on

         del256                         ;short delay - temp

         adch0                          ;select A/D channel 0

         del256                         ;short delay - temp

         bsf     adcon0,go_done   ;start conversion
         nop
         nop
         btfsc   adcon0,go_done   ;test for end of sampling
         goto    $-1

         movf    adresh,w       ;convert hi / lo to ASCII
         movwf   hi
         bank1
         movf    adresl,w
         bank0
         movwf   lo
         call    ascii16
         call    line1
         call    dig_out        ;display

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