Hey guys


I'm in a bit of a muddle with a little home project of mine and am wondering if any of you want to help.
I'm building a very simple light sensing circuit using a 1M ohm LDR (with the 1M value being the max value when in the dark), as it's getting dark the program (written in Assembler) will monitor and test the incoming ADC values until it reaches ~60% of the LDR's resistance value through the voltage that it carries, once it reaches this threshold the program would then activate a simple LED to symbolise this. Easy right? Yeah, that's what I thought until I found out that I can't get it to work .
This is but the first stage of a much larger project, of which I want to build up in 'building blocks', this project would eventually grow to that which looks after plantlife within my conservatory so I don't have to.
I'm relatively new to programming in general and I thought that Assembler was a good place to start, I know all the basics as I've been learning this through the Version 3 PICmicro® microcontroller development board from Matrix Multimedia, it's a little old I know being as it is a evaluation board that was released way back in 2003 and it still has usage in it yet. So I'll be developing this project off of this for the time being.

I'm using the PIC:16F88 for this project.

And the following is the Program that I've been working on for the last 2 weeks:

;PROGRAMMING OPTIONS************************************************
;
; When programming the PIC 16f88 using the Assembler (ASM:IDE), the following options are selected:
;
; Oscillator selection; EXTRC as clock-out
;Watchdog timer - disabled
; Power up timer - disabled
; Pin function select; MCLR
; Brown-out protection - enabled
; Code Proection - diabled
;Low Voltage program - enabled
; data EE read protect - disabled
;Flash program write enable: Write protect - disabled
;Background debug - disabled
;CCP1 Mux pin; RB0
;code proect - disabled
;fail-safe clock monitor - enabled
;internal/eternal switch over mode - enabled
;
;I/O ALLOCATION*****************************************************
;
;INPUTS...........................................................
;
;Analogue sensors (input) AN4-AN6(VDD = 5.0V) ; There is only going to be one temperature sensor to be used through one of these pins, the reason why three have been selected is for other sensors to be added after the temperature sensor has been tried and tested successfully
;Digital I/O   RA0-RA3   
;
;OUPUTS...........................................................
;
; LED
;
;PORT DATA DIRECTION CODES REQUIRED...............................;
;
;
;ADC SETUP********************************************************
;
;ANSEL bit 7 0= unimplimated
; bits 6543 1= analog input
; bits  210 0= digital I/O
;
;ANSEL = 01111000 
;
;ADCON1 bit 7 1= right justify result in ADESH/ADRESL
; bit 6 0= disabled (not needed)
; bits 54 10== VREF-VSS
; bits 3210 0= unimplemented
;
;ADCON1 = 1010000
;
;ADCON0  bits 76 0= A/D clock = f/8
; bits  543 channel select (AN0-AN7)
; bit 2 GO=1/DONE=0
; bit 0 A/D Module enable = 1
;
;ADCON0 = 01111001
;
; Create  list file and select processor :
 list p = 16f88
;
#DEFINE PAGE0 BCF STATUS,5
#DEFINE PAGE1 BSF STATUS,5
;
; Include file containing register labels:
 Include "p16f88.inc"
;
STATUS EQU H'03' ; STATUS register
count  EQU 020  ; assign General Purpose Register, Bank 0 for counter 
z EQU 2  ;Zero flag
;
;set origin at address 000
org 0x000
 
 ORG 0  ; Reset vector
 GOTO 5  ; Goto start of program
 ORG 4  ; Interrupt vector
 GOTO 5  ; Goto start of program
 ORG 5  ; Start of program memory
 ; set up code for 16F88 ports
 BSF 3,5 ;switch to page 1
 CLRF H'9b' ;clear ansel file - set ports to digital io
 BCF  3,5 ;switch to page 0
;
;SETUP STATUS REGISTER............................................
;
;
;SETUP ADC........................................................
;
 banksel ANSEL  ;select register bank
 movlw b'01111000' 
 movwf ANSEL  ;write A/D control word
;
 banksel ADCON1  ;select register bank
 movlw b'10100000' 
 movwf ADCON1  ;write A/D control word
;
 banksel ADCON0  ;select register bank
 movlw b'01111001'
 movwf ADCON0  ;write A/D control word
;
;SUBROUTINE TO WAIT ABOUT 0.8MS..................................
;
delay movlw 256  ;load time delay of 256x3=768
 movwf count  ;load counter down decfsz count  ;decrement and test counter
 goto  count
;
;SUBROUTINE TO GET ANALOGU INPUT - 20US SETTLING TIME.............
;
A2D movlw 007  ;time delay of 7x3=21us
 movwf count  ;load counter
again decfsz count  ;decrement until zero
 goto  again  ;decrement until zero
;
;GET ANALOGUE INPUT..............................................
;
 movlw b'01000001'
 movwf ADCON0
adc bsf ADCON0, GO ;start a2d conversion
wait btfsc ADCON0, GO ;wait for conversion to complete
 goto  wait
 movf ADRESL, h'08' ;place in register location for testing
 movf ADRESH, h'09' ;place in register loaction for testing
;
 movlw H'66'  ;place the total of 614-bits
 movwf h'35'  ;in two empty locations of memory bank 0
 movlw H'02'  ;these are to test the thermistor component
 movwf H'36'  ;to see if it is >60% of it's original value
; 
 movf H'35', w  
 subwf H'08', H'08' ;subtract loaded ADC value from 102-bytes and place into memory
 movf H'36', w
 subwf H'09', H'09' ;subtract loaded ADC value from 2-bytes and palce into memory
;
 btfsc h'08', z ;and test ADRESL...
 goto  part2
 movlw H'0F'  ;...if the thermistor is >60% of it's original value, place the value 0F...
 movwf H'4B'  ;...into an empty register
;
part2 btfsc H'09', z ;and then test ADRESH...
 goto adc
 movlw H'0F'  ;...if the thermistor is >60% of it's original value, place the value 0F...
 movwf H'4A'  ;...into an empty register
;
;TEST TO SEE IF BOTH ADRESL AND ADRESH ARE BOTH POSITIVE.................
;
 movf H'4A', w ;load the value of ADRESH into the working register
 ADDWF H'4B', H'4A' ;add both ADRESH's and ADRESL's positive 'flags' (the values of 0F for both results), which would make the value of H'1E'
 btfss H'4A', H'1E' ;...and test to see if this result is positive
 goto adc
 goto ledop  ;if it is; turn on LED RB0
;
;
;
;LED OUTPUT IF THERMISTOR READS 61% OF ITS MAXIMUM VALUE..........
;
ledop  CLRF 6  ; set all Port B pins to logic 0 
  BSF 3,5  ; instruct program that a Page 1   
      ; command comes next 
  CLRF 6  ; set all Port B pins as outputs 
  BCF 3,5  ; instruct program that a Page 0   
      ; command comes next 
  BSF 6,0  ; set Port B pin 0 to logic 
 goto adc  ;keep testing and provide outputs as per programme parameters
 end

I've connected this up like this, the board itself is connected to the mains supply using an adapter set to 13.5v. The ADC inputs uses a +Vref of 2.55v connected into pin 2(Vref) and from that, this is then connected to the LDR which is connected to the ADC input pin 17 (AN0). The LED is already part of the Eval. Board itself.
References to the relevant datasheets can be found in the following:

PIC:16F88
Version 3 PICmicro® microcontroller development board

And, I'm using the ASM:IDE v1 debugger for assembling/debugging/building it onto the PIC:16F88
If there's anything that I missed let me know and I reply as best as I'll can, as I don't really know what's wrong with it for as far as I know, the programming and connections are correct. Can someone help me on this as I'm getting a bit confused over this .
Thanks for your time.



-Kai-Itza-

 

Please declare variables like this:

    cblock 0x20
    count
    ledon1
    ledon2
    ledon3
    ledon4
    ledon5
    ledon6
    direction
    position
    endc

It's so much easier to read code like:
movf count, W
than
movf h'20', 0

I think at some point you are using register 8 and 9 which don't exist. That wouldn't happen if you defined the variables.