;    Tutorial3.asm - A/D delayed LED Blink
;    Copyright (C) 2007 www.pic18f.com
;
;    This program is free software: you can redistribute it and/or modify
;    it under the terms of the GNU General Public License as published by
;    the Free Software Foundation, either version 3 of the License, or
;    (at your option) any later version.
;
;    This program is distributed in the hope that it will be useful,
;    but WITHOUT ANY WARRANTY; without even the implied warranty of
;    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
;    GNU General Public License for more details.
;
;    You should have received a copy of the GNU General Public License
;    along with this program.  If not, see <http://www.gnu.org/licenses/>.
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

#include <p18F4550.inc>
	
	CONFIG WDT=OFF; disable watchdog timer
	CONFIG MCLRE = ON; MCLEAR Pin on
	CONFIG DEBUG = ON; Enable Debug Mode
	CONFIG LVP = OFF; Low-Voltage programming disabled (necessary for debugging)
	CONFIG FOSC = INTOSCIO_EC;Internal oscillator, port function on RA6 
	
	org 0; start code at 0
		
Delay1 res 1;reserve 1 byte for the variable Delay1
Delay2 res 1;reserve 1 byte for the variable Delay2

Start:
	CLRF PORTD ;clear PORT D
	CLRF TRISD ;set PORT D to input
	
	CLRF Delay1
	CLRF Delay2
	
	MOVLW B'00001110';ADCON1 setup: VSS,VDD ref. AN0 analog only
	MOVWF ADCON1

	CLRF ADCON0 ;clear ADCON0 to select channel 0 (AN0)
	
	;ADCON2 setup: Left justified, Tacq=2Tad, Tad=2*Tosc (or Fosc/2)
	MOVLW B'00001000' 
	MOVWF ADCON2
	
	BSF ADCON0,ADON ;Enable A/D Conversion Module

MainLoop:

	BSF ADCON0,GO_DONE ;Start A/D Conversion
	BTFSC ADCON0,GO_DONE ;Loop here until A/D conversion completes
	GOTO $-2
	BTG PORTD,RD1 ;Toggle PORT D PIN 1 (20)
	CALL DelayAD ;Call A/D result-based Delay Function
	goto MainLoop ;Restart

DelayAD: ;Delay function based on A/D result
	MOVFF ADRESH,Delay2 ;move 8 MSb from A/D result to Delay2
	
	;Make sure no overflows occur
	INFSNZ Delay2,F
	DECF Delay2,F
	
Delay:
	DECFSZ    Delay1,1 ;Decrement Delay1 by 1, skip next instruction if Delay1 is 0
	GOTO Delay
	DECFSZ	  Delay2,1
	GOTO Delay
	RETURN
	
	end