; irtest.asm
; Simple PIC16F876 Program to test my IR emitter
; uses PWM to modulate LED output at 38KHz
; IR receiver PNA4602 will output logic '1' when
; it detects IR light.  Since receiver probably
; can't source current to turn on an LED indicator,
; have PIC turn on indicator LED for it

; TMR2 prescalar = 1
; PR2 = 0x82
; CCPR1L:CCP1CON<5:4> = 0x106

; Include the header file for our target chip
	#include "p16f876.inc"

; First line, declare that we want a 16F876 PIC
; and that our numbers will be in Hexadecimal
; unless otherwise noted
	LIST P=16f876, R=HEX

; Tell the programmer what options we want to use
; In this case:
; _WDT_OFF -- Watchdog Timer Off
; _XT_OSC -- Crystal Oscillator
; _CP_OFF -- Code Protect Off

	__CONFIG _WDT_OFF & _XT_OSC & _CP_OFF & _LVP_OFF

; Variable Declarations
; Here we assign memory locations for our variables

	cblock	0x20
	  counter1
	endc

	cblock 	0x70			; global variables -- visible across all banks
	  StatusSave
	  WRegSave
	endc

; First column is always for labels.  Anything in the first
; column will be interpreted by the assembler as a label

	org 	0
	goto	Start

	org	0x04				; interrupt handler goes here

Interrupt:
	; for now, the interrupt routine will just step the motor once

	btfss	INTCON, T0IF		; test for non-TMR0 interrupts
	retfie				; and return on them

	movwf	WRegSave		; save accumulator
	swapf	STATUS, w
	movwf	StatusSave

	bcf	STATUS, RP0

	decfsz	counter1
	goto	int_done

	movlw	0x10
	movwf	counter1

	btfss	CCP1CON, 3
	goto	int_e_pwm
	call	PWM_Disable
	goto	int_done

int_e_pwm:
	call	PWM_Enable
	
	
int_done:

	swapf	StatusSave, w
	movwf	STATUS
	swapf	WRegSave, f
	swapf	WRegSave, w
	bcf	INTCON, T0IF
	retfie

Start
	CLRF	PORTB			; Initialize Port B
	CLRW				; Clear W register
	BSF	STATUS,RP0		; Select Register Bank 1
	MOVWF	TRISB			; Set B to all outputs
	movlw	b'11111111'
	movwf	TRISA			; set A to all inputs
	movlw	0x06
	movwf	ADCON1			; set porta to digital inputs

	bcf	OPTION_REG, T0CS
	movlw	b'00000111'
	iorwf	OPTION_REG, f
	bcf	OPTION_REG, 3
	bsf	INTCON, T0IE
	bsf	INTCON, GIE
	bcf	STATUS, RP0
	clrf	TMR0
	movlw	0x10
	movwf	counter1


	call	SetupPWM		; start IR led blinking on RC2
	call	PWM_Enable
	
loop	btfss	CCP1CON, 4
	goto	loop
	btfss	PORTA, 0
	bsf	PORTB, 7
	btfsc	PORTA, 0
	bcf	PORTB, 7
	goto	loop

SetupPWM:
; initializes PWM to 38KHz for IR LED
	bsf	STATUS, RP0
	movlw	0x82
	movwf	PR2
	bcf	STATUS, RP0
	bsf	CCP1CON, 4
	bcf	CCP1CON, 5
	movlw	b'01000000'
	movwf	CCPR1L
	bsf	STATUS, RP0	
	bcf	TRISC, 2	
	bcf	STATUS, RP0
	movlw	b'00000100'
	movwf	T2CON
	return

PWM_Enable:
	bsf	CCP1CON, 3
	bsf	CCP1CON, 2
	return

PWM_Disable:
	bcf	CCP1CON, 3
	bcf	CCP1CON, 2
	return


	END				; End of program