
;	Candle Simulation
;	6/04 Luhan Monat
;
;	Simulate flicker of candle using incandescent lamp
;


	device	PIC12F675,intrc_osc,pwrte_on,wdt_off


	org	20h

del1	ds	1
del2	ds	1
pcnt	ds	1
temp	ds	1
lev1	ds	1
lev2	ds	1
level	ds	1
rbuf	ds	5


LAMP	=	gp.5

	org	0
	goto	start
	
	org	4
	reti


start	bsf	RP0
	movlw	0
	movwf	GP
	movlw	127
	movwf	OSCCAL
	bcf	RP0
	bsf	rbuf,0		;seed random number
	movlw	127
	movwf	lev1		;initial light level
	movwf	lev2


; Main Loop
; Create hi and low power levels
; Switch between levels
	
candle	movf	lev1,w
	movwf	level
	call	power		;do lev1 power
	call	rando
	andlw	7
	btfss	z
	goto	:run		;skip 7 out of 8
	call	rmid		;generate new hi and low levels
	movwf	lev1
	sublw	0
	movwf	lev2
:run	movf	lev2,w		;do lev2 power
	movwf	level
	call	power
	goto	candle
	

; PWM power control

power	movlw	100		;set flicker rate: higher=slower
	movwf	pcnt		;set loop count
:p1	movf	level,w		;get target level
	movwf	del1		;set 1st delay
	sublw	0
	movwf	del2		;set 2nd delay
	bsf	LAMP		;power on
:p3	nop
	decfsz	del1		;do 1st delay
	goto	:p3
	bcf	LAMP		;power off
:p4	nop
	decfsz	del2		;second delay
	goto	:p4
	decfsz	pcnt
	goto	:p1	


; find sum of 4 random numbers
; skews results around 127

rmid	call	rando
	andlw	3fh
	movwf	temp
	call	rando
	andlw	3fh
	addwf	temp
	call	rando
	andlw	3fh
	addwf	temp
	call	rando
	andlw	3fh
	addwf	temp,w
	ret


; Pseudo Rando Number
; "Chop Suey Machine"

rando	movf	rbuf,w
	addwf	rbuf+1,w
	movwf	rbuf+1
	addwf	rbuf+2,w
	movwf	rbuf+2
	addwf	rbuf+3,w
	movwf	rbuf+3
	addwf	rbuf+4,w
	movwf	rbuf+4
	bcf	c
	rlf	rbuf+4
	btfsc	c
	bsf	rbuf+4,0
	movf	rbuf+4,w
	addwf	rbuf
	ret
	

	end


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