PWM TEST PROGRAM

PWM (Pulse Width Modulation) Test Program for the Mainboard (PIC16F876)

The main part of the code at "Start" performs the following function:

Motor Left Forward
Motor Right Forward
Wait 1mS
Motor Left off
Motor Right off
Wait 1mS
goto Start

The program loops forever and has the following effect:
Motors Run Forward at half Power.

The Code:

	list p=16f876

#include "P16F876.inc"

;Define ports so we can use them by name
#define ML1 PORTB,5	;OUTPUT
#define ML2 PORTB,4	;OUTPUT
#define MR1 PORTB,3	;OUTPUT
#define MR2 PORTB,2	;OUTPUT

	cblock	20h
	VLDelay, LDelay, MDelay, SDelay		;variables for delay routines
	endc

	org 0
	goto init	;jump over interrupt vectors
	

	org 10
init 
	bsf	STATUS, RP0
	bcf	STATUS, RP1	;select bank 1
	movlw	b'11000011'
	movwf	TRISB		;RB2,RB3,RB4,RB5 set as outputs
	bcf	STATUS, RP0	;select bank 0

Start
	bsf	ML1		
	bcf	ML2		;Motor Left Forward 
	bsf	MR1		
	bcf	MR2		;Motor Right Forward 
	movlw	.100		;100*10uS=1mS
	call	ShortDelay	;wait for 1 milli Second
	bcf	ML1		
	bcf	ML2		;Motor Left off 
	bcf	MR1		
	bcf	MR2		;Motor Right off 
	movlw	.100		;100*10uS=1mS
	call	ShortDelay	;wait for 1 milli second
	goto	Start		;loop forever
	 

;***** Short Delay 10 uS to 3 mSec, value in w on entry, 1 tick = 12 uS

ShortDelay
	movwf	SDelay
WaitSDF
	nop
	nop
	nop
	nop
	nop
	nop
	nop
	decfsz	SDelay,F
	goto	WaitSDF
	Return

;**************************
;***    Config word     ***
;**************************

	__CONFIG h'3FFF' & _LVP_OFF & _BODEN_OFF & _XT_OSC & _PWRTE_ON & _WDT_OFF 

	end

The Results:

Note the frequency is approx 500Hz as per the design.