PIC16F628 Pulse Width Modulation Controls Brightness of LED

by Lewis Loflin

Code example main loop:


main
	; first loop increases brightness of LEDs
	clrf val ; val = 0
gg  call delay_100ms 
 	movf val, w 
	movwf CCPR1L ; output val to pwm RB3
	movlw d'10'
	addwf val, F ; add 10 to val
	btfss STATUS, C ; check for carry
	goto gg ; no carry loop again
	; decreases brightness of LEDs
	movlw 0xFF
	movwf val
hh	call delay_100ms
	movfw val
	movwf CCPR1L ; save val to register
	movlw d'10'
	subwf val, F ; subtract 10 from val save in val
	btfsc STATUS, C ; check for less than 0
	goto hh  ; no loop again
	clrf CCPR1L
goto main

For how to calculate frequency and duty cycle for PIC PWM
see Working with Pulse-Width Modulation and the PIC Microcontroller

Download ASM code pwmdemo1.asm

See How I got into Electronics

You Tube Videos for this Series
Home Built PIC Development Board
PIC16F628 PIC Using Rotary Encoder to Operate Stepper Motor
Using a Serial ADC with PIC16F628
Calculating Pulse-Width Modulation with a PIC
PIC16F84A-628A Hardware Time Delays
PIC16F84A-628A Timer Interrupt Delays
PIC16F84A-628A Pullups and Interrupts
PIC16F84A-628A Hardware Interrupts Tutorial

Projects using PIC16F628:
Home Built PIC16F628 Prototyping Board
Exploring the Microchip PIC in Assembly
Using a Microchip PIC with TLC548 Serial ADC
Controlling PIC Pulse Width Modulation with a Serial ADC
Using TMR0 on a PIC with Interrupts
External Clock Crystal with PIC16F628 TMR1 Generates Interrupt
PIC Using Rotary Encoder to Operate Stepper Motor
PIC16F628 Pulse Width Modulation Controls Brightness of LED
Another way to Turn On-Off PWM in a PIC
TLC548 Serial ADC Spec. Sheet

Programming PIC16F84A-PIC16F628A Interrupts by Example
PIC16F84A-PIC16F628A Pull Up Resistors with Interrupts
Programming PIC16F84A-PIC16f628a Timers by Example
Programming PIC16F84A-PIC16F628A TMR0 Interrupts
Programming PIC16F84A Software Delay Routines by Example