PWM Led fade out with Pic 16f628
I have use this circuit for test the hardware pwm with Pic 16f628, but a pwm signal can be software generated.
Source code for PIC16F628:
;=======pwm.ASM=================================15/11/06== ; standard INTRC_OSC_NOCLKOUT 4MHz ; http://www.module.ro ;------------------------------------------------------------ ; configure programmer LIST P=16F628;f=inhx8m #include "P16F628.INC" ; Include header file __CONFIG _PWRTE_ON & _WDT_OFF & _INTRC_OSC_NOCLKOUT & _BODEN_ON & _LVP_OFF & _CP_OFF & _MCLRE_OFF ;------------------------------------------------------------ cblock 0x20 ; Beginn General Purpose-Register ;-------------------------- counters count1 count2 count3 ;-------------------------- endc ;-------------------------- #DEFINE pwmu PORTB,3 ;--- Reset -------------------------------------------------- org h'00' goto init ; reset -> init ;--- Interrupt ---------------------------------------------- org h'04' ;-------------------------- init clrf PORTA clrf PORTB movlw 0x07 ; Turn comparators off and enable pins for I/O movwf CMCON bcf STATUS,RP1 call usi ; port settings call pause movlw 0xFF movwf PORTB call pause ; wait 126ms call set_timer ;-------------------------- uu call pause movlw 0x02 ; set pwm at 2/256 movwf CCPR1L call pause ; wait 126ms movlw 0x10 movwf CCPR1L ; set pwm at 10/256 call pause movlw 0x40 movwf CCPR1L call pause movlw 0x80 movwf CCPR1L call pause movlw 0xFF ; max. power movwf CCPR1L call pause movlw 0x80 movwf CCPR1L call pause movlw 0x40 movwf CCPR1L call pause movlw 0x10 movwf CCPR1L goto uu ; repeat ;~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ set_timer clrf T2CON clrf TMR2 clrf INTCON bsf STATUS,RP0 clrf PIE1 bcf STATUS,RP0 clrf PIR1 bsf STATUS,RP0 movlw 0xFF movwf PR2 ; compare with 255 bcf STATUS,RP0 movlw 0x02 movwf CCPR1L movlw 0x03 movwf T2CON ; prescaler 1:16 and postscaler 1:1 movlw 0x3C movwf CCP1CON bsf T2CON,TMR2ON ;turn on timer, see pic16f628 datasheet return ;************************************************************************ ; Delay * ;************************************************************************ pause movlw 0x02 ;126 ms movwf count3 d3 movlw 0x3F ;63 ms movwf count1 d1 movlw 0xFA ; 1ms movwf count2 d2 nop decfsz count2,F goto d2 decfsz count1,F goto d1 decfsz count3,F goto d3 retlw 0x00 ;============================================================ usi bsf STATUS,RP0 ; Bank 1 movlw 0xFF ; all input movwf TRISA movlw 0x00 movwf TRISB ; all output bcf STATUS,RP0 ; Bank 0 return ;============================================================ end ;============================================================
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Last updated October, 2006