16 bit PWM using CCP1

[Darrel Taylor]

Hi Norm,

To set the pin High, simply clear the CCP1CON register, then load it_(Bruce) with the compare mode again %00001001 (9).

And, only do it on a Timer1 interrupt. The CCP changes the pin low on its own, so you don't need to enable the CCP interrupt.

A few other things are either not needed or can be done differently.
Have a go at this ...

    'FL PIC18F4520 
    ; @ __CONFIG _CONFIG1H, _OSC_XT_1H 
     @ __CONFIG _CONFIG1H, _OSC_HSPLL_1H
     @ __CONFIG _CONFIG2L, _BOREN_ON_2L
     @ __CONFIG _CONFIG2H, _WDT_ON_2H
     @ __CONFIG _CONFIG3H, _MCLRE_ON_3H & _PBADEN_OFF_3H
     @ __CONFIG _CONFIG4L, _LVP_OFF_4L & _XINST_OFF_4L  

 
    DEFINE OSC 40  
    DEFINE  INTHAND myint 

    Clear 

    sSEROUT_PIN VAR PORTA.2
    sBAUD CON 16416  '16416 = 19200 BAUD 

    yTEMP VAR Byte 
 
    wDUTY  VAR WORD EXT    ' map wDuty to CCPR1L:H as a word
    @wDUTY = CCPR1L

    '***********************************************
START:
    ADCON1 = $0F           ' disable analog functions
    CMCON = 7              ' disable comparators

    '********************
    '16 BIT CCP1 PWM
    T1CON   = %00110000    ' Turn off Timer1 with a Prescaler value of 1:8
    PIE1    = %00000001    ' enable TMR1 overflow interrupt 
    INTCON  = %11000000    ' enable global and peripheral interrupts 
    CCP1CON = %00001001    ' LOW PORTC.2 ON MATCH TM1 WITH DUTY
    OUTPUT PORTC.2         ' Set PORTC.2 (CCP1) to output, starts High
    
    wDUTY = 32768          ' 32768 = 50% DUTY PWM
    T1CON.0 = 1            ' TMR1 ON
    
    PAUSE 800 
    SerOut2 sSEROUT_PIN,sBAUD,["START",13] 

    '***********************************************

MAIN:
    yTEMP = yTEMP +1 
    SerOut2 sSEROUT_PIN,sBAUD,["LOOP ",Dec yTEMP,13] 
    PAUSE 500
Goto MAIN


  '**** ASSEMBLY INTERRUPT ROUTINE ****  
  Asm
myint
    movlw     9                  ; %00001001 compare mode, low on match
    clrf      CCP1CON            ; clrf added per Bruce's suggestion
    movwf     CCP1CON            ; Set Pin to default state (High)
    bcf       PIR1,0             ; Clear Timer Int Flag
    retfie    FAST               ; Return from interrupt with shadow regs
  EndAsm
  '**** END ASSEMBLY INTURRUPT ROUTINE **** 
 

End

P.S. Using both CCP's with this method would make a great 2 channel hardware driven servo driver.
Dutycycles between 2500-5000 would give pulses between 1-2ms at ~40hz.