18f4680 pwm

Hello,

I am trying to use the ECCP for a full H-bridge. I can not seem to get it working, any help would be appreciated in resolving my issue... see below.

Code:

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              INCLUDE "Modedefs.Bas"   
        DEFINE OSC 20

               
; Set port direction and turn off unused peripherals
        CMCON  = 7                                  ' shut offcomparators
        TRISA = %00011111                                ' Set PORTA to input "1" or output "0"
        TRISB = %00000000                            ' set portB to output "0" or input "1"
        TRISC = %00000000
        TRISD = %00000000
        TRISE = %00000000
       
        ADCON1 = %00001111                                ' bit 0 ~ bit 3 sets ports as digital I/O. 1 = digital, 0 = analog
        ADCON0 = %00000000              ' bit 0 disables A/D converter module.
        ECCP1CON = %00000000            ' bit 0 ~ bit 3 turns off capture/compare/PWM
       
       
; Declare variables and aliases

duty var byte

PAA var LATA
PBB var LATB
PCC var LATC                           
PDD var LATD                          ' used to re/set portD.1, can not use portd.1 = x on latch ports
PEE var LATE


; initialize power on state of ports
LATA = 0
LATB = 0
LATC = 0
LATD = 0                                ' force latches on portD to low
LATE = 0


        ECCP1CON = %11001100            ' bit 0 ~ bit 3 turns off capture/compare/PWM
        T2CON = %00010101                        ' Turn on Timer2, Prescale=4
        PR2 = 249                                        ' Set PR2 to get 5KHz PWM out
       
        duty = 100                     
        ECCPR1L = DUTY
        ECCP1CON.4 = duty.0                           
        ECCP1CON.5 = duty.1                           
             
       
Mainloop:
       
      pauseus 1000
       
      goto mainloop

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It works as is.... traces lifted off PCB...

I played with this code a little today and it works well....Thanks

Just a few minor changes can give 10 bits PWM resolution.

Change duty var byte to duty var word.

Add the line ECCPR1L = duty >> 2 after ECCP1CON.5 = duty.1.

now the duty cycle can be set from 0 to 1023 instead of 0 to 255.

Bob W.