using the pwm's in pic18f2431-2331-4331-4431

[Bruce]

HPWM is for control of CCP PWM. Not Power Control PWM. To use PCPWM you'll need to do
things manually.

The example below is for the 18F2431. It's all in PBP.

 
    DEFINE LOADER_USED 1
    DEFINE OSC 20
    
    ' At 20MHz, to figure a PWM frequency of 19.455kHz
    '
    ' TPWM = time period of PWM frequency
    ' PTPER = 12-bit period register PTPERL and PTPERH
    ' PTMRPS = PWM time base prescaler
    ' 
    '        (PTPER+1)*PTMRPS         257
    ' TPWM = ----------------  =  ------------ = 0.0000514 
    '             Fosc/4            5000000
    '
    ' Frequency = 1/TPWM = 1/0.0000514 = 19.455kHz
    '
    ' PWM resolution (bits resolution for duty cycle)
    '
    '              log(20MHz/19.455kHz)    3.01
    ' Resolution = ------------------ = ----------- = 10 bits
    '                    .301              .301
      
    ' so we'll need a word sized var for Duty
    Duty Var Word
   
    PORTB = 0               ' clear port latch
    TRISB = %11000000       ' PWM0,1,2,3,4,5 outputs
    
    TRISC = 2               ' RC1 = FLTA input (ground RC1 to halt PWM)
                            ' RC1 should be pulled high for normal PWM operation
                            ' when fault A is enabled.
    ' PCPWM init
    DTCON = %00000101       ' ~500nS dead-time (for complementary outputs only)
    PTCON0 = %00000000      ' 1:1 postscale, Fosc/4 1:1 prescale, free running mode
                            ' PTCON0 = %00000100 would give 19.45kHz/4
    PTPERL = 0              ' 
    PTPERH = 1              ' PTPER = $0100 or 256d for ~19.45kHz
	
    ' PWM4,5 independent, PWM0,1,2,3 complementary
    PWMCON0 = %01010100     ' PWM[5:0] outputs enabled
    PWMCON1 = 1             ' updates enabled, overrides sync w/timebase
    PTCON1 = %10000000      ' PWM time base is ON, counts up
    FLTCONFIG = %00000011   ' enable fault A, cycle-by-cycle mode

    Duty = 800              ' ~50%
    PDC2L = Duty.LowByte    ' maintain a fixed 50% duty cycle on PWM4,5
    PDC2H = Duty.HighByte   ' independent PWM outputs.
        
Main: ' ramps up & down duty-cycle on complementary PWM0,1,2,3 outputs
  For Duty = 800 To 200 STEP-1 ' ~20% to 80%
    PDC0L = Duty.LowByte
    PDC0H = Duty.HighByte
    PDC1L = Duty.LowByte
    PDC1H = Duty.HighByte
    Pause 5
  Next Duty
  
  Pause 500 ' 1/2 second delay between ramp up/down
  
  For Duty = 200 To 800   ' ~80% to 20%
    PDC0L = Duty.LowByte
    PDC0H = Duty.HighByte
    PDC1L = Duty.LowByte
    PDC1H = Duty.HighByte
    Pause 5
  Next Duty

  Pause 500 ' 1/2 second delay between ramp up/down
  
  GoTo Main

  End

The .gif attached shows all 6 PWM channels captured with a logic analyzer. PWM0 to PWM3
operate in complementary mode. PWM4 and PWM5 operate in independent mode.

PCPWM is a tad more complex than CCP PWM, but with a little time spent experimenting and
going over the data sheet, it's fairly easy to figure out.

[Sergeant]

Bruce,

What Logic Analyzer did/do you use, that you posted the screen capture (I'm making at least one or two assumptions here...) in the above post? A BitScope? or something else? I'm in the market for a USB MSO (I have a Tek 1220 LA and two Tek Scopes, but they're all analog with no comms for a PC for data analysis, etc.).

Thanks,

Brad

[Bruce]

Hi Brad,

The DigiView shown here http://www.tech-tools.com/dv_main.htm

I have the DV1-100 shown in the hand.

[jorge_jaqa]

thanks all you guys for ypur time to answer this threat!!.
but i think i will gonna use the code you post for checkin!!!!, thanks a lot for this forum!
thanks all your guys!!!

[Johan]

Hi Bruce,

I also got the PWM's working, but there is a problem now : LCD displays doesn't work properly, say I want to display " Welcome " , LCD displays " We$&ome" or something like that
If I delete the PWM config & code, LCD working fine.

Johan

[Bruce]

Hi Johan,

Which port/ports are you using for the LCD?

[Johan]

I am using RD2,RD3,RD4,RD5,RD6,RD7 ( cannot change these , as these are hardwired on my easypic4 )

The problem starts even before PWM channels are active