18F4431 Quaduature Encoder

[Rleonard]

I wish I could help but I am using the 18F4431 in a completely
different manner.
Richard

[Bruce]

I don't have the 18F4431 or Microchip motor control board, but this works
on the 18F2431. It outputs PWM on RB0,RB1,RB2,RB3,RB4 and RB5 with a
varying duty cycle. Ramps up, then down.

It should be at least enough to get you started.

    DEFINE OSC 20
    
    Duty VAR WORD
    PORTB = $FF
    TRISB = 0
    
    PTCON0=$00 'page 8,step 1
    PTPERL=$A0      ' $01A0 = 12kHz
    PTPERH=$01
    PWMCON0=%01011110 'would be %01011111 for the 18F4431
    PWMCON1=%00000001 'step 4
    DTCON=$00
    ;OVDCOND=$00 'step 6  ; May want to un-comment these based on your PIC & board.
    ;OVDCONS=$00
    ;FLTCONFIG=%10110011
    ;POVD=00000000
    ;SEVTCMP=$0000
    ;step 8
    SEVTCMPL=$00
    SEVTCMPH=$00
    PDC0L=$00
    PDC0H=$00
    PDC1L=$00
    PDC1H=$00
    PDC2L=$00
    PDC2H=$00
    ;PDC3L=$FF ; un-comment for 18F4431
    ;PDC3H=$00
    PTCON1=%10000000
    
Main:
    FOR Duty = 50 TO $500 STEP 4
        ASM
        bsf   PWMCON1,UDIS	    ;Disable the PWM buffer update
        MOVFF _Duty,PDC0L
        MOVFF _Duty+1,PDC0H
        MOVFF _Duty,PDC1L
        MOVFF _Duty+1,PDC1H
        MOVFF _Duty,PDC2L
        MOVFF _Duty+1,PDC2H
        ;MOVFF _Duty,PDC3L      ;un-comment for 18F4431
        ;MOVFF _Duty+1,PDC3H
        bcf	  PWMCON1,UDIS	    ;Enable the PWM buffer update
        ENDASM
        PAUSE 50
    NEXT Duty
    FOR Duty = $500 TO 50 STEP-4
        ASM
        bsf	  PWMCON1,UDIS	    ;Disable the PWM buffer update
        MOVFF _Duty,PDC0L
        MOVFF _Duty+1,PDC0H
        MOVFF _Duty,PDC1L
        MOVFF _Duty+1,PDC1H
        MOVFF _Duty,PDC2L
        MOVFF _Duty+1,PDC2H
        ;MOVFF _Duty,PDC3L      ;un-comment for 18F4431
        ;MOVFF _Duty+1,PDC3H
        bcf	  PWMCON1,UDIS	    ;Enable the PWM buffer update
        ENDASM
        PAUSE 50
    NEXT Duty
    GOTO Main
    
    END

This is just a slight modification to what you posted before. To work with the
18F2431. I haven't done much beyond this with the PCPWM module. Not yet
at least..;o}

HTH

[BigWumpus]

I'm using the 18F2431 too.
And I begun with the PICDEm MC LV board...

It's a great uC ! (UART, I2C, fast AD, 3-times PWM...)
I use it as a PI(D)-Controller for a BLDC-Motor.
And I use it for his fast AD-Converters in a CR-Tuning-Box.

The Quadrature-Encoder isn't very strange ... the whole business with this chip is to use the right timers for the right tasks and use the right prescalers !!

;-)

[Bruce]

Yeah this one is a nifty series PIC for sure. Sampling 4 x A/D inputs at once is
a very handy feature.

See this post http://www.picbasic.co.uk/forum/showthread.php?t=6768

I just received a few samples of the new USB 18F2553. 12-bit A/D on this
one is nice, but the 18F2431 is still my favorite. Now, if I can just find more
time to play with it..;o}

[hell_pk]

Thanks a lot Bruce.
I just want to get started with PPWM and then build my own code for brushless DC motor control.
Thanks for your code although its in assembly.i will figure it out.

[Bruce]

Here's the BASIC equivalent commands to the right of the assembly version.

FOR Duty = 50 TO $500 STEP 4
        ASM
        bsf   PWMCON1,UDIS    ; PWMCON1.1 = 1
        MOVFF _Duty,PDC0L     ; PDCOL = Duty.LowByte
        MOVFF _Duty+1,PDC0H   ; PDC0H = Duty.HighByte
        MOVFF _Duty,PDC1L     ; PDC1L = Duty.LowByte
        MOVFF _Duty+1,PDC1H   ; PDC1H = Duty.HighByte
        MOVFF _Duty,PDC2L     ; PDC2L = Duty.LowByte
        MOVFF _Duty+1,PDC2H   ; PDC2H = Duty.HighByte
        ;MOVFF _Duty,PDC3L    ; PDC3L = Duty.LowByte
        ;MOVFF _Duty+1,PDC3H  ; PDC3H = Duty.HighByte
        bcf   PWMCON1,UDIS    ; PWMCON1.1 = 0
        ENDASM
        PAUSE 50
    NEXT Duty

bsf PWMCON1,UDIS just sets bit 1 in PWMCON1. bcf PWMCON1,UDIS then
clears the UDIS bit.

MOVFF is move file to file.

MOVFF _Duty,PDC0L moves the low byte of Duty into file register PDC0L.

MOVFF _Duty+1, PDC0H moves the high byte of Duty into file register PDC0H.

Placing the underscore before the _Duty variable allows you to access the
variable declared in BASIC with assembler.

So the BASIC version would look like this;

  FOR Duty = 50 TO $500 STEP 4
    PWMCON1.1 = 1
    PDC0L = Duty.LowByte
    PDC0H = Duty.HighByte
    PDC1L = Duty.LowByte
    PDC1H = Duty.HighByte
    PDC2L = Duty.LowByte
    PDC2L = Duty.HighByte
    PDC3L = Duty.LowByte
    PDC3H = Duty.HighByte
    PWMCON1.1 = 0
    PAUSE 50
  NEXT Duty

  FOR Duty = $500 TO 50 STEP-4
    PWMCON1.1 = 1
    PDC0L = Duty.LowByte
    PDC0H = Duty.HighByte
    PDC1L = Duty.LowByte
    PDC1H = Duty.HighByte
    PDC2L = Duty.LowByte
    PDC2L = Duty.HighByte
    PDC3L = Duty.LowByte
    PDC3H = Duty.HighByte
    PWMCON1.1 = 0
    PAUSE 50
  NEXT Duty

[NatureTech]

Bruce,

That's a super start to a beginner like me.

But,i gotta some problem with the PWM Period value.I mean how to find the values for .. say...a PIC18F4431 running at OSC 20 , wish to set base period 19.5KHZ.How to find this using equation 17-1 ( i use this equ since it's free running mode here).Apart from that , how to calculate the min & max value of dutycycle?.Dohh...it's really bothering me no matter how many times i try it.

Could you guide me how to do this.I am a bit confused.The rest seems yeeha as it's taught in "863 MTR" from Microchip.


Regards.