1 Continuous MCPWM at a time

[barneyfrance]

Hello guys,

I am currently trying to use the MCPWM on my pic18F4331 (20 MHZ external oscillator)
I am trying to control a brushless dc motor with 12 IGBT's so I need 12 outputs. Amongst these 6 outputs, I want to use the PMW0 to PMW5 one at a time. Because I get inputs from my encoder, telling me when to switch which PWM.

I have been searching the forum, and it helped me a lot, I have used the code described here : http://www.picbasic.co.uk/forum/show...3820#post43820
I'm looking over the datasheet, i'm still pretty new at this but, i can't figure out how to use one pwm at a time. (I only need one duty cycle for all of them)

Thank you very much in advance for your answers..

[mark_s]

Barney,

Have a look at this thread. One of the guys discovered that the "ovdcond" register can be used to switch
the pwms on and off.

http://www.picbasic.co.uk/forum/show...hlight=ovdcond

[barneyfrance]

Hello mark_s,

Thank you for your quick reply, it is exactly what I was looking for.

I Know need to adjust my pwm duty cycle with a potentiometer 1K on AN0.
Is 1K enough ?

Can someone help me to understand the process with that A/D module ?
I'm not sure i'm understanding quite well the process.

[barneyfrance]

Hello, it's me again.
I went through the registers in the datasheet and used the example of Bruce here : http://www.picbasic.co.uk/forum/showthread.php?t=6768
I tried to understand and apply it to my case, but it's not doing anything my duty cycle ?

Thank you in advance for your help, it'd be really appreciated

Duty VAR Word

TRISA  = %11111111
TRISB  = %00000000
TRISC  = %00000010
TRISD  = %00000000
TRISE  = %00000000 

 ' Analog setup
    ' Single shot, single channel, Group A is taken and converted, A/D converter enabled 
    ADCON0 = %00000001
    
    ' 
    ADCON1 = %00010000
    
    ADCON2 = %11001111   ' Right justified, 24 Tad, Frc
    ADCON3 = 0           ' Disable all triggers
    ADCHS = 0            ' Channel select for AN0
    ANSEL0 = %00000001   ' AN0 analog input, rest digital
    
    

PORTB = 0
PORTD = 0 ' clear port


PTCON0=$00 'timebase
PTPERL=$A0 ' $01A0 = 12kHz
PTPERH=$01

PWMCON0 = %01001111
PWMCON1=%00000001
DTCON=$00
OVDCOND = %00000000
OVDCONS = %00000000 'PORT PINS

PDC0L=$00
PDC0H=$00
PDC1L=$00
PDC1H=$00
PDC2L=$00
PDC2H=$00

PDC0L = Duty.LowByte
PDC0H = Duty.HighByte

PDC1L = Duty.LowByte
PDC1H = Duty.HighByte

PDC2L = Duty.LowByte
PDC2H = Duty.HighByte


PTCON1=%10000000


 
GoTo Main

Main:
    ADCON0.1 = 1         ' Start the conversion
    While ADCON0.1=1     ' Wait for it to complete
    Wend

    Duty.HighByte = ADRESH ' get result from AN0
    Duty.LowByte = ADRESL  ' Increment buffer pointer

    OVDCOND = %00000010 'PWM on PWM1

[Bruce]

Is this all of your code? If it is, can you explain what you "think" should be happening, and how you know it's not?

Folks here love to help, but what you're showing here doesn't indicate even a modest amount of homework..;o)

[cncmachineguy]

If it is the entire code, maybe looping back to main would help? Otherwise I agree with Bruce.