1 Continuous MCPWM at a time

[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.

[Bruce]

Something like this might help so it doesn't drop-off the end and restart from the beginning. It also loads the new duty-cycle values.

PTCON1=%10000000
OVDCOND = %00000010 'PWM on PWM1
 
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
   PDC0L = Duty.LowByte
   PDC0H = Duty.HighByte
   PDC1L = Duty.LowByte
   PDC1H = Duty.HighByte
   PDC2L = Duty.LowByte
   PDC2H = Duty.HighByte
   GoTo Main

It's untested, but should work. I didn't check the A/D part, but it looks ok at a glance.

You might want to insert a PAUSE before the GOTO Main?

[barneyfrance]

Hello,

Thank you very much for your answers guys ! For you that code is nothing but for me it is what I wrote after spending hours on the forum and on the datasheet... trying to understand what i'm writing. So I am sorry if you feel that way..
Bruce, thank you for putting in the right order my code, it is working now but somehow when my potentiometer is at its maximum i'm only able to have 50% duty cycle ? Where does this come from ?

[Bruce]

We're just messing with you when you miss something simple. Don't take any of it personal..

When you forget to loop back to Main it runs off the end and loops back to the start. But that wasn't the only problem.

PCPWM on these can be a bit intimidating. Give this a shot.

DEFINE OSC 20
 
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 = 0 ' timebase
PTPERL = 0 ' ~19.4kHz at 20MHz
PTPERH = 1
PWMCON0 = %01001111
PWMCON1 = %00000001
DTCON = 0
OVDCOND = 0
OVDCONS = 0 
PTCON0 = 0
PTCON1 = %10000000
OVDCOND = %00000010 'PWM on PWM1
 
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
   PDC0L = Duty.LowByte
   PDC0H = Duty.HighByte
   PDC1L = Duty.LowByte
   PDC1H = Duty.HighByte
   PDC2L = Duty.LowByte
   PDC2H = Duty.HighByte
   PAUSE 500
   GoTo Main

All-in-all I would say you're doing pretty darn good just getting started with one of the hardest to use/understand PIC types in this range....

[barneyfrance]

Hi bruce,

Thank you for your quick reply, and yes apparently this chip is pretty complicated but well I do not mind it's challenging.
I have tried your code, changing the register "PTPERH" seems to do changing, I now have around 66% duty cycle.

Now i'm looking at the datasheet of the pic page 187, and I am wondering one thing and maybe it has to do something with my duty cycle problem.
Figure 18-11 shows the duty cycle comparison. Now PTMR(H and L) has 14 bits with 2 reserved for a clock and PDC(H and L) register has 14 bits as well.
However, tell me if I am wrong but the analog digital converter module only operate on 10 bit. Would this be one of the reason ?

If I could figure this out, it'd be amazing.. Thank you again for your help, I really appreciate !

[Bruce]

You're getting the picture..

12kHz you tried before bumped it up over 10-bit resolution. If you're stuck with 10-bit A/D just figure out a frequency with 10-bit resolution.

I think 12kHz worked out to around 10.7-bit, but it was enough to shift it up >10-bits.