PWM object not enough control

grasshopper

Any one know of a way that i can modify the PWM object for better control? Instead of 0 - 100 I am looking for something that I can adjust from 0 - 10_00 or even better if possible.
Some things i thought of changing were below

PUB SetDuty(counts)
   if (counts < 0)
     counts := 0
   if (counts > 10_000)
     counts := 10_000
   sDuty :=counts*sPeriod/10_000
   

Any ideas if this is the right aproach?

Phil Pilgrim (PhiPi)

If you use the PWM_x8 object, the resolution is settable by a CONstant in the object itself. Just make sure it's a multiple of four.

-Phil

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T Chap

If you look at pwmasm, you can set the duty like below(this is set to duty 1000) as this does work.

PUB SetDuty(counts)
   if (counts < 0)
     counts := 0
   if (counts > 1000)                       '100 = 100 duty, 1000 = 1000 duty, etc
     counts := 1000                         '100 = 100 duty  
   sDuty :=counts*sPeriod/1000      '100 = 100 duty

Post Edited (TChapman) : 12/18/2008 8:45:25 PM GMT

Paul Rowntree

Hi Grasshopper;
Oddly enough, I was just working on that for a motor driver. I use the PWM to drive the base of a TIP120, and it gives a very nice ramp from about 10 Hz up to 200 Hz, apparently linear in duty cycle. This is taken from other files on the Parallax site, I claim no originality or cleverness in the modifications. It is here buzzing away beside me as I type!

Note that I changes the start method as well for my own style. I also added some parentheses in the driver to avoid overflows.

Cheers!

grasshopper

Yea,

Thanks all. I think I got it working better now. Using the modified code works.