Need pwm!

Robofreak · 2007-12-24 15:01

Hello all!
I just need someone to give me a link or something for a SPIN program/technique to·generate PWM. I'm relatively new to the Propeller (I built my programming board at the end of November) and I don't know of any function to generate PWM signals.

MERRY CHRISTMAS!

Thanks!
Austin

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Austin Bowen,

Robo-freak.com

"One must watch out for mechanics. They start out with a sewing machine, and end up with the atomic bomb" - A quote from someone that I saw on Addall.com

Post Edited (Robofreak) : 12/24/2007 3:06:25 PM GMT

deSilva · 2007-12-24 15:23

No, not again!
---
Austin, you can't be serious! Among the last 100 postings 20 had to do with PWM, giving explanations, links, etc. etc..

Post Edited (deSilva) : 12/24/2007 3:28:25 PM GMT

Robofreak · 2007-12-24 16:32

... Wow... Okay, I'll go try to find a link somewhere.

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Austin Bowen,

Robo-freak.com

"One must watch out for mechanics. They start out with a sewing machine, and end up with the atomic bomb" - A quote from someone that I saw on Addall.com

DynamoBen · 2007-12-24 16:38

I know how you feel I was new here once too and the search function on the forum isn't the best.

Try here:

http://forums.parallax.com/showthread.php?p=685997

Also there are a couple of objects in the object exchange that might help.

Post Edited (DynamoBen) : 12/24/2007 5:06:31 PM GMT

Ale · 2007-12-24 17:39

deSilva. how about suggesting to make a sticky post about PWM ?, with your threads of course

Frohe Festtage.

In the front page there are at least 2 threads about PWM:

http://forums.parallax.com/showthread.php?p=696627
http://forums.parallax.com/showthread.php?p=696682
http://forums.parallax.com/showthread.php?p=667521
http://forums.parallax.com/showthread.php?p=696702

There are more [noparse]:)[/noparse]

Post Edited (Ale) : 12/24/2007 5:45:27 PM GMT

deSilva · 2007-12-24 17:52

I have thought of the WIKI... It is quite extraordinary what a few of our comrades have accomplished here in such short a time.

Robofreak · 2007-12-24 18:12

Thanks for all the links!

Perhaps I'm wrong, but isn't PWM the action of simply bringing high, then bringing low, in this case, a pin, repeatedly (or vice versa)?

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Austin Bowen,

Robo-freak.com

"One must watch out for mechanics. They start out with a sewing machine, and end up with the atomic bomb" - A quote from someone that I saw on Addall.com

Ale · 2007-12-24 18:13

yes, with different widths...

Robofreak · 2007-12-24 18:15

Okay, well, I designed a simple program to toggle pin 22 on and off, trying to get it to dim an LED, but there was no visable dimming to me... Is there something else I need to get it to dim and not just blink on and off rapidly? A capacitor perhaps?

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Austin Bowen,

Robo-freak.com

"One must watch out for mechanics. They start out with a sewing machine, and end up with the atomic bomb" - A quote from someone that I saw on Addall.com

deSilva · 2007-12-24 18:57

*sigh* I started the wiki page - finally propeller.wikispaces.com/PWM

Ale · 2007-12-24 19:22

Robofreak: Try with smaller duty cycles (with ratio) for the high pulse. If you integrate the signal for -inf to +inf will give you the resulting slice of "on time", well that was simple

The page at wikipedia en.wikipedia.org/wiki/Pulse-width_Modulation has a nice explanation

BEEP · 2007-12-24 23:24

CON                                                       
  _clkmode = xtal1 + pll16x
  _xinfreq = 5_000_000
  
PUB DimLed | duty, on, off

  duty := 50 ' set duty cycle, 1-99
  
  on   := 8_000 * duty  
  off  := 800_000 - on

  dira[noparse][[/noparse] 22 ] := 1 
  
  repeat
    outa[noparse][[/noparse] 22 ] := 1
    waitcnt(on+cnt)
    outa[noparse][[/noparse] 22 ] := 0
    waitcnt(off+cnt)

CON                                                       
  _clkmode = xtal1 + pll16x
  _xinfreq = 5_000_000
  
PUB DimLed | duty, on, off

  dira[noparse][[/noparse] 22 ] := 1 

  repeat
    repeat duty from 1 to 99
      on   := 8_000 * duty  
      off  := 800_000 - on
      outa[noparse][[/noparse] 22 ] := 1
      waitcnt(on+cnt)
      outa[noparse][[/noparse] 22 ] := 0
      waitcnt(off+cnt)
    repeat duty from 99 to 1
      on   := 8_000 * duty  
      off  := 800_000 - on   
      outa[noparse][[/noparse] 22 ] := 1
      waitcnt(on+cnt)
      outa[noparse][[/noparse] 22 ] := 0
      waitcnt(off+cnt)

Wikipedia - PWM
Wikipedia - Duty cycle

Post Edited (BEEP) : 12/25/2007 4:03:43 AM GMT

Need pwm!

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