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Dead time generation for PWM — Parallax Forums

Dead time generation for PWM

wiebelwiebel Posts: 7
edited 2008-09-24 18:43 in Propeller 1
Hello, i haven't started with the Propeller yet, but after looking into the manual I had a few questions.
As I have been doing some BLDC stuff I have seen the need for some dead time to prevent a shoot-through in half H-Bridges especially for higher currents.
As far as I have seen it the NCO/PWM differential mode (CRTMODE %00101) has a directly inverted B-Pin which, of course, is a nice thing to switch the high and low side of a half bridge but which doesn't contain any dead time, so in this mode one have to provide this externally (rising edge delay). But having this in software would be much more convenient so,
is there any easy way to generate this dead time without having to use an Counter for each of the High- Low-sides?

If this has been answered before you might point me to the right post. - wiebel

Comments

  • evanhevanh Posts: 15,863
    edited 2008-09-21 20:24
    I don't know the answer to your question but it would be easy enough to bit bash it in software instead. One of those advantages of deterministic execution.
  • RinksCustomsRinksCustoms Posts: 531
    edited 2008-09-24 02:02
    not to put to fine a point on it, yes. and there is more than a few ways to go about it. I'm no expert either but you could implement a pinmask or two, add a waitcnt, then NOT the pinmask directly to OUTA, or alternate pinmasks with variable waitcnts in a finite or infinite loop via "cognew"... so i guess that would answer the question. I probably only served to confuse the Smile out of you, sorry. There are a few GURU's on the forums, ask nicely, show them your trying and they can steer you in the right direction. Were all self taught here pretty much, welcome to the forums [noparse]:)[/noparse]

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  • wiebelwiebel Posts: 7
    edited 2008-09-24 18:43
    Thanks for your answers and welcoming. [noparse];)[/noparse]
    I still seem to underestimate the Propellers capabilities.
    I think I'm gonna get one and ask more while trying to implement things.
    The Linux "support" also seems to be working (homespun+pyloader).
    So I just have to decide whether to start with the Starter kit (the book is a nice to have) or the Oled thingie, which leaves me only with 4 Pins, but hey a Oled. [noparse];)[/noparse] -wiebel
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