Subject:
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Re: "Servo" Driver for NQC
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Newsgroups:
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lugnet.robotics
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Date:
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Sat, 2 Feb 2002 17:09:55 GMT
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Original-From:
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Steve Baker <SJBAKER1@AIRMAILsaynotospam.NET>
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Reply-To:
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sjbaker1@airmail.STOPSPAMMERSnet
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Viewed:
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830 times
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Matthias Jetleb wrote:
>
> > But it doesn't need to. The 'power' settings built into the RCX firmware
> > are already using pulse-width modulation to adjust the amount of power
> > the motor delivers.
>
> Yes, but only one of 8 settings (why not all 256??? I don't understand
> why they limited this). Sometimes only 8 settings doesn't give you
> enough finesse.
That was explained earlier. They are using an 8 bit number to store
the *pattern* of the modulation. With 8 bits, there are only 8 different
ratios of 1's to 0's - and one of those is to have no power at all. Hence
there are seven power levels.
I suppose they could have used a byte to count the duration of the on period
and the duration of the off period - but for some reason they chose not to
implement it that way. Without analysing the software in a lot more detail
than I'd care to do, it's hard to know whether that was a good design decision
or a bad one.
Personally, I doubt that you could really tell the difference between power
levels that are just one step apart - so it's probably irrelevent.
----------------------------- Steve Baker -------------------------------
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Message is in Reply To:
 | | Re: "Servo" Driver for NQC
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| (...) Yes, but only one of 8 settings (why not all 256??? I don't understand why they limited this). Sometimes only 8 settings doesn't give you enough finesse. Matthias Jetleb (22 years ago, 2-Feb-02, to lugnet.robotics)
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