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'[PIC:] max hardware PWM'
2004\08\21@201821 by Z S

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Fellow members:

     I have bowed down to learning assembly after rather forceful suggestions ;-)  I have calculated the amount of resolution I could get at the top of my range for ADC based PWM (which was 10-250 KHz).  Whoever said that I was going to get crumby resolution was dead right.   At 250KHz the resolution is oh so bad.

     I am asking for suggestions for a higher resolution option for my project (otherwise I'll have to go to analogue, GASP!).  Any suggestions are welcome.



Thanks in advance,



Zack


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2004\08\21@202442 by Dave VanHorn

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>
>      I am asking for suggestions for a higher resolution option for my project (otherwise I'll have to go to analogue, GASP!).  Any suggestions are welcome.

Look into PLL based RF synthesizers.
You can get up through a GHz, in 1-5ish kHz steps, and you can divide that down to get fractional Hz resolution.

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2004\08\21@215244 by Jan-Erik Soderholm

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Z S wrote :

> Fellow members:
>
> I have calculated the amount of
> resolution I could get at the top of my range for ADC based
> PWM (which was 10-250 KHz).  Whoever said that I was going to
> get crumby resolution was dead right.   At 250KHz the
> resolution is oh so bad.
> I am asking for suggestions for a higher resolution
> option for my project (otherwise I'll have to go to analogue,
> GASP!).  Any suggestions are welcome.

Probably something external to the PIC.
Perhaps you could refresh our memory...

The range is 10-250Khz, right ?
In how large steps (resolution) ? 10/1/0.1 Khz ?
How fast has it to change ?
What would the output signal be used for ? (Might look as it
doesn't matter, but it helps understanding the problem/application.)
And, it could also be usefull to know where the input
analog signal comes from.

Regards,
Jan-Erik.

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2004\08\21@231945 by Z S

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Its basically being used as a device to find the resonant frequency of a liquid.  Yes, 10-250KHz is the range, and I would like a pretty good resolution.  1Khz would be good, but .5 or .1 would be better.  The frequency changes can be slow, in fact that might be necessary. The pulsewidth change on the other hand must be quite fast. The input is two potentiometers, one for pulse width and one for frequency.  Or, buttons for the frequency and a pot for the pulse width.  Either way works.  Hope that answers you question, sorry for being vague (I have a tendency to do that).
-Also, on this thread someone mentioned an PLL RF synthesizer for high speed PWM

Jan-Erik Soderholm <spam_OUTjan-erik.soderholmTakeThisOuTspamTELIA.COM> wrote:
Z S wrote :

{Quote hidden}

Probably something external to the PIC.
Perhaps you could refresh our memory...

The range is 10-250Khz, right ?
In how large steps (resolution) ? 10/1/0.1 Khz ?
How fast has it to change ?
What would the output signal be used for ? (Might look as it
doesn't matter, but it helps understanding the problem/application.)
And, it could also be usefull to know where the input
analog signal comes from.

Regards,
Jan-Erik.

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2004\08\22@014620 by Jinx

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This is similar to the recent strobe thread

Variable duty cycle analogue function generator - could be as
basic as a 555 or 4000/7400 - with the PIC as a meter (could
make the control voltages / switch range too)

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