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'FFT with 16C84?'
1997\02\10@150813 by icebyte

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Hello all.

We are thinking of building a simple audio-spectrum-analyzer.
The output would consist of a LED-matrix (7 bars, 8 LEDs / bar).

Is this possible with the C84 (or F84 :) and an A/D-conv + FFT in
software?

Maybe another pic would be more suitable (with an A/D build in)?
At the time we lack an eprom-programmer though.

Any suggestions welcome.

/Henrik & David

1997\02\10@194344 by Steve Hardy

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> From: Henrik Lewander <spam_OUTicebyteTakeThisOuTspamas-if.com>
> Hello all.
>
> We are thinking of building a simple audio-spectrum-analyzer.
> The output would consist of a LED-matrix (7 bars, 8 LEDs / bar).
>
> Is this possible with the C84 (or F84 :) and an A/D-conv + FFT in
> software?
>
> Maybe another pic would be more suitable (with an A/D build in)?
> At the time we lack an eprom-programmer though.
>
> Any suggestions welcome.
>
> /Henrik & David
>

The short answer is no.  The '84 does not have anywhere near enough
resources to perform real-time FTs.  Even 'touch-tone' decoding
is a challenge.

You are better off using 7 analogue band pass filters and sampling
the output peaks.  This could be done with a MUX input ADC such as
the PIC16C74, or an external unit such as NSC's ADC8017 (16 input).

If this seems like too much hardware, then use a DSP such as TI's
DSP320Cxxx series.  I think some have inbuilt ADCs.

Regards,
SJH
Canberra, Australia

1997\02\11@221352 by John Payson

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> > Is this possible with the C84 (or F84 :) and an A/D-conv + FFT in
> > software?
>
> The short answer is no.  The '84 does not have anywhere near enough
> resources to perform real-time FTs.  Even 'touch-tone' decoding
> is a challenge.
>
> You are better off using 7 analogue band pass filters and sampling
> the output peaks.  This could be done with a MUX input ADC such as
> the PIC16C74, or an external unit such as NSC's ADC8017 (16 input).

With a 16C622 I have managed to do a pretty good job of DTMF detection at
11.0592MHz (looking for all 7 frequencies simultaneously).  If you don't
need terribly good accuracy, a 16C84 may be able to handle the job.


'FFT with 16C84?'
1997\03\11@212053 by mauscaff
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I'm trying to do something like this.
I need to decode 6 tones that came in a combination of 2 ( 1+2, 1+3, ...,
5+6) and i'd like to know if you can help me and if possible show the part
of the code used to decode the DTMF tones.

Thanks, Mauricio

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