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PICList Thread
'DTMF Recognition/generation with PIC only'
2000\03\11@173754 by Andrew T Kelley

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HI!

How can I recognize/generate a DTMF tone with only a pic?

Thanks very much!
Andrew
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2000\03\11@174411 by David Covick

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Andrew,

I've done something similar (but not DTMF) and have used an A/D within the
PIC to capture the signal and determine it's "approximate" frequency by a
math routine.  This PIC is the 8-pin 12C671 (as an example).

David


{Original Message removed}

2000\03\11@180114 by picxpert

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You can get theory on it from
http://www.dattalo.com/technical/theory/dtmf.html

Didn't there used to be some DTMF code there, Mr. Dattalo?

-Randy Glenn
spam_OUTPICxpertTakeThisOuTspamtechie.com - http://i.am/PICxpert

Ineptitude is a sure indicator of intellect.
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{Original Message removed}

2000\03\11@181602 by Scott Dattalo

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On Sat, 11 Mar 2000, Randy Glenn wrote:

> You can get theory on it from
> http://www.dattalo.com/technical/theory/dtmf.html
>
> Didn't there used to be some DTMF code there, Mr. Dattalo?

No.

I had written some MATLAB/Octave programs to do some of the theoretical
analysis, but I never did make the code public. The PIC code I did write
was for a contract and consequently can't be disclosed. Prior to the
contract, I did have a version that didn't work too well. A few people saw
it (and the MATLAB code), but I really don't want to release it. Since
the contract I had thought of another way to implement the algorithm.
Unfortunately, it takes a considerable amount of time to thoroughly test
this. BTW, the algorithm - which is described on the web page, is public.
It is only the code (written by me) that implements it that is not public.

But, in all honesty I'd recommend getting a DTMF decoder IC. The only
reason to implement this is if cost or space is a really critical issue.

Scott

2000\03\11@191739 by Andrew T Kelley

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<snip>
> But, in all honesty I'd recommend getting a DTMF decoder IC. The
> only reason to implement this is if cost or space is a really critical
> issue.

Decoders are not available from digikey or I wouldn't be asking this
question.  Decoders *WERE* available but are now 'no longer carried' or
'obsolete'. Also space is a *small* issue.

Thanks,
Andrew

> Scott

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YOU'RE PAYING TOO MUCH FOR THE INTERNET!
Juno now offers FREE Internet Access!
Try it today - there's no risk!  For your FREE software, visit:
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2000\03\11@205405 by Dan Michaels

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>----- Original Message -----
>From: Andrew T Kelley <k_andrewspamKILLspamJUNO.COM>
>To: <.....PICLISTKILLspamspam.....MITVMA.MIT.EDU>
>Sent: Saturday, March 11, 2000 2:30 PM
>Subject: DTMF Recognition/generation with PIC only
>
>> HI!
>> How can I recognize/generate a DTMF tone with only a pic?
>>
>> Thanks very much!
>> Andrew
>>

If you are really intent on doing it with a PIC, you might checkout
something called "Goertzel's algorithm", but I don't know where
you can get code for it. It's a real tone filtering algorithm, and
not something that counts zero-crossings, etc. Requires analog A/D
input.

I once did some calculations and decided a PIC running at 4 Mhz
could do Goertzel just fast enough to meet the DTMF minimum speed
requirements - better if running 10-20 Mhz.

However, then I just went ahead and used a $5 MC145436 chip anyway.
[what can I say?]. BTW, I still have a few of the '436 chips left
that I could part with for less than what I paid for them [did I
say that?].

regards,
- Dan Michaels
Oricom Technologies
http://www.sni.net/~oricom
==========================

2000\03\12@012029 by Bill Pierce

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<x-flowed>Scenix has a Virtual Peripheral to do this for the SX parts.
http://www.scenix.com.

Bill

>From: Dan Michaels <EraseMEoricomspam_OUTspamTakeThisOuTLYNX.SNI.NET>
>Reply-To: pic microcontroller discussion list <PICLISTspamspam_OUTMITVMA.MIT.EDU>
>To: @spam@PICLISTKILLspamspamMITVMA.MIT.EDU
>Subject: Re: DTMF Recognition/generation with PIC only
>Date: Sat, 11 Mar 2000 18:52:38 -0700
>
> >{Original Message removed}

2000\03\12@201419 by Wagner Lipnharski

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Harris CD22204 DTMF Receiver, $4.00 at Gerber.

Andrew T Kelley wrote:
> Decoders are not available from digikey or I wouldn't be asking this
> question.  Decoders *WERE* available but are now 'no longer carried' or
> 'obsolete'. Also space is a *small* issue.

2000\03\12@211722 by Charles L. Stackhouse

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>Harris CD22204 DTMF Receiver, $4.00 at Gerber.

Andrew T Kelley wrote:
> Decoders are not available from digikey or I wouldn't be asking this
> question.  Decoders *WERE* available but are now 'no longer carried' or
> 'obsolete'. Also space is a *small* issue.


Motorola MC145436P  DTMF decoder (pin for pin compatible with SSI 204
chip) - $2.49 !! at JDR(http://www.jdr.com)

See ARRL 1990 Handbook (p. 34-3) for a simple DTMF decoder project that
works very well and has good noise immunity - MC145436P and 4514 (4 bit
latch/ 4-16 decoder) are the only chips. PC boards available from FAR
Circuits at  http://www.cl.ais.net/farcir/  ("SIMPLE DTMF DECODER USING THE
SSI202 IC WITH BCD & DECADE OUTPUT FOR LED's" and he might well have copies
of the original article. I have built 2 and there are probably thousands in
use by hams.

Charlie WA2IPZ
Burley, Idaho
KILLspamcstackKILLspamspamsafelink.net

2000\03\13@041652 by Dr. Imre Bartfai
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Hi,
AFAIK the MT8870 is generally available. It does a wonder, really!

Regards,
Imre


On Sat, 11 Mar 2000, Andrew T Kelley wrote:

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