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'DTMF decoder'
1998\08\03@003957 by ghfkj D hum

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I 'm pretty new to PIC programming and what to make a DUAL  TONE
MULTI-FREQUENCY decoder. It should preferably be handheld and have a fair
memory. Can any body give me advice,pointers, or anything else for a
newbie?

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1998\08\03@014304 by Mike Ghormley

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ghfkj D hum wrote:

> I 'm pretty new to PIC programming and what to make a DUAL  TONE
> MULTI-FREQUENCY decoder. It should preferably be handheld and have a fair
> memory. Can any body give me advice,pointers, or anything else for a
> newbie?

If you want a hardware solution (a dedicated chip) you might look at the Holtek
HT9170 part at:
       http://www.digikey.com/D.DKS$336411H73157
$2.63 in onesies.

If a software solution is your quest, I am not aware of any software encoders,
but there are a couple of software DTMF dialer/encoders at:
       http://www.brouhaha.com/~eric/pic/dtmf.html
and
       http://www.rt66.com/dthomas/pic/dtmf.txt

Also, there used to be a DTMF FAQ at:
       www.paranoia.com/~filipg/LINK/F_DTMF.html
but I have not visited it in a while.

Not exactly what you wanted but perhaps there is a start in there somewhere.
Good luck!

Michael

*************************************************************************
When the way of the Tao is forgotten, kindness and ethics must be taught.
Men must learn to pretend to be wise and good.  --  Lao Tzu
*************************************************************************

1998\08\03@034428 by Dr. Imre Bartfai

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Hi,

try to use the dedicated MT8870 IC. It is a DTMF decoder, with a 4-bit
parallel output, and a strobe line. I use the strobe line to control the
PIC INTR0 line. The AC characteristic of that IC is great, about 100 mV or
so drives it already. It requires an 3.58 MHz XTAL and the oscillation can
be used also to drive a PIC.

Imre


On Wed, 5 Aug 1998, ghfkj D hum wrote:

{Quote hidden}

1998\08\03@114558 by Scott Dattalo

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On Sun, 2 Aug 1998, Mike Ghormley wrote:

> ghfkj D hum wrote:
>
> > I 'm pretty new to PIC programming and what to make a DUAL  TONE
> > MULTI-FREQUENCY decoder. It should preferably be handheld and have a fair
> > memory. Can any body give me advice,pointers, or anything else for a
> > newbie?
>

<snip>

> If a software solution is your quest, I am not aware of any software encoders,

Here's the theory for a software decoder algorithm.

http://www.interstice.com/~sdattalo/technical/theory/dtmf.html

Except for a few caveats which I can't disclose, this algorithm works.

Scott

> *************************************************************************
> When the way of the Tao is forgotten, kindness and ethics must be taught.
> Men must learn to pretend to be wise and good.  --  Lao Tzu
> *************************************************************************

1998\08\03@184747 by : Cassie Carstens

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Hi
Agree. Do you want the 17K PDF?
Cassie

> try to use the dedicated MT8870 IC. It is a DTMF decoder, with a 4-bit
> parallel output, and a strobe line. I use the strobe line to control the
> PIC INTR0 line. The AC characteristic of that IC is great, about 100 mV or
> so drives it already. It requires an 3.58 MHz XTAL and the oscillation can
> be used also to drive a PIC.
>
> Imre
>
>


'DTMF decoder'
1999\07\13@220610 by Harry Febianto
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Hi,

I have a final project for my college. I plan to detect dtmf signal from

telephone to be decoded. I use PIC 16F84. And I have some
possibilities/theorys. Using interrupt and counter together or counter
only
or ADC 1bit (or 8 bit ADC).

I think I need some literatures, and many thanks if you can give me some

references that I can download. Which one is better for above theorys ?
Or
do you have any advise or some example program ?

Thank you very much for your help.


Best Regards,

Harry Febianto

1999\07\13@231558 by Steve
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I assume that you are trying to do it with signal processing because it's
for school???  If all you want to do is detect the DTMF, you do know there
are chips for that, right!?

-Steve

{Original Message removed}

1999\07\13@235955 by Robert K. Johnson

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YES Try the Mitel MT8870CE. 4 bit binary output, Data Valid, Built in
Filters AND input preamp

At 11:12 PM 7/13/99 -0400, you wrote:
>I assume that you are trying to do it with signal processing because it's
>for school???  If all you want to do is detect the DTMF, you do know there
>are chips for that, right!?
>
>-Steve
>
>{Original Message removed}

1999\07\14@003141 by Steve Ridley

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Hi Harry

If you want to do the DTMF decoding yourself, there was a detailed
discussion about this on the list a while ago. Check the archives on
http://www.i.can't.remember
Can someone help me please.

Steve

{Original Message removed}

1999\07\14@054709 by root

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Hi,

why do not use an MT8870 DTMF decoder IC? It interfaces to the PIC with
4+1 lines. It is superior and cheap.

Here is my $0.02

Imre


On Wed, 14 Jul 1999, Harry Febianto wrote:

{Quote hidden}

1999\07\14@062800 by Mark Willis

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PicList Archives:  http://www.iversoft.com/piclist/ <G>

 Mark

Steve Ridley wrote:
>
> Hi Harry
>
> If you want to do the DTMF decoding yourself, there was a detailed
> discussion about this on the list a while ago. Check the archives on
> http://www.i.can't.remember
> Can someone help me please.
>
> Steve

1999\07\14@121937 by Scott Dattalo

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Harry Febianto wrote:
{Quote hidden}

As others have already said, using a dedicated DTMF decoder IC is the
preferred way to decode DTMF. But..., if you're somewhat demented like
myself then take a look at:


http://www.interstice.com/~sdattalo/technical/theory/dtmf.html

As I've said in previous posts on this subject: this algorithm works
well, but additional analog signal processing is required to make it
robust.

Scott

1999\07\14@130237 by Wagner Lipnharski

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My personal 2 cents for this matter:

The effort to make things like that, using a microcontroller and
software to decode DTMF is 100% valid upon the point of view of learning
things, but for the sake of functionality just use dedicated microchips
to do the job, they were done with much more knowledge and it will saves
your time and money.  It is the same to build up a microcontroler using
TTL discrete chips... imagine the board size and problems...
educationally, or school projects speaking it is fantastic... but that's
all.  There are several DTMF decoders available for less than $2.  Your
school project could be the one to read the chip, display the numbers,
store them, and so on, not the decoding itself...

Wagner

Scott Dattalo wrote:
{Quote hidden}

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