DTMF decoder

[Ayax Mayagoitia]

Hello does anybody knows how to decode DTMF signals
I want to do it in software not in hardware.
Thanks
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This message was ported from CCS's old forum
Original Post ID: 144515972

[John Yaron]

:=Hello does anybody knows how to decode DTMF signals
:=I want to do it in software not in hardware.
:=Thanks

I always liked referencing algo's targetting the
analog devices ADSP2105.

<a href="http://www.analog.com/Analog_Root/static/library/dspManuals/pdf/Volume1/Chapter_14.pdf" TARGET="_blank">http://www.analog.com/Analog_Root/static/library/dspManuals/pdf/Volume1/Chapter_14.pdf</a>

modified Goertzel ... I implemented them and results were
superior talk-off and sensitivity. It may be possible
to implement on uChip's DSP... but, never looked at it.

DSP experience is a plus when doing these routines.
___________________________
This message was ported from CCS's old forum
Original Post ID: 144516085

[Ayax Mayagoitia]

:=:=Hello does anybody knows how to decode DTMF signals
:=:=I want to do it in software not in hardware.
:=:=Thanks
:=
:=I always liked referencing algo's targetting the
:= analog devices ADSP2105.
:=
:= <a href="http://www.analog.com/Analog_Root/static/library/dspManuals/pdf/Volume1/Chapter_14.pdf" TARGET="_blank"> <a href="http://www.analog.com/Analog_Root/static/library/dspManuals/pdf/Volume1/Chapter_14.pdf" TARGET="_blank">http://www.analog.com/Analog_Root/static/library/dspManuals/pdf/Volume1/Chapter_14.pdf</a></a>
:=
:=modified Goertzel ... I implemented them and results were
:= superior talk-off and sensitivity. It may be possible
:= to implement on uChip's DSP... but, never looked at it.
:=
:=DSP experience is a plus when doing these routines.


Thanks John but I mean using the PIC to decode DTMF signals
something like the DTMFIN command on basic stamp.Feeding
the DTMF tone to pic pin and decode this information.
Thanks again for the info.
___________________________
This message was ported from CCS's old forum
Original Post ID: 144516103

[PCM programmer]

:=Thanks John but I mean using the PIC to decode DTMF signals
:=something like the DTMFIN command on basic stamp.Feeding
:=the DTMF tone to pic pin and decode this information.
----------------------------------------------------------

I did a web search and could not find anything on a DTMFIN
command for the basic stamp.

Here is a link to the BS2 manual. It only lists DTMFOUT.
<a href="http://www.parallax.com/Downloads/Documentation/bs/BASIC_Stamp_Manual_v2-0.pdf" TARGET="_blank">http://www.parallax.com/Downloads/Documentation/bs/BASIC_Stamp_Manual_v2-0.pdf</a>

___________________________
This message was ported from CCS's old forum
Original Post ID: 144516109

[John Yaron]

:=:=:=Hello does anybody knows how to decode DTMF signals
:=:=:=I want to do it in software not in hardware.
:=:=:=Thanks
:=:=
:=:=I always liked referencing algo's targetting the
:=:= analog devices ADSP2105.
:=:=
:=:= <a href="http://www.analog.com/Analog_Root/static/library/dspManuals/pdf/Volume1/Chapter_14.pdf" TARGET="_blank"> <a href="http://www.analog.com/Analog_Root/static/library/dspManuals/pdf/Volume1/Chapter_14.pdf" TARGET="_blank"> <a href="http://www.analog.com/Analog_Root/static/library/dspManuals/pdf/Volume1/Chapter_14.pdf" TARGET="_blank">http://www.analog.com/Analog_Root/static/library/dspManuals/pdf/Volume1/Chapter_14.pdf</a></a></a>
:=:=
:=:=modified Goertzel ... I implemented them and results were
:=:= superior talk-off and sensitivity. It may be possible
:=:= to implement on uChip's DSP... but, never looked at it.
:=:=
:=:=DSP experience is a plus when doing these routines.
:=
:=
:=Thanks John but I mean using the PIC to decode DTMF signals
:=something like the DTMFIN command on basic stamp.Feeding
:=the DTMF tone to pic pin and decode this information.
:=Thanks again for the info.

Running a decent decoder on a PIC would be something to see.
I'm somewhat skeptical due to it's limited horsepower.
... unless there was no voiced speech on the channel
(i.e. vowels). If not, be prepared to handle the false
digit detects while speech is occurring. I've got some
years under my belt in the telephone sector (about 10) and
have seen some pretty mickey-mouse decoders cause many
people some bad headaches. Sometimes using dedicated silicon
is worth the effort in the long run.
___________________________
This message was ported from CCS's old forum
Original Post ID: 144516121

[Ayax Mayagoitia]

:=:=Thanks John but I mean using the PIC to decode DTMF signals
:=:=something like the DTMFIN command on basic stamp.Feeding
:=:=the DTMF tone to pic pin and decode this information.
:=----------------------------------------------------------
:=
:=I did a web search and could not find anything on a DTMFIN
:=command for the basic stamp.
:=
:=Here is a link to the BS2 manual. It only lists DTMFOUT.
:= <a href="http://www.parallax.com/Downloads/Documentation/bs/BASIC_Stamp_Manual_v2-0.pdf" TARGET="_blank"> <a href="http://www.parallax.com/Downloads/Documentation/bs/BASIC_Stamp_Manual_v2-0.pdf" TARGET="_blank">http://www.parallax.com/Downloads/Documentation/bs/BASIC_Stamp_Manual_v2-0.pdf</a></a>

Thanks guys
I appreciate your replies... Great !
Probably I got confussed somehow as John said this task might not be easy for the PIC. I think I should use a hardware solution instead. I did that many years back ..I should brouse
my files and remember how I did it.
Thanks again !




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This message was ported from CCS's old forum
Original Post ID: 144516362

[subi]

Hello everybody,

I would like to ask, that somebody has a good CCS program to detect DTMF please share it and to do upload it.

Sorry for my English.

Thank you for you help and kindness.
Subi

[asmboy]

i'll make this simple:

there Are ways to count squared up input frequencies - ONE AT A TIME
but DTMF is TWO frequencies blended together.

That is a DSP operation - NOT a pic coding undertaking that you
will find already done for you -

enjoy yourself thinking of how to do it - but i personally would use one of several external very nice chips to do the heavy lifting - and
then harvest the results on your pic.


best o luck 2 U

[temtronic]

You could try 'Google' !


the very first hit(of a few hundred) found a complete article using a 16F877 as a 'remote DTMF' decoder....tones in---->LCD of the keys pressed.

sorry I didn't save the link, but then Google is easy to use.

[subi]

Dear Everybody,

Thank you for your advice and I have really found DTMF decoder program code in the WEB but unfortunately it is in asm. So I would like to get it in CCS if it is possible. My English knowledge is not to good so I have not understood the Goetzer description. This was the reason what I ask it for you.

Sorry for my trouble....

Thank you

Subi

[sahu77]

[bkamen]

[ckielstra]

Techniques for DTMF decoding can be band-pass filters or Discrete Fourier Transformation, but using Google I just stumbled upon a third method that is very lightweight to implement in software: read chapter 10.10 from EMBEDDED SYSTEMS PROGRAMMING WITH THE PIC16F877
It uses the fact that DTMF is specified with very tight 2% tolerances. By sampling at clever chosen time intervals and some simple arithmetic the frequencies can be determined.

The example code is in PIC assembly but using the #asm/#endasm directives you can mix assembly and C code in your program.

[temtronic]

Another option, though I haven't read the entire site....I have my own battles today...


http://www.romanblack.com/DTMF/DTMF_alg.htm

Has C code for DTMF decoding, very impressive what a small PIC can do !
You'll have to convert to CCS C but it can be done.

The other option is to use the ASM program as a 'subroutine' from your C program. Again, it can be done, though might be harder depending on what level you cut code at.

[asmboy]

well now i'm very interested to hear how you do with this.

I wonder is your DTMF for "in" or "out" - of band signaling ?

if "in band" please share your experience with issues like:

baseband noise rejection
talk-up
false detection
amplitude susceptibility