DTMF Detection

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DTMF Detection

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Contributor I
Along similar lines, I would like to see code for DFMF detection. Most DTMF decoding IC’s are going away and I’m sure they are being replaced by Micro’s. It would be nice to have a Micro with a hardware DTMF decoder on board but short of that I believe Freescale is missing the boat by not supplying some minimum code for DTMF apps. Maybe they do.
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Contributor IV
hi microjock,
you can try MT8888 from ZARLINK.
They works well with my AW60.
 
Regards,
mingyee
Message Edited by t.dowe on 2009-10-20 01:30 PM
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Contributor I
Thanks for the suggestions. Although never played with one I am familiar with the MT8888 decoder. They are one of the few still being manufactured. I'll check out the C program also. I figured that a DSP would probably end up being the answer. Somewhere, some time back, on some forum someone mentioned that they had personally been involved with developing a DTMF device with a 6805 core. I never heard anymore about it.
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Contributor II
Hi
A long, long time ago i developed hard and software for a computer controlled telephone. The first try was to use a Motorola MPU called HC05F4  (if i remember right). But the F4 was never released and as i heard it was only produced for one customer. So finally i used a HC905B16 and a MT88L85 for the DTMF decoding.

Saluti Joerg

PS. maybe Freescale has somewhat like the HC05F4 (or HC05F12, also used in telephones) in the HC(S)08 technology?


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Contributor I
Well, years ago in their data book Mitsubishi had a 6502 derivative (yea I know I’m showing my age) with a tone decoder on board, if I remember correctly. I tried to get a couple but they just wouldn’t sell to individuals although I had a company name. I figured if they were going to be that snobbish then I didn’t want to do business with them. Many moons ago I designed a board and built a decoder using Signetics 567 phase locked loop IC’s along with the glue logic. I never mounted enough of them to do the whole 16 buttons but I had enough to do what I need to do.
It’s probably not worth the software hassle when you can still get IC’s like the MT8888.
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Specialist III
Hello,
 
The CML Microcircuits CMX865A Telecom signalling device might be another possibility, for a hardware solution.  This seems to be quite a recent device, and has 3.3V operation.
 
On previous occasions, I had successfully used the MC145436, but I presume this is one of the devices that is no longer available.
 
Regards,
Mac

Message Edited by bigmac on 2007-04-1808:39 AM

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Contributor I
Thanks for all the help. I’m still toying with this idea. Not sure how I want approach it. I’ll check into the CMX865A Telecom device. I haven’t heard of that one. I’m pretty sure the MC145436 is one of several no longer made.
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Contributor I
I can attest to the goodness of the CMX867 chip. I'm using it in my current project, and I'm surprised at its sensitivity and tolerance for decoding in the presence of distortion and interfering audio. It's also a good DTMF generator, has call progress tone detection, a TELCO line driver, and is an FSK modem on top of all that. Haven't done any FSK with it yet but that's the next step.

And give yourself plenty of quiet time to read their data sheet.
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Contributor II
Hi  microjock
if you need some DTMF ic's i can you offer some MT88L89AS (i found them in a drawer). If helpful i can extract the software for this device from the old project.

Saluti Joerg

PS: I think in this case a private mail would be helpful!

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Contributor I

Hi Joerg - I was doing some research as I am seeking to locate MT88L85AN  ( I can also take MT88L85AN1 or MT88L85ANR1)

I was wondering if you'd happen to have any of those in your drawer as well?

Feel free to reach out to me at samir.elmessaoudi@sourceability.com

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Senior Contributor II
Hi,

Detection by only MCUs seems to be mostly done via DSP because of computation of the Goertzel algorithm used.

I found a nice Silabs Application Notes on the C8051. But embedded C is embedded C...
Up to you to see if you have enough space on your MCU to use the same algorithm or not.
Instead of doing calculation, you could keep tables in flash memory.

Generating DTMF is quite easy with PWM modules, detecting is more difficult.

Cheers,
Alban.
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