Post by thread:DTMF decoder

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? _____________________________________________________________________ You don't need to buy Internet access to use free Internet e-mail. Get completely free e-mail from Juno at http://www.juno.com Or call Juno at (800) 654-JUNO [654-5866]

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 *************************************************************************

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}> 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? > > _____________________________________________________________________ > You don't need to buy Internet access to use free Internet e-mail. > Get completely free e-mail from Juno at http://www.juno.com > Or call Juno at (800) 654-JUNO [654-5866] > >

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 > *************************************************************************

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 > >

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

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}> 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 > >

Harry Febianto wrote: {Quote hidden}> > 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 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

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}> > Harry Febianto wrote: > > > > 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 > > 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