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DTMF ( Touch-Tone ) — Parallax Forums

DTMF ( Touch-Tone )

securemansecureman Posts: 11
edited 2010-11-01 07:17 in Propeller 1
··

·· Is it possible connect a dtmf decoder to the propeller chip !
·· If so how about adding a lcd readout to !






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Doug Smith

Comments

  • w8anw8an Posts: 176
    edited 2010-06-22 22:46
    With something like the HT9172 or the BU8872 DTMF receiver, it would be very simple to do.

    LCD drivers are available at the obex

    Steve
  • eod_punkeod_punk Posts: 146
    edited 2010-06-22 23:04
    Yes it is possible, you can find some old demo code for the 8870 for the BS2 to help you get started. I have a 8880 that I have yet to play with long enough to get working. Adding a LCD to show the read out would be trivial compared to getting the DTMF up and running. If your going to hook it up to your phone line you'll need a 600:600 transformer I believe.

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    There is no problem that can't be solved with a suitable amount of explosives!

    EOD Memorial
  • w8anw8an Posts: 176
    edited 2010-06-23 00:40
    A 600 ohm 1:1 transformer is the simplest way to get audio from the phone line. You can harvest one from most any old computer modem.

    Also it's pretty simple to make an opto-isolator circuit to detect the ring signal.
  • Brian RileyBrian Riley Posts: 626
    edited 2010-06-24 22:32
    eod_punk said...
    Yes it is possible, you can find some old demo code for the 8870 for the BS2 to help you get started.

    The 8870 is the simplest and easiest to work with. You use 5 pins ... a data valid pin and 4 bits of data (0-15 ... digits 0-9, A, B, C, D, *, #) ... loop and monitor the data valid, when it asserts, read the 4 pins. The wonderful thing about the 8870 is that the internal chip firmware does all the work of validating the tone. It doesn't assert data valid until it has 1 second of a clear valid DTMF digit. Now if you are fussy and want to do some of that work yourself it has another that asserts as soon as it gets anything that is vaguely familiar.

    For some reason, 8870's are hard to find in small quantities .. you want to buy a couple of thousand, plenty of offers, but 1, 10, a hundred ... not so easy. I scored a bunch of them a couple of years ago and have been selling them in a 'complete kit' with either a Zarlink MT8870D chip or Clare M8870-01 in PDIP-18 package, color burst crystal, socket, three precision resistors and 2 caps for 5$ plus s/h. My website has the data sheets and a kit schematic. If you are interested it can be found at (scroll down about 1/3rd of the way)

    www.wulfden.org/TheShoppe/accessories.shtml

    I also have some BS2 code I can send you for the 8870. I had the 8870 hooked to a ham radio HT and was using it for remote control. It was amazing how well it pulled the tones out of some moderately crappy noise.

    cheers ... BBR

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    cheers ... brian riley, n1bq, underhill center, vermont
    The Shoppe at Wulfden
    www.wulfden.org/TheShoppe/
    www.wulfden.org/TheShoppe/prop/ - Propeller Products
    www.wulfden.org/TheShoppe/k107/ - Serial LCD Display Gear
  • eod_punkeod_punk Posts: 146
    edited 2010-06-24 22:45
    I'd be interested in see your BS2 code, maybe you could post in the BS2 forum.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    There is no problem that can't be solved with a suitable amount of explosives!

    EOD Memorial
  • securemansecureman Posts: 11
    edited 2010-07-12 09:09
    ·sorry it took so long to post this reply, But i have been dealing with health problems

    ·thanks for the help !

    ·signed Up all Night !·(Ha, Ha)


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    Doug Smith
  • bambinobambino Posts: 789
    edited 2010-07-13 15:51
    I have a device that is meant to be used with a phone line where you have to dial 9 to get an outside line. For years I have wanted to build or find a device that would allow me to use this with a normal house line. Anyone have any ideas on how the two chips mentioned in this thread could do this?
  • securemansecureman Posts: 11
    edited 2010-07-14 02:34
    ·I perfer to use the tel-tone M927 Short Data Below

    · 40pins, Tip and Ring Connect to Pins 1 and 40

    · All formats output Direct to a microcontroller

    · Has anyone used this Chip and if so do you have any code for the Propeller Or·· the·· BS2

    ·

    ·

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    Doug Smith
  • Brian CarpenterBrian Carpenter Posts: 728
    edited 2010-10-10 23:08
    Brian Riley wrote: »
    The 8870 is the simplest and easiest to work with. You use 5 pins ... a data valid pin and 4 bits of data (0-15 ... digits 0-9, A, B, C, D, *, #) ... loop and monitor the data valid, when it asserts, read the 4 pins. The wonderful thing about the 8870 is that the internal chip firmware does all the work of validating the tone. It doesn't assert data valid until it has 1 second of a clear valid DTMF digit. Now if you are fussy and want to do some of that work yourself it has another that asserts as soon as it gets anything that is vaguely familiar.

    Brian, if i understand correctly, i can feed the output from my HT ham radio into this device of yours and read the DTMF codes with the propeller and then have my prop drive outputs like honk the horn or flash the lights? This is what i want to be able to accomplish. Thank you for the reply in advance.
  • kwinnkwinn Posts: 8,697
    edited 2010-10-11 08:07
    Yes, the 8870 can decode the dtmf tones from your ham radio provided they are not badly distorted, buried in noise and the tones level is in range. Having the prop read the 5 pins out of the 8870 (4 data and valid tones) and driving up to 16 outputs based on the 4 bit binary number (0 - F hex) is very simple.
  • Brian CarpenterBrian Carpenter Posts: 728
    edited 2010-10-11 21:40
    Kwinn,
    do i feed this right out on my audio jack? do i need anything special between it and the jack?
  • kwinnkwinn Posts: 8,697
    edited 2010-10-12 06:54
    You may need a voltage divider to set the input signal level. Nothing other than that should be required. See the attached data sheet for a typical circuit and complete info on the chip.
  • Brian CarpenterBrian Carpenter Posts: 728
    edited 2010-10-29 21:42
    two more questions about this chip. I have one i am wiring up now. Can this chip operate at 3.3v? If not, what circuitry needs to be added between it and the Prop? Also, what do i need to check to determine if i need a voltage divider circuit?

    Thanks again all.
  • kwinnkwinn Posts: 8,697
    edited 2010-10-30 08:28
    It is a 5V chip (4.75 - 5.25V) so you will need resistors between the prop pins and the 8870. 2.2K or a bit higher should work. Data sheet says input signal should be between 27.5 to 869mV RMS so I would shoot for about 500mV RMS or 700mV P-P.
  • eod_punkeod_punk Posts: 146
    edited 2010-10-31 06:52
    I'm playing with a MT8880 currently as well, and here's what I've learned. It will not operate at 3.3v, so you must use 5v. The MT8880 will work just fine with 3.3v going into the 4 bit data bus for writing to the registers.

    I used the octal buffer that Parallax sells in between the Prop and the MT8880.http://www.parallax.com/StoreSearchResults/tabid/768/List/0/SortField/4/ProductID/653/Default.aspx?txtSearch=octal+buffer It has two groups of 4 buffer pins. I used one set as data from the prop to the MT8880, and the other set for data from the MT8880 to the Prop. I also used a PN2222 (NPN) transistor to choose which buffer was active(Thanks Chris Savage!). Friday I finished up the wiring and was able to receive DTMF tones into the prop from the MT8880 and have the number press displayed in the serial terminal.
  • Brian CarpenterBrian Carpenter Posts: 728
    edited 2010-11-01 07:17
    Kwinn,
    I used some 2k6 resistors that i had in the pile. connected it all up to the prop and it works great. Thanks for the help.
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