DTMF Shield

This is the working prototype. The eagle files have some minor changes made to it. Fixed some mistakes and re-positioned a few parts.
This one is for the phreakers of the past.
A simple Arduino shield to decode DTMF tones using an audio input.
It can easily be hooked up to a cell phone or radio.
The shield uses an MT8870 to decode the audio and outputs BCD to
a 74LS145 BCD to Decimal chip. It also uses a CD4543 BCD to 7 segment
to display the number. The 74LS145 gives a logic low on one of
the ten output pins depending on what number is decoded.
The board also gives output pins for BCD that can be wired direct to the arduino
for more options. The idea came from the desire to use a ham radio to control an
arduino. Some searching led me to razorconcepts.net and my discovery of the MT8870.
I built the first version of the board and had to fix some mistakes I made.
It works great. Now I gotta get a video of it.
You can download the Eagle Files and data sheets


24 responses

  1. Pingback: DTMF shield adds touchtones to the Arduino | Daring Minds.Com

  2. David Robertson

    Well you could make it also hjave the ability to generate DTMF tones and have 2 hooked up together over the phone line…

    June 26, 2010 at 1:23 pm

  3. Pingback: DTMF shield adds touchtones to the Arduino | All my RSS

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  5. Pingback: DTMF shield adds touchtones to the Arduino | SquareCows

  6. Sean

    So, when’s the Arduino Repeater Controller going to be ready for operation?

    COR, real time clock, ptt relay board. A few more building blocks and someone’s probably gonna do it!

    June 27, 2010 at 11:36 am

  7. Andy

    I like this project. Do you have any updates to it or sample Arduino code for interfacing with the shield?

    March 23, 2011 at 9:56 pm

    • I really should update it with a video or something. There is no sample code because it acts more like a button, or a bunch of buttons rather than anything requiring special code. Using jumper wires you connect the outputs for numbers 1-9 to any digital pin on the Arduino and use basic code to read the pin and do something when the pin is low. Its an easy long distance way to remotely control an input using a phone or ham radio as the remote.

      March 24, 2011 at 5:50 pm

  8. Bill

    Great project. Didn’t see the electrolytic capacitor in the parts list – whats the appropriate part to use?


    April 11, 2011 at 7:19 am

    • Sorry, Ill have to add that to the parts list. I used a 330uf but you can use some other value if you have one laying around. Its really only there for power filtering.

      April 15, 2011 at 8:04 pm

  9. Pingback: DTMF shield aimed at ham controlled Arduino - Hack a Day

  10. Pretty cool! I’m working on something similar but not for amateur radio work. Instead I have a Western Electric 1D2 pay phone. I’ve seen a lot of mods for the phone but I don’t want to modify mine.

    Instead I want to interface it to an arduino and some audio interface hardware. I already have the chips that generate precise phone system tones (RBT, busy, reorder, dialtone, etc)

    But I want the DTMF side to decode the dialed number and match it to valid NPA/NXX, do timing for call cutoff, etc.

    April 17, 2011 at 12:46 pm

  11. Pingback: DTMF shield aimed at ham controlled Arduino « Black Hat Security

  12. Pingback: DTMF shield aimed at ham controlled Arduino | House of Mods

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  15. alfredo

    great proyect,
    I built one and dosen´t work……… where i can get the arduino sketch?

    February 27, 2012 at 11:24 am

    • The arduino sketch depends on what you want to do with it. The DTMF shield acts more like a button or multiple buttons. The arduino monitors its io pins for an input the same way you would code it to monitor for a button.

      March 12, 2012 at 8:01 am

  16. Pingback: tapeDuino — the concept.

  17. Richard

    Dude, are you interested is selling me one?
    I love arduinos, and this thing is perfect!
    It is much easier to deal with than breadboarding all those components, or interfacing displays to already available kits.
    (also having a board house make PCB’s is outside of my budget)

    March 13, 2012 at 1:34 am

    • I currently only have the one prototype. I can see what it will cost for a complete kit and also for just the printed PCB by its self. What would be an acceptable price on a kit? If I did just the PCB it would probably be about $10 shipped within the US.

      March 13, 2012 at 12:19 pm

  18. MedicTech

    Great job!!!
    I successfully got the 8870 circuit working with my HAM radio audio output, and have the normal BCD output. I was going to put that into a 4028(like the razor site) then into the Arduino, but was wondering if I can delete the 4028 and let it do the BCD converter work. I also would want the Arduino to activate an output after a 4 digit DTMF code is input. I have some of that code made, but an stuck on how to not use the 4028 to keep things smaller..Any ideas?.. Thank you for the time…:-)

    May 11, 2012 at 8:52 am

  19. Great work Collin,

    I would also be very interested in PCB or kit 🙂

    June 16, 2012 at 11:53 am

  20. Pingback: Arduino Shield (modül) Listesi 3 | Elektronik Hobi

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