DTMF shield adds touchtones to the Arduino

DTMF shield adds touchtones to the Arduino

Collin Schulz of the Twin Cities wrote in with a fun project he’s working on: a DTMF shield.

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.

Download Collin’s Eagle files and data sheets from his website.

6 thoughts on “DTMF shield adds touchtones to the Arduino

  1. John Park says:

    This is like a dream from my phreaker youth! I remember wanting a pin register sooo bad.

  2. John Park says:

    I meant “pen” register. So you could log all the outgoing numbers on a line. Radio Shack inadvertently sold one that printed out on a roll of paper for $99.

  3. cowgirl says:

    Back in the day, if you had perfect pitch, or wanted to spend the time comparing tones, you could figure out the digits being output/input from/into a telephone line. Or you could build a circuit board to do it for you… if you knew how. I’ve never been that great with electronics engineering and stuff like that, so it’s cool to see phreaking-handy equipment on the mainstream market and to see people putting the blue prints for such equipment out there.

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My interests include writing, electronics, RPGs, scifi, hackers & hackerspaces, 3D printing, building sets & toys. @johnbaichtal nerdage.net

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