Using MT8870 DTMF Decoder With Arduino




DTMF DECODERS Are used to detect DTMF TONES Genrated by mobile phone DTMF Keypad.
In this project we are going to decode the DTMF Tones into 4bit Output and this output is given to the arduino which detects the keypress and displays it on LCD

Teacher Notes

Teachers! Did you use this instructable in your classroom?
Add a Teacher Note to share how you incorporated it into your lesson.

Step 1: Components Used

The components that I have used are easily available locally in most of the cities or you can also buy it online

Step 2: Circuit Diagram

Use the above Circuit Diagram and build the circuit.You can change it according to your need

Step 3: Giving DTMF Input to Circuit

The input is given by a mobile phone with a 3.5mm jack which provides the DTMF signals to MT8870 decoder

Step 4: Programming the Arduino

I used USBasp to program arduino u directly program it using usb it is better to use usbasp if you are building the circuit on breadboard

Step 5: Arduino Code

Use the code to program arduino
it uses hex codes for numbers pressed on dialpad of mobile

The Hex Codes For Keypress Are As Follows
1 = 0x01
2 = 0x02
3 = 0x03
4 = 0x04
5 = 0x05
6 = 0x06
7 = 0x07
8 = 0x08
9 = 0x09
0 = 0x0A
# = 0x0C

Step 6: Getting Output on LCD

The decoded key shown on a LCD Module In this picture the # key is pressed on mobile phone and it is also shown on LCD Module

Be the First to Share


    • Made with Math Contest

      Made with Math Contest
    • Multi-Discipline Contest

      Multi-Discipline Contest
    • Robotics Contest

      Robotics Contest

    12 Discussions

    tanu shradhali

    Question 1 year ago on Introduction

    if we wanna to interface to dtmf and arduino .so will be the requremeny libraries


    2 years ago


    Very nice project. But I would like to ask if it is possible to add a sequence at startup, where you should "login" first then give commands to the arduino.

    This way will be safer in use this project!

    Thanks a lot.


    2 years ago

    My bad - theres a perfect image in the zipped files I just wasn't smart enough to look.


    2 years ago

    Is it possible to get a clearer image of the circuit layout. I can't quite read it but i really want to build it.



    4 years ago on Introduction

    hello sir plz tell me what type arduino use and what the process to burn the program in it.


    4 years ago

    it available in Arduino IDE to Compile .


    4 years ago

    Pin is function for Atmel microcontroller which reads the state of a specific pin

    C Means The PortC Of Microcontroller
    its the analog input port of Arduino the function pin reads the state of portC or Analog port


    4 years ago on Introduction

    Can u pls guide me what is PINC and the program is compiling with this. In Which module the PINC variable available ?


    4 years ago

    If You Like My Projects
    Like My Facebook Page