DTMF Decoder Interfacing with Arduino UNO and Serial Monitor

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DTMF is as acronym for Dual Tone Multi-frequency Signalling. It is used in telecommunication signalling, basically it is a signal that is sent to the switching centre (phone company) when the phones keys are pressed. DTMF is also called as Multi Frequency Signalling because for each key you press two tones of specific frequencies are generated. This is done so that a voice cannot imitate the tones. One tone is generated from a high frequency group and the other from a low frequency group with duration of 100ms. In all there are 16 DTMF tones but currently only 12 tones are being used in our phones. At the switching centre, an electronics circuit called DTMF decoder is used to decode or to know the value of the pressed key. The DTMF decoder gives 4-bit signal as the output.

In this project, we will learn How to interface a DTMF Decoder with Arduino UNO and Serial Monitor. Here, we will find the value of the key pressed in a mobile through DTMF Decoder and we will display the value of the pressed key in Serial Monitor of Arduion Sketch Software. In this project, we will use two mobiles, one will be connected with the DTMF circuit and another will be used to call the mobile attached with DTMF circuit. The Mobile attached with DTMF circuit will be kept in auto-answering mode. The DTMF decoder can decode DTMF signal of both mobiles. The user will press different keys of the mobile attached with the DTMF circuit and the DTMF Decoder will decode the DTMF signal of mobile. After decoding the DTMF signal, the DTMF decoder will output a 4-bit value. Arduino UNO will read this 4-bit output of DTMF decoder and will process it to find the value of the pressed key. After processing the DTMF output, the Arduino UNO will display the value of the pressed key in the Serial Monitor. Now, we will press different keys of the attached mobile and we will see the changes in Serial Monitor. After doing the above process, call the mobile attached with DTMF circuit from the other mobile. After the Call is being received, press keys from the calling mobile and see the changes in the Serial Monitor.