what is dtmf and how to interface MT8870 with AVR microcontroller

It is acronym for Dual Tone Multi-Frequency, also known as Touch Tone.
It is a method, used by the telephone system to communicate the pressed
keys when dialing. Each key represents a digit or a character and
generates two distinct tones.

The MT8870 is a compact DTMF receiver integrating both the band split filter and digital encoder functions. The filter section uses switched capacitor techniques for high and low group filters, the decoder uses digital counting techniques to detect and decode all 16 DTMF tone-pairs into a 4-bit code.
The MT8870 monolithic DTMF receiver offers small size, low power consumption and high performance.

dtmf circuit diagram

Its architecture consist of a band split filter section, which separates the high and low group tones, followed by a digital counting section which verifies the frequency and duration of the received tones before passing the corresponding code to the output bus.
The MT8870 IC i.e. DTMF decoder IC is to be connected in our circuit for decoding the DTMF tones transmitted by the DTMF devices like our mobile phone key-pad tones. It will connected with the +ve output pin of the mobile headphones.

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• Low power consumption
• Internal gain setting amplifier
• Adjustable guard time
• Central office quality
• Power-down mode
• Inhibit mode
• Backward compatible with MT8870

interfacing of atmega and mt8870

About the author

Abhay Kalmegh

Hey Guys, I’m Abhay Kalmegh, I’m a Electronics hobbyest and digital marketing nut – it’s my career, hobby, and passion.

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