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DTMF Generator with Arduino

Hello mate,
I have telephone with only receiver and no keypad. So, i need to generate DTMF tones to dial the number. Is it possible for me to generate a DTMF tone generator by programming arduino with the frequencies and attaching speaker to it? Also, how can i club two tones which are required to be sent at a single moment?
Thank You. 

anuragkanase (author) 3 years ago
Thanks Steve.
I had an idea of MT8870 which is decoder.
Can you name the generator chip? I think AT94 is for DTMF generator. But, most of these chips are not available.
Try 5089 for a generator, the newer 8880 is transceiver part, so it can do both jobs

Steve
Try this  MT8880  circuit out for size.
Pull it out of a dead phone, perhaps..
I don't know how easy it is to generate precise timing with the Arduino. The frequencies need to be correct to within 2% to be recognized by the phone company. It can be tricky to generate the two tones simultaneously in software via "bit banging".
Use a DTMF tone generator chip - cheaper and simpler than an arduino.
MT8870 is a pretty good device The MT8880 is a decoder as well.
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