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Topic: CM8880 DTMF Transreciever Interfacing (Read 928 times) previous topic - next topic

dakudiv

Hi,
Following program is for decoding CM8880 DTMF Receiver Transmitter.
Decoding part is being done correctly.
Routine for dialing using CM8880 has not been tested.

Attached circuit has been referred for prototyping.

Issues I am facing in interfacing with CM8880..

I do not have a transformer to connect in the circuit .So to suppress the DC from the incoming telephone line a resistance (10K)and capacitor (100 nf) has been placed on (CM8880 IN- line).
Without the transformer the decoder section works perfectly fine but it's not able to generate DTMF Tone output.

So if anybody has implemented CM8880 w/o using transformer kindly share with me .Also do let me know if the code works on your board too.

Ty

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