I need a simple circuit design based on the MT8880. See datasheet and screen shot from datasheet attached. You don't have to worry about micro controller connection, the most important part is this:
The <DTMF Output> should be in such a way, that it can be connected to an android mic input (via headset audio jack) - so the signal needs to be correct impedance and level for mic input. Vice versa the <DTMF Input> should be designed in such a way, that it can be connected to android audio out (via headset audio jack as well).
The circuit can be designed in any way - even a foto of drawing would be acceptable!
8 freelancers are bidding on average €133 for this job
I DO NOT OUTSOURCE I have been a freelancer for the past 8 years, I believe that my experience and skill in this background will prove to be of great help to you. Contact me to discuss more on the details