“Like playing tic-tac-toe, just call your Arduino and play.
It’s been a while that I wanted to build a basic mobile device/phone with Arduino and SIM900.
I finally got the time to play with it, and after few sleepless nights I came up with this great setup and code.
I was able to detect an incoming call and play a ring tone using good old rtttl – which was a tricky thing on its own.
Get and make a call.
And the most cool feature, that was suggested by a good friend, is activating the DTMF detection.
Which in return allows me to detect when people punch in numbers on their keypad. In this example I show how I toggle state of 4 LED.”