Hello, guys! I have Arduino mega 2560. The problem is that my phone don't wanna listen to AT commands (for example, Serial1.println("ATDT89162007839;"); .
I used cacharreoelectronico's implementation and code as a base.
But i do not have siemens data cable so i used a telephone line copper wire as connector to the phone's Rx pin, together with connector from power adapter for Siemens.
When i send AT commands to the phone it just turns on screen's background light, thats all. No call is made. When i dial this number from phone manually, it calls.
Same with cacharreoelectronico's example, i don't have phone's Tx connected. The only pins that are used are ground and power connected to power adapter and Rx.
The reason i dont use a bluetooth - it has high power consumption. I must leave this arduino for months during winter with solar battery. And i must have 24/7 opportunity to query it.
I have 1k resistor between Arduino's Tx and phone's Rx, and 2,5k resistor (2,2k+LED) between Tx->Rx and Arduino's ground. I attached Cirquit.jpg for details.
Pin map of my phone: http://pinouts.ru/CellularPhones-P-W/siemens_c55.shtml