===== Rasbperry Pi 3 with GSM module =====

==== Modem ====
It's a generic chinese modem with SIM800C GSM chip, has microphone and audio input.

==== Connection ====

==== Serial port ====

The modem uses a serial port to communicates with you, by default the serial port is redirected to a terminal port, to change it you need to follow this steps in Raspbian 8.0.

Launch raspi-config:
<code>
$ sudo raspi-config
</code>

Select 9. Advanced Options, next A7 Serial, choose no to question "Would you like a login shell to be accessible over serial?". Select Finish button.

We need also to enable UART, follow this steps, edit /boot/config.txt and add or change the next lines:
<code>
enable_uart=1
dtoverlay=pi3-miniuart-bt
</code>

You can follow the same steps with RPi and RPi2 but omitting the "dtoverlay=pi3-miniuart-bt" line.

Restart.

==== minicom and serial port ====
Now you can start to test your modem:
<code>
sudo minicom -b 115200 -o -D /dev/ttyAMA0
</code>

==== References ====
  * https://www.cube-controls.com/2015/11/02/disable-serial-port-terminal-output-on-raspbian/
  * https://kb.op5.com/display/FAQ/HowTo+test+SMS-Modem+using+minicom