Connecting the Shield With Arduino UNO

If you are using an Arduino Uno, follow the instructions below. If you are using an Arduino Mega, Mega ADK, or Leonardo, you must follow other instructions( see our next post ). The GSM shield is not currently supported on the Due.
To use the shield, you'll need to insert a SIM card into the holder. Slide the metal bracket away from the edge of the shield and lift the cradle up. 

Insert the SIM in the plastic holder so the metal contacts are facing the shield, with the notch of the card at the top of the bracket. 

Slide the SIM all the way into the bracket 

Push the SIM to the board and slide the metal bracket towards the edge of the shield to lock it in place. 

Once the SIM is inserted, mount it on top of an Arduino board. 

To upload sketches to the board, connect it to your computer with a USB cable and upload your sketch with the Arduino IDE. Once the sketch has been uploaded, you can disconnect the board from your computer and power it with an external power supply. 

Digital pins 2, 3 and 7 are reserved for communication between the Arduino and modem and cannot be used by your sketches. Communication between the moden and Arduino is handled by the Software Serial library on pins 2 and 3. Pin 7 is used for the modem reset.
When the yellow status LED turns on, it means the modem is powered, and you can try connecting to the network.
Developer versions of the GSM shield required you to press press the Power button on the shield for a few moments to turn the modem on. If you have an early version of the shield, and it does not turn on automatically, you can solder a jumper to the CTRL/D7 pad on the reverse side of the board, and it will turn on when an attached Arduino receives power. 

The shield should work in any area with GSM coverage. Before buying the shield please verify that there is this kind of coverage where you plan to use it.

GSM Library

The GSM library handles communication between Arduino and the GSM shield. The majority of functions are for managing data, voice, and SMS communication. There are also a number of utilities for managing information about the modem and the SIM card's PIN.