The data is sent to the module or received from the module though UART interface. And the power source should be able to deliver a peak current of 2A. The UART interface is established as shown in figure. The ground of controller and module must be connected for voltage reference.
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Learn how to send and receive SMS and how to make and receive phone calls with Arduino. You can use the preceding links or go directly to MakerAdvisor. By GSM we mean 2G. Otherwise, if something goes wrong, you may need to pay a huge bill for hundreds of SMS text messages sent by mistake. The shield uses the original SIM card size, not micro or nano. If you have micro or nano you may consider getting a SIM card size adapter. The easiest way to do this, is to insert the SIM card in your smartphone and turn off the pin lock in the phone security settings.
Getting the right power supply The shield has a DC socket for power as shown in figure below. Next to the power jack there is a toggle switch to select the power source. Next to the toggle switch on the board, there is an arrow indicating the toggle position to use an external power supply — move the toggle switch to use the external power supply as shown above.
To power up the shield, it is advisable to use a 5V power supply that can provide 2A as the one shown below. It can also be powered with 9V 1A, or 12V 1A. You can find the right power adapter for this shield here.
Make sure you select the model with 5V and 2A. The figure below shows the shield most important components on the board that you need to pay attention to. Make sure you select the external power source with the toggle switch next to the DC jack. See how to do that in the Automatically turn on the shield section, after the code examples. For that, you need an FTDI programmer as the one shown in figure below. You can get an FTDI programmer like this here.
Write AT at the box highlighted in red and then press enter. See figure below. Connecting the Shield to Arduino Connect the shield to the Arduino as shown in the schematics below.
Then, at the following line you can edit the text you want to send. After uploading, wait 20 seconds for the shield to establish communication. The SMS is shown on the Arduino serial monitor — baud rate: You read the chars using the SIM Making a phone call To make a phone call, upload the following code to your Arduino. The idea is that you use the ATH command when an event is triggered. For example, connect a push button to the Arduino, that when pressed sends the ATH command to hang up the phone.
Answering incoming phone calls The following code answers incoming calls. Try repeating the process by changing the TX with the RX pins. Also check if you have selected the software serial by placing the jumper cap on the appropriate place on the serial selector. However, if you need to change the shield baud rate, you can send the following AT command to change it to or other appropriate baud rate.
You can apply the concepts learned in this tutorial to build your own projects to communicate over a cell network. We have other projects that use GSM, check them below:.
Guide to SIM900 GSM GPRS Shield with Arduino