Today I received from Banggood a GSM module based on the SIM800 chip by SIMCom. I’m going to use this module in a future Arduino project that will allow me to remotely control devices. In this article I’ll show you how to test the module.
The SIM800 is a quad-band (850/900/1800/1900MHz) chip and allows to trasmit/receive voice, SMS and data (using the GPRS network).
The small module (about 3x4cm) has the SIM800 chip and most of the components on one side, while on the other side you can find the sim card connector:
I chose to buy the module with an external antenna… in addition to the module you therefore receive the antenna and a short (about 20cm) cable to connect it:
The module is powered with 5V, offers a serial interface and you can control it using AT commands.
It is very important to connect the module to a power supply able to provide up to 2A, otherwise you may face problems on the stability of the GSM connection.
To verify if the module works you can therefore connect it to your PC using a simple USB – serial converter and send the correct AT commands as the manual explains. Be careful to invert the TX and RX pins: the TX pin of your adapter must be connected to the RX pin of the GSM module and viceversa:
The simplest test is to send and receive an SMS. For simplicity first configure the text mode (=1) with the command AT+CMGF=1. The module will answer with the command you send (without the starting AT) followed by OK.
Now you can specify the recipient of the message with the command AT+CMGS=”number“. After having sent the “carriage return” character, the module will send the > prompt, after which you can type the text of the message. End the message with the character 0x1A (CTRL-Z); the module will answer with the command you sent followed by the number of characters in the message (26):
When a new SMS is received, the module sends the +CMTI message. You can read the messages with the AT+CMGL command and you can also specify a filter (for example REC UNREAD, that is all the messages received but not read yet):
The filters available are listed in the manual:
After having verified that the module works, you can now realize a more complex project, for example interfacing it with your Arduino…