In this article we show how to use the SIM800 GSM module and how you make an HTTP-Post request via GPRS. There are many uses such as alarm systems, weather stations, traffic telematics or smarthome applications. The price for the SIM800 module is between 10 and 20 €. On the internet, there is no information about how to make an HTTP request. We have developed a solution with which you can control the SIM800 module with the Arduino. We also show you how to send data to a webserver via HTTP-POST.

Instructions for use

The module is controlled with the Arduino Uno via the software serial connection. The module operates with a voltage between three and four volts. A 3.7 V Li Ion cell or a controllable power supply can be used as power supply. The module can not be supplied with 5 volts! Everything is controlled by AT commands. The wiring between the Arduino and the module takes place directly without any voltage divider or resistors. In order for everything to work, you also need a SIM card as well as the APN and possible access data from the network operator.

Wiring schematic

There are many PINs on the GSM module. The following pins are required: VCC, GND, TX & RX. Ground is connected to the Arduino as well as to the ground of the battery. At the Arduino, the TX line goes to pin 8 and the RX line goes to pin 9. If everything is wired, download the source code for the Arduino board. In the Arduino IDE, all access data are entered at the top. After that, everything should work. The serial monitor shows all error messages.