#include //Create software serial object to communicate with SIM800L In the first diagram, a 1200mAh Li-Po battery is connected. We’ve included two different wiring diagrams to show you how it’s done. The only thing left to do is connect the power supply to the module. A 10K resistor between SIM800L’s Rx and Arduino’s D2, and a 20K resistor between SIM800L’s Rx and GND, will work just fine. There are numerous ways to accomplish this, but the simplest is to use a resistor divider. Therefore, the Tx signal from the Arduino must be stepped down to 3.3V.

Simply put, the SIM800L module’s Rx pin is not 5V tolerant. We cannot connect the module’s Rx pin directly to the Arduino’s digital pin because Arduino UNO has a 5V logic level and the SIM800L module has a 3.3V logic level. Next, connect the module’s Tx pin to the Arduino’s digital pin #3, as we will be communicating with the module via software UART. To begin, connect the antenna to the module and insert a micro SIM card into the socket. Now that you are familiar with the SIM800L module, it is time to connect it to Arduino! Wiring a SIM800L GSM Module to an Arduino You can connect a speaker to these two pins directly.

SPK± is a differential speaker interface. You can connect an external electret microphone to these two pins directly. Pulling it LOW for approximately 50 ms will wake up the module. Pulling it HIGH causes the module to enter sleep mode, disabling serial communication. It is by default HIGH and can be configured to go LOW when a call or SMS is received.ĭTR pin controls the sleep mode. This is basically the ‘interrupt-out’ pin from the module. TxD (Transmitter) pin transmits data from the module to the microcontroller. This pin is auto-baud so the baud rate at which you send the “AT” command after reset is the baud rate used.

RxD (Receiver) pin is used to send commands to the module. If you got the module in an absolutely bad space, pull this pin LOW for 100ms to perform a hard reset. It doesn’t even run on 3.3 V! Use a Li-Po battery or a DC-DC buck converter instead. Keep in mind that the SIM800L chip has an operating voltage range of 3.4 V to 4.4 V, so connecting this module to the Arduino’s 5V output is probably going to cause damage to the module.

NET pin is where you can solder the helical antenna that comes with the module.

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