Interfacing SIM 800l GSM Module with Arduino

Global System for Mobile Communication (GSM) is a mobile communication modem. It was created to describe the protocols for second-generation (2G) digital cellular networks used by mobile phones and is now the default global standard for mobile communications. And in this tutorial, i am using SIM 800l Module because it is very tiny and easy to use.

Note: Use a micro sim card and it must have a load.

What Will I Learn?

This tutorial aims to:

Interface SIM 800l GSM Module with Arduino
Send message using GSM Module

Software Requirements

Arduino IDE

Hardware Requirements

Arduino Uno
SIM 800l GSM Module
Connecting Wires

Difficulty

Basic

Tutorial Contents

Step 1: Physical Connection of SIM 800l GSM Module to Arduino Uno

Circuit developed using fritzing

Connect the following:

GSM Module	Arduino Uno
5VIN	5V
GND	GND
SIM_TXD	RX0 or pin 0
SIM RXD	TX0 or pin 1
GND	GND

Insert the micro sim card to the GSM Module

Step 2: Software Connection

Connect the USB Cable from Arduino Uno to a PC/Laptop
Open your Arduino IDE
Change your board to Arduino Uno: Go to Tools > Board: > Arduino/Genuino Uno
Also, change the Port settings: Go to Tools > Port: > COM6 (Arduino/ Genuino Uno)

Step 3: The Arduino Code

GSM Module uses the AT Commands this instructions are used to control modems. AT is a short term for ATtention. There are different commands to perform different tasks using the GSM module. GSM modems and mobile phones support AT commands set that is specific to the GSM technology, which includes SMS-related commands like AT+CMGS (Send SMS message), AT+CMSS (Send SMS message from storage), AT+CMGL (List SMS messages) and AT+CMGR (Read SMS messages). Read more.

Code inside the setup function, the code to run once.

void setup() {
}

First, initialize the baud rate of the GSM Module

Serial.begin(9600);

Second, \r will start the message and followed by 1 second delay everytime we use an AT command.

  Serial.print("\r");
  delay(1000);

Third, set the GSM Module in Text Mode

  Serial.print("AT+CMGF=1\r");  
  delay(1000);

Fourth, input the number to which you want to send the sms with country code

  Serial.print("AT+CMGS=\"+639xxxxxxxxxx\"\r");  //replace x with the mobile number you want to send the message.
  delay(1000);

Fifth, input the message you want to send.

  Serial.print("This is a test message using GSM Module with Arduino.\r");
  delay(1000);

Then, to end the SMS content it is identified with CTRL+Z symbol. The ASCII value of this CTRL+Z is 26. So we need to send a char(26) to GSM module using this line

  Serial.println((char)26);
  delay(1000);

And lastly, to read the message with the correct format we need to write this hex values.

  Serial.write(0x1A);
  Serial.write(0x0D);
  Serial.write(0x0A);
  delay(1000);

We leave the loop function empty because we have nothing to do after the setup

void loop() {
}

Copy the code, compile it and click the check button to Verify or just simply press Ctrl+R
And check the dialog box below that contains the message if it has error
If no error, then upload the program, just click the arrow-sign or just simply press Ctrl+U

Note: Before uploading the program disconnect the pins 0 and 1 or the TX and RX in Arduino Uno so that it would not give an error message. And just re-connect after uploading.

This is the screenshot of the message sent from the GSM Module