Interfacing GSM Module with Arduino

interfacing gsm module with arduino

Summary

If you're looking to interface a SIM900A GSM module with an Arduino to send and receive SMS, this blog has got you covered!

Learn about the components you'll need, how to set up the connection between the GSM module and the Arduino, and even get some sample Arduino code to get you started.

With this informative guide, you'll be sending and receiving SMS messages in no time!

Introduction

The Arduino platform is one of the most popular microcontrollers available. Combining it with a GSM module can provide numerous project possibilities such as home security, remote vehicle monitoring and control systems, tracking packages and even running solar energy projects.

Interfacing GSM Module with Arduino

Interfacing an Arduino with a GSM module gives users access to send and receive data through text messages – making any project carriable remotely over cellular networks virtually anywhere in the world!

Interfacing a GSM module to Arduino has never been easier before - giving anyone needing advanced communication capabilities limitless opportunities beyond their imagination!

SIM900A is a GSM module used to connect devices like Arduino to the mobile network, similar to how your smartphone does.

This allows the device to access features such as SMS and mobile networks through GPRS.

In this guide, we will be primarily be focusing on how you can interface SIM900A to give your microcontroller the capability to send SMS messages.

Interfacing GSM Module with Arduino

How to use SIM900A?

SIM900A will typically be available in modules with breakout pins for easy interfacing along with connectors for SIM cards, antennas and a few more extra features.

For this guide, we will be using the AE GSM SIM900A module.

It has features such as direct

  • UART pinout
  • SPI pinout
  • RS232 connector, for connecting the module to PC
  • Support for external antenna (comes with one antenna)
  • SIM slot to add in SIM card
  • 12V external DC power jack 
AE GSM SIM900A module

Components Required to Interface GSM Module with Arduino

Connection Setup of GSM Module with Arduino

 

Interfacing GSM Module with Arduino

1. First, we will need to insert the SIM card onto the SIM card tray on the GSM module and lock it.

2. Connect the external antenna to the module, if not done already.

3. Make the following connections between your Arduino and the GSM module.

Arduino Uno  GSM Module
D9 Tx
D10 Rx
GND GND

      3. We won’t be connecting VCC from the GSM module to the Arduino since the GSM module will be directly powered by the 12V supply we plug into the barrel jack. But we will connect GNDs to make the ground plane common between the two devices.

      4. Once the connections are done, you can power on the GSM module by plugging in your external 12V DC Jack.

      5. The onboard Network LED will initially blink rapidly. After a few minutes, the blinking should slow down to a steady pace. This means the GSM module has successfully been registered on the mobile network and is ready to be used.

      Arduino Code to Send and Receive SMS with GSM Module:

      
      #include 
      
      SoftwareSerial Sim(9, 10);
      
       
      
      void setup()
      
      {
      
        Sim.begin(9600);                            // Setting the baud rate of Sim Module  
      
        Serial.begin(9600);                         // Setting the baud rate of Serial Monitor (Arduino)
      
        delay(100);
      
      }
      
       
      
      void loop()
      
      {
      
        if (Serial.available()>0)
      
         switch(Serial.read())                      // Read data given in Serial Monitor
      
        {
      
          case 's':                                 // If data is 's', goto SendMessage() function
      
            SendMessage();
      
            break;
      
          case 'r':                                 // If data is 'r', goto ReceiveMessage() function
      
            ReceiveMessage();
      
            break;
      
        }
      
       
      
       if (Sim.available()>0)
      
         Serial.write(Sim.read());                  // If SIM module sends messages, print it to Serial monitor
      
      }
      
       
      
       void SendMessage()
      
      {
      
        Sim.println("AT+CMGF=1");                    // Sets the Sim Module in send SMS mode
      
        delay(1000);                                 // Delay of 1 second
      
        Sim.println("AT+CMGS=\"+91xxxxxxxxxx\"\r");  // Replace x with mobile number
      
        delay(1000);                                 // Delay of 1 second
      
        Sim.println("I am SMS from Sim Module");     // Type in the SMS text you want to send
      
        delay(100);                                  // Delay of 0.1 second
      
        Sim.println((char)26);                       // ASCII code of CTRL+Z (to exit out)
      
        delay(1000);                                 // Delay of 1 second
      
      }
      
       
      
       void ReceiveMessage()
      
      {
      
        Sim.println("AT+CNMI=2,2,0,0,0");            // AT Command to receive a live SMS
      
        delay(1000);                                 // Delay of 1 second
      
       }
      

      To upload the code to your Arduino, follow the steps below:

      Step 1: Open Arduino IDE
      Step 2: Copy paste the same code into your IDE
      Step 3: Change the phone number and the message you would like to send to the required values
      Step 4: Connect your Arduino to your PC
      Step 5: Select the Board as “Arduino Uno” under Tools
      Step 6: Select the correct COM port under Tools
      Step 7: Click on upload

      After uploading is done, open the Serial Monitor and set baud rate to 9600.

      The above sketch we have uploaded has a feature to both send and receive SMS. To send SMS, send the character ‘s’ in ther Serial Monitor.

      The Arduino will programmatically send a text SMS with the message and the phone number you have provided. Note, this may take a few seconds depending on the range and network connectivity

      To receive SMSs, you can set the GSM module to listen for SMS by sending the character ‘r’.

      The GSM module will be set to listen mode and check for any SMSs every 1 second. If the SMS arrives, the GSM module will print the contents of the message to the Serial Monitor.

      Also, read our blog on Buzzer Arduino detailing step by step guide about how to use the buzzer with your Arduino board.

      Conclusion

      The GSM module can add an extra superpower for your Arduino and other microcontroller projects by giving it access to the extensive mobile network.

      These modules can be added to controllers to enable IoT like functions in areas without reliable access to a network or internet, by programmatically sending in updates and commands through SMS functions.

      For example, the Arduino can be programmed to turn on an irrigation pump if it receives a message to do so through the GSM module, giving you the ability to control your irrigation fields through your phone from anywhere in the world. 

      It can also be programmed to send in periodic updates via SMS of various environmental parameters, allowing you to better manage the entire system


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      Please do check out other blog posts about Interfacing ACS712 with Arduino , Arduino Interfacing with Ultrasonic Sensor , LED Interfacing with Arduino , Interfacing MAX30100 Pulse Oximeter with Arduino , IR Sensor Interfacing with Arduino , How to connect ZMPT101B to Arduino and  How to use Buzzer with Arduino.

       

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      Frequently Asked Questions

      1. How can I receive SMS using GSM module with Arduino?

      You can receive SMS by setting the GSM module to a specific state using this AT command below

      AT+CNMI=2,2,0,0,0

      The AT command can also be given to the module programmatically as per our example above

      2. Which GSM module is better for Arduino?

      Ans: All the most common GSM modules work with Arduino without any issues. The differentiating factor between each type of module are the feature sets they each offer.

      3. Is GSM module a microcontroller?

      A GSM module can be connected to a microcontroller for multiple functions, but it's not itself a microcontroller. It's also possible to operate the GSM module without a microcontroller by utilizing the AT command mode.

      4. What is the use of GSM module in Arduino?

      The GSM module can be coupled with an Arduino board for internet connectivity, sending and receiving SMS messages, and making voice calls via the GSM library. The module acts as a GSM modem that links to a PCB, which produces a variety of signals, such as TTL output. When integrated with an Arduino board, the GSM module can extend the capabilities of microcontroller projects by granting them mobile network connectivity.

      5. Is GSM module part of IoT?

      The GSM module is a significant component of IoT. This network technology, called GSM or Global System for Mobile Communications, is commonly utilized in IoT applications because of its cellular structure's simplicity and low complexity. It enables the creation of IoT devices that can send data to a web server from anywhere in the world. Moreover, there are Low Power Wide Area technologies like EC-GSM-IoT available that are intended for long-range, high-capacity, and low power consumption IoT applications. Many IoT projects also integrate the SIM800L GSM/GPRS module.

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