Interfacing GSM Module with Arduino| SIM 900 Module

Hello There. Welcome to Techatronic. In this article, We will see the interfacing of the SIM 900 GSM Module with Arduino. I hope you will find this article helpful. If you Are building a project using this module or need something to control your project from a faraway place without internet. you will find this helpful. We will also look into the working of the module to know more about it. On our website, we have already uploaded a lot many Arduino tutorials and Arduino projects. You may check them if you are a beginner in electronics and learn more. You may also find some cool DIY projects using Arduino.

What is GSM SIM 900 Module?

The GSM SIM 900 Module is a type of Arduino Shield, which means it can also be mounted on top of Arduino UNO. This is a type of modem, used for long-distance data transmission with the use of GSM technology where there is no internet connectivity. this makes it useful in projects which require remote data transmission. Many projects can be made using this module such as call or text message-based trigger which can be used in our day-to-day life.

Farmers can extensively use this technology in their day-to-day life, such as controlling water pumps with a simple silent call or a text message sitting at their home. This can also be used to send the data from the module to our mobile phones without the use of the internet. Other project ideas include intruder alert notification, Receive timely updates from the sensor to your mobile, etc.

How Does the SIM 900 Module work?

The GSM module uses GSM and GPRS technology to communicate with another device wirelessly. It uses 2G network to connect with the internet and supports Quad-band(EGSM 900, GSM 850, DCS 1800, PCS1900). Because of this, one can send or receive messages from this or make or receive voice calls using the module by connecting the microphone and speakers to the respective ports given on it.

This Module also houses an inbuilt RTC to keep track of time, which is very helpful for timer-based applications. the versatility of this module is very high due to its ability to read and send messages without any hassle. Because of the use of AT Commands, it is very easy to configure. because of the presence of an external antenna, the module can also be used in areas with low signal areas.

Components Required

  • Arduino UNO
  • SIM 900 GSM Module
  • Full-Size SIM Card (Unlocked)
  • 12V 2Amp Power Supply
  • Connecting Wires
  • Breadboard
  • USB cable for uploading code into Arduino UNO

Interfacing GSM Module with Arduino Circuit Diagram

Interfacing GSM Module with Arduino| SIM 900 Module

Interfacing GSM Module with Arduino Code

NOTE: Before uploading the code, Download the serial software library from HERE and install it in your Arduino IDE.

 // Download Library of SoftwareSerial link given  
 #include <SoftwareSerial.h>  
 SoftwareSerial SIM900A(10,11); // SoftSerial( RX , TX );  
 // 10 pin connect to TX of GSM SIM 900 Module  
 // 11 pin connect to RX of GSM SIM 900 Module  
 void setup()  
  SIM900A.begin(9600);  // Setting the baud rate of GSM Module   
  Serial.begin(9600);  // Setting the baud rate of Serial Monitor (Arduino)  
  Serial.println ("SIM900A Ready");  
  Serial.println ("Type s to send message or r to receive message");  
 void loop()  
  if (Serial.available()>0)  
   case 's':  
   case 'r':  
  if (SIM900A.available()>0)  
  void SendMessage()  
  Serial.println ("Sending Message");  
  SIM900A.println("AT+CMGF=1");  //Sets the GSM Module in Text Mode  
  Serial.println ("Set SMS Number");  
  SIM900A.println("AT+CMGS=\"911234567890\"\r"); //Type Your Mobile number to send message  
  Serial.println ("Set SMS Content");  
  SIM900A.println("Good morning, how are you doing?");// Messsage content  
  Serial.println ("Finish");  
  SIM900A.println((char)26);// ASCII code of CTRL+Z  
  Serial.println ("Message has been sent ->SMS Selesai dikirim");  
  void RecieveMessage()  
  Serial.println ("SIM900A Membaca SMS");  
  delay (1000);  
  SIM900A.println("AT+CNMI=2,2,0,0,0"); // AT Command to receive a live SMS  
  Serial.write ("Unread Message done");  

Before Uploading the code put the SIM card inside the given socket. After the code is uploaded and powering the module with an external supply, you may see the serial monitor open. Hence your code is running properly. I hope you found this article helpful. If you have any queries or doubts, you can ask them in the comment section below.