Tutorial: How to use SIM800L GSM Module using Arduino | Send and Receive SMS

There are actually a lot of GSM module available in the market but I personally recommend and prefer SIM800L due to its size and simplicity. It has a small footprint so it occupies a very small space. This is because SIM800L only provides the basic core of GSM. Meaning to say, you need to provide additional circuitry to use it but don’t worry I will show you the simplest way to use it.

To send SMS:
1. Send AT+CMGF=1 <CR><LF>
– this is to configure the GSM module to text mode
CR – Cariage Return, ASCII character 13 or r
LF – Line Feed, ASCII character 10 or n
2. Sent AT+CMGS=”+ZZxxxxxxxxxx”<CR><LF>
– this is for entering the sim number
ZZ – is the country code
xx – is the 10-digit mobile number
CR – Cariage Return, ASCII character 13 or r
LF – Line Feed, ASCII character 10 or n
3. Wait for the ‘>’ reply from SIM800L before sending the next
4. When the GSM replied with ‘>’, this is the time to send your message such as:
“Hello from SIM800L”<CR><LF>
Hello from SIM800L – is the SMS you want to send.
CR – Cariage Return, ASCII character 13 or r
LF – Line Feed, ASCII character 10 or n
5. Send a CTRL+Z character or ASCII character 26.

To receive SMS:
1. Send AT+CMGF=1 <CR><LF>
– this is to configure the GSM module to text mode
CR – Cariage Return, ASCII character 13 or r
LF – Line Feed, ASCII character 10 or n
2. Send AT+CNMI=1,2,0,0,0<CR><LF>
– this is to configure the GSM module to forward via serial when SMS is receive.
CR – Cariage Return, ASCII character 13 or r
LF – Line Feed, ASCII character 10 or n

Video Demonstration:

Source Code:

#include "SoftwareSerial.h"

SoftwareSerial mySerial(2, 3);

String cmd = "";

void setup()
{
  mySerial.begin(9600);
  Serial.begin(9600);
  Serial.println("Initializing...");
  delay(1000);

  mySerial.println("AT");                 // Sends an ATTENTION command, reply should be OK
  updateSerial();
  mySerial.println("AT+CMGF=1");          // Configuration for sending SMS
  updateSerial();
  mySerial.println("AT+CNMI=1,2,0,0,0");  // Configuration for receiving SMS
  updateSerial();
}

void loop()
{
  updateSerial();
}

void updateSerial()
{
  delay(500);
  while (Serial.available()) 
  {

    cmd+=(char)Serial.read();
 
    if(cmd!=""){
      cmd.trim();  // Remove added LF in transmit
      if (cmd.equals("S")) {
        sendSMS();
      } else {
        mySerial.print(cmd);
        mySerial.println("");
      }
    }
  }
  
  while(mySerial.available()) 
  {
    Serial.write(mySerial.read());//Forward what Software Serial received to Serial Port
  }
}

void sendSMS(){
  mySerial.println("AT+CMGF=1");
  delay(500);
  mySerial.println("AT+CMGS="+639175291539"r");
  delay(500);
  mySerial.print("Hi! TechToTinker!");
  delay(500);
  mySerial.write(26);
}

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