Send SMS

This sketch send a SMS message from an Arduino board equipped with a GSM shield. Using the serial monitor of the Arduino Software (IDE), you'll enter the number to connect with, and the text message to send.

Hardware Required

• Arduino Board

• Arduino + Telefonica GSM/GPRS Shield

• SIM card

Circuit

Code

First, import the GSM library

#include <GSM.h>

SIM cards may have a PIN number that enables their functionality. Define the PIN for your SIM. If your SIM has no PIN, you can leave it blank :

#define PINNUMBER ""

Initialize instances of the classes you're going to use. You're going to need both the GSM and GSM_SMS class.

Copy
1GSM gsmAccess;
2
3GSM_SMS sms;

In

setup

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1void setup(){
2
3  Serial.begin(9600);
4
5  Serial.println("SMS Messages Sender");

Create a local variable to track the connection status. You'll use this to keep the sketch from starting until the SIM is connected to the network :

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1boolean notConnected = true;

Connect to the network by calling

gsmAccess.begin()

while()

gsmAccess()

GSM_READY

notConnected

true

false

setup

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1while(notConnected)
2
3  {
4
5    if(gsmAccess.begin(PINNUMBER)==GSM_READY)
6
7      notConnected = false;
8
9    else
10
11    {
12
13      Serial.println("Not connected");
14
15      delay(1000);
16
17    }
18
19  }

Finish

setup

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1Serial.println("GSM initialized.");
2}

Create a function named

readSerial

int

char

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1int readSerial(char result[])
2{

Create a variable to count through the items in the serial buffer, and start a

while

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1int i = 0;
2
3  while(1)
4
5  {

As long as there is serial information available, read the data into a variable named

inChar

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1while (Serial.available() > 0)
2
3    {
4
5      char inChar = Serial.read();

If the character being read is a newline, terminate the array, clear the serial buffer and exit the function.

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1if (inChar == '\n')
2
3      {
4
5        result[i] = '\0';
6
7        Serial.flush();
8
9        return 0;
10
11      }

If the incoming character is an ASCII character other than a newline or carriage return, add it to the array and increment the index. Close up the

while

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1if(inChar!='\r')
2
3      {
4
5        result[i] = inChar;
6
7        i++;
8
9      }
10
11    }
12
13  }
14}

In

loop

char

remoteNumber

readSerial

remoteNumber

readSerial

remoteNumber

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1Serial.print("Enter a mobile number: ");
2
3  char remoteNumber[20];
4
5  readSerial(remoteNumber);
6
7  Serial.println(remoteNumber);

Create a new

char

txtMsg

txtMsg

readSerial

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1Serial.print("Now, enter SMS content: ");
2
3  char txtMsg[200];
4
5  readSerial(txtMsg);

Call

sms.beginSMS()

remoteNumber

sms.print()

sms.endSMS()

loop

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1Serial.println("SENDING");
2
3  Serial.println();
4
5  Serial.println("Message:");
6
7  Serial.println(txtMsg);
8
9  sms.beginSMS(remoteNumber);
10
11  sms.print(txtMsg);
12
13  sms.endSMS();
14
15  Serial.println("\nCOMPLETE!\n");
16}

Once your code is uploaded, open the serial monitor. Make sure the serial monitor is set to only send a newline character on return. When prompted to enter the number you wish to call, enter the digits and press return. You'll then be asked to enter your message. Once you've typed that, press return again to send it.

Complete Sketch

The complete sketch is below.

Last revision 2018/08/23 by SM