Sending and Receiving SMS using GSM module (contd...)

Hello everyone!

Hope you are being benefited from the information I have been sharing. Many of you have been working with GSM based projects and have been highly benefited from the earlier post of sending and receiving sms using gsm module. This is the continued version of the similar topic.

Note: We recommend you to visit Sending and Receiving SMS using GSM module before you read further.

Many were benefited from the earlier but faced problem while receiving sms from the mobile on gsm so I have tried my best to solve the issue with description and additional code in this post. Receiving a text message on SIM900 module is a bit difficult because now you need to place a check when user will send a message. So, ideally whenever anyone send a message to your SIM900 module, you should get notified. These are to be covered in detail.

Now, after we get notified, there is a need to read message as well and who has sent the message. So, all we will place a check that whenever someone sends a message to our SIM900 module, we get notified and we will extract message and mobile number of sender.

I have explained in previous post about sending the sms from GSM to mobile using AT command and similar is for receiving the SMS.

1. ATE0 - It is used to turn off the Echo of GSM shields
2. AT - Just to check your GSM is working fine
3. AT+CMGF = 1 - This command will convert the message style to text
4. AT+ CNMI=1,2,0,0,0 - This command will alert GSM shield and whenever it receive message, it will automatically send an alert on the serial port.

These four commands are used in the code in order to receive text in GSM. We have to put Enter after each of the AT commands. For each AT command, we get a response "OK" from the GSM shield.

Now, GSM shield is ready to receive the text message.

When you send a message to GSM shield it will notify and the received message will start with "+CMT" and after that it has a mobile number of the sender and at the end lies the body of message.

If you want to receive SMS in GSM then add below code in earlier one:

void Config()

{

delay(1000);

Serial.print("ATE0r");

Response();

Serial.print("ATr");

Response();

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

Response();

Serial.print("AT+CNMI=1,2,0,0,0r");

Response();

}

void Response()

{

int count = 0;

Serial.println();

while(1)

{

if(Serial.available())

{

char data =Serial.read();

if(data == 'K'){Serial.println("OK");break;}

if(data == 'R'){Serial.println("GSM Not Working");break;}

}

count++;

delay(10);

if(count == 1000){Serial.println("GSM not Found");break;}

}

}

If you want to go further and get the data out of the string out of serial monitor you follow the following steps however it might not be necessary for most of the cases.

• Save the CMT string into an array, which named as RcvMsg[index] but be sure you are not receiving the garbage value.
• To do so you can check first these character"+CMT" and make index = 0
• To get a complete string "n" used as null character because there is no end character and 2 null character = complete string so you can stop receiving string
• Now you can count the mobile number and mark as sender mobile number and other as message text.
• Now the change you get is instead of "+CMT" you get  " SENDER Mobile Number" and " MESSAGE TEXT."

Now, its awesome; isn't it. Now you can not only send but also receive the message text. Sending SMS is better method than Call in case of projects and cost factors.

If you want a complete and bug-free working code of GSM based Dual Communication which I was lucky enough to supervise then click here.

Hope this was very much helpful. You can buy an arduino code from different websites but I am trying to provide my skills for free however you can help me by like, share and subscribe.

Also if you need any support with any kind of projects or codes then you can just post your code or ideas in the comment section. Feel free to share your problems.