Receiving SMS using GSM and controlling LED using Arduino

Question

Has someone come up with a solution with the above stated problem?

We are using Arduino Duemilanove and SIM 900 GSM module (http://robokits.co.in/shop/index.php?main_page=product_info&products_id=303)

We've tried to work on the similar problem of lightning LEDs from port 9-12 when we send an sms #aibicidi, where i = 0 or 1, 0 =off, 1=on. E.g. #a1b1c1d1 will switch on all the LEDs.

When we upload the code and run it through serial monitor and enter the #a1b1c1d1 in the serial monitor, we can see all the LEDs lighten up. But if we send the sms with having content "#a1b1c1d1", we don't see any function of LEDs.

It would be great if anyone can give some guidance about the same.

 char inchar; //Will hold the incoming character from the Serial Port.

 int led1 = 9;
 int led2 = 10;
 int led3 = 11;
 int led4 = 12;

 void setup()
 {
 // prepare the digital output pins
 pinMode(led1, OUTPUT);
 pinMode(led2, OUTPUT);
 pinMode(led3, OUTPUT);
 pinMode(led4, OUTPUT);
 digitalWrite(led1, LOW);
 digitalWrite(led2, LOW);
 digitalWrite(led3, LOW);
 digitalWrite(led4, LOW);
 //Initialize GSM module serial port for communication.


 Serial.begin(9600);
 delay(3000); // give time for GSM module to register on network etc.
 Serial.println("AT+CMGF=1"); // set SMS mode to text
 delay(200);
 Serial.println("AT+CNMI=3,3,0,0"); // set module to send SMS data to serial out upon receipt 
 delay(200);
 }

 void loop() 
 {
 //If #a1b1c1d1 comes as sms, all LEDs should light up.
 if(Serial.available() >0)
 {
 inchar=Serial.read(); 
 if (inchar=='#')
   {
   delay(10);
   inchar=Serial.read(); 

 //first led
   if (inchar=='a')
     {
   delay(10);
   inchar=Serial.read();

 if (inchar=='0')
   {
   digitalWrite(led1, LOW);
   } 
 else if (inchar=='1')
   {
   digitalWrite(led1, HIGH);
   }
 delay(10);


 //Second led
 inchar=Serial.read(); 

 if (inchar=='b')
   {
   inchar=Serial.read();
 if (inchar=='0')
 {
 digitalWrite(led2, LOW);
 } 

 else if (inchar=='1')
 {
 digitalWrite(led2, HIGH);
 }
 delay(10);

 // Third led
 inchar=Serial.read(); 
 if (inchar=='c')
 {
 inchar=Serial.read();
 if (inchar=='0')
 {
 digitalWrite(led3, LOW);
 } 
 else if (inchar=='1')
 {
 digitalWrite(led3, HIGH);
 }
 delay(10);

 //Fourth led

 inchar=Serial.read(); 
 if (inchar=='d')
 {
 delay(10);
 inchar=Serial.read();
 if (inchar=='0')
 {
 digitalWrite(led4, LOW);
 } 
 else if (inchar=='1')
 {
 digitalWrite(led4, HIGH);
 }
 delay(10);
 }
 }
 Serial.println("AT+CMGD=1,4"); // delete all SMS
 }
 }
 }
 }
 }

Answer 1

First do not use delay

Serial.begin(9600);
delay(3000); // give time for GSM module to register on network etc.

This is neither necessary nor reliable. Instead of waiting some random time, you can check the network status with AT+CFUN and/or AT+COPS. If the GSM module is already attached to a network when you open the serial connection, it is a waste of time waiting like that. And if is not attached you should wait explicitly for that to happen (polling CFUN/COPS or enabling AT+CREG), otherwise you risk waiting too short time. See the 27.007 specification for more information for those commands.

Second do not use delay

Serial.println("AT+CMGF=1"); // set SMS mode to text
delay(200);

Please do not write code like this. See this answer on why using delay is such a bad idea, and this answer for suggestion to how to handle properly.