Hi,
I am new to arduino & trying to find out how to control relays by sending sms to my arduino platform. I am using naked SIM300 GSM module with Tx, Rx & GND pins. I am using InduinoX board (UNO Clone). Pin 4,5,6,7 are connected to 4 relays with common ground. I have a sample code...
#include <SoftwareSerial.h>
// EN: String buffer for the GPRS shield message
String msg = String("");
// EN: Set to 1 when the next GPRS shield message will contains the SMS message
int SmsContentFlag = 0;
//control pins of relay.
int relay_a=4;
int relay_b=5;
int relay_c=6;
int relay_d=7;
// EN: Code PIN of the SIM card (if applied)
//String SIM_PIN_CODE = String( "XXXX" );
void setup()
{
Serial.begin(19200); // the GPRS baud rate
// Initialize PINs
pinMode( 4, OUTPUT );
pinMode( 5, OUTPUT );
pinMode( 6, OUTPUT );
pinMode( 7, OUTPUT );
digitalWrite( 4, LOW );
digitalWrite( 5, LOW );
digitalWrite( 6, LOW );
digitalWrite( 7, LOW );
Serial.println( "AT+CMGF=1" );
delay(200);
}
void loop()
{
char SerialInByte;
if(Serial.available())
{
SerialInByte = (unsigned char)Serial.read();
delay(5);
// -------------------------------------------------------------------
// EN: Program also listen to the GPRS shield message.
// -------------------------------------------------------------------
// EN: If the message ends with <CR> then process the message
if( SerialInByte == 13 ){
// EN: Store the char into the message buffer
ProcessGprsMsg();
}
if( SerialInByte == 10 ){
// EN: Skip Line feed
}
else {
// EN: store the current character in the message string buffer
msg += String(SerialInByte);
}
}
}
// EN: Make action based on the content of the SMS.
// Notice than SMS content is the result of the processing of several GPRS shield messages.
void ProcessSms( String sms ){
if( sms.indexOf("ona") >= 0 ){
digitalWrite( relay_a, HIGH );
}
if( sms.indexOf("onb") >= 0 ){
digitalWrite( relay_b, HIGH );
}
if( sms.indexOf("onc") >= 0 ){
digitalWrite( relay_c, HIGH );
}
if( sms.indexOf("ond") >= 0 ){
digitalWrite( relay_d, HIGH );
}
if( sms.indexOf("offa") >= 0 ){
digitalWrite( relay_a, LOW );
}
if( sms.indexOf("offb") >= 0 ){
digitalWrite( relay_b, LOW );
}
if( sms.indexOf("offc") >= 0 ){
digitalWrite( relay_c, LOW );
}
if( sms.indexOf("offd") >= 0 ){
digitalWrite( relay_d, LOW );
}
}
// EN: Request Text Mode for SMS messaging
void GprsTextModeSMS(){
Serial.println( "AT+CMGF=1" );
}
void GprsReadSmsStore( String SmsStorePos ){
Serial.print( "AT+CMGR=" );
Serial.println( SmsStorePos );
}
// EN: Clear the GPRS shield message buffer
void ClearGprsMsg(){
msg = "";
}
// EN: interpret the GPRS shield message and act appropiately
void ProcessGprsMsg() {
if( msg.indexOf( "Call Ready" ) >= 0 ){
// Serial.println( "*** GPRS Shield registered on Mobile Network ***" );
GprsTextModeSMS();
}
// EN: unsolicited message received when getting a SMS message
if( msg.indexOf( "+CMTI" ) >= 0 ){
// Serial.println( "*** SMS Received ***" );
// EN: Look for the coma in the full message (+CMTI: "SM",6)
// In the sample, the SMS is stored at position 6
int iPos = msg.indexOf( "," );
String SmsStorePos = msg.substring( iPos+1 );
// Serial.print( "SMS stored at " );
// Serial.println( SmsStorePos );
// EN: Ask to read the SMS store
GprsReadSmsStore( SmsStorePos );
}
// EN: SMS store readed through UART (result of GprsReadSmsStore request)
if( msg.indexOf( "+CMGR:" ) >= 0 ){
// EN: Next message will contains the BODY of SMS
SmsContentFlag = 1;
// EN: Following lines are essentiel to not clear the flag!
ClearGprsMsg();
return;
}
// EN: +CMGR message just before indicate that the following GRPS Shield message
// (this message) will contains the SMS body
if( SmsContentFlag == 1 ){
// Serial.println( "*** SMS MESSAGE CONTENT ***" );
// Serial.println( msg );
// Serial.println( "*** END OF SMS MESSAGE ***" );
ProcessSms( msg );
}
ClearGprsMsg();
// EN: Always clear the flag
SmsContentFlag = 0;
}
Now, I am trying to modify the code because my sim300 module has only 25 sms memory.
From the AT command set I learned to delete the entire sms memory by AT+CMGDA="DEL ALL" if TEXT mode u[/u] is selected. Now I am trying to implement the "DELETE SMS" code into the main example code.
I have tried a few alterations but they are not working. I can see what actually happens in the serial communication from the SerialMonitor option of Arduino. The first two Images are my attempt to delete the sms memory & it is the screenshot of the system after sending the "onb" (relay b ON) mesege to sim300. There is no confirmation of receiving any sms, neither my code worked at all. 
The example code works fine but the issue is it cant delete the SMS memory. Kindly check my altered code & give any suggestion to get my code into work.
First Attempt...
Nothing happens after sending sms to gsm module
Second Attempt...
How the example code works...
AT+CMGR=8 confirms that the new sms has been strored & read from no. 8 sms location.
the example code prints that a new sms arrived & activates the relay but my code doesn't....
What should be altered..? any clue?
Thanks for putting time to read my post... cheers
