Interfacing GSM module code optimization

Projects General Guidance
3

Getting rid of delays in code that's not weaved and can be called over and over.

//SMS sending function un-delayed

void sms(String text, String phone) {

  static word startTimer, waitTimer;  // waitTimer > 0 causes the timer to run, good up to 65 second intervals
  static byte procState;

  if ( waitTimer > 0 )
  {
    if ( word( millis() ) - startTimer < waitTimer )      return;     // time is not up yet
    else                                                                  waitTimer = 0; // and on to the switch-case      
  }

  switch ( procState )
  {
        case 0 :
	mySerial.print( F( "AT+CMGD=1,4\n\r" )); // Delete all messages so there are no conflicts with accidentally unread or stored SMS
        procState = 1;      //  run case 1 next time
        waitTimer = 1000;
        startTimer = millis();
        break;

        case 1 :
	mySerial.println("AT+CMGS=\"" + phone + "\"");  // send to desired phone
        procState = 2;      //  run case 2 next time
        waitTimer = 1000;
        startTimer = millis();
        break;

	case 2 :
	mySerial.print("\"" + text + "\""); // containing desired text
        procState = 3;      //  run case 1 next time
        waitTimer = 1000;
        startTimer = millis();
        break;

	case 3 :
	mySerial.print((char)26); // signals end of text message
        procState = 0;      //  run case 0 next time
        waitTimer = 2000;
        startTimer = millis();
        break;
  }
}

Some of the rest of the sketch should be re-arranged to get the delays out.

BTW, in small memory environments you should avoid using String variables.