Set the Date and Time of a TTL GSM/GPRS Modem using Arduino Mega

          If a new SIM card is inserted to your phone, when the phone restarts, it will ask us to set date and time. In SIM900-TTL GSM/GPRS modem also, we can set the date and time. Since there is no user interface, some AT commands are used to set and read the date and time from modem. Different methods are there to input AT commands to SIM900-TTL GSM/GPRS modem. Here we will use an Arduino mega to input the AT commands. I used SIM900-TTL GSM/GPRS modem from Rhydolabz.

Important : SIM card should be inserted to the slot provided on top of modem. Antenna should be fitted to modem.

          Circuit is done as shown in the diagram. Modem requires two voltage sources. One is Vinterface and other is Vin. Vin is given from a DC power supply which is capable of handling an output current of 1A. Vinterface is given from 5V pin of arduino. RX pin of modem is connected to the TX pin of Arduino and TX pin of modem is connected to the RX pin of arduino.

Arduino program to run the test command

          Now upload the following program to your arduino board. Before pressing the upload button, either turn off the GSM modem or disconnect the modem pins connected to the RX and TX pins of arduino. Otherwise, uploading will fail.

---

void setup()
{

  Serial.begin(2400);
  Serial.write("AT+CMGF=1\r");              //set GSM to text mode
  delay(1500);

  Serial.write("AT+CCLK=?\r");              //Test command

  while(1)
  {
    if(Serial.available())
    {
      Serial.write(Serial.read());
    }
  }
}

void loop()
{

}

---

          If the uploading is successfull, open your serial monitor. Serial monitor will display OK. Don't forget to change the baud rate to 2400. Otherwise serial monitor will display an unexpected result.

Arduino program to read current date and time from modem

          To read current date and time, upload the following program to your arduino board. Before pressing the upload button, either turn off the GSM modem or disconnect the modem pins connected to the RX and TX pins of arduino. Otherwise, uploading will fail.

---

void setup()
{

  Serial.begin(2400);
  Serial.write("AT+CMGF=1\r");              //set GSM to text mode
  delay(1500);

  Serial.write("AT+CCLK?\r");                 //Read command

  while(1)
  {
    if(Serial.available())
    {
      Serial.write(Serial.read());
    }
  }
}

void loop()
{

}

---

          If the uploading is successfull, open your serial monitor. Serial monitor will display current date and time. Don't forget to change the baud rate to 2400. Otherwise serial monitor will display an unexpected result.

Arduino program to update date and time

          If you want to change the date and time already set in the modem, upload the following program to your arduino board. Before pressing the upload button, either turn off the GSM modem or disconnect the modem pins connected to the RX and TX pins of arduino. Otherwise, uploading will fail.

---

void setup()
{

  Serial.begin(2400);
  Serial.write("AT+CMGF=1\r");              //set GSM to text mode
  delay(1500);

  Serial.write("AT+CCLK=\"99/12/12,04:06:30+08\"\r");  //Set date and time YY/MM/DD,hh:mm:ss+zz
  while(1)
  {
    if(Serial.available())
    {
      Serial.write(Serial.read());
    }
  }
}

void loop()
{

}

---

          If the uploading is successfull, open your serial monitor. Old date and time will be replaced by the new date and time given as input. Don't forget to change the baud rate to 2400. Otherwise serial monitor will display an unexpected result.

          Now read the current date and time by uploading corresponding arduino program. Date and time displayed will be the new date and time.