int8_t answer;
int onModulePin= 2;
char aux_str[30];

//Change here your data
const char pin[]="****";
const char phone_number[]="MYNUMBER";
const char sms_text[]="Anytext"; 

void setup(){

  pinMode(onModulePin, OUTPUT);
  Serial.begin(115200);   

  Serial.println("Starting...");
  //power_on();

  sendsms();
  delay(10000);
  sendsms();
 
}


void loop(){

}

void sendsms(){

  //sets the PIN code
  sprintf(aux_str, "AT+CPIN=%s", pin);
  sendATcommand(aux_str, "OK", 2000);

  delay(3000);

  Serial.println("Connecting to the network...");

  while( (sendATcommand("AT+CREG?", "+CREG: 0,1", 500) ||
    sendATcommand("AT+CREG?", "+CREG: 0,5", 500)) == 0 );

  Serial.print("Setting SMS mode...");
  sendATcommand("AT+CMGF=1", "OK", 1000);    // sets the SMS mode to text
  Serial.println("Sending SMS");

  sprintf(aux_str,"AT+CMGS=\"%s\"", phone_number);
  answer = sendATcommand(aux_str, ">", 2000);    // send the SMS number
  if (answer == 1)
  {
    Serial.println(sms_text);
    Serial.write(0x1A);
    answer = sendATcommand("", "OK", 20000);
    if (answer == 1)
    {
      Serial.print("Sent ");   
    }
    else
    {
      Serial.print("error ");
    }
  }
  else
  {
    Serial.print("error ");
    Serial.println(answer, DEC);
  }

 
}


void power_on(){

  uint8_t answer=0;

  // checks if the module is started
  answer = sendATcommand("AT", "OK", 2000);
  if (answer == 0)
  {
    // power on pulse
    digitalWrite(onModulePin,HIGH);
    delay(3000);
    digitalWrite(onModulePin,LOW);

    // waits for an answer from the module
    while(answer == 0){     // Send AT every two seconds and wait for the answer
      answer = sendATcommand("AT", "OK", 2000);   
    }
  }

}

int8_t sendATcommand(char* ATcommand, char* expected_answer, unsigned int timeout){

  uint8_t x=0,  answer=0;
  char response[100];
  unsigned long previous;

  memset(response, '\0', 100);    // Initialice the string

  delay(100);

  while( Serial.available() > 0) Serial.read();    // Clean the input buffer

  Serial.println(ATcommand);    // Send the AT command


    x = 0;
  previous = millis();

  // this loop waits for the answer
  do{
    // if there are data in the UART input buffer, reads it and checks for the answer
    if(Serial.available() != 0){   
      response[x] = Serial.read();
      x++;
      // check if the desired answer is in the response of the module
      if (strstr(response, expected_answer) != NULL)   
      {
        answer = 1;
      }
    }
    // Waits for the answer with time out
  }
  while((answer == 0) && ((millis() - previous) < timeout));   

  return answer;
}