#include <SoftwareSerial.h>

SoftwareSerial SIM900A(7, 8);

//Flag to just inform the user one time
boolean user_informed_movement = false;

byte trigPin = 3; //Pin from HC-SR04 "Trig"
byte echoPin = 2; //Pin from HC-SR04 "Echo"



void setup() {


  //Define HC-SR04 pins
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);

  Serial.begin(9600); //Start a Serial COM
  SIM900A.begin(9600);   // Setting the baud rate of GSM Module
  Serial.println ("SIM900A Ready");
  delay(100);
  Serial.println ("Type s to send message or r to receive message");
  delay(15000);
  SendMessage1();
}



void loop() {

  if (movement())
  {
    Serial.println(F("Movement"));
    delay(1000);
    SendMessage2();
    delay(30000);
  }
  if (SIM900A.available() > 0)
    Serial.write(SIM900A.read());

}// end of LOOP



//******************************************************************************
//****************************    MOVEMENT    **********************************
//******************************************************************************

byte movement()
{

  long duration, distance;

  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);

  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);

  digitalWrite(trigPin, LOW);
  duration = pulseIn(echoPin, HIGH);

  //Calculate the distance (in cm) based on the speed of sound.
  distance = duration / 58.2;

  Serial.print(F("Dist:"));
  Serial.println(distance);

  delay(50);

  if (distance >= 80 || distance <= 0)  return 0; //Ajust this values according to your needs

  else
  {
    return 1;
  }

}

void SendMessage1()
{
  Serial.println ("Sending Message");
  SIM900A.println("AT+CMGF=1");    //Sets the GSM Module in Text Mode
  delay(1000);
  Serial.println ("Set SMS Number");
  //                             *********
  SIM900A.println("AT+CMGS=\"+966591192998\"\r"); //Mobile phone number to send message
  delay(1000);
  Serial.println ("Set SMS Content");
  SIM900A.println("GSM Connected, Project is ON");// Messsage content
  delay(100);
  Serial.println ("Finish");
  SIM900A.println((char)26);// ASCII code of CTRL+Z
  delay(1000);
  Serial.println ("Message has been sent");
}

void SendMessage2()
{
  Serial.println ("Sending Message");
  SIM900A.println("AT+CMGF=1");    //Sets the GSM Module in Text Mode
  delay(1000);
  Serial.println ("Set SMS Number");
  //                             *********
  SIM900A.println("AT+CMGS=\"+966591192998\"\r"); //Mobile phone number to send message
  delay(1000);
  Serial.println ("Set SMS Content");
  SIM900A.println("Movement Detected!!");// Messsage content
  delay(100);
  Serial.println ("Finish");
  SIM900A.println((char)26);// ASCII code of CTRL+Z
  delay(1000);
  Serial.println ("Message has been sent");
}