/* HC-SR04 Sensor
   https://www.dealextreme.com/p/hc-sr04-ultrasonic-sensor-distance-measuring-module-133696


   This sketch reads a HC-SR04 ultrasonic rangefinder and returns the

   distance to the closest object in range. To do this, it sends a pulse

   to the sensor to initiate a reading, then listens for a pulse
   to return.  The length of the returning pulse is proportional to

   the distance of the object from the sensor.


   The circuit:
	* VCC connection of the sensor attached to +5V

	* GND connection of the sensor attached to ground
	* TRIG connection of the sensor attached to digital pin 2

	* ECHO connection of the sensor attached to digital pin 4



   Original code for Ping))) example was created by David A. Mellis

   Adapted for HC-SR04 by Tautvidas Sipavicius


   This example code is in the public domain.
 */



const int trigPin = 2;
const int speakerPin = 13;
const int echoPin = 4;


void setup() {

  // initialize serial communication:
  Serial.begin(9600);
  //pinMode(led, OUTPUT);
  pinMode(speakerPin,OUTPUT);

}

void loop()

{
  // establish variables for duration of the ping,

  // and the distance result in inches and centimeters:
  long duration, inches, cm;


  // The sensor is triggered by a HIGH pulse of 10 or more microseconds.

  // Give a short LOW pulse beforehand to ensure a clean HIGH pulse:

  pinMode(trigPin, OUTPUT);

  digitalWrite(trigPin, LOW);

  delayMicroseconds(2);

  digitalWrite(trigPin, HIGH);

  delayMicroseconds(10);

  digitalWrite(trigPin, LOW);


  // Read the signal from the sensor: a HIGH pulse whose

  // duration is the time (in microseconds) from the sending
  // of the ping to the reception of its echo off of an object.

  pinMode(echoPin, INPUT);

  duration = pulseIn(echoPin, HIGH);


  // convert the time into a distance

 // inches = microsecondsToInches(duration);

  cm = microsecondsToCentimeters(duration);


 // Serial.print(inches);

//  Serial.print("in, ");



  Serial.print(cm);

  Serial.print("cm");

  Serial.println();

  if (cm < 110) {  // This is where the LED On/Off happens
   // digitalWrite(led,HIGH); // When the Red condition is met, the Green LED should turn off
    tone(speakerPin, 800);
    delay(10000);
 // digitalWrite(led2,LOW);
}
  else {
   // digitalWrite(led,LOW);
 //   digitalWrite(led2,HIGH);
 noTone(speakerPin);
  }
  if (cm >= 200 || cm <= 0){
    Serial.println("Out of range");
  }


  delay(100);

}

long microsecondsToInches(long microseconds)

{
  // According to Parallax's datasheet for the PING))), there are

  // 73.746 microseconds per inch (i.e. sound travels at 1130 feet per

  // second).  This gives the distance travelled by the ping, outbound
  // and return, so we divide by 2 to get the distance of the obstacle.

  // See: http://www.parallax.com/dl/docs/prod/acc/28015-PING-v1.3.pdf

  return microseconds / 74 / 2;

}

long microsecondsToCentimeters(long microseconds)

{
  // The speed of sound is 340 m/s or 29 microseconds per centimeter.

  // The ping travels out and back, so to find the distance of the

  // object we take half of the distance travelled.
  return microseconds / 29 / 2;

}