// void setup() {
//   // put your setup code here, to run once:
//   pinMode(7, OUTPUT);
// }

// void loop() {
//   // put your main code here, to run repeatedly:
//   digitalWrite(7, HIGH);
// }


#define echoPin	4     // attach pin D4 Arduino to pin Echo of HC-SR04
#define trigPin	7     // attach pin D7 Arduino to pin Trig of HC-SR04										 \


long duration; // Variable to store time taken to the pulse
			          // to reach receiver

int distance; // Variable to store distance calculated using formula

void setup()
{
	pinMode(trigPin,OUTPUT); // Sets the trigPin as an OUTPUT
	pinMode(echoPin, INPUT); // Sets the echoPin as an INPUT

	// Serial Communication is starting with 9600 of
	// baudrate speed
	Serial.begin(9600);
  pinMode(8, OUTPUT);

	// The text to be printed in serial monitor
	Serial.println("Distance measurement using Arduino Uno.");
	delay(500);
}

void loop()
{
	digitalWrite(trigPin, LOW);
	delayMicroseconds(2); // wait for 2 ms to avoid collision in serial monitor

	digitalWrite(trigPin, HIGH); // turn on the Trigger to generate pulse
	delayMicroseconds(10); // keep the trigger "ON" for 10 ms to generate pulse for 10 ms.

	digitalWrite(trigPin,LOW); // Turn off the pulse trigger to stop pulse generation

	// If pulse reached the receiver echoPin
	// become high Then pulseIn() returns the
	// time taken by the pulse to reach the
	// receiver

	duration = pulseIn(echoPin, HIGH);

	distance = duration * 0.0344 / 2; // Expression to calculate
								// distance using time

  if(distance < 200)
    digitalWrite(8, HIGH);
  else
    digitalWrite(8, LOW);

	Serial.print("Distance: ");
	Serial.print(distance); // Print the output in serial monitor
	Serial.println(" cm");
	delay(100);
}