Ultrasonic Distance Sensor

/**

* @file: Ping))) Sensor

* @date: 4/5/2011

*

* @DESCRIPTION

* This sketch reads a PING))) 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:

* +V connection of the PING))) attached to +5V

* GND connection of the PING))) attached to ground

* SIG connection of the PING))) attached to digital pin 7

**/

#define pingPin 7 // pin number of the sensor's output

//--- Function: Setup ()

void setup()

{

    Serial.begin(9600); // initialize serial communication

}

//--- Function: Setup ()

void loop()

{

    // establish variables for duration of the ping,

    // and the distance result in inches:

    long duration, inches;

    // The PING))) is triggered by a HIGH pulse of 2 or more microseconds.

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

    pinMode(pingPin, OUTPUT);

    digitalWrite(pingPin, LOW);

    delayMicroseconds(2);

    digitalWrite(pingPin, HIGH);

    delayMicroseconds(5);

    digitalWrite(pingPin, LOW);

    // The same pin is used 

to read the signal from the PING))): 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(pingPin, INPUT);

    duration = pulseIn(pingPin, HIGH);

    Serial.print(inches);

    Serial.print("in, ");

    delay(100);

}