arduino-0018-windows

arduino-0018-windows/examples/Sensors/Ping/Ping.pde

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+/* Ping))) Sensor
+  
+   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
+
+   http://www.arduino.cc/en/Tutorial/Ping
+   
+   created 3 Nov 2008
+   by David A. Mellis
+   modified 30 Jun 2009
+   by Tom Igoe
+
+ */
+
+// this constant won't change.  It's the pin number
+// of the sensor's output:
+const int pingPin = 7;
+
+void setup() {
+  // initialize serial communication:
+  Serial.begin(9600);
+}
+
+void loop()
+{
+  // establish variables for duration of the ping, 
+  // and the distance result in inches and centimeters:
+  long duration, inches, cm;
+
+  // 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);
+
+  // 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();
+  
+  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;
+}