Adding examples for Ping ultrasound distance sensor and Memsic 2125 accelerometer from Parallax.

build/shared/dist/examples/Sensors/Ping/Ping.pde

@@ -0,0 +1,55 @@
+int pingPin = 7;
+int ledPin = 13;
+
+void setup()
+{
+  pinMode(13, OUTPUT);
+}
+
+void loop()
+{
+  long duration, inches, cm;
+
+  // The PING))) is triggered by a HIGH pulse of 2 or more microseconds.
+  // We 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);
+
+  // the closer an object is, the faster the led will blink
+  digitalWrite(ledPin, HIGH);
+  delay(cm);
+  digitalWrite(ledPin, LOW);
+  delay(cm);
+}
+
+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;
+}