A distance measurement class using ultrasonic sensor HC-SR04.

The purpose of this library is to encourage students to develope their own classes. Instructions how to follow the development of this library for ultrasonic distance measurement are given here.

Revision:
4:aae70f15357f
Parent:
3:9a7899cf5e3a
Child:
5:a667b621f625
```--- a/HCSR04.h	Sun Dec 06 15:13:54 2015 +0000
+++ b/HCSR04.h	Mon Dec 07 09:37:21 2015 +0000
@@ -29,11 +29,32 @@
*/
HCSR04(PinName echoPin, PinName triggerPin);

-    /** Calculates the distance in cm, with the calculation time of 25 ms.
+    /** Calculates the distance in cm, with the calculation time of approximatelly 23.7 ms.
* @returns distance of the measuring object in cm.
*/
float getDistance_cm();

+    /** Calculates the distance in mm, with the calculation time of approximatelly 23.7 ms.
+     * @returns distance of the measuring object in mm.
+     */
+    float getDistance_mm();
+
+    /** Sets the minimum and maximum ranges between the factory values of 2 cm and 400 cm.
+     *  @param minRange Minimum range in cm. Must be between 2 cm and maxRange.
+     *  @param maxRange Maximum range in cm. Must be between minRange and 400 cm.
+     */
+    void setRanges(float minRange, float maxRange);
+
+    /** Retreives the minimum sensor range set by the user.
+     * @returns the minimum sensor range set by the user in cm.
+     */
+    float getMinRange();
+
+    /** Retreives the maximum sensor range set by the user.
+     * @returns the maximum sensor range set by the user in cm.
+     */
+    float getMaxRange();
+
private:

InterruptIn echo;       // echo pin
```