TVZ Mechatronics Team / HCSR04

A distance measurement class using ultrasonic sensor HC-SR04.

Dependents:   Esercitazione4_4 HC-SR04 Group10_slave Oled_Gus ... more

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.

Diff: HCSR04.h

Revision:
6:cf3e4e307d15
Parent:
5:a667b621f625
--- a/HCSR04.h	Mon Dec 07 09:57:48 2015 +0000
+++ b/HCSR04.h	Sat Dec 10 08:26:18 2016 +0000
@@ -9,15 +9,24 @@
  * #include "HCSR04.h"
  *
  * Serial pc(USBTX, USBRX);
+ * Timer timer;
  *
  * int main() {
  *     HCSR04 sensor(p5, p7);
  *     sensor.setRanges(10, 110);
  *     pc.printf("Min. range = %g cm\n\rMax. range = %g cm\n\r",
  *       sensor.getMinRange(), sensor.getMaxRange());
- *     while(1) {
+ *     while(true) {
+ *         timer.reset();
+ *         timer.start();
+ *         sensor.startMeasurement();
+ *         while(!sensor.isNewDataReady()) {
+ *             // wait for new data
+ *             // waiting time depends on the distance
+ *         }
  *         pc.printf("Distance: %5.1f mm\r", sensor.getDistance_mm());
- *         wait_ms(500);
+ *         timer.stop();
+ *         wait_ms(500 - timer.read_ms()); // time the loop
  *     }
  * }
  * @endcode
@@ -32,12 +41,17 @@
      */
     HCSR04(PinName echoPin, PinName triggerPin);
     
-    /** Calculates the distance in cm, with the calculation time of approximatelly 23.7 ms.
+    /** Start the measurement. Measurement time depends on the distance.
+     *  Maximum measurement time is limited to 25 ms (400 cm).
+     */
+    void startMeasurement();
+    
+    /** Returns the distance in cm. Requires previous call of startMeasurement().
      * @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 the distance in mm. Requires previous call of startMeasurement().
      * @returns distance of the measuring object in mm.
      */
     float getDistance_mm();
@@ -58,6 +72,11 @@
      */
     float getMaxRange();
     
+    /** Checks if the new data is ready.
+     * @returns true if new data is ready, false otherwise.
+     */
+    bool isNewDataReady();
+    
     private:
     
     InterruptIn echo;       // echo pin
@@ -66,6 +85,8 @@
     float distance;         // store the distance in cm
     float minDistance;      // minimum measurable distance
     float maxDistance;      // maximum measurable distance
+    Timeout triggerTimeout, echoTimeout;
+    bool newDataReady, timerStarted;
     
     /** Start the timer. */
     void startTimer();
@@ -76,8 +97,7 @@
     /** Initialization. */
     void init();
     
-    /** Start the measurement. */
-    void startMeasurement();
+    void turnOffTrigger();
 };
 
 #endif
\ No newline at end of file