Revision 6:cf3e4e307d15, committed 2016-12-10

Comitter:

tbjazic

Date:

Sat Dec 10 08:26:18 2016 +0000

Parent:

5:a667b621f625

Commit message:

Filtering with Ticker object corrected.

Changed in this revision

--- a/HCSR04.cpp	Mon Dec 07 09:57:48 2015 +0000
+++ b/HCSR04.cpp	Sat Dec 10 08:26:18 2016 +0000
@@ -6,52 +6,66 @@
 }
 
 void HCSR04::init() {
-    /** configure the rising edge to start the timer */
-    echo.rise(this, &HCSR04::startTimer);
-    
-    /** configure the falling edge to stop the timer */
-    echo.fall(this, &HCSR04::stopTimer);
-    
     distance = -1;      // initial distance
     minDistance = 2;
     maxDistance = 400;
+    newDataReady = timerStarted = false;
 }
 
 void HCSR04::startTimer() {
-    timer.start(); // start the timer
+    if (!timerStarted) {
+        timer.start(); // start the timer
+        timerStarted = true;
+        echoTimeout.attach_us(this, &HCSR04::stopTimer, 25000); // in case echo fall does not occur
+        echo.fall(this, &HCSR04::stopTimer);
+        echo.rise(NULL);
+    }
 }
 
 void HCSR04::stopTimer() {
     timer.stop(); // stop the timer
+    if (timerStarted) {
+        distance = timer.read() * 1e6 / 58;
+        if (distance < minDistance)
+            distance = minDistance;
+        if (distance > maxDistance)
+            distance = maxDistance;
+        newDataReady = true;
+    }
+    timer.reset();
+    timerStarted = false;
+    echoTimeout.detach();
+    echo.fall(NULL);
+}
+
+void HCSR04::turnOffTrigger() {
+    trigger = 0; 
 }
 
 void HCSR04::startMeasurement() {
     trigger = 1;
-    wait_us(10);
-    trigger = 0;
-    wait_us(23660); // just enough time to measure 400 cm
-    timer.stop(); // just in case echo fall did not occur
-    distance = timer.read() * 1e6 / 58;
-    if (distance < minDistance)
-        distance = minDistance;
-    if (distance > maxDistance)
-        distance = maxDistance;
-    timer.reset();
+    triggerTimeout.attach_us(this, &HCSR04::turnOffTrigger, 10);
+    echo.rise(this, &HCSR04::startTimer);
+    newDataReady = false;
 }
 
 float HCSR04::getDistance_cm() {
-    startMeasurement();
+    newDataReady = false;
     return distance;
 }
 
 float HCSR04::getDistance_mm() {
-    startMeasurement();
+    newDataReady = false;
     return distance * 10;
 }
 
+bool HCSR04::isNewDataReady() {
+    return newDataReady;
+}
+
 void HCSR04::setRanges(float minRange, float maxRange) {
     if (minRange < maxRange) {
-        if (minRange >= 2) 
+        if (minRange >= 2 && minRange < 400) // bug from revs. 4 and 5 corrected
             minDistance = minRange;
         if (maxRange <= 400)
             maxDistance = maxRange;

--- 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