Revision 1:0b3bdb910fe7, committed 2016-06-21

Comitter:

yruiewyrui3

Date:

Tue Jun 21 07:45:27 2016 +0000

Parent:

0:86b2086be101

Commit message:

.

Changed in this revision

diff -r 86b2086be101 -r 0b3bdb910fe7 hcsr04.cpp
--- a/hcsr04.cpp	Mon Apr 14 08:23:09 2014 +0000
+++ b/hcsr04.cpp	Tue Jun 21 07:45:27 2016 +0000
@@ -3,7 +3,7 @@
 /*
 *HCSR04.cpp
 */
-HCSR04::HCSR04(PinName t, PinName e) : trig(t), echo(e) {}
+HCSR04::HCSR04(PinName t, PinName e, long to) : trig(t), echo(e), time_out(to){}
  long HCSR04::echo_duration() {
         
     timer.reset();  //reset timer
@@ -12,18 +12,25 @@
     trig=1;   //  trigger high
     wait_us(10);
     trig=0;  // trigger low
-         while(!echo); // start pulseIN
-      timer.start();
-     while(echo);
-      timer.stop();
-     return timer.read_us(); 
+        while(!echo); // start pulseIN
+    timer.start();
+    while(echo)
+    {
+        if(timer.read_us()>time_out)        
+            break;
+    }
+    timer.stop();
+    long czas=timer.read_us();
+    if(czas<300)
+        return 0;
+    return timer.read_us(); 
  
 }
  
 //return distance in cm 
 long HCSR04::distance(){
     duration = echo_duration();
-  distance_cm = (duration/2)/29.1  ;
+  distance_cm = (duration/2.00)/29.10  ;
         return distance_cm;
 
 }
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