Diff: hcsr04.cpp

Revision:

8:c69fe28366d8

Parent:

7:939fdc8df95b

Child:

10:338191178cbf

diff -r 939fdc8df95b -r c69fe28366d8 hcsr04.cpp
--- a/hcsr04.cpp	Wed May 06 02:53:36 2015 +0000
+++ b/hcsr04.cpp	Wed May 06 04:02:08 2015 +0000
@@ -38,11 +38,11 @@
 void HCSR04::isr_rise(void)
 {
     pulsetime.start();
+    pulsetime.reset();
 }
 void HCSR04::start(void)
 {
     pulsedur = 0;
-    distance = 0;
     
     trigger=1;
     wait_us(10);
@@ -53,8 +53,6 @@
 {
     pulsetime.stop();
     pulsedur = pulsetime.read_us();
-    distance= (pulsedur*343)/20000;
-    pulsetime.reset();
 }
 
 void HCSR04::rise (void (*fptr)(void))
@@ -66,9 +64,11 @@
     echo.fall(fptr);
 }
 
-unsigned int HCSR04::get_dist_cm()
+double HCSR04::get_dist_cm()
 {
-    return distance;
+    if (pulsedur == 0)
+        return -1;
+    return pulsedur * kMicrosecondsToCentimeters;
 }
 unsigned int HCSR04::get_pulse_us()
 {