Diff: HCSR04.cpp

Revision:

0:0bda99bb39a4

Child:

1:62f97e90a58c

diff -r 000000000000 -r 0bda99bb39a4 HCSR04.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/HCSR04.cpp	Tue Oct 18 14:32:12 2011 +0000
@@ -0,0 +1,41 @@
+#include "HCSR04.h"
+#include "mbed.h"
+
+
+HCSR04::HCSR04(PinName t, PinName e) : trig(t), echo(e) {}
+
+//      Trigger          Echo
+//      _______           _____________,,,,,,,,,
+// ____|  10us |_________| 150us-25ms, or 38ms if no obstacle
+// 
+
+//return echo duration in us (refer to digram above)
+long HCSR04::echo_duration() {
+    timer.reset();
+    trig = 0;
+    wait_us(2);
+    trig = 1;
+    wait_us(10);
+    trig = 0;
+    while(echo == 0);
+    timer.start();
+    while(echo == 1);
+    timer.stop();
+    return timer.read_us();
+}
+
+//return distance to nearest obstacle or returns -1 
+//if no obstacle within range
+//set sys to cm or inch accordingly
+long HCSR04::distance(int sys){
+    duration = echo_duration();
+    if(duration > 30000)
+        return -1;
+    distacne_cm = duration /29 / 2 ;
+    distance_inc = duration / 74 / 2;
+    if (sys)
+        return distacne_cm;
+    else
+        return distance_inc;
+}
+