Diff: Ping.cpp

Revision:

0:1e4b66122368

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Ping.cpp	Sat Mar 12 22:26:10 2011 +0000
@@ -0,0 +1,54 @@
+#include "Ping.h"
+
+#include "mbed.h"
+
+Ping::Ping(PinName PING_PIN)
+        : _event(PING_PIN)
+        , _cmd(PING_PIN)
+        , _timer()
+        {
+            _event.rise(this,&Ping::_Starts);
+            _event.fall(this,&Ping::_Stops);
+            _SPEED_OF_SOUND_CM = 33;
+        } 
+        
+void Ping::_Starts(void)
+{
+      _Valid = false;  // start the timere, and invalidate the current time.
+      _Busy = true;
+      _timer.start();
+      _Time = _timer.read_us();      
+}
+
+void Ping::_Stops(void)
+{
+      _Valid = true;  // When it stops, update the time
+      _Busy = false;
+      _Time = _timer.read_us()-_Time;
+}
+
+void Ping::Send()
+{
+     
+     _cmd.output();
+     _cmd.write(0);  // see the ping documentation http://www.parallax.com/Portals/0/Downloads/docs/prod/acc/28015-PING-v1.6.pdf
+     wait_us(3);
+     _cmd.write(1);
+     wait_us(3);
+     _cmd.write(0);
+     _cmd.input();
+     
+}
+void Ping::Set_Speed_of_Sound(int SoS_ms )
+{
+     _SPEED_OF_SOUND_CM = SoS_ms;
+}
+
+int Ping::Read_cm()
+// -1 means not valid.
+{
+    if(_Valid && ~_Busy) 
+        return ((_Time*_SPEED_OF_SOUND_CM)/1000);
+    else 
+        return -1;
+}
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