Revision 0:02a23e3031ee, committed 2012-09-24

Comitter:

mio

Date:

Mon Sep 24 15:52:56 2012 +0000

Commit message:

Import PING code to local.

Changed in this revision

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/PING.cpp	Mon Sep 24 15:52:56 2012 +0000
@@ -0,0 +1,91 @@
+#include "PING.h"
+#include "mbed.h"
+
+/*
+ * Constructor
+ */
+PING::PING(PinName trigger) : _trigger(trigger)
+{
+   // Attach interrupts
+   _ticker.attach(this, &PING::_startRange, 0.1);
+   _invalidctr = 0 ;
+}
+
+void PING::_startRange()
+{
+   int invalid ;
+   invalid = 0 ;
+
+   // send a trigger pulse, 20uS long
+   _trigger.output(); // set pin to output trigger pulse
+   _trigger = 0; // ensure pin starts low
+   wait_us(2); // wait two microseconds
+   _trigger = 1; // send trigger pulse by setting pin high
+   wait_us(5); // keep sending pulse for 5 microseconds
+   _trigger = 0; // set pin low to stop pulse
+   _trigger.input();
+
+   // pulseIn
+   _timer.reset();
+   _timer.start();
+   while (!_trigger) {
+    if (_timer.read_us() > 10000) { // invalid thre
+        invalid = 1;
+        break ;
+    }
+   } // wait for high
+   if (invalid == 0) 
+   {
+    _timer.stop();
+    _timer.reset();
+    _timer.start();
+    while (_trigger) {
+     if (_timer.read_us() > 10000) 
+     { // invalid thre
+            invalid = 1 ;
+            break ;
+     }
+    } // wait for low
+    _timer.stop();
+   }
+   if (invalid == 0) {
+        _dist = _timer.read_us(); //provides echo time in microseconds
+        _invalidctr = 0 ;
+   } else {
+        _invalidctr++ ;
+        if (_invalidctr > 5) { // Invalid (none) thre
+            _dist = 0.0 ;
+            _invalidctr = 0 ;
+        }
+   }
+}
+
+// returns distance in meters
+// The speed of sound is 340 m/s or 58 microseconds per meter.
+// The ping travels out and back, so to find the distance of the
+// object we take half of the distance travelled.
+float PING::read(void)
+{
+   // spin until there is a good value
+   return (_dist/29/2);
+}
+
+// returns distance in inches
+// According to Parallax's datasheet for the PING))), there are
+// 73.746 microseconds per inch (i.e. sound travels at 1130 feet per
+// second).  This gives the distance travelled by the ping, outbound
+// and return, so we divide by 2 to get the distance of the obstacle.
+// See: http://www.parallax.com/dl/docs/prod/acc/28015-PING-v1.3.pdf
+
+// 2012.9.25 : Add check echo timeout detection
+
+float PING::read_in(void)
+{
+   // spin until there is a good value
+   return (_dist/74/2);
+}
+
+PING::operator float()
+{
+   return read();
+}
\ No newline at end of file

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/PING.h	Mon Sep 24 15:52:56 2012 +0000
@@ -0,0 +1,72 @@
+#ifndef MBED_PING_H
+#define MBED_PING_H
+#include "mbed.h"
+
+/* Class: PING
+ *  Abstraction for the PING Ultrasonic range finder
+ *
+ * Example:
+ * > // Print measured distance
+ * >
+ * > #include "mbed.h"
+ * > #include "PING.h"
+ * >
+ * > PING ping(p9);
+ * >
+ * > int main() {
+ * >     while(1) {
+ * >         printf("Measured : %.1f\n", ping.read());
+ * >         wait(0.2);
+ * >     }
+ * > }
+ */
+class PING
+{
+// Public functions
+public:
+   /* Constructor: PING
+    *  Create a PING object, connected to the specified pins
+    *
+    * Variables:
+    *  trigger - Output to trigger the PING
+    */
+   PING(PinName trigger);
+
+   /* Function: read
+    *  A non-blocking function that will return the last measurement
+    *
+    * Variables:
+    *  returns - floating point representation in cm.
+    */
+   float read(void);
+
+   /* Function: read_in
+    *  A non-blocking function that will return the last measurement
+    *
+    * Variables:
+    *  returns - floating point representation in in.
+    */
+   float read_in(void);
+
+   /* Function: operator float
+    *  A short hand way of using the read function
+    *
+    * Example:
+    * > float range = ping.read();
+    * > float range = ping;
+    * >
+    * > if(ping.read() > 0.25) { ... }
+    * > if(ping > 0.25) { ... }
+    */
+   operator float();
+
+private :
+   DigitalInOut _trigger;
+   Timer _timer;
+   Ticker _ticker;
+   void _startRange(void);
+   float _dist;
+   int _invalidctr;
+};
+
+#endif
\ No newline at end of file

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/main.cpp	Mon Sep 24 15:52:56 2012 +0000
@@ -0,0 +1,14 @@
+#include "mbed.h"
+#include "PING.h"
+
+PING ping(p9);
+Serial pc(USBTX,USBRX) ;
+int main() 
+{
+    pc.baud(115200) ;
+    pc.printf("start!\r\n") ;
+    while(1) {
+        pc.printf("Measured : %.1f\r\n", ping.read());
+        wait(0.2);
+    }
+}

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mbed.bld	Mon Sep 24 15:52:56 2012 +0000
@@ -0,0 +1,1 @@
+http://mbed.org/users/mbed_official/code/mbed/builds/cd19af002ccc
\ No newline at end of file