Revision 0:5461d44a187c, committed 2013-11-24

Comitter:

rabad1

Date:

Sun Nov 24 21:45:46 2013 +0000

Commit message:

initial release

Changed in this revision

diff -r 000000000000 -r 5461d44a187c HCSR04.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/HCSR04.cpp	Sun Nov 24 21:45:46 2013 +0000
@@ -0,0 +1,100 @@
+/* File: HCSR04.h
+ * Author: Robert Abad  Copyright (c) 2013
+ *
+ * Desc: driver for HCSR04 Ultrasonic Range Finder.  See header file,
+ *       HCSR04.h, for more details.
+ */
+
+#include "mbed.h"
+#include "HCSR04.h"
+
+#define SPEED_OF_SOUND      (343.2f)    // meters/sec
+
+// HCSR04 TRIGGER pin
+#define SIGNAL_HIGH     (1)
+#define SIGNAL_LOW      (0)
+
+#define TRIGGER_TIME    (10)            // microseconds
+
+
+// Name: HCSR04
+// Desc: HCSR04 constructor
+// Inputs: PinName - pin used for trigger signal
+//         PinName - pin used for echo signal
+// Outputs: none
+//
+HCSR04::HCSR04( PinName pinTrigger, PinName pinEcho ) : 
+trigger(pinTrigger),
+echo(pinEcho),
+measTimeStart_us(0),
+measTimeStop_us(0)
+{
+    echo.rise( this, &HCSR04::ISR_echoRising );
+    echo.fall( this, &HCSR04::ISR_echoFalling );
+    echoTimer.start();
+}
+
+// Name: startMeas
+// Desc: initiates range measurement driving the trigger signal HIGH then sets
+//       a timer to keep trigger HIGH for the duration of TRIGGER_TIME
+// Inputs: none
+// Outputs: none
+//
+void HCSR04::startMeas(void)
+{
+    trigger = SIGNAL_HIGH;
+    echoTimer.reset();
+    triggerTicker.attach_us(this, &HCSR04::triggerTicker_cb, TRIGGER_TIME);
+}
+ 
+// Name: getMeas
+// Desc: returns range measurement in meters
+// Inputs: float & - reference to range measurement
+// Outputs: etHCSR04 - RANGE_MEAS_VALID or RANGE_MEAS_INVALID
+//
+etHCSR04_RANGE_STATUS HCSR04::getMeas(float &rRangeMeters)
+{
+    unsigned long dTime_us;
+    if ( !measTimeStart_us || !measTimeStop_us )
+    {
+        return RANGE_MEAS_INVALID;
+    }
+    
+    dTime_us = measTimeStop_us - measTimeStart_us;
+    rRangeMeters = (float)dTime_us / 1000000. * SPEED_OF_SOUND / 2;
+    measTimeStart_us = 0;
+    measTimeStop_us = 0;
+    return ( RANGE_MEAS_VALID );
+}
+
+// Name: triggerTicker_cb
+// Desc: Timer ticker callback function used to drive trigger signal LOW
+// Inputs: none
+// Outputs: none
+//
+void HCSR04::triggerTicker_cb(void)
+{
+    trigger = SIGNAL_LOW;
+}
+
+
+// Name: ISR_echoRising
+// Desc: ISR for rising edge of HCSR04 ECHO signal
+// Inputs: none
+// Outputs: none
+//
+void HCSR04::ISR_echoRising(void)
+{
+    measTimeStart_us = echoTimer.read_us();
+}
+
+// Name: ISR_echoFalling
+// Desc: ISR for falling edge of HCSR04 ECHO signal
+// Inputs: none
+// Outputs: none
+//
+void HCSR04::ISR_echoFalling(void)
+{
+    measTimeStop_us = echoTimer.read_us();
+}
+

diff -r 000000000000 -r 5461d44a187c HCSR04.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/HCSR04.h	Sun Nov 24 21:45:46 2013 +0000
@@ -0,0 +1,72 @@
+/* File: HCSR04.h
+ * Author: Robert Abad  Copyright (c) 2013
+ *
+ * Desc: driver for HCSR04 Ultrasonic Range Finder.  The returned range
+ *       is in units of meters.
+ *
+ *       To use this driver you must call the methods ::startMeas()
+ *       and ::getMeas().  The HCSR04 requires a trigger time of
+ *       10 usec (microseconds) which is initiated by ::startMeas().
+ *       If a successful measurement is made, getMeas() will return
+ *       RANGE_MEAS_VALID.  If unsuccessful, initiate a new measurement.
+ *
+ *       The datasheet for this device can be found here:
+ *       http://www.elecfreaks.com/store/download/product/Sensor/HC-SR04/HC-SR04_Ultrasonic_Module_User_Guide.pdf
+ *
+ *       Below is some sample code:
+ *
+ *       #include "mbed.h"
+ *       #include "HCSR04.h"
+ *
+ *       #define PIN_TRIGGER    (p14)
+ *       #define PIN_ECHO       (p15)
+ *
+ *       int main(void)
+ *       {
+ *           HCSR04 rangeFinder( PIN_TRIGGER, PIN_ECHO );
+ *           float range;
+ *           
+ *           while (1)
+ *           {
+ *               rangeFinder.startMeas();
+ *               wait(0.1);
+ *               if ( rangeFinder.getMeas(range) == RANGE_MEAS_VALID )
+ *               {
+ *                   printf("range = %f\n\r", range);
+ *               }
+ *           }
+ *       }
+ */
+
+#ifndef __HCSR04_H__
+#define __HCSR04_H__
+
+#include "mbed.h"
+
+typedef enum
+{
+    RANGE_MEAS_INVALID,
+    RANGE_MEAS_VALID
+} etHCSR04_RANGE_STATUS;
+
+class HCSR04
+{
+public:
+    HCSR04( PinName pinTrigger, PinName pinEcho );
+    void startMeas(void);
+    etHCSR04_RANGE_STATUS getMeas(float &rRangeMeters);
+
+private:
+    DigitalOut trigger;
+    Ticker triggerTicker;
+    InterruptIn echo;
+    Timer echoTimer;
+    unsigned long measTimeStart_us;
+    unsigned long measTimeStop_us;
+    
+    void triggerTicker_cb(void);    // trigger ticker callback function
+    void ISR_echoRising(void);      // ISR for rising edge
+    void ISR_echoFalling(void);     // ISR for falling edge
+};
+
+#endif /* __HCSR04_H__ */