HCSR04.h

00001 /* File: HCSR04.h
00002  * Author: Robert Abad  Copyright (c) 2013
00003  *
00004  * Desc: driver for HCSR04 Ultrasonic Range Finder.  The returned range
00005  *       is in units of meters.
00006  *
00007  *       To use this driver you must call the methods ::startMeas()
00008  *       and ::getMeas().  The HCSR04 requires a trigger time of
00009  *       10 usec (microseconds) which is initiated by ::startMeas().
00010  *       If a successful measurement is made, getMeas() will return
00011  *       RANGE_MEAS_VALID.  If unsuccessful, initiate a new measurement.
00012  *
00013  *       The datasheet for this device can be found here:
00014  *       http://www.elecfreaks.com/store/download/product/Sensor/HC-SR04/HC-SR04_Ultrasonic_Module_User_Guide.pdf
00015  *
00016  *       Below is some sample code:
00017  *
00018  *       #include "mbed.h"
00019  *       #include "HCSR04.h"
00020  *
00021  *       #define PIN_TRIGGER    (p14)
00022  *       #define PIN_ECHO       (p15)
00023  *
00024  *       int main(void)
00025  *       {
00026  *           HCSR04 rangeFinder( PIN_TRIGGER, PIN_ECHO );
00027  *           float range;
00028  *           
00029  *           while (1)
00030  *           {
00031  *               rangeFinder.startMeas();
00032  *               wait(0.1);
00033  *               if ( rangeFinder.getMeas(range) == RANGE_MEAS_VALID )
00034  *               {
00035  *                   printf("range = %f\n\r", range);
00036  *               }
00037  *           }
00038  *       }
00039  */
00040 
00041 #ifndef __HCSR04_H__
00042 #define __HCSR04_H__
00043 
00044 #include "mbed.h"
00045 
00046 typedef enum
00047 {
00048     RANGE_MEAS_INVALID,
00049     RANGE_MEAS_VALID
00050 } etHCSR04_RANGE_STATUS;
00051 
00052 class HCSR04
00053 {
00054 public:
00055     HCSR04( PinName pinTrigger, PinName pinEcho );
00056     void startMeas(void);
00057     etHCSR04_RANGE_STATUS getMeas(float &rRangeMeters);
00058 
00059 private:
00060     DigitalOut trigger;
00061     Ticker triggerTicker;
00062     InterruptIn echo;
00063     Timer echoTimer;
00064     unsigned long measTimeStart_us;
00065     unsigned long measTimeStop_us;
00066     
00067     void triggerTicker_cb(void);    // trigger ticker callback function
00068     void ISR_echoRising(void);      // ISR for rising edge
00069     void ISR_echoFalling(void);     // ISR for falling edge
00070 };
00071 
00072 #endif /* __HCSR04_H__ */