ping.h

00001 #ifndef PING_H
00002 #define PING_H
00003 
00004 #include "mbed.h"
00005 #include "FPointer.h"
00006 
00007 #define DEFAULT_MEASUREMENT_DELAY_US    5000
00008 #define SPEED_OF_SOUND_CM_PER_US        0.034029
00009 #define SPEED_OF_SOUND_IN_PER_US        0.0133972441
00010 
00011 /**
00012  * Class for interfacing with the Parallax Ping))) Ultrasonic Sensor
00013  *
00014  * See the Ping)) documentation for more information.
00015  * http://www.parallax.com/sites/default/files/downloads/28015-PING-Documentation-v1.6.pdf
00016  */
00017 class Ping {
00018     public:
00019         /**
00020          * @param pin Digital I/O pin used for communicating with the Ping)))
00021          */
00022         Ping (PinName pin);
00023     
00024         /**
00025          * Starts a one shot reading.
00026          *
00027          * @return True if the reading was successfuly started, false if not.
00028          */
00029         bool startReading();
00030         
00031         /**
00032          * Starts a reading.
00033          *
00034          * @param continuous Continuous readings if true, one-shot if false.
00035          * @return True if the reading was successfuly started, false if not.
00036          */
00037         bool startReading(bool continuous);
00038 
00039         /**
00040          * Returns whether the sensor is busy getting a reading
00041          *
00042          * @return True if busy, false if not.
00043          */
00044         bool isBusy() { return mBusy; }
00045         
00046         /**
00047          * Returns whether the valid reading is available
00048          *
00049          * @return True if valid, false if not.
00050          */
00051         bool isValid() { return mValid; }
00052         
00053         /**
00054          * Returns the raw reading from the sensor.
00055          *
00056          * @return The time in uS that the sound travelled from the sensor to an object.
00057          */
00058         uint32_t getRawReading() { return mRawReading; }
00059         
00060         /**
00061          * Sets the delay between continuous readings.
00062          *
00063          * @param delay_us Delay between readings in microseconds.
00064          */
00065         void setContinuousReadingDelay(uint32_t delay_us) { mDelayBetweenReadings = delay_us; }
00066         
00067         /**
00068          * Gets the distance sound can travel, in centimeters, for a given time in uS.
00069          *
00070          * @param time_us Time traveled in microseconds.
00071          * @return The distance traveled in centimeters.
00072          */
00073         static float getDistanceCm(uint32_t time_us) { return time_us * SPEED_OF_SOUND_CM_PER_US; }
00074         
00075         /**
00076          * Gets the distance sound can travel, in inches, for a given time in uS.
00077          *
00078          * @param time_us Time traveled in microseconds.
00079          * @return The distance traveled in inches.
00080          */
00081         static float getDistanceIn(uint32_t time_us) { return time_us * SPEED_OF_SOUND_IN_PER_US; }
00082         
00083         /**
00084          * Attach a callback function that will be called when a valid reading is available.
00085          *
00086          * @param function Function pointer for callback.
00087          */
00088         void attach(uint32_t (*function)(uint32_t) = 0) { mCallback.attach(function); }
00089         
00090         /**
00091          * Attach a class method that will be called when a valid reading is available.
00092          *
00093          * @param item Class object that contains the method to call.
00094          * @param method Method to call.
00095          */ 
00096         template<class T> 
00097         void attach(T* item, uint32_t (T::*method)(uint32_t)) { mCallback.attach(item, method); }
00098     
00099     private:
00100         DigitalInOut mSignalIo;
00101         InterruptIn mEvent;
00102         
00103         bool mBusy;
00104         bool mValid;
00105         bool mContinuous;
00106         uint32_t mDelayBetweenReadings;
00107         
00108         Timer mTimer;
00109         Ticker mMeasureDelayTicker;
00110         
00111         uint32_t mRawReading;
00112         
00113         FPointer mCallback;
00114         
00115         void start();
00116         void stop();
00117         void nextMeasurement();
00118 };
00119 
00120 #endif