Parallax_X-Band.h

00001 #ifndef PARALLAX_X_BAND_H
00002 #define PARALLAX_X_BAND_H
00003 #include "mbed.h"
00004 
00005 /**
00006  * Wrapper for the Parallax X-Band Motion Detector
00007  */
00008 class xband
00009 {
00010 public:
00011 
00012     /** 
00013     * Initialize the xband motion detector and setup interrupts on specified pins.
00014     * Default is to be disabled.
00015     *
00016     * @param pin_enable Enable pin. Connected to EN on xband.
00017     * @param pin_input Data pin. Connected to OUT on xband.
00018     */ 
00019     xband(PinName pin_enable, PinName pin_input);
00020     
00021     /**
00022     * Destructor
00023     */
00024     ~xband();
00025     
00026     /** 
00027     * Subroutine to enable and disable the detector.
00028     *
00029     * @param enable True to enable, False to disable.
00030     */ 
00031     void enable(bool enable);
00032 
00033     /** 
00034     * Get count value and return it as an integer.
00035     *
00036     * @return Integer value of current count.
00037     */ 
00038     int read_count();
00039     
00040     /** 
00041     * Resets the count variable to 0.
00042     */ 
00043     void reset_count();
00044     
00045     /** 
00046     * Checks if a new velocity value has been calculated.
00047     *
00048     * @return True if a new velocity value is avaliable. False if the value has
00049     * already been read.
00050     */ 
00051     bool velocityack();
00052     
00053     /** 
00054     * Get current velocity reading in ticks/sec. Sets a flag to false to indicate a stale value after reading.
00055     *
00056     * @return Float value of currently measured velocity.
00057     */ 
00058     float read_velocity();
00059     
00060     /** 
00061     * Default overload to read velocity.
00062     *
00063     * @return Float value of currently measured velocity.
00064     */ 
00065     operator float();
00066     
00067 private:    
00068     /** 
00069     * Interrupt service routine to collect data on the input pin.
00070     */ 
00071     void xband_RiseISR();
00072     
00073     /** 
00074     * Interrupt service routine to calculate the velocity of the moving object.
00075     */ 
00076     void xband_velocityISR();
00077 
00078     // Setup pin input types.
00079     DigitalOut _pin_enable;
00080     InterruptIn _pin_input;
00081 
00082     // Stores count value.
00083     volatile int _count;
00084     // Old count value.
00085     volatile int _lastcount;
00086     // Store calculated velocity.
00087     float _velocity;
00088     // Velocity read status flag.
00089     bool _velocityflag;
00090 
00091     // Timer for differentiation
00092     Timer _sampletime;
00093     
00094     // Interrupt to calculate velocity.
00095     Ticker _samplevelocity;
00096 };
00097 
00098 #endif