Parallax_X-Band.cpp

00001 #include "Parallax_X-Band.h"
00002 
00003 /** 
00004 * Initialize the xband motion detector and setup interrupts. Default is to be disabled.
00005 *
00006 * @param pin_enable Enable pin. Connected to EN on xband.
00007 * @param pin_input Data pin. Connected to OUT on xband.
00008 */ 
00009 xband::xband(PinName pin_enable, PinName pin_input)
00010     : _pin_enable(pin_enable), _pin_input(pin_input)
00011 {
00012     // Default disabled.
00013     _pin_enable=0;
00014     
00015     // Initialize count to be 0.
00016     _count = 0;
00017     
00018     // No velocity reading has been calculated yet.
00019     _velocityflag = false;
00020     
00021     // Setup interrupt on input pin.
00022     _pin_input.rise(this, &xband::xband_RiseISR);
00023     
00024     // Timer for count differntiation.
00025     _sampletime.start();
00026 
00027     // Interrupt to calculate the velocity. Default every half second.
00028     _samplevelocity.attach(this, &xband::xband_velocityISR, 0.5);
00029 }
00030 
00031 /**
00032 * Destructor
00033 */
00034 xband::~xband() {}
00035 
00036 
00037 
00038 /** 
00039 * Subroutine to enable and disable the detector.
00040 *
00041 * @param enable True to enable, False to disable.
00042 */ 
00043 void xband::enable(bool enable)
00044 {
00045     _pin_enable=enable;
00046 }
00047 
00048 /** 
00049 * Interrupt service routine to collect data on the input pin.
00050 */ 
00051 void xband::xband_RiseISR()
00052 {
00053     // Increment count for every positive rising edge pulse on input pin.
00054     _count++;
00055 }
00056 
00057 /** 
00058 * Interrupt service routine to calculate the velocity of the moving object.
00059 */ 
00060 void xband::xband_velocityISR()
00061 {
00062     // Differentiate current count value change during time slice.
00063     _velocity = ((_count - _lastcount)/(_sampletime.read_ms()/1000.0));
00064     
00065     // Set a flag to indicate a new velocity calculation.
00066     _velocityflag = true;
00067     
00068     // Reset timer for next differentiation.
00069     _sampletime.reset();
00070     _lastcount = _count;
00071 }
00072 
00073 /** 
00074 * Get count value and return it as an integer.
00075 *
00076 * @return Integer value of current count.
00077 */ 
00078 int xband::read_count()
00079 {
00080     return _count;
00081 }
00082 
00083 /** 
00084 * Get current velocity reading in ticks/sec. Sets a flag to false to indicate a stale value after reading.
00085 *
00086 * @return Float value of currently measured velocity.
00087 */
00088 float xband::read_velocity()
00089 {
00090     _velocityflag = false;
00091     return _velocity;
00092 }
00093 
00094 /** 
00095 * Resets the count variable to 0.
00096 */ 
00097 void xband::reset_count()
00098 {
00099     _count = 0;
00100 }
00101 
00102 /** 
00103 * Checks if a new velocity value has been calculated.
00104 *
00105 * @return True if a new velocity value is avaliable. False if the value has
00106 * already been read.
00107 */ 
00108 bool xband::velocityack()
00109 {
00110     return _velocityflag;
00111 }
00112 
00113 /** 
00114 * Default overload to read velocity.
00115 *
00116 * @return Float value of currently measured velocity.
00117 */ 
00118 xband::operator float() {
00119     return read_velocity();
00120 }