text: /*
    PololuQTRSensors.h - Library for using Pololu QTR reflectance
  	sensors and reflectance sensor arrays: QTR-1A, QTR-8A, QTR-1RC, and 
  	QTR-8RC.  The object used will determine the type of the sensor (either
  	QTR-xA or QTR-xRC).  Then simply specify in the constructor which 
  	Arduino I/O pins are connected to a QTR sensor, and the read() method
  	will obtain reflectance measurements for those sensors.  Smaller sensor
  	values correspond to higher reflectance (e.g. white) while larger
  	sensor values correspond to lower reflectance (e.g. black or a void).
  	
  	* PololuQTRSensorsRC should be used for QTR-1RC and QTR-8RC sensors.
  	* PololuQTRSensorsAnalog should be used for QTR-1A and QTR-8A sensors.
  */
  	
  /*
   * Written by Ben Schmidel et al., May 28, 2008.
   * Copyright (c) 2008 Pololu Corporation. For more information, see
   *
   *   http://www.pololu.com
   *   http://forum.pololu.com
   *   http://www.pololu.com/docs/0J18/9
   *
   * You may freely modify and share this code, as long as you keep this
   * notice intact (including the two links above).  Licensed under the
   * Creative Commons BY-SA 3.0 license:
   *
   *   http://creativecommons.org/licenses/by-sa/3.0/
   *
   * Disclaimer: To the extent permitted by law, Pololu provides this work
   * without any warranty.  It might be defective, in which case you agree
   * to be responsible for all resulting costs and damages.
   */
  
  #ifndef PololuQTRSensors_h
  #define PololuQTRSensors_h
  
  #define QTR_EMITTERS_OFF 0
  #define QTR_EMITTERS_ON 1
  #define QTR_EMITTERS_ON_AND_OFF 2
  
  // This class cannot be instantiated directly (it has no constructor).
  // Instead, you should instantiate one of its two derived classes (either the
  // QTR-A or QTR-RC version, depending on the type of your sensor).
  class PololuQTRSensors
  {
    public:
  	
  	// Reads the sensor values into an array. There *MUST* be space
  	// for as many values as there were sensors specified in the constructor.
  	// Example usage:
  	// unsigned int sensor_values[8];
  	// sensors.read(sensor_values);
  	// The values returned are a measure of the reflectance in abstract units,
  	// with higher values corresponding to lower reflectance (e.g. a black
  	// surface or a void).
  	// If measureOffAndOn is true, measures the values with the
  	// emitters on AND off and returns on - (timeout - off).  If this
  	// value is less than zero, it returns zero.
  	// This method will call the appropriate derived class' readPrivate(), as
  	// determined by the _type data member.  Making this method virtual
  	// leads to compiler warnings, which is why this alternate approach was
  	// taken.
  	void read(unsigned int *sensor_values, unsigned char readMode = QTR_EMITTERS_ON);
  	
  	// Turn the IR LEDs off and on.  This is mainly for use by the
  	// read method, and calling these functions before or
  	// after the reading the sensors will have no effect on the
  	// readings, but you may wish to use these for testing purposes.
  	void emittersOff();
  	void emittersOn();
    
  	// Reads the sensors for calibration.  The sensor values are
  	// not returned; instead, the maximum and minimum values found
  	// over time are stored internally and used for the
  	// readCalibrated() method.
  	void calibrate(unsigned char readMode = QTR_EMITTERS_ON);
  
  	// Returns values calibrated to a value between 0 and 1000, where
  	// 0 corresponds to the minimum value read by calibrate() and 1000
  	// corresponds to the maximum value.  Calibration values are
  	// stored separately for each sensor, so that differences in the
  	// sensors are accounted for automatically.
  	void readCalibrated(unsigned int *sensor_values, unsigned char readMode = QTR_EMITTERS_ON);
  
  	// Operates the same as read calibrated, but also returns an
  	// estimated position of the robot with respect to a line. The
  	// estimate is made using a weighted average of the sensor indices
  	// multiplied by 1000, so that a return value of 0 indicates that
  	// the line is directly below sensor 0, a return value of 1000
  	// indicates that the line is directly below sensor 1, 2000
  	// indicates that it's below sensor 2000, etc.  Intermediate
  	// values indicate that the line is between two sensors.  The
  	// formula is:
  	// 
  	//    0*value0 + 1000*value1 + 2000*value2 + ...
  	//   --------------------------------------------
  	//         value0  +  value1  +  value2 + ...
  	//
  	// By default, this function assumes a dark line (high values)
  	// surrounded by white (low values).  If your line is light on
  	// black, set the optional second argument white_line to true.  In
  	// this case, each sensor value will be replaced by (1000-value)
  	// before the averaging.
  	int readLine(unsigned int *sensor_values, unsigned char readMode = QTR_EMITTERS_ON, unsigned char white_line = 0);
  
  	// Calibrated minumum and maximum values. These start at 1000 and
  	// 0, respectively, so that the very first sensor reading will
  	// update both of them.
  	//
  	// The pointers are unallocated until calibrate() is called, and
  	// then allocated to exactly the size required.  Depending on the
  	// readMode argument to calibrate, only the On or Off values may
  	// be allocated, as required.
  	//
  	// These variables are made public so that you can use them for
  	// your own calculations and do things like saving the values to
  	// EEPROM, performing sanity checking, etc.
  	unsigned int *calibratedMinimumOn;
  	unsigned int *calibratedMaximumOn;
  	unsigned int *calibratedMinimumOff;
  	unsigned int *calibratedMaximumOff;
  	
  	~PololuQTRSensors();
  
    protected:
  
  	PololuQTRSensors()
  	{
  	
  	};
  
  	void init(unsigned char numSensors, unsigned char emitterPin,
  		unsigned char type);
  	unsigned char _numSensors;
  
  	unsigned char _emitterBitmask;
  	// pointer to emitter PORT register
  	volatile unsigned char* _emitterPORT;	// needs to be volatile
  	// pointer to emitter DDR register
  	volatile unsigned char* _emitterDDR;		// needs to be volatile
  	
  	unsigned int _maxValue; // the maximum value returned by this function
  
    private:
  	
  	unsigned char _type;	// the type of the derived class (QTR_RC
  							// or QTR_A)
  
  	// Handles the actual calibration. calibratedMinimum and
  	// calibratedMaximum are pointers to the requested calibration
  	// arrays, which will be allocated if necessary.
  	void calibrateOnOrOff(unsigned int **calibratedMinimum,
  						  unsigned int **calibratedMaximum,
  						  unsigned char readMode);
  };
  
  
  
  // Object to be used for QTR-1RC and QTR-8RC sensors
  class PololuQTRSensorsRC : public PololuQTRSensors
  {
  	// allows the base PololuQTRSensors class to access this class' 
  	// readPrivate()
  	friend class PololuQTRSensors;
  	
    public:
    
  	// if this constructor is used, the user must call init() before using
  	// the methods in this class
  	PololuQTRSensorsRC() { }
  	
  	// this constructor just calls init()
  	PololuQTRSensorsRC(unsigned char* pins, unsigned char numSensors, 
  		  unsigned int timeout = 4000, unsigned char emitterPin = 255);
  
  	// the array 'pins' contains the Arduino pin assignment for each
  	// sensor.  For example, if pins is {3, 6, 15}, sensor 1 is on
  	// Arduino digital pin 3, sensor 2 is on Arduino digital pin 6,
  	// and sensor 3 is on Arduino analog input 1 (digital pin 15).
  	// Note that Arduino digital pins 0 - 7 correpsond to port D
  	// pins PD0 - PD7, respectively.  Arduino digital pins 8 - 13
  	// correspond to port B pins PB0 - PB5.  Arduino analog inputs
  	// 0 - 5 are referred to as digital pins 14 - 19 (these are the
  	// enumerations you should use for this library) and correspond
  	// to port C pins PC0 - PC5.
  	
  	// 'numSensors' specifies the length of the 'pins' array (i.e. the
  	// number of QTR-RC sensors you are using).  numSensors must be 
  	// no greater than 8.
  	
  	// 'timeout' specifies the length of time in timer2 counts beyond
  	// which you consider the sensor reading completely black.  That is to say,
  	// if the pulse length for a pin exceeds 'timeout', pulse timing will stop
  	// and the reading for that pin will be considered full black.
  	// It is recommended that you set timeout to be between 1000 and
  	// 3000 us, depending on things like the height of your sensors and
  	// ambient lighting.  Using timeout allows you to shorten the
  	// duration of a sensor-reading cycle while still maintaining
  	// useful analog measurements of reflectance.  On a 16 MHz microcontroller,
  	// you can convert timer2 counts to microseconds by dividing by 2
  	// (i.e. 2000 us = 4000 timer2 counts = 'timeout' of 4000).  On a 20 MHz
  	// microcontroller, you can convert timer2 counts to microseconds by
  	// dividing by 2.5 or multiplying by 0.4 
  	// (i.e. 2000 us = 5000 timer2 counts = 'timeout' of 5000).
  	
  	// emitterPin is the Arduino digital pin that controls whether the IR LEDs
  	// are on or off.  This pin is optional and only exists on the 8A and 8RC
  	// QTR sensor arrays.  If a valid pin is specified,
  	// the emitters will only be turned on during a reading.  If an invalid
  	// pin is specified (e.g. 255), the IR emitters will always be on.
  	void init(unsigned char* pins, unsigned char numSensors, 
  		  unsigned int timeout = 4000, unsigned char emitterPin = 255);
  		  
  
    
    private:
  
  	// Reads the sensor values into an array. There *MUST* be space
  	// for as many values as there were sensors specified in the constructor.
  	// Example usage:
  	// unsigned int sensor_values[8];
  	// sensors.read(sensor_values);
  	// The values returned are a measure of the reflectance in timer2 counts,
  	// with higher values corresponding to lower reflectance (e.g. a black
  	// surface or a void).  Timer2 will be running at the MCU clock / 8, which
  	// means 2 MHz for a 16 MHz MCU and 2.5 MHz for a 20 MHz MCU.
  	void readPrivate(unsigned int *sensor_values);
   
  
    private:
  
  	unsigned char _bitmask[8];
  	// pointer to PIN registers
  	volatile unsigned char* _register[8];	// needs to be volatile
  		
  	unsigned char _portBMask;
  	unsigned char _portCMask;
  	unsigned char _portDMask;
  };
  
  
  
  // Object to be used for QTR-1A and QTR-8A sensors
  class PololuQTRSensorsAnalog : public PololuQTRSensors
  {
  	// allows the base PololuQTRSensors class to access this class' 
  	// readPrivate()
  	friend class PololuQTRSensors;
  	
    public:
    
  	// if this constructor is used, the user must call init() before using
  	// the methods in this class
  	PololuQTRSensorsAnalog() { }
  	
  	// this constructor just calls init()
  	PololuQTRSensorsAnalog(unsigned char* analogPins, 
  		unsigned char numSensors, unsigned char numSamplesPerSensor = 4,
  		unsigned char emitterPin = 255);
  
  	// the array 'pins' contains the Arduino analog pin assignment for each
  	// sensor.  For example, if pins is {0, 1, 7}, sensor 1 is on
  	// Arduino analog input 0, sensor 2 is on Arduino analog input 1,
  	// and sensor 3 is on Arduino analog input 7.  The ATmega168 has 8
  	// total analog input channels (0 - 7) that correspond to port C
  	// pins PC0 - PC7.
  	
  	// 'numSensors' specifies the length of the 'analogPins' array (i.e. the
  	// number of QTR-A sensors you are using).  numSensors must be 
  	// no greater than 8.
  	
  	// 'numSamplesPerSensor' indicates the number of 10-bit analog samples
  	// to average per channel (i.e. per sensor) for each reading.  The total
  	// number of analog-to-digital conversions performed will be equal to
  	// numSensors*numSamplesPerSensor.  Note that the amount of time it takes
  	// to perform a single analog-to-digital conversion is approximately:
  	// 128 * 13 / F_CPU = 1664 / F_CPU
  	// If F_CPU is 16 MHz, as on most Arduinos, this becomes:
  	// 1664 / 16 MHz = 104 us
  	// So if numSamplesPerSensor is 4 and numSensors is, say, 6, it will take
  	// 4 * 6 * 104 us = 2.5 ms to perform a full readLine() if F_CPU is 16 MHz.
  	// Increasing this parameter increases noise suppression at the cost of
  	// sample rate.  Recommended value: 4.
  	
  	// emitterPin is the Arduino digital pin that controls whether the IR LEDs
  	// are on or off.  This pin is optional and only exists on the 8A and 8RC
  	// QTR sensor arrays.  If a valid pin is specified, the emitters will only
  	// be turned on during a reading.  If an invalid pin is specified 
  	// (e.g. 255), the IR emitters will always be on.
  	void init(unsigned char* analogPins, unsigned char numSensors, 
  		unsigned char numSamplesPerSensor = 4, unsigned char emitterPin = 255);
  		  
  
    
    private:
  
  	// Reads the sensor values into an array. There *MUST* be space
  	// for as many values as there were sensors specified in the constructor.
  	// Example usage:
  	// unsigned int sensor_values[8];
  	// sensors.read(sensor_values);
  	// The values returned are a measure of the reflectance in terms of a
  	// 10-bit ADC average with higher values corresponding to lower 
  	// reflectance (e.g. a black surface or a void).
  	void readPrivate(unsigned int *sensor_values);
   
  
    private:
  
  	unsigned char _analogPins[8];
  	unsigned char _numSamplesPerSensor;
  	unsigned char _portCMask;
  };
  
  
  #endif
  
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