encoder.h

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/*----------------------------------------------------------------------------*/
/* Copyright (c) FIRST 2008. All Rights Reserved.							  */
/* Open Source Software - may be modified and shared by FRC teams. The code   */
/* must be accompanied by the FIRST BSD license file in $(WIND_BASE)/WPILib.  */
/*----------------------------------------------------------------------------*/

#ifndef QUAD_ENCODER_H_
#define QUAD_ENCODER_H_

#include "ChipObject.h"
#include "CounterBase.h"
#include "SensorBase.h"
#include "Counter.h"
#include "PIDSource.h"

class DigitalSource;

/**
 * Class to read quad encoders.
 * Quadrature encoders are devices that count shaft rotation and can sense direction. The output of
 * the QuadEncoder class is an integer that can count either up or down, and can go negative for
 * reverse direction counting. When creating QuadEncoders, a direction is supplied that changes the
 * sense of the output to make code more readable if the encoder is mounted such that forward movement
 * generates negative values. Quadrature encoders have two digital outputs, an A Channel and a B Channel
 * that are out of phase with each other to allow the FPGA to do direction sensing. 
 */
class Encoder: public SensorBase, public CounterBase
{
public:
	Encoder(UINT32 aChannel, UINT32 bChannel, bool reverseDirection=false, EncodingType encodingType = k4X);
	Encoder(UINT32 aSlot, UINT32 aChannel, UINT32 bSlot, UINT32 _bChannel, bool reverseDirection=false, EncodingType encodingType = k4X);
	Encoder(DigitalSource *aSource, DigitalSource *bSource, bool reverseDirection=false, EncodingType encodingType = k4X);
	Encoder(DigitalSource &aSource, DigitalSource &bSource, bool reverseDirection=false, EncodingType encodingType = k4X);
	virtual ~Encoder();

	// CounterBase interface
	void Start();
	INT32 Get();
	INT32 GetRaw();
	void Reset();
	void Stop();
	double GetPeriod();
	void SetMaxPeriod(double maxPeriod);
	bool GetStopped();
	bool GetDirection();
	double GetDistance();
	double GetRate();
	void SetMinRate(double minRate);
	void SetDistancePerPulse(double distancePerPulse);
	void SetReverseDirection(bool reverseDirection);

private:
	void InitEncoder(bool _reverseDirection, EncodingType encodingType);
	double DecodingScaleFactor();

	DigitalSource *m_aSource;		// the A phase of the quad encoder
	DigitalSource *m_bSource;		// the B phase of the quad encoder
	bool m_allocatedASource;		// was the A source allocated locally?
	bool m_allocatedBSource;		// was the B source allocated locally?
	tEncoder* m_encoder;
	UINT8 m_index;
	double m_distancePerPulse;		// distance of travel for each encoder tick
	Counter *m_counter;				// Counter object for 1x and 2x encoding
	EncodingType m_encodingType;	// Encoding type
};

#endif