azaleasource/WPILibCProgramming/trunk/WPILib/AnalogTriggerOutput.h

/*----------------------------------------------------------------------------*/
/* 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 ANALOG_TRIGGER_OUTPUT_H_
#define ANALOG_TRIGGER_OUTPUT_H_

#include "DigitalSource.h"

class AnalogTrigger;

/**
 * Class to represent a specific output from an analog trigger.
 * This class is used to get the current output value and also as a DigitalSource
 * to provide routing of an output to digital subsystems on the FPGA such as
 * Counter, Encoder, and Interrupt.
 * 
 * The TriggerState output indicates the primary output value of the trigger.  If the analog
 * signal is less than the lower limit, the output is false.  If the analog value is greater
 * than the upper limit, then the output is true.  If the analog value is in between, then
 * the trigger output state maintains its most recent value.
 * 
 * The InWindow output indicates whether or not the analog signal is inside the range defined
 * by the limits.
 * 
 * The RisingPulse and FallingPulse outputs detect an instantaneous transition from above the
 * upper limit to below the lower limit, and vise versa.  These pulses represent a rollover
 * condition of a sensor and can be routed to an up / down couter or to interrupts.  Because
 * the outputs generate a pulse, they cannot be read directly.  To help ensure that a rollover
 * condition is not missed, there is an average rejection filter available that operates on the
 * upper 8 bits of a 12 bit number and selects the nearest outlyer of 3 samples.  This will reject
 * a sample that is (due to averaging or sampling) errantly between the two limits.  This filter
 * will fail if more than one sample in a row is errantly in between the two limits.  You may see
 * this problem if attempting to use this feature with a mechanical rollover sensor, such as a
 * 360 degree no-stop potentiometer without signal conditioning, because the rollover transition
 * is not sharp / clean enough.  Using the averaging engine may help with this, but rotational speeds of
 * the sensor will then be limited.
 */
class AnalogTriggerOutput: public DigitalSource
{
	friend class AnalogTrigger;
public:
	typedef enum {kInWindow=0, kState=1, kRisingPulse=2, kFallingPulse=3} Type;
	
	virtual ~AnalogTriggerOutput();
	bool Get();

	// DigitalSource interface
	virtual UINT32 GetChannelForRouting();
	virtual UINT32 GetModuleForRouting();
	virtual bool GetAnalogTriggerForRouting();
	virtual void RequestInterrupts(tInterruptHandler handler, void *param=NULL); ///< Asynchronus handler version.
	virtual void RequestInterrupts();		///< Synchronus Wait version.
protected:
	AnalogTriggerOutput(AnalogTrigger *trigger, Type outputType);

private:
	AnalogTrigger *m_trigger;
	Type m_outputType;
};


#endif