wpilibc/Athena/include/AnalogTriggerOutput.h

/*----------------------------------------------------------------------------*/
/* Copyright (c) FIRST 2008-2016. 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 the root directory of */
/* the project.                                                               */
/*----------------------------------------------------------------------------*/

#pragma once

#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:
  virtual ~AnalogTriggerOutput();
  bool Get() const;

  // DigitalSource interface
  virtual uint32_t GetChannelForRouting() const override;
  virtual uint32_t GetModuleForRouting() const override;
  virtual bool GetAnalogTriggerForRouting() const override;

 protected:
  AnalogTriggerOutput(const AnalogTrigger &trigger, AnalogTriggerType outputType);

 private:
  // Uses reference rather than smart pointer because a user can not construct
  // an AnalogTriggerOutput themselves and because the AnalogTriggerOutput
  // should always be in scope at the same time as an AnalogTrigger.
  const AnalogTrigger &m_trigger;
  AnalogTriggerType m_outputType;
};