Class to read quad encoders. More...

#include <frc/Encoder.h>

Inheritance diagram for frc::Encoder:

Public Types
enum	IndexingType { kResetWhileHigh , kResetWhileLow , kResetOnFallingEdge , kResetOnRisingEdge }
	Encoder indexing types. More...

Public Types inherited from frc::CounterBase
enum	EncodingType { k1X , k2X , k4X }

Public Member Functions
	Encoder (int aChannel, int bChannel, bool reverseDirection=false, EncodingType encodingType=k4X)
	Encoder constructor. More...

	Encoder (DigitalSource aSource, DigitalSource bSource, bool reverseDirection=false, EncodingType encodingType=k4X)
	Encoder constructor. More...

	Encoder (DigitalSource &aSource, DigitalSource &bSource, bool reverseDirection=false, EncodingType encodingType=k4X)
	Encoder constructor. More...

	Encoder (std::shared_ptr< DigitalSource > aSource, std::shared_ptr< DigitalSource > bSource, bool reverseDirection=false, EncodingType encodingType=k4X)

	~Encoder () override

	Encoder (Encoder &&)=default

Encoder &	operator= (Encoder &&)=default

int	Get () const override
	Gets the current count. More...

void	Reset () override
	Reset the Encoder distance to zero. More...

units::second_t	GetPeriod () const override
	Returns the period of the most recent pulse. More...

void	SetMaxPeriod (units::second_t maxPeriod) override
	Sets the maximum period for stopped detection. More...

bool	GetStopped () const override
	Determine if the encoder is stopped. More...

bool	GetDirection () const override
	The last direction the encoder value changed. More...

int	GetRaw () const
	Gets the raw value from the encoder. More...

int	GetEncodingScale () const
	The encoding scale factor 1x, 2x, or 4x, per the requested encodingType. More...

double	GetDistance () const
	Get the distance the robot has driven since the last reset. More...

double	GetRate () const
	Get the current rate of the encoder. More...

void	SetMinRate (double minRate)
	Set the minimum rate of the device before the hardware reports it stopped. More...

void	SetDistancePerPulse (double distancePerPulse)
	Set the distance per pulse for this encoder. More...

double	GetDistancePerPulse () const
	Get the distance per pulse for this encoder. More...

void	SetReverseDirection (bool reverseDirection)
	Set the direction sensing for this encoder. More...

void	SetSamplesToAverage (int samplesToAverage)
	Set the Samples to Average which specifies the number of samples of the timer to average when calculating the period. More...

int	GetSamplesToAverage () const
	Get the Samples to Average which specifies the number of samples of the timer to average when calculating the period. More...

void	SetIndexSource (int channel, IndexingType type=kResetOnRisingEdge)
	Set the index source for the encoder. More...

void	SetIndexSource (const DigitalSource &source, IndexingType type=kResetOnRisingEdge)
	Set the index source for the encoder. More...

void	SetSimDevice (HAL_SimDeviceHandle device)
	Indicates this encoder is used by a simulated device. More...

int	GetFPGAIndex () const

void	InitSendable (wpi::SendableBuilder &builder) override
	Initializes this Sendable object. More...

Public Member Functions inherited from frc::CounterBase
	CounterBase ()=default

virtual	~CounterBase ()=default

	CounterBase (CounterBase &&)=default

CounterBase &	operator= (CounterBase &&)=default

virtual int	Get () const =0

virtual void	Reset ()=0

virtual units::second_t	GetPeriod () const =0

virtual void	SetMaxPeriod (units::second_t maxPeriod)=0

virtual bool	GetStopped () const =0

virtual bool	GetDirection () const =0

Public Member Functions inherited from wpi::Sendable
virtual	~Sendable ()=default

virtual void	InitSendable (SendableBuilder &builder)=0
	Initializes this Sendable object. More...

Public Member Functions inherited from wpi::SendableHelper< Encoder >
	SendableHelper (const SendableHelper &rhs)=default

	SendableHelper (SendableHelper &&rhs)

SendableHelper &	operator= (const SendableHelper &rhs)=default

SendableHelper &	operator= (SendableHelper &&rhs)

Friends
class	DMA

class	DMASample

class	DigitalGlitchFilter

Additional Inherited Members
Protected Member Functions inherited from wpi::SendableHelper< Encoder >
	SendableHelper ()=default

	~SendableHelper ()

Detailed Description

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.

All encoders will immediately start counting - Reset() them if you need them to be zeroed before use.

Member Enumeration Documentation

◆ IndexingType

enum frc::Encoder::IndexingType

Encoder indexing types.

Enumerator
kResetWhileHigh	Reset while the signal is high.
kResetWhileLow	Reset while the signal is low.
kResetOnFallingEdge	Reset on falling edge of the signal.
kResetOnRisingEdge	Reset on rising edge of the signal.

Constructor & Destructor Documentation

◆ Encoder() [1/5]

frc::Encoder::Encoder	(	int	aChannel,
		int	bChannel,
		bool	reverseDirection = `false`,
		EncodingType	encodingType = `k4X`
	)

Encoder constructor.

Construct a Encoder given a and b channels.

The counter will start counting immediately.

Parameters

aChannel	The a channel DIO channel. 0-9 are on-board, 10-25 are on the MXP port
bChannel	The b channel DIO channel. 0-9 are on-board, 10-25 are on the MXP port
reverseDirection	represents the orientation of the encoder and inverts the output values if necessary so forward represents positive values.
encodingType	either k1X, k2X, or k4X to indicate 1X, 2X or 4X decoding. If 4X is selected, then an encoder FPGA object is used and the returned counts will be 4x the encoder spec'd value since all rising and falling edges are counted. If 1X or 2X are selected then a counter object will be used and the returned value will either exactly match the spec'd count or be double (2x) the spec'd count.

◆ Encoder() [2/5]

frc::Encoder::Encoder	(	DigitalSource *	aSource,
		DigitalSource *	bSource,
		bool	reverseDirection = `false`,
		EncodingType	encodingType = `k4X`
	)

Encoder constructor.

Construct a Encoder given a and b channels as digital inputs. This is used in the case where the digital inputs are shared. The Encoder class will not allocate the digital inputs and assume that they already are counted.

The counter will start counting immediately.

Parameters

aSource	The source that should be used for the a channel.
bSource	the source that should be used for the b channel.
reverseDirection	represents the orientation of the encoder and inverts the output values if necessary so forward represents positive values.
encodingType	either k1X, k2X, or k4X to indicate 1X, 2X or 4X decoding. If 4X is selected, then an encoder FPGA object is used and the returned counts will be 4x the encoder spec'd value since all rising and falling edges are counted. If 1X or 2X are selected then a counter object will be used and the returned value will either exactly match the spec'd count or be double (2x) the spec'd count.

◆ Encoder() [3/5]

frc::Encoder::Encoder	(	DigitalSource &	aSource,
		DigitalSource &	bSource,
		bool	reverseDirection = `false`,
		EncodingType	encodingType = `k4X`
	)

Encoder constructor.

Construct a Encoder given a and b channels as digital inputs. This is used in the case where the digital inputs are shared. The Encoder class will not allocate the digital inputs and assume that they already are counted.

The counter will start counting immediately.

Parameters

aSource	The source that should be used for the a channel.
bSource	the source that should be used for the b channel.
reverseDirection	represents the orientation of the encoder and inverts the output values if necessary so forward represents positive values.
encodingType	either k1X, k2X, or k4X to indicate 1X, 2X or 4X decoding. If 4X is selected, then an encoder FPGA object is used and the returned counts will be 4x the encoder spec'd value since all rising and falling edges are counted. If 1X or 2X are selected then a counter object will be used and the returned value will either exactly match the spec'd count or be double (2x) the spec'd count.

◆ Encoder() [4/5]

frc::Encoder::Encoder	(	std::shared_ptr< DigitalSource >	aSource,
		std::shared_ptr< DigitalSource >	bSource,
		bool	reverseDirection = `false`,
		EncodingType	encodingType = `k4X`
	)

◆ ~Encoder()

frc::Encoder::~Encoder ( )

override

◆ Encoder() [5/5]

frc::Encoder::Encoder ( Encoder && )

default

Member Function Documentation

◆ Get()

int frc::Encoder::Get ( ) const

overridevirtual

Gets the current count.

Returns the current count on the Encoder. This method compensates for the decoding type.

Returns: Current count from the Encoder adjusted for the 1x, 2x, or 4x scale factor.

Implements frc::CounterBase.

◆ GetDirection()

bool frc::Encoder::GetDirection ( ) const

overridevirtual

The last direction the encoder value changed.

Returns: The last direction the encoder value changed.

Implements frc::CounterBase.

◆ GetDistance()

double frc::Encoder::GetDistance ( ) const

Get the distance the robot has driven since the last reset.

Returns: The distance driven since the last reset as scaled by the value from SetDistancePerPulse().

◆ GetDistancePerPulse()

double frc::Encoder::GetDistancePerPulse ( ) const

Get the distance per pulse for this encoder.

Returns: The scale factor that will be used to convert pulses to useful units.

◆ GetEncodingScale()

int frc::Encoder::GetEncodingScale ( ) const

The encoding scale factor 1x, 2x, or 4x, per the requested encodingType.

Used to divide raw edge counts down to spec'd counts.

◆ GetFPGAIndex()

int frc::Encoder::GetFPGAIndex ( ) const

◆ GetPeriod()

units::second_t frc::Encoder::GetPeriod ( ) const

overridevirtual

Returns the period of the most recent pulse.

Returns the period of the most recent Encoder pulse in seconds. This method compensates for the decoding type.

Warning: This returns unscaled periods. Use GetRate() for rates that are scaled using the value from SetDistancePerPulse().

Returns: Period in seconds of the most recent pulse.

Deprecated:: Use getRate() in favor of this method.

Implements frc::CounterBase.

◆ GetRate()

double frc::Encoder::GetRate ( ) const

Get the current rate of the encoder.

Units are distance per second as scaled by the value from SetDistancePerPulse().

Returns: The current rate of the encoder.

◆ GetRaw()

int frc::Encoder::GetRaw ( ) const

Gets the raw value from the encoder.

The raw value is the actual count unscaled by the 1x, 2x, or 4x scale factor.

Returns: Current raw count from the encoder

◆ GetSamplesToAverage()

int frc::Encoder::GetSamplesToAverage ( ) const

Get the Samples to Average which specifies the number of samples of the timer to average when calculating the period.

Perform averaging to account for mechanical imperfections or as oversampling to increase resolution.

Returns: The number of samples being averaged (from 1 to 127)

◆ GetStopped()

bool frc::Encoder::GetStopped ( ) const

overridevirtual

Determine if the encoder is stopped.

Using the MaxPeriod value, a boolean is returned that is true if the encoder is considered stopped and false if it is still moving. A stopped encoder is one where the most recent pulse width exceeds the MaxPeriod.

Returns: True if the encoder is considered stopped.

Implements frc::CounterBase.

◆ InitSendable()

void frc::Encoder::InitSendable ( wpi::SendableBuilder & builder )

overridevirtual

Initializes this Sendable object.

Parameters

builder sendable builder

Implements wpi::Sendable.

◆ operator=()

Encoder & frc::Encoder::operator= ( Encoder && )

default

◆ Reset()

void frc::Encoder::Reset ( )

overridevirtual

Reset the Encoder distance to zero.

Resets the current count to zero on the encoder.

Implements frc::CounterBase.

◆ SetDistancePerPulse()

void frc::Encoder::SetDistancePerPulse ( double distancePerPulse )

Set the distance per pulse for this encoder.

This sets the multiplier used to determine the distance driven based on the count value from the encoder.

Do not include the decoding type in this scale. The library already compensates for the decoding type.

Set this value based on the encoder's rated Pulses per Revolution and factor in gearing reductions following the encoder shaft.

This distance can be in any units you like, linear or angular.

Parameters

distancePerPulse The scale factor that will be used to convert pulses to useful units.

◆ SetIndexSource() [1/2]

void frc::Encoder::SetIndexSource	(	const DigitalSource &	source,
		IndexingType	type = `kResetOnRisingEdge`
	)

Set the index source for the encoder.

When this source is activated, the encoder count automatically resets.

Parameters

source	A digital source to set as the encoder index
type	The state that will cause the encoder to reset

◆ SetIndexSource() [2/2]

void frc::Encoder::SetIndexSource	(	int	channel,
		IndexingType	type = `kResetOnRisingEdge`
	)

Set the index source for the encoder.

When this source is activated, the encoder count automatically resets.

Parameters

channel	A DIO channel to set as the encoder index
type	The state that will cause the encoder to reset

◆ SetMaxPeriod()

void frc::Encoder::SetMaxPeriod ( units::second_t maxPeriod )

overridevirtual

Sets the maximum period for stopped detection.

Sets the value that represents the maximum period of the Encoder before it will assume that the attached device is stopped. This timeout allows users to determine if the wheels or other shaft has stopped rotating. This method compensates for the decoding type.

Parameters

maxPeriod The maximum time between rising and falling edges before the FPGA will report the device stopped. This is expressed in seconds.

Deprecated:: Use SetMinRate() in favor of this method. This takes unscaled periods and SetMinRate() scales using value from SetDistancePerPulse().

Implements frc::CounterBase.

◆ SetMinRate()

void frc::Encoder::SetMinRate ( double minRate )

Set the minimum rate of the device before the hardware reports it stopped.

Parameters

minRate The minimum rate. The units are in distance per second as scaled by the value from SetDistancePerPulse().

◆ SetReverseDirection()

void frc::Encoder::SetReverseDirection ( bool reverseDirection )

Set the direction sensing for this encoder.

This sets the direction sensing on the encoder so that it could count in the correct software direction regardless of the mounting.

Parameters

reverseDirection true if the encoder direction should be reversed

◆ SetSamplesToAverage()

void frc::Encoder::SetSamplesToAverage ( int samplesToAverage )

Set the Samples to Average which specifies the number of samples of the timer to average when calculating the period.

Perform averaging to account for mechanical imperfections or as oversampling to increase resolution.

Parameters

samplesToAverage The number of samples to average from 1 to 127.

◆ SetSimDevice()

void frc::Encoder::SetSimDevice ( HAL_SimDeviceHandle device )

Indicates this encoder is used by a simulated device.

Parameters

device simulated device handle

Friends And Related Function Documentation

◆ DigitalGlitchFilter

friend class DigitalGlitchFilter

friend

◆ DMA

friend class DMA

friend

◆ DMASample

friend class DMASample

friend

The documentation for this class was generated from the following file:

frc/Encoder.h

Public Types

Public Member Functions

Friends

Additional Inherited Members

Detailed Description

Member Enumeration Documentation

◆ IndexingType

Constructor & Destructor Documentation

◆ Encoder() [1/5]

◆ Encoder() [2/5]

◆ Encoder() [3/5]

◆ Encoder() [4/5]

◆ ~Encoder()

◆ Encoder() [5/5]

Member Function Documentation

◆ Get()

◆ GetDirection()

◆ GetDistance()

◆ GetDistancePerPulse()

◆ GetEncodingScale()

◆ GetFPGAIndex()

◆ GetPeriod()

◆ GetRate()

◆ GetRaw()

◆ GetSamplesToAverage()

◆ GetStopped()

◆ InitSendable()

◆ operator=()

◆ Reset()

◆ SetDistancePerPulse()

◆ SetIndexSource() [1/2]

◆ SetIndexSource() [2/2]

◆ SetMaxPeriod()

◆ SetMinRate()

◆ SetReverseDirection()

◆ SetSamplesToAverage()

◆ SetSimDevice()

Friends And Related Function Documentation

◆ DigitalGlitchFilter

◆ DMA

◆ DMASample