WPILibC++ 2024.3.1
frc::Encoder Class Reference

Class to read quad encoders. More...

#include <frc/Encoder.h>

Inheritance diagram for frc::Encoder:
frc::CounterBase wpi::Sendable wpi::SendableHelper< 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
 
Encoderoperator= (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
 
CounterBaseoperator= (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)
 
SendableHelperoperator= (const SendableHelper &rhs)=default
 
SendableHelperoperator= (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

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
aChannelThe a channel DIO channel. 0-9 are on-board, 10-25 are on the MXP port
bChannelThe b channel DIO channel. 0-9 are on-board, 10-25 are on the MXP port
reverseDirectionrepresents the orientation of the encoder and inverts the output values if necessary so forward represents positive values.
encodingTypeeither 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
aSourceThe source that should be used for the a channel.
bSourcethe source that should be used for the b channel.
reverseDirectionrepresents the orientation of the encoder and inverts the output values if necessary so forward represents positive values.
encodingTypeeither 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
aSourceThe source that should be used for the a channel.
bSourcethe source that should be used for the b channel.
reverseDirectionrepresents the orientation of the encoder and inverts the output values if necessary so forward represents positive values.
encodingTypeeither 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
buildersendable 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
distancePerPulseThe 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
sourceA digital source to set as the encoder index
typeThe 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
channelA DIO channel to set as the encoder index
typeThe 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
maxPeriodThe 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
minRateThe 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
reverseDirectiontrue 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
samplesToAverageThe 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
devicesimulated 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: