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frc::Encoder Class Reference

Class to read quad encoders. More...

#include <Encoder.h>

Inheritance diagram for frc::Encoder:
frc::ErrorBase frc::SendableBase frc::CounterBase frc::PIDSource frc::Sendable

Public Types

enum  IndexingType { kResetWhileHigh, kResetWhileLow, kResetOnFallingEdge, kResetOnRisingEdge }
 
- 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 (Encoder &&rhs)
 
Encoderoperator= (Encoder &&rhs)
 
int Get () const override
 Gets the current count. More...
 
void Reset () override
 Reset the Encoder distance to zero. More...
 
double GetPeriod () const override
 Returns the period of the most recent pulse. More...
 
void SetMaxPeriod (double 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...
 
double PIDGet () override
 
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...
 
int GetFPGAIndex () const
 
void InitSendable (SendableBuilder &builder) override
 Initializes this Sendable object. More...
 
- Public Member Functions inherited from frc::ErrorBase
 ErrorBase (ErrorBase &&)=default
 
ErrorBaseoperator= (ErrorBase &&)=default
 
virtual ErrorGetError ()
 Retrieve the current error. More...
 
virtual const ErrorGetError () const
 Retrieve the current error. More...
 
virtual void ClearError () const
 Clear the current error information associated with this sensor.
 
virtual void SetErrnoError (const wpi::Twine &contextMessage, wpi::StringRef filename, wpi::StringRef function, int lineNumber) const
 Set error information associated with a C library call that set an error to the "errno" global variable. More...
 
virtual void SetImaqError (int success, const wpi::Twine &contextMessage, wpi::StringRef filename, wpi::StringRef function, int lineNumber) const
 Set the current error information associated from the nivision Imaq API. More...
 
virtual void SetError (Error::Code code, const wpi::Twine &contextMessage, wpi::StringRef filename, wpi::StringRef function, int lineNumber) const
 Set the current error information associated with this sensor. More...
 
virtual void SetErrorRange (Error::Code code, int32_t minRange, int32_t maxRange, int32_t requestedValue, const wpi::Twine &contextMessage, wpi::StringRef filename, wpi::StringRef function, int lineNumber) const
 Set the current error information associated with this sensor. More...
 
virtual void SetWPIError (const wpi::Twine &errorMessage, Error::Code code, const wpi::Twine &contextMessage, wpi::StringRef filename, wpi::StringRef function, int lineNumber) const
 Set the current error information associated with this sensor. More...
 
virtual void CloneError (const ErrorBase &rhs) const
 
virtual bool StatusIsFatal () const
 Check if the current error code represents a fatal error. More...
 
- Public Member Functions inherited from frc::SendableBase
 SendableBase (bool addLiveWindow=true)
 Creates an instance of the sensor base. More...
 
 SendableBase (SendableBase &&rhs)
 
SendableBaseoperator= (SendableBase &&rhs)
 
std::string GetName () const final
 Gets the name of this Sendable object. More...
 
void SetName (const wpi::Twine &name) final
 Sets the name of this Sendable object. More...
 
std::string GetSubsystem () const final
 Gets the subsystem name of this Sendable object. More...
 
void SetSubsystem (const wpi::Twine &subsystem) final
 Sets the subsystem name of this Sendable object. More...
 
- Public Member Functions inherited from frc::Sendable
 Sendable (Sendable &&)=default
 
Sendableoperator= (Sendable &&)=default
 
void SetName (const wpi::Twine &subsystem, const wpi::Twine &name)
 Sets both the subsystem name and device name of this Sendable object. More...
 
- Public Member Functions inherited from frc::CounterBase
 CounterBase (CounterBase &&)=default
 
CounterBaseoperator= (CounterBase &&)=default
 
- Public Member Functions inherited from frc::PIDSource
virtual void SetPIDSourceType (PIDSourceType pidSource)
 Set which parameter you are using as a process control variable. More...
 
virtual PIDSourceType GetPIDSourceType () const
 

Friends

class DigitalGlitchFilter
 

Additional Inherited Members

- Static Public Member Functions inherited from frc::ErrorBase
static void SetGlobalError (Error::Code code, const wpi::Twine &contextMessage, wpi::StringRef filename, wpi::StringRef function, int lineNumber)
 
static void SetGlobalWPIError (const wpi::Twine &errorMessage, const wpi::Twine &contextMessage, wpi::StringRef filename, wpi::StringRef function, int lineNumber)
 
static const ErrorGetGlobalError ()
 Retrieve the current global error.
 
- Protected Member Functions inherited from frc::SendableBase
void AddChild (std::shared_ptr< Sendable > child)
 Add a child component. More...
 
void AddChild (void *child)
 Add a child component. More...
 
void SetName (const wpi::Twine &moduleType, int channel)
 Sets the name of the sensor with a channel number. More...
 
void SetName (const wpi::Twine &moduleType, int moduleNumber, int channel)
 Sets the name of the sensor with a module and channel number. More...
 
- Protected Attributes inherited from frc::ErrorBase
Error m_error
 
- Protected Attributes inherited from frc::PIDSource
PIDSourceType m_pidSource = PIDSourceType::kDisplacement
 

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.

Constructor & Destructor Documentation

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.
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.
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.

Member Function Documentation

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.

bool frc::Encoder::GetDirection ( ) const
overridevirtual

The last direction the encoder value changed.

Returns
The last direction the encoder value changed.

Implements frc::CounterBase.

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().
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.
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.

double 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.

Implements frc::CounterBase.

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.
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
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)
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.

void frc::Encoder::InitSendable ( SendableBuilder builder)
overridevirtual

Initializes this Sendable object.

Parameters
buildersendable builder

Implements frc::Sendable.

void frc::Encoder::Reset ( )
overridevirtual

Reset the Encoder distance to zero.

Resets the current count to zero on the encoder.

Implements frc::CounterBase.

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.
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
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
channelA digital source to set as the encoder index
typeThe state that will cause the encoder to reset
void frc::Encoder::SetMaxPeriod ( double  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.

Deprecated:
Use SetMinRate() in favor of this method. This takes unscaled periods and SetMinRate() scales using value from SetDistancePerPulse().
Parameters
maxPeriodThe maximum time between rising and falling edges before the FPGA will report the device stopped. This is expressed in seconds.

Implements frc::CounterBase.

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().
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
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.

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