QEI Class Reference

Handle reading pulses from encoder. More...

#include <QEI.h>

Inheritance diagram for QEI:

Public Types
enum	Encoding { X2_ENCODING , X4_ENCODING }
typedef enum QEI::Encoding	Encoding

Public Member Functions
	QEI (PinName channelA, PinName channelB, PinName index, int pulsesPerRev, Encoding encoding=X2_ENCODING)
	Constructor. More...
void	reset (void)
	Reset the encoder. More...
int	getCurrentState (void)
	Read the state of the encoder. More...
int	getInvalidCount (void)
	Read the number of invalid counts. More...
int	getPulses (void)
	Read the number of pulses recorded by the encoder. More...
int	getRevolutions (void)
	Read the number of revolutions recorded by the encoder on the index channel. More...
void	setPulses (int newCount)
	Set the current pulse count in case you want to init it. More...
void	setRevolutions (int newRevs)
	Set the current revolution count in case you want to init it. More...

Private Member Functions
void	encode (void)
	Update the pulse count. More...
void	index (void)
	Called on every rising edge of channel index to update revolution count by one. More...

Private Attributes
Encoding	encoding_
InterruptIn	channelA_
InterruptIn	channelB_
InterruptIn	index_
int	pulsesPerRev_
int	prevState_
int	currState_
volatile int	invalid_
volatile int	pulses_
volatile int	revolutions_

Detailed Description

Handle reading pulses from encoder.

Member Typedef Documentation

Encoding

typedef enum QEI::Encoding QEI::Encoding

Member Enumeration Documentation

Encoding

enum QEI::Encoding

Enumerator
X2_ENCODING
X4_ENCODING

Constructor & Destructor Documentation

QEI()

QEI::QEI	(	PinName	channelA,
		PinName	channelB,
		PinName	index,
		int	pulsesPerRev,
		Encoding	encoding = X2_ENCODING
	)

Constructor.

Reads the current values on channel A and channel B to determine the initial state.

Attaches the encode function to the rise/fall interrupt edges of channels A and B to perform X4 encoding.

Attaches the index function to the rise interrupt edge of channel index (if it is used) to count revolutions.

Parameters

channelA	mbed pin for channel A input.
channelB	mbed pin for channel B input.
index	mbed pin for optional index channel input, (pass NC if not needed).
pulsesPerRev	Number of pulses in one revolution.
encoding	The encoding to use. Uses X2 encoding by default. X2 encoding uses interrupts on the rising and falling edges of only channel A where as X4 uses them on both channels.

Member Function Documentation

reset()

void QEI::reset

(

void

)

Reset the encoder.

Sets the pulses and revolutions count to zero.

getCurrentState()

int QEI::getCurrentState

(

void

)

Read the state of the encoder.

Returns

The current state of the encoder as a 2-bit number, where: bit 1 = The reading from channel B bit 2 = The reading from channel A

getInvalidCount()

int QEI::getInvalidCount

(

void

)

Read the number of invalid counts.

Note

Reading this resets the counter!

Returns

the number of times the gray-code transition was violated.

getPulses()

int QEI::getPulses

(

void

)

Read the number of pulses recorded by the encoder.

Returns

Number of pulses which have occured.

getRevolutions()

int QEI::getRevolutions

(

void

)

Read the number of revolutions recorded by the encoder on the index channel.

Returns

Number of revolutions which have occured on the index channel.

setPulses()

void QEI::setPulses

(

int

newCount

)

Set the current pulse count in case you want to init it.

Parameters

[in]

newCount

is the count to set it to.

setRevolutions()

void QEI::setRevolutions

(

int

newRevs

)

Set the current revolution count in case you want to init it.

Parameters

[in]

newRevs

is the count to set it to.

encode()

void QEI::encode ( void  )

private

Update the pulse count.

Called on every rising/falling edge of channels A/B.

Reads the state of the channels and determines whether a pulse forward or backward has occured, updating the count appropriately.

index()

void QEI::index ( void  )

private

Called on every rising edge of channel index to update revolution count by one.

Member Data Documentation

encoding_

Encoding QEI::encoding_

private

channelA_

InterruptIn QEI::channelA_

private

channelB_

InterruptIn QEI::channelB_

private

index_

InterruptIn QEI::index_

private

pulsesPerRev_

int QEI::pulsesPerRev_

private

prevState_

int QEI::prevState_

private

currState_

int QEI::currState_

private

invalid_

volatile int QEI::invalid_

private

pulses_

volatile int QEI::pulses_

private

revolutions_

volatile int QEI::revolutions_

private

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

• /github/workspace/include/QEI/QEI.h