Class for reading 8 rotary encoders using a MCP23017 I²C port expander. More...

#include <AH/Hardware/MCP23017Encoders.hpp>

Collaboration diagram for MCP23017Encoders< WireType, EncoderPositionType, InterruptSafe >:

Classes
class	MCP23017Encoder
	Proxy to access a single encoder of the 8 encoders managed by MCP23017Encoders. More...

Public Member Functions
	MCP23017Encoders (WireType &wire, uint8_t addr_offset=0, pin_t interrupt_pin=NO_PIN)
	Constructor. More...

void	begin ()
	Initialize the MCP23017. More...

void	update ()
	If the state of the MCP23017's GPIO changed, read the new state and update the encoder positions. More...

EncoderPositionType	read (uint8_t idx) const
	Read the position of the given encoder. More...

EncoderPositionType	readAndReset (uint8_t idx)
	Read the position of the given encoder and reset it to zero. More...

void	write (uint8_t idx, EncoderPositionType pos)
	Set the position of the given encoder. More...

MCP23017Encoder	operator[] (uint8_t index)
	Get a proxy to one of the encoders managed by this MCP23017. More...

Protected Member Functions
template<size_t N>
void	writeI2C (const uint8_t(&values)[N])
	Write any data to the MCP23017. More...

template<class... Args>
void	writeI2C (uint8_t addr, Args... values)
	Write any data to the MCP23017. More...

uint16_t	readGPIO ()
	Read the state of all GPIO pins. More...

Private Types
using	EncoderPositionStorageType = typename std::conditional< InterruptSafe, volatile EncoderPositionType, EncoderPositionType >::type

using	StateStorageType = typename std::conditional< InterruptSafe, volatile uint16_t, uint16_t >::type

Private Attributes
WireType *	wire

uint8_t	address

pin_t	interrupt_pin

StateStorageType	state

EncoderPositionStorageType	positions [8]

Static Private Attributes
constexpr static uint8_t	I2C_BASE_ADDRESS = 0x20

Detailed Description

template<class WireType, class EncoderPositionType = int32_t, bool InterruptSafe = false>
class AH::MCP23017Encoders< WireType, EncoderPositionType, InterruptSafe >

Class for reading 8 rotary encoders using a MCP23017 I²C port expander.

Encoders are indexed by a number from 0 to 7. Encoder #0 is connected to pins GPA0 and GPA1, Encoder #1 is connected to pins GPA2 and GPA3, ..., Encoder #7 is connected to pins GPB6 and GPB7.

Template Parameters

WireType	The type of the `Wire` I²C driver to use.
EncoderPositionType	The type used for saving the encoder positions. `int32_t` is the default because this matches the Encoder library. You can use small unsigned types such as `uint8_t` or `uint16_t` if you're just interrested in the deltas.
InterruptSafe	Make the `update` method safe to use inside of an interrupt. It makes the necessary variables `volatile` and disables interrupts while reading the positions from the main program.

Definition at line 58 of file MCP23017Encoders.hpp.

Member Typedef Documentation

◆ EncoderPositionStorageType

using EncoderPositionStorageType = typename std::conditional<InterruptSafe, volatile EncoderPositionType, EncoderPositionType>::type

private

Definition at line 60 of file MCP23017Encoders.hpp.

◆ StateStorageType

using StateStorageType = typename std::conditional<InterruptSafe, volatile uint16_t, uint16_t>::type

private

Definition at line 63 of file MCP23017Encoders.hpp.

Constructor & Destructor Documentation

◆ MCP23017Encoders()

MCP23017Encoders	(	WireType &	wire,
		uint8_t	addr_offset = `0`,
		pin_t	interrupt_pin = `NO_PIN`
	)

inline

Constructor.

Parameters

wire	The Wire/I²C interface to use.
addr_offset	A number between 0 and 7 reflecting the state of the I2C address pins of the MCP23017.
interrupt_pin	The pin connected to the MCP23017 interrupt pin. This doesn't have to be an interrupt pin of the Arduino. The interrupt pin of the MCP23017 is configured as open-drain active-low output, and the interrupt pins of GPIO banks A and B are mirrored/OR'ed together. This means that you only need to connect a single interrupt pin for each MCP23017, and you can connect the interrupt pins of multiple MCP23017s to a single Arduino pin.

Definition at line 136 of file MCP23017Encoders.hpp.

Member Function Documentation

◆ writeI2C() [1/2]

void writeI2C ( const uint8_t(&) values[N] )

inlineprotected

Write any data to the MCP23017.

Definition at line 79 of file MCP23017Encoders.hpp.

◆ writeI2C() [2/2]

void writeI2C	(	uint8_t	addr,
		Args...	values
	)

inlineprotected

Write any data to the MCP23017.

Parameters

addr	The address of the register to write to.
values	The values to write.

Definition at line 94 of file MCP23017Encoders.hpp.

◆ readGPIO()

uint16_t readGPIO ( )

inlineprotected

Read the state of all GPIO pins.

Definition at line 100 of file MCP23017Encoders.hpp.

◆ begin()

void begin ( )

inline

Initialize the MCP23017.

The configuration register is set to the right config, all GPIO pins are set to input mode, the pin change interrupts are enabled, and the internal pull-up resistors are enabled as well.

The interrupt pin on the Arduino is configured as input with the internal pull-up resistor enabled, because the MCP23017's interrupt output is configured in open-drain mode.

This function does not initialize the I²C interface. You have to call Wire.begin() before calling this function.

Initialize the state

Definition at line 155 of file MCP23017Encoders.hpp.

◆ update()

void update ( )

inline

If the state of the MCP23017's GPIO changed, read the new state and update the encoder positions.

Can be called from within an ISR on boards that support I²C inside of ISRs, on the condition that InterruptSafe is set to true.

Don't call this function both from the ISR and from your main program, only call it from one of the two.

Definition at line 209 of file MCP23017Encoders.hpp.

◆ read()

EncoderPositionType read ( uint8_t idx ) const

inline

Read the position of the given encoder.

Does not update the state, just reads it from the buffered position.

Don't call this function from within an ISR.

Parameters

idx	The index of the encoder to read [0, 7].

Definition at line 255 of file MCP23017Encoders.hpp.

◆ readAndReset()

EncoderPositionType readAndReset ( uint8_t idx )

inline

Read the position of the given encoder and reset it to zero.

Does not update the state, just reads it from the buffered position.

Don't call this function from within an ISR.

Parameters

idx	The index of the encoder to read [0, 7].

Definition at line 276 of file MCP23017Encoders.hpp.

◆ write()

void write	(	uint8_t	idx,
		EncoderPositionType	pos
	)

inline

Set the position of the given encoder.

Don't call this function from within an ISR.

Parameters

idx	The index of the encoder to write [0, 7].
pos	The position value to write.

Definition at line 300 of file MCP23017Encoders.hpp.

◆ operator[]()

MCP23017Encoder operator[] ( uint8_t index )

inline

Get a proxy to one of the encoders managed by this MCP23017.

Parameters

index The index of the encoder to access.

Definition at line 374 of file MCP23017Encoders.hpp.

Member Data Documentation

◆ I2C_BASE_ADDRESS

constexpr static uint8_t I2C_BASE_ADDRESS = 0x20

staticconstexprprivate

Definition at line 67 of file MCP23017Encoders.hpp.

◆ wire

WireType* wire

private

Definition at line 69 of file MCP23017Encoders.hpp.

◆ address

uint8_t address

private

Definition at line 70 of file MCP23017Encoders.hpp.

◆ interrupt_pin

pin_t interrupt_pin

private

Definition at line 71 of file MCP23017Encoders.hpp.

◆ state

StateStorageType state

private

Definition at line 73 of file MCP23017Encoders.hpp.

◆ positions

EncoderPositionStorageType positions[8]

private

Definition at line 74 of file MCP23017Encoders.hpp.

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

MCP23017Encoders.hpp

Classes

Public Member Functions

Protected Member Functions

Private Types

Private Attributes

Static Private Attributes

Detailed Description

template<class WireType, class EncoderPositionType = int32_t, bool InterruptSafe = false> class AH::MCP23017Encoders< WireType, EncoderPositionType, InterruptSafe >

Member Typedef Documentation

◆ EncoderPositionStorageType

◆ StateStorageType

Constructor & Destructor Documentation

◆ MCP23017Encoders()

Member Function Documentation

◆ writeI2C() [1/2]

◆ writeI2C() [2/2]

◆ readGPIO()

◆ begin()

◆ update()

◆ read()

◆ readAndReset()

◆ write()

◆ operator[]()

Member Data Documentation

◆ I2C_BASE_ADDRESS

◆ wire

◆ address

◆ interrupt_pin

◆ state

◆ positions

template<class WireType, class EncoderPositionType = int32_t, bool InterruptSafe = false>
class AH::MCP23017Encoders< WireType, EncoderPositionType, InterruptSafe >