ace_wire::TwoWireInterface< T_WIRE > Class Template Reference

A thin wrapper around an I2C TwoWire class and its Wire object. More...

#include <TwoWireInterface.h>

Public Member Functions
	TwoWireInterface (T_WIRE &wire)
	Constructor. More...
void	begin ()
	Initial the interface. More...
void	end ()
	End the interface. More...
uint8_t	beginTransmission (uint8_t addr)
	Prepare the write buffer to accept a sequence of data, and save the addr for transmission when endTransmission() is called. More...
uint8_t	write (uint8_t data)
	Write data into the write buffer. More...
uint8_t	endTransmission (bool sendStop)
	Send the data in the buffer, with a STOP condition if sendStop is true. More...
uint8_t	endTransmission ()
	Same as endTransmission(bool) but always send STOP condition.
uint8_t	requestFrom (uint8_t addr, uint8_t quantity, bool sendStop)
	Read bytes from the slave and store in buffer owned by T_WIRE and send a STOP condition if sendStop is true. More...
uint8_t	requestFrom (uint8_t addr, uint8_t quantity)
	Read bytes from the slave and store in buffer owned by T_WIRE, and always send a STOP condition. More...
uint8_t	read ()
	Read byte from buffer.
	TwoWireInterface (const TwoWireInterface &)=default
TwoWireInterface &	operator= (const TwoWireInterface &)=default

Detailed Description

template<typename T_WIRE>
class ace_wire::TwoWireInterface< T_WIRE >

A thin wrapper around an I2C TwoWire class and its Wire object.

This is a template class to avoid including the <Wire.h> header file, which increases flash memory on AVR by about 1000 byte even if the Wire object is never used.

This wrapper can also be used with alternative implementations of I2C (software or hardware) so long as they implement some basic API of the TwoWire class: specifically the beginTransmission(), write() and endTransmission() methods. SinceTwoWireInterface` is a template, the alternative implementation classes do not need to inherit from the TwoWire class.

Template Parameters

T_WIRE

underlying class that implements the I2C protocol, usually TwoWire from the pre-installed Wire library, but can be used with other third party libraries that look like TwoWire

Definition at line 50 of file TwoWireInterface.h.

Constructor & Destructor Documentation

TwoWireInterface()

template<typename T_WIRE >

ace_wire::TwoWireInterface< T_WIRE >::TwoWireInterface ( T_WIRE &  wire )

inlineexplicit

Constructor.

Parameters

wire	instance of T_WIRE. If the pre-installed Wire.h is used, then T_WIRE is TwoWire and wire is the precreated Wire object

Definition at line 58 of file TwoWireInterface.h.

Member Function Documentation

begin()

template<typename T_WIRE >

void ace_wire::TwoWireInterface< T_WIRE >::begin ( )

inline

Initial the interface.

Currently does nothing.

Definition at line 61 of file TwoWireInterface.h.

beginTransmission()

template<typename T_WIRE >

uint8_t ace_wire::TwoWireInterface< T_WIRE >::beginTransmission ( uint8_t  addr )

inline

Prepare the write buffer to accept a sequence of data, and save the addr for transmission when endTransmission() is called.

For unbuffered implementations, immediately send the address byte on the I2C bus with the Write bit set.

Returns

always returns 0 to indicate success because the addr is simply written into a buffer

Definition at line 75 of file TwoWireInterface.h.

end()

template<typename T_WIRE >

void ace_wire::TwoWireInterface< T_WIRE >::end ( )

inline

End the interface.

Currently does nothing.

Definition at line 64 of file TwoWireInterface.h.

endTransmission()

template<typename T_WIRE >

uint8_t ace_wire::TwoWireInterface< T_WIRE >::endTransmission ( bool  sendStop )

inline

Send the data in the buffer, with a STOP condition if sendStop is true.

For unbuffered implementations, just send the STOP condition.

Returns the value returned by the underlying T_WIRE::endTransmission() method. For the preinstalled Wire library, the status value definitions are buried in the twi_writeTo() function:

• 0: success
• 1: length too long for buffer
• 2: address send, NACK received
• 3: data send, NACK received
• 4: other twi error (lost bus arbitration, bus error, ..)

Definition at line 106 of file TwoWireInterface.h.

requestFrom() [1/2]

template<typename T_WIRE >

uint8_t ace_wire::TwoWireInterface< T_WIRE >::requestFrom ( uint8_t  addr, uint8_t  quantity  )

inline

Read bytes from the slave and store in buffer owned by T_WIRE, and always send a STOP condition.

Some I2C implementations do not provide a 3-argument version of requestFrom(), so we need to provide an explicit 2-argument versions instead of using a default argument of sendStop = true.

Returns

the value returned by the underlying T_WIRE::requestFrom() method, which will normally be 'quantity' or 0 if an error is encountered.

Definition at line 140 of file TwoWireInterface.h.

requestFrom() [2/2]

template<typename T_WIRE >

uint8_t ace_wire::TwoWireInterface< T_WIRE >::requestFrom ( uint8_t  addr, uint8_t  quantity, bool  sendStop  )

inline

Read bytes from the slave and store in buffer owned by T_WIRE and send a STOP condition if sendStop is true.

Returns

the value returned by the underlying T_WIRE::requestFrom() method, which will normally be 'quantity'. Some implementations, particularly the unbuffered ones, will return 0 to indicate a NACK response from the slave device.

Definition at line 124 of file TwoWireInterface.h.

write()

template<typename T_WIRE >

uint8_t ace_wire::TwoWireInterface< T_WIRE >::write ( uint8_t  data )

inline

Write data into the write buffer.

For unbuffered implementations, immediately send the address byte on the I2C bus with the Write bit set.

Returns

the number of bytes written into buffer, will always be 1. For unbuffered implementations, 0 can be returned if the device responds with a NACK

Definition at line 88 of file TwoWireInterface.h.

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

• /home/brian/src/AceWire/src/ace_wire/TwoWireInterface.h