I2cDiscreteIoExpander Class Reference

Public Member Functions
	I2cDiscreteIoExpander (uint8_t)
	Constructor. More...
uint8_t	digitalRead ()
	Retrieve discrete values from device. More...
uint8_t	digitalWrite (uint16_t)
	Write discrete values to device. More...
uint8_t	getAddress ()
	Retrieve device address. More...
uint16_t	getPorts ()
	Retrieve ports 1 (P17..P10), 0 (P07..P00). More...
void	enableBitwiseInversion ()
	Enable bitwise inversion. More...
void	disableBitwiseInversion ()
	Disable bitwise inversion. More...
bool	isInverted ()
	Indicate whether bitwise inversion is enabled. More...

Private Attributes
uint8_t	address_
	Device address as defined by pins A2, A1, A0.
uint16_t	ports_
	Storage object for I2cDiscreteIoExpander ports 1 (P17..P10), 0 (P07..P00).
bool	shouldInvert_
	Flag indicating whether bits are to be inverted before read/write (false=don't invert, true=invert).

Static Private Attributes
static const uint8_t	BASE_ADDRESS_ = 0x20
	Factory pre-set slave address.

Related Functions
(Note that these are not member functions.)
static const uint8_t	TWI_SUCCESS = 0
	I2C/TWI success (transaction was successful).
static const uint8_t	TWI_DEVICE_NACK = 2
	I2C/TWI device not present (address sent, NACK received).
static const uint8_t	TWI_DATA_NACK = 3
	I2C/TWI data not received (data sent, NACK received).
static const uint8_t	TWI_ERROR = 4
	I2C/TWI other error.

Detailed Description

Examples:

examples/BareMinimum/BareMinimum.ino, and examples/MultipleDevices/MultipleDevices.ino.

Constructor & Destructor Documentation

I2cDiscreteIoExpander()

I2cDiscreteIoExpander::I2cDiscreteIoExpander

(

uint8_t

address

)

Constructor.

Assigns device address, resets storage object, enables bitwise inversion.

Required Function:

Call this to construct I2cDiscreteIoExpander object.

Usage:

...
I2cDiscreteIoExpander exampleA(1);             // device with address 1
I2cDiscreteIoExpander exampleB[2] = { 2, 3 };  // devices with addresses 2, 3
I2cDiscreteIoExpander exampleC[2] = { I2cDiscreteIoExpander(4), I2cDiscreteIoExpander(5) }; // alternate constructor syntax; devices with addresses 4, 5
I2cDiscreteIoExpander exampleD[8] = { 0, 1, 2, 3, 4, 5, 6, 7 }; // addresses 0..7
...

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

Assigns device address, resets storage object, enables bitwise inversion.

Usage:

...
I2cDiscreteIoExpander device;        // implies device address 0
...

{
  address_ = address & 0b111;
  ports_ = 0;
  shouldInvert_ = true;
}

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Member Function Documentation

digitalRead()

uint8_t I2cDiscreteIoExpander::digitalRead

(

)

Retrieve discrete values from device.

Required Function:

Call this from within loop() in order to read from device.

Return values

0	success
1	length too long for buffer
2	address send, NACK received (device not on bus)
3	data send, NACK received
4	other twi error (lost bus arbitration, bus error, ...)

Usage:

...
I2cDiscreteIoExpander device;
...
uint8_t status = device.digitalRead();
if (TWI_SUCCESS == status)
{
  // do something with device.getPorts()
}
...

Examples:

examples/BareMinimum/BareMinimum.ino, and examples/MultipleDevices/MultipleDevices.ino.

{
  uint8_t hi, lo, status;
  
  Wire.beginTransmission(BASE_ADDRESS_ | address_);
  status = Wire.endTransmission();

  if (TWI_SUCCESS == status)
  {
    if (Wire.requestFrom(BASE_ADDRESS_ | address_, 2) == 2)
    {
      lo = Wire.read();
      hi = Wire.read();
      ports_ = shouldInvert_ ? word(~hi, ~lo) : word(hi, lo);
    }
    else
    {
      return TWI_ERROR;
    }
  }

  return status;
}

digitalWrite()

uint8_t I2cDiscreteIoExpander::digitalWrite

(

uint16_t

ports

)

Write discrete values to device.

Required Function:

Call this from within loop() in order to write to device.

Parameters

ports

word to be written to device (0x0000..0xFFFF)

Return values

0	success
1	length too long for buffer
2	address send, NACK received (device not on bus)
3	data send, NACK received
4	other twi error (lost bus arbitration, bus error, ...)

Usage:

...
I2cDiscreteIoExpander device;
...
uint8_t status = device.digitalWrite(0xFFFF);
if (TWI_SUCCESS == status)
{
  // do something
}
...

Examples:

examples/BareMinimum/BareMinimum.ino, and examples/MultipleDevices/MultipleDevices.ino.

{
  ports_ = shouldInvert_ ? ~ports : ports;
  Wire.beginTransmission(BASE_ADDRESS_ | address_);
  Wire.write(lowByte(ports_));
  Wire.write(highByte(ports_));
  // Wire.write(lowByte(shouldInvert_ ? ~ports_ : ports_));
  // Wire.write(highByte(shouldInvert_ ? ~ports_ : ports_));

  return Wire.endTransmission();
}

getAddress()

uint8_t I2cDiscreteIoExpander::getAddress

(

)

Retrieve device address.

Optional Function (Troubleshooting):

This function is for testing and troubleshooting.

Returns

address of device (0..7)

Usage:

...
I2cDiscreteIoExpander device;
...
address = device.getAddress();
...

Examples:

examples/BareMinimum/BareMinimum.ino.

{
  return address_;
}

getPorts()

uint16_t I2cDiscreteIoExpander::getPorts

(

)

Retrieve ports 1 (P17..P10), 0 (P07..P00).

Required Function:

Call this from within loop() to retrieve ports.

Returns

ports of device (0x0000..0xFFFF)

Usage:

...
I2cDiscreteIoExpander device;
...
ports = device.getPorts();
...

Examples:

examples/BareMinimum/BareMinimum.ino.

{
  return ports_;
}

enableBitwiseInversion()

void I2cDiscreteIoExpander::enableBitwiseInversion

(

)

Enable bitwise inversion.

All bits will be inverted prior to future read/write operations.

Usage:

...
I2cDiscreteIoExpander device;
...
device.enableBitwiseInversion();      // bits will now inverted
...

See also

I2cDiscreteIoExpander::disableBitwiseInversion()

I2cDiscreteIoExpander::isInverted()

{
  ports_ = shouldInvert_ ? ports_ : ~ports_;
  shouldInvert_ = true;
}

disableBitwiseInversion()

void I2cDiscreteIoExpander::disableBitwiseInversion

(

)

Disable bitwise inversion.

Bits will not be inverted prior to future read/write operations.

Usage:

...
I2cDiscreteIoExpander device;
...
device.disableBitwiseInversion();     // bits will no longer be inverted
...

See also

I2cDiscreteIoExpander::enableBitwiseInversion()

I2cDiscreteIoExpander::isInverted()

{
  ports_ = shouldInvert_ ? ~ports_ : ports_;
  shouldInvert_ = false;
}

isInverted()

bool I2cDiscreteIoExpander::isInverted

(

)

Indicate whether bitwise inversion is enabled.

Returns

status of bitwise inversion (false=not inverted, true=inverted)

Usage:

...
I2cDiscreteIoExpander device;
...
if (device.isInverted())
{
  // do something
}
...

See also

I2cDiscreteIoExpander::enableBitwiseInversion()

I2cDiscreteIoExpander::disableBitwiseInversion()

{
  return shouldInvert_;
}

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

• I2cDiscreteIoExpander.h
• I2cDiscreteIoExpander.cpp