TCA9555

Arduino library for TCA9555 16 channel I2C port expander.

Description

This library gives easy control over the 16 pins of a TCA9555 chip.

The TCA9555 supports up to 400 kHz I2C.

TCA9535

from datasheet:

The TCA9535 is identical to the TCA9555, except that the TCA9535 does not include the internal I/O pull-up resistor, which requires pull-ups and pull-downs on unused I/O pins when configured as an input and not driven. This reduces power consumption when the I/O is held low.

There is a TCA9535 class which is a (convenience) wrapper around the TCA9555 class. This allows one to create TCA9535 objects.

Interface

Check the datasheet for details

Constructor

TCA9555(uint8_t address, TwoWire *wire = &Wire) constructor, with default Wire interface. Can be overruled with Wire0..WireN.
TCA9535(uint8_t address, TwoWire *wire = &Wire) idem.
bool begin() for UNO, returns true if successful.
bool begin(uint8_t sda, uint8_t scl) for ESP32, returns true if successful.
bool isConnected() returns true if connected, false otherwise.

1 pin interface

bool pinMode(uint8_t pin, uint8_t mode) idem.
bool digitalWrite(uint8_t pin, uint8_t value) pin = 0..15, value = LOW(0) HIGH (!0), returns true if successful.
uint8_t digitalRead(uint8_t pin) pin = 0..15, returns the value of the pin HIGH or LOW.
bool setPolarity(uint8_t pin, uint8_t value) inverts polarity of an INPUT pin.
uint8_t getPolarity(uint8_t pin) returns 1 if a pin is inverted.

8 pin interface

port = 0..1
mask = 0..255

bool pinMode8(uint8_t port, uint8_t mask) set the mode of eight pins in one call.
bool write8(uint8_t port, uint8_t mask) returns true if successful. Especially useful if one needs to trigger multiple pins at the exact same time.
uint8_t read8(uint8_t port) returns a bit pattern for pins 0..7 or pins 8..15.
bool setPolarity8(uint8_t port, uint8_t mask) inverts polarity of the 8 INPUT pins in one action.
uint8_t getPolarity(uint8_t port) returns a mask with a 1 for every INPUT pin that is inverted.

16 pin interface

Be aware that the 16 pins interface does two calls to the 8 pins interface. So it is impossible to switch pins from the 2 groups of 8 at exactly the same time without additional hardware.

bool pinMode16(uint16_t mask) set the mode of sixteen pins in one call.
bool write16(uint16_t mask) mask = 0x0000 .. 0xFFFF, returns true if successful.
uint16_t read16() Returns a bit pattern for pins 0..15.
bool setPolarity16(uint16_t mask) inverts polarity of the 8 INPUT pins in one action. Returns true upon success.
uint16_t getPolarity() returns a mask of 16 bits with a 1 for every INPUT pin that is inverted.

Error codes

int lastError() Above functions set an error flag that can be read with this function. Reading it will reset the flag to TCA9555_OK.

DESCRIPTION	VALUE
TCA9555_OK	0x00
TCA9555_PIN_ERROR	0x81
TCA9555_I2C_ERROR	0x82
TCA9555_VALUE_ERROR	0x83
TCA9555_PORT_ERROR	0x84
TCA9555_INVALID_READ	-100

Operation

See examples

Future

Must

test all functionality (initial version is written with no hardware around)
add TCA9535 error codes

Could

buy TCA9555 / TCA9535
rethink class hierarchy?
investigate internal pull up etc.

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