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# 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
- buy TCA9555 / TCA9535
- test all functionality (initial version is written with no hardware around)

#### Should
- INPUT_PULLUP mappen op INPUT (pinMode ?)
- investigate internal pull up etc.
- add TCA9535 error codes
- investigate TCA9535 differences
  - elaborate derived class 

#### Could
- rethink class hierarchy