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# TCA9548

Arduino Library for TCA9548 I2C multiplexer.


## Description

Library for the TCA9548 and TCA9548a I2C multiplexer.
The library allows you to enable 0 to 7 I2C channels (ports) uniquely or simultaneously.
This is especially useful if you have multiple devices/sensors that have a fixed address,
or you have address conflicts between I2C devices

**Warning**
The library is not tested extensively.

I2C address is 0x70 .. 0x77.

The library caches the channels enabled, and if a channel is enabled,
it will not be enabled again (low level) to optimize performance.


## Interface


### Constructor

- **TCA9548(const uint8_t deviceAddress, TwoWire \*wire = &Wire)** Constructor, address = 0x70 .. 0x77, wire = Wire or WireN.
- **bool begin(uint8_t sda, uint8_t scl, uint8_t mask = 0x00)**  Set I2C pins for ESP32, set mask of channels to be enabled.
- **bool begin(uint8_t mask = 0x00)**  set mask of channels to be enabled.
- **bool isConnected()** returns true if address of the multiplexer is found on I2C bus.


### Find device

- **bool isConnected(uint8_t address)** returns true if arbitrary address is found on I2C bus.
This can be used to verify a certain device is available (or not) on an enabled channel.


### Channel functions

- **void enableChannel(uint8_t channel)** enables channel 0 .. 7 non-exclusive. 
Multiple channels can be enabled in parallel.
- **void disableChannel(uint8_t channel)** disables channel 0 .. 7. 
Will not disable other channels.
- **void selectChannel(uint8_t channel)** enables a single channel 0 .. 7 exclusive. 
All other channels will be disabled in the same call, so not before or after.
- **bool isEnabled(uint8_t channel)** returns true if the channel is enabled.
- **void setChannelMask(uint8_t mask)** enables 0 or more channels simultaneously with a bit mask.
- **uint8_t getChannelMask()** reads back the bit mask of the channels enabled.
- **void setResetPin(uint8_t resetPin)** sets the pin to reset the chip. (Not tested)
- **void reset()** trigger the reset pin.
- **int getError()** returns the last I2C error.


### Forced IO

When forced IO is set all writes and read - **getChannelMask()** - will go to the device.
If the flag is set to false it will cache the value of the channels enabled.
This will result in more responsive / faster calls. 
Note that writes are only optimized if the channels are already set.

- **void setForced(bool forced = false)** set forced write, slower but more robust.
  - forced == false == fast mode (default).
  - forced == true == robust mode.
- **bool getForced()** returns set flag.


## Operation

See example


## Future

#### must
- improve documentation.
- improve error handling 

#### should
- add examples
- test test and test
- write unit test
- add **disableAll()**  == setChannelMask(0)

#### could
- set an "always enabled" mask  (have to investigate the consequences)
- check PCA9548 compatibility