### Initialize Library with begin()

Source: https://context7.com/wifwaf/tca9548a/llms.txt

Initialize the library with a TwoWire instance. For ESP32 boards, ensure custom SDA/SCL pins are set before calling this method.

```cpp
#include <Arduino.h>
#include "TCA9548A.h"

TCA9548A I2CMux;

void setup() {
  Serial.begin(9600);

  // For ESP32 with custom pins (call before begin)
  // Wire.setPins(21, 22);  // SDA, SCL

  // Initialize with default Wire instance
  I2CMux.begin(Wire);

  // Set known initial state
  I2CMux.closeAll();

  Serial.println("TCA9548A initialized");
}

void loop() {
  // I2C multiplexer ready for use
}
```

--------------------------------

### begin(TwoWire &inWire)

Source: https://context7.com/wifwaf/tca9548a/llms.txt

Initializes the library with a specific TwoWire instance.

```APIDOC
## void begin(TwoWire &inWire)

### Description
Initializes the TCA9548A library. Must be called before other functions.

### Parameters
#### Request Body
- **inWire** (TwoWire&) - Required - The I2C bus instance to use.
```

--------------------------------

### Open all channels with openAll()

Source: https://context7.com/wifwaf/tca9548a/llms.txt

Opens all 8 channels simultaneously by writing 0xFF to the control register. Ensure all connected devices have unique I2C addresses to prevent bus conflicts.

```cpp
#include <Arduino.h>
#include "TCA9548A.h"

TCA9548A I2CMux;

void setup() {
  Serial.begin(9600);
  I2CMux.begin(Wire);
  I2CMux.closeAll();
}

void loop() {
  Serial.println("Opening all channels...");
  I2CMux.openAll();

  Serial.print("Register value: ");
  Serial.println(I2CMux.readRegister());  // Output: 255 (binary: 11111111)

  // Warning: Only use openAll() when devices on different channels
  // have unique I2C addresses to avoid bus conflicts

  delay(1000);

  I2CMux.closeAll();
  Serial.print("After closeAll: ");
  Serial.println(I2CMux.readRegister());  // Output: 0

  delay(2000);
}
```

--------------------------------

### Initialize TCA9548A Instance

Source: https://context7.com/wifwaf/tca9548a/llms.txt

Create a multiplexer instance using the default address 0x70 or a custom address based on hardware pin configuration.

```cpp
#include <Arduino.h>
#include "TCA9548A.h"

// Create instance with default address 0x70
TCA9548A I2CMux;

// Create instance with custom address (0x70-0x77 based on A0-A2 pins)
TCA9548A I2CMux2(0x71);

void setup() {
  Serial.begin(9600);
  I2CMux.begin(Wire);
  I2CMux2.begin(Wire);
}
```

--------------------------------

### Manage Channels with openChannel()

Source: https://context7.com/wifwaf/tca9548a/llms.txt

Open one or multiple channels simultaneously for parallel device communication. Channels remain open until explicitly closed.

```cpp
#include <Arduino.h>
#include "TCA9548A.h"

TCA9548A I2CMux;

void setup() {
  Serial.begin(9600);
  I2CMux.begin(Wire);
  I2CMux.closeAll();
}

void loop() {
  // Open single channel for device communication
  I2CMux.openChannel(0);
  // Communicate with device on channel 0
  // ... your I2C device code here ...
  I2CMux.closeChannel(0);

  // Open multiple channels simultaneously
  I2CMux.openChannel(1);
  I2CMux.openChannel(2);
  I2CMux.openChannel(3);
  // All three channels now active
  // ... communicate with devices on channels 1, 2, and 3 ...
  I2CMux.closeAll();

  delay(1000);
}
```

--------------------------------

### Open All Channels

Source: https://context7.com/wifwaf/tca9548a/llms.txt

Opens all 8 channels simultaneously. Use with caution as this exposes all connected devices to the I2C bus at once. Ensure devices on different channels have unique I2C addresses to avoid bus conflicts.

```APIDOC
## openAll()

### Description
Opens all 8 channels simultaneously by writing 0xFF to the control register.

### Method
`openAll()`

### Parameters
None

### Request Example
```cpp
#include "TCA9548A.h"

TCA9548A I2CMux;

void setup() {
  I2CMux.begin(Wire);
  I2CMux.openAll();
}
```

### Response
None (modifies hardware state)

### Response Example
None
```

--------------------------------

### Reset Channels with closeAll()

Source: https://context7.com/wifwaf/tca9548a/llms.txt

Close all channels simultaneously to reset the multiplexer to a known state, preventing cross-talk between devices.

```cpp
#include <Arduino.h>
#include "TCA9548A.h"

TCA9548A I2CMux;

void setup() {
  Serial.begin(9600);
  I2CMux.begin(Wire);

  // Always start with a known state
  I2CMux.closeAll();
  Serial.println("All channels closed");
}

void loop() {
  // Scan through each channel individually
  for (uint8_t channel = 0; channel < 8; channel++) {
    I2CMux.openChannel(channel);

    Serial.print("Channel ");
    Serial.print(channel);
    Serial.println(" open - scanning for devices...");

    // ... perform I2C scan or device communication ...

    delay(500);
  }

  // Reset all channels at end of scan
  I2CMux.closeAll();
  Serial.println("Scan complete, all channels closed\n");

  delay(2000);
}
```

--------------------------------

### Channel Constants

Source: https://context7.com/wifwaf/tca9548a/llms.txt

Predefined hex constants for each channel to use with writeRegister() for direct bitmask operations.

```APIDOC
## Channel Constants

### Description
Predefined constants representing each I2C channel on the TCA9548A multiplexer. These are used to construct bitmasks for the `writeRegister()` function.

### Constants
- **TCA_CHANNEL_0**: `0x01` (bit 0)
- **TCA_CHANNEL_1**: `0x02` (bit 1)
- **TCA_CHANNEL_2**: `0x04` (bit 2)
- **TCA_CHANNEL_3**: `0x08` (bit 3)
- **TCA_CHANNEL_4**: `0x10` (bit 4)
- **TCA_CHANNEL_5**: `0x20` (bit 5)
- **TCA_CHANNEL_6**: `0x40` (bit 6)
- **TCA_CHANNEL_7**: `0x80` (bit 7)

### Usage Example
```cpp
#include "TCA9548A.h"

TCA9548A I2CMux;

// Open channels 1, 3, 5, and 7
uint8_t oddChannels = TCA_CHANNEL_1 | TCA_CHANNEL_3 | TCA_CHANNEL_5 | TCA_CHANNEL_7;
I2CMux.writeRegister(oddChannels);
```
```

--------------------------------

### openChannel(uint8_t channel)

Source: https://context7.com/wifwaf/tca9548a/llms.txt

Opens a specific channel on the multiplexer.

```APIDOC
## void openChannel(uint8_t channel)

### Description
Opens a specific channel (0-7). Channels remain open until explicitly closed.

### Parameters
#### Request Body
- **channel** (uint8_t) - Required - The channel index to open (0-7).
```

--------------------------------

### TCA9548A Constructor

Source: https://context7.com/wifwaf/tca9548a/llms.txt

Creates a new instance of the TCA9548A multiplexer with an optional custom I2C address.

```APIDOC
## Constructor TCA9548A(uint8_t address)

### Description
Creates a TCA9548A multiplexer instance. The default address is 0x70.

### Parameters
#### Path Parameters
- **address** (uint8_t) - Optional - I2C address of the multiplexer (0x70-0x77).
```

--------------------------------

### closeAll()

Source: https://context7.com/wifwaf/tca9548a/llms.txt

Closes all channels simultaneously.

```APIDOC
## void closeAll()

### Description
Closes all channels by writing 0x00 to the control register.
```

--------------------------------

### Selectively Close Channels with closeChannel()

Source: https://context7.com/wifwaf/tca9548a/llms.txt

Close a specific channel while leaving other active channels unaffected. Use readRegister() to verify the current state of the multiplexer.

```cpp
#include <Arduino.h>
#include "TCA9548A.h"

TCA9548A I2CMux;

void setup() {
  Serial.begin(9600);
  I2CMux.begin(Wire);
  I2CMux.closeAll();
}

void loop() {
  // Open channels 0, 1, and 2
  I2CMux.openChannel(0);
  I2CMux.openChannel(1);
  I2CMux.openChannel(2);

  Serial.print("Register after opening 0,1,2: ");
  Serial.println(I2CMux.readRegister());  // Output: 7 (binary: 00000111)

  // Close only channel 1, channels 0 and 2 remain open
  I2CMux.closeChannel(1);

  Serial.print("Register after closing 1: ");
  Serial.println(I2CMux.readRegister());  // Output: 5 (binary: 00000101)

  I2CMux.closeAll();
  delay(2000);
}
```

--------------------------------

### Use channel constants for bitmask operations

Source: https://context7.com/wifwaf/tca9548a/llms.txt

Utilizes predefined hex constants for each channel to perform bitwise operations for channel selection.

```cpp
#include <Arduino.h>
#include "TCA9548A.h"

// Available channel constants:
// TCA_CHANNEL_0 = 0x01  (bit 0)
// TCA_CHANNEL_1 = 0x02  (bit 1)
// TCA_CHANNEL_2 = 0x04  (bit 2)
// TCA_CHANNEL_3 = 0x08  (bit 3)
// TCA_CHANNEL_4 = 0x10  (bit 4)
// TCA_CHANNEL_5 = 0x20  (bit 5)
// TCA_CHANNEL_6 = 0x40  (bit 6)
// TCA_CHANNEL_7 = 0x80  (bit 7)

TCA9548A I2CMux;

void setup() {
  Serial.begin(9600);
  I2CMux.begin(Wire);
  I2CMux.closeAll();
}

void loop() {
  // Example: Open channels 0, 2, 4, and 6 (even channels)
  uint8_t evenChannels = TCA_CHANNEL_0 | TCA_CHANNEL_2 | TCA_CHANNEL_4 | TCA_CHANNEL_6;
  I2CMux.writeRegister(evenChannels);
  Serial.print("Even channels (0,2,4,6): ");
  Serial.println(I2CMux.readRegister());  // Output: 85

  delay(1000);

  // Example: Open channels 1, 3, 5, and 7 (odd channels)
  uint8_t oddChannels = TCA_CHANNEL_1 | TCA_CHANNEL_3 | TCA_CHANNEL_5 | TCA_CHANNEL_7;
  I2CMux.writeRegister(oddChannels);
  Serial.print("Odd channels (1,3,5,7): ");
  Serial.println(I2CMux.readRegister());  // Output: 170

  delay(1000);
  I2CMux.closeAll();
  delay(2000);
}
```

--------------------------------

### Read control register with readRegister()

Source: https://context7.com/wifwaf/tca9548a/llms.txt

Reads the current control register value to identify open channels. Returns 255 if a communication error occurs.

```cpp
#include <Arduino.h>
#include "TCA9548A.h"

TCA9548A I2CMux;

void setup() {
  Serial.begin(9600);
  I2CMux.begin(Wire);
  I2CMux.closeAll();
}

void loop() {
  Serial.println("--- Channel State Monitor ---");

  // Iterate through all channels
  for (uint8_t channel = 0; channel < 8; channel++) {
    I2CMux.openChannel(channel);

    byte regValue = I2CMux.readRegister();

    Serial.print("After opening channel ");
    Serial.print(channel);
    Serial.print(": Register = ");
    Serial.print(regValue);
    Serial.print(" (binary: ");

    // Print binary representation
    for (int bit = 7; bit >= 0; bit--) {
      Serial.print((regValue >> bit) & 1);
    }
    Serial.println(")");

    delay(500);
  }

  Serial.println("All 8 channels now open");
  I2CMux.closeAll();
  Serial.println("All channels closed\n");

  delay(3000);
}
```

--------------------------------

### Write to control register with writeRegister()

Source: https://context7.com/wifwaf/tca9548a/llms.txt

Writes a byte value to the control register for precise channel control. Use predefined TCA_CHANNEL_x constants to build the bitmask.

```cpp
#include <Arduino.h>
#include "TCA9548A.h"

TCA9548A I2CMux;

void setup() {
  Serial.begin(9600);
  I2CMux.begin(Wire);
  I2CMux.closeAll();
}

void loop() {
  uint8_t channelMask = 0x00;

  // Build channel mask using predefined constants
  // TCA_CHANNEL_0 = 0x01, TCA_CHANNEL_3 = 0x08
  // TCA_CHANNEL_4 = 0x10, TCA_CHANNEL_7 = 0x80
  channelMask |= TCA_CHANNEL_0;  // Add channel 0
  channelMask |= TCA_CHANNEL_3;  // Add channel 3
  channelMask |= TCA_CHANNEL_4;  // Add channel 4
  channelMask |= TCA_CHANNEL_7;  // Add channel 7

  Serial.print("Writing channel mask: ");
  Serial.println(channelMask);  // Output: 153 (binary: 10011001)

  // Write directly to control register
  I2CMux.writeRegister(channelMask);

  // Verify the write
  Serial.print("Register readback: ");
  Serial.println(I2CMux.readRegister());  // Output: 153

  delay(1000);
  I2CMux.closeAll();
  delay(2000);
}
```

--------------------------------

### closeChannel(uint8_t channel)

Source: https://context7.com/wifwaf/tca9548a/llms.txt

Closes a specific channel on the multiplexer.

```APIDOC
## void closeChannel(uint8_t channel)

### Description
Closes a specific channel (0-7) while leaving other open channels unaffected.

### Parameters
#### Request Body
- **channel** (uint8_t) - Required - The channel index to close (0-7).
```

--------------------------------

### Write to Control Register

Source: https://context7.com/wifwaf/tca9548a/llms.txt

Directly writes a byte value to the control register for precise channel control. Each bit corresponds to a channel (bit 0 = channel 0, bit 7 = channel 7). Use the predefined TCA_CHANNEL_x constants for easier bitmask calculation.

```APIDOC
## writeRegister(uint8_t value)

### Description
Directly writes a byte value to the control register for precise channel control. Each bit corresponds to a channel (bit 0 = channel 0, bit 7 = channel 7).

### Method
`writeRegister(uint8_t value)`

### Parameters
#### Path Parameters
None

#### Query Parameters
None

#### Request Body
- **value** (uint8_t) - Required - The byte value to write to the control register. Each bit represents a channel (1 = open, 0 = closed).

### Request Example
```cpp
#include "TCA9548A.h"

TCA9548A I2CMux;

// Example: Open channels 0 and 3
uint8_t channelMask = TCA_CHANNEL_0 | TCA_CHANNEL_3; // 0x01 | 0x08 = 0x09
I2CMux.writeRegister(channelMask);
```

### Response
None (modifies hardware state)

### Response Example
None
```

--------------------------------

### Read Control Register

Source: https://context7.com/wifwaf/tca9548a/llms.txt

Reads the current value of the control register to determine which channels are currently open. Returns 255 if no data is available (communication error).

```APIDOC
## readRegister()

### Description
Reads the current value of the control register to determine which channels are currently open.

### Method
`readRegister()`

### Parameters
None

### Request Example
```cpp
#include "TCA9548A.h"

TCA9548A I2CMux;

// Assuming channels 0 and 1 are open
byte regValue = I2CMux.readRegister(); // Expected value: 3 (binary: 00000011)
```

### Response
#### Success Response (200)
- **returnValue** (byte) - The current value of the control register. Returns 255 if a communication error occurs.

### Response Example
```json
{
  "returnValue": 3
}
```
```

=== COMPLETE CONTENT === This response contains all available snippets from this library. No additional content exists. Do not make further requests.