How to Use the TCA9548A I2C Multiplexer with Arduino

The TCA9548A is an I2C multiplexer that allows you to connect multiple devices with the same I2C address to a single Arduino. It achieves this by creating up to eight separate I2C buses, which can be accessed individually. This tutorial will guide you through interfacing and using the TCA9548A with Arduino to manage multiple I2C devices.

What You Will Need

TCA9548A I2C Multiplexer Module
Arduino Board (e.g., Uno, Mega, Nano)
I2C Devices (e.g., sensors, displays)
Breadboard and Jumper Wires
A computer with the Arduino IDE installed

Step 1: Understanding the TCA9548A

The TCA9548A can control up to 8 independent I2C buses (channels). Each channel can be turned on or off to isolate devices with the same address.

Pinout

Pin	Function
VCC	Power Supply (3.3V/5V)
GND	Ground
SDA	I2C Data Line
SCL	I2C Clock Line
SDx/SCx	Individual I2C Buses (0-7)
A0, A1, A2	Address Configuration

I2C Address Configuration

The TCA9548A’s I2C address is determined by A0, A1, and A2 pins:
- All pins to GND: 0x70 (default address)
- Combinations of HIGH and LOW can set addresses from 0x70 to 0x77.

Step 2: Wiring the TCA9548A to Arduino

Connect the TCA9548A to Arduino

TCA9548A Pin	Arduino Pin
VCC	5V
GND	GND
SDA	A4
SCL	A5

Connect I2C Devices to the TCA9548A

Connect the SDA and SCL lines of your I2C devices to the corresponding SDx and SCx pins on the TCA9548A.
Ensure the VCC and GND pins of the devices are also connected.

Step 3: Install the Required Library

To simplify working with the TCA9548A, install the "Wire" library (pre-installed in the Arduino IDE).

If you prefer a library for easier handling, you can use the Adafruit TCA9548A library:

Steps to Install:

Open the Arduino IDE.
Go to Sketch > Include Library > Manage Libraries.
Search for "Adafruit TCA9548A" and click Install.

Step 4: Upload the Code

The following example demonstrates how to select a specific I2C bus and communicate with a device:

Example Code

#include <Wire.h>

#define TCA9548A_ADDR 0x70 // Default I2C address of TCA9548A

void tcaSelect(uint8_t bus) {
  if (bus > 7) return; // Ensure the bus number is valid
  Wire.beginTransmission(TCA9548A_ADDR);
  Wire.write(1 << bus); // Select the specific bus
  Wire.endTransmission();
}

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

  Serial.println("TCA9548A Test");

  // Test selecting each channel
  for (uint8_t i = 0; i < 8; i++) {
    tcaSelect(i);
    Serial.print("Channel ");
    Serial.print(i);
    Serial.println(" selected.");
    delay(500);
  }
}

void loop() {
  // Add specific I2C communication here
}

Step 5: Communicating with Devices on Each Channel

To communicate with a device on a specific channel, call the tcaSelect(bus) function before initiating I2C communication. For example:

Reading Data from Sensors

#include <Wire.h>

#define TCA9548A_ADDR 0x70

void tcaSelect(uint8_t bus) {
  if (bus > 7) return;
  Wire.beginTransmission(TCA9548A_ADDR);
  Wire.write(1 << bus);
  Wire.endTransmission();
}

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

  Serial.println("Reading from multiple sensors");
}

void loop() {
  for (uint8_t i = 0; i < 8; i++) {
    tcaSelect(i); // Select channel
    Serial.print("Reading from channel ");
    Serial.println(i);

    Wire.requestFrom(0x40, 1); // Replace 0x40 with the I2C address of your sensor
    if (Wire.available()) {
      int data = Wire.read();
      Serial.print("Data: ");
      Serial.println(data);
    }
    delay(500);
  }
}

Applications of the TCA9548A

Managing multiple identical I2C devices (e.g., multiple sensors with the same address).
Expanding I2C devices in a project.
Reducing wiring complexity in large systems.

Troubleshooting

No response from devices: Ensure the correct I2C bus is selected and check the wiring.
Address conflicts: Verify the I2C addresses of connected devices to avoid conflicts.
Incorrect bus switching: Ensure the TCA9548A’s address is correctly configured and matches the code.

Conclusion

You’ve successfully interfaced the TCA9548A I2C multiplexer with Arduino. This powerful module allows you to connect and control multiple I2C devices with the same address, making it a valuable tool for complex projects. Experiment with different devices and configurations to unlock its full potential!