How to Use TCA9548 8-Way: Examples, Pinouts, and Specs

The TCA9548 is an 8-channel I2C multiplexer designed to simplify communication between a master device and multiple I2C devices. It allows the master to select one of eight downstream channels, enabling seamless management of multiple I2C devices on a single bus. This is particularly useful in applications where devices share the same I2C address, as the TCA9548 eliminates address conflicts by isolating each device on its own channel.

• Managing multiple I2C devices with identical addresses
• Expanding the number of I2C devices on a single bus
• Sensor arrays in robotics and industrial automation
• Multi-display systems
• Data acquisition systems

The TCA9548 is a versatile and robust component. Below are its key technical details:

The TCA9548 has 16 pins, as described in the table below:

The TCA9548 is straightforward to use in I2C-based systems. Below are the steps and considerations for integrating it into your circuit:

1. Power the Device: Connect the VCC pin to a power supply (1.65V to 5.5V) and the GND pin to ground.
2. Set the I2C Address: Configure the address by connecting the A0, A1, and A2 pins to either VCC (logic high) or GND (logic low). This determines the base address (0x70 to 0x77).
3. Connect the I2C Bus: Attach the SDA and SCL lines from the master device to the TCA9548's SDA and SCL pins.
4. Connect Downstream Devices: Attach the SDA and SCL lines of each downstream I2C device to the corresponding SDx and SCx pins of the TCA9548.
5. Control the Multiplexer: Use the master device to send commands to the TCA9548, selecting the desired channel(s) for communication.

• Pull-Up Resistors: Ensure proper pull-up resistors are present on the SDA and SCL lines. Typically, 4.7kΩ resistors are used.
• Channel Selection: Only one channel can be active at a time. Sending a control byte to the TCA9548 determines which channel is active.
• Reset Functionality: Use the RESET pin to reset the device if communication issues occur.
• Voltage Compatibility: Ensure that the voltage levels of the master and downstream devices are compatible with the TCA9548.

Below is an example of how to use the TCA9548 with an Arduino UNO to communicate with a device on channel 0:

#include <Wire.h> // Include the Wire library for I2C communication

#define TCA9548_ADDRESS 0x70 // Base address of the TCA9548

void selectChannel(uint8_t channel) {
  // Ensure the channel is within the valid range (0-7)
  if (channel > 7) return;

  Wire.beginTransmission(TCA9548_ADDRESS); // Start communication with TCA9548
  Wire.write(1 << channel); // Send the control byte to select the channel
  Wire.endTransmission(); // End the transmission
}

void setup() {
  Wire.begin(); // Initialize I2C communication
  Serial.begin(9600); // Start serial communication for debugging

  Serial.println("Selecting channel 0...");
  selectChannel(0); // Select channel 0
}

void loop() {
  // Add your code to communicate with the device on channel 0
  delay(1000); // Delay for demonstration purposes
}

1. No Communication with Downstream Devices

   • Cause: Incorrect channel selection or wiring issues.
   • Solution: Verify the channel selection command and check all connections.

2. Address Conflicts

   • Cause: Multiple devices on the same channel with the same address.
   • Solution: Ensure only one device is connected to each channel.

3. Device Not Responding

   • Cause: Incorrect I2C address configuration.
   • Solution: Double-check the A0, A1, and A2 pin connections to set the correct address.

4. High Power Consumption

   • Cause: Pull-up resistors with low resistance values.
   • Solution: Use appropriate pull-up resistor values (e.g., 4.7kΩ).

Q: Can I activate multiple channels simultaneously?
A: No, the TCA9548 allows only one channel to be active at a time.

Q: What happens if the RESET pin is left unconnected?
A: The RESET pin has an internal pull-up resistor, so it can be left unconnected. However, connecting it to a microcontroller for manual resets is recommended.

Q: Can the TCA9548 work with 3.3V and 5V devices simultaneously?
A: Yes, the TCA9548 supports level translation between 1.65V and 5.5V, but ensure proper pull-up resistors are used for each voltage level.

Q: How do I know which channel is currently active?
A: The TCA9548 does not provide feedback on the active channel. You must track the channel selection in your code.