How to Use TCA9548A i2c Multiplexer [Bill Ludwig] : Examples, Pinouts, and Specs

The TCA9548A I2C Multiplexer is a versatile electronic component designed to expand the capabilities of an I2C bus. It allows multiple I2C devices to be connected to a single I2C bus by providing up to eight selectable channels. This eliminates address conflicts when using multiple devices with the same I2C address. The TCA9548A is particularly useful in applications where multiple sensors, displays, or other I2C peripherals need to coexist on the same bus.

• Connecting multiple I2C devices with identical addresses to a single microcontroller.
• Expanding the I2C bus for complex systems with numerous peripherals.
• Applications in robotics, IoT devices, and sensor arrays.
• Prototyping and testing multiple I2C devices simultaneously.

The TCA9548A is a robust and efficient solution for I2C bus expansion. Below are its key technical details:

• Operating Voltage (Vcc): 1.65V to 5.5V
• I2C Bus Voltage Compatibility: Supports both 3.3V and 5V logic levels
• Maximum Clock Frequency: 400 kHz (I2C Fast Mode)
• Number of Channels: 8 (individually selectable)
• I2C Address Range: Configurable via three address pins (A0, A1, A2)
• Low Standby Current: Typically 1 µA
• Operating Temperature Range: -40°C to +85°C
• Package Type: TSSOP-24 or similar

The TCA9548A has 24 pins, with the following configuration:

The TCA9548A 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 source (1.65V to 5.5V).
   • Connect the GND pin to the ground of your circuit.

2. Connect the I2C Bus:

   • Attach the main I2C bus lines to the SCL and SDA pins of the TCA9548A.
   • Ensure proper pull-up resistors (typically 4.7kΩ) are present on the I2C lines.

3. Configure the Address:

   • Use the A0, A1, and A2 pins to set the I2C address of the multiplexer. These pins can be tied to GND or Vcc to select one of 8 possible addresses.

4. Connect I2C Devices:

   • Attach the I2C devices to the appropriate channel pins (SDx and SCx). Each channel corresponds to a specific device or group of devices.

5. Control the Channels:

   • Use I2C commands to select the active channel(s). Only the selected channel(s) will communicate with the main I2C bus.

Below is an example of how to use the TCA9548A with an Arduino UNO to communicate with a device on channel 0.

#include <Wire.h>

// Define the I2C address of the TCA9548A (default is 0x70)
#define TCA9548A_ADDR 0x70

// Function to select a specific channel on the TCA9548A
void selectChannel(uint8_t channel) {
  if (channel > 7) return; // Ensure the channel is valid (0-7)
  Wire.beginTransmission(TCA9548A_ADDR);
  Wire.write(1 << channel); // Send the channel selection command
  Wire.endTransmission();
}

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

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

void loop() {
  // Example: Communicate with a device on channel 0
  Wire.beginTransmission(0x40); // Replace 0x40 with the device's I2C address
  Wire.write(0x00); // Example command to the device
  Wire.endTransmission();

  delay(1000); // Wait for 1 second
}

• Pull-Up Resistors: Ensure that each I2C bus (main and channels) has appropriate pull-up resistors.
• Channel Selection: Only one channel can be active at a time. Switching channels too quickly may cause communication errors.
• Address Conflicts: Avoid address conflicts by carefully assigning devices to different channels.
• Reset Pin: Use the RESET pin to recover from unexpected errors or to reinitialize the multiplexer.

1. Devices Not Responding:

   • Ensure the correct channel is selected using the appropriate I2C command.
   • Verify that the device's I2C address is correct and matches the code.

2. Communication Errors:

   • Check for proper pull-up resistors on all I2C lines.
   • Ensure the I2C clock frequency does not exceed 400 kHz.

3. Multiplexer Not Detected:

   • Verify the TCA9548A's I2C address configuration (A0, A1, A2 pins).
   • Check the power supply voltage and connections.

4. Unexpected Behavior:

   • Use the RESET pin to reinitialize the multiplexer.
   • Ensure no two devices on the same channel share the same I2C address.

Q: Can I use multiple TCA9548A multiplexers in the same circuit?
A: Yes, you can use up to 8 TCA9548A multiplexers by configuring their addresses using the A0, A1, and A2 pins.

Q: Do I need pull-up resistors on each channel?
A: Yes, each channel should have its own pull-up resistors to ensure proper I2C communication.

Q: What happens if no channel is selected?
A: If no channel is selected, the TCA9548A will not forward any I2C communication to the connected devices.

Q: Can I use the TCA9548A with 3.3V and 5V devices simultaneously?
A: Yes, the TCA9548A supports mixed voltage levels, but ensure proper level shifting if required.

This concludes the documentation for the TCA9548A I2C Multiplexer.