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 independent I2C channels. This is particularly useful in applications where multiple devices with the same I2C address need to coexist on the same bus, as the TCA9548A can isolate and enable communication with one device at a time.

• Connecting multiple sensors or modules with identical I2C addresses to a single microcontroller.
• Expanding the I2C bus in complex systems with numerous peripherals.
• Applications in robotics, IoT devices, and data acquisition systems.
• Prototyping and testing multiple I2C devices simultaneously.

The following table outlines the key technical details of the TCA9548A I2C Multiplexer:

The TCA9548A has 24 pins, with the following key pin assignments:

1. Power the Device: Connect the VCC pin to a power source (1.65V to 5.5V) and the GND pin to ground.
2. Set the I2C Address: Use the A0, A1, and A2 pins to configure the I2C address. These pins can be connected to VCC or GND to set the address in the range 0x70 to 0x77.
3. Connect the I2C Bus: Attach the SDA and SCL lines of the microcontroller to the SDA and SCL pins of the TCA9548A.
4. Connect I2C Devices: Attach the SDA and SCL lines of each I2C device to the corresponding SDx and SCx pins of the desired channel.
5. Control the Channels: Use I2C commands to select and enable the desired channel for communication.

• Pull-Up Resistors: Ensure that appropriate pull-up resistors are present on the SDA and SCL lines of the primary I2C bus. Each channel may also require pull-up resistors depending on the connected devices.
• Reset Pin: The RESET pin can be used to reset the multiplexer if communication issues occur. Connect it to a GPIO pin or pull it high if not used.
• Channel Selection: Only one channel can be active at a time. Use I2C commands to switch between channels as needed.
• Voltage Compatibility: Ensure that the voltage levels of the I2C devices are compatible with the TCA9548A's operating voltage.

The following example demonstrates 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_ADDRESS 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_ADDRESS);
  Wire.write(1 << channel); // Send the channel selection command
  Wire.endTransmission();
}

void setup() {
  Wire.begin(); // Initialize the I2C bus
  Serial.begin(9600); // Initialize 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 I2C address of your device
  Wire.write(0x00); // Example command to the device
  Wire.endTransmission();

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

1. No Communication with I2C Devices:

   • Ensure the correct channel is selected using the appropriate I2C command.
   • Verify that the pull-up resistors are properly connected on the SDA and SCL lines.
   • Check the wiring and ensure all connections are secure.

2. Address Conflicts:

   • Verify that the TCA9548A's I2C address is correctly configured using the A0, A1, and A2 pins.
   • Ensure that only one device is active on a channel at a time.

3. Device Not Responding:

   • Check the power supply voltage and ensure it is within the operating range (1.65V to 5.5V).
   • Use the RESET pin to reset the TCA9548A and reinitialize communication.

Q: Can multiple channels be active simultaneously?
A: No, the TCA9548A allows only one channel to be active at a time. You must switch between channels using I2C commands.

Q: Do I need pull-up resistors on each channel?
A: It depends on the connected devices. If the devices on a channel do not have built-in pull-up resistors, you will need to add them.

Q: What happens if I select an invalid channel?
A: The TCA9548A will ignore the command, and no channel will be active. Ensure the channel number is between 0 and 7.

Q: Can the TCA9548A work with 3.3V and 5V devices simultaneously?
A: No, the TCA9548A does not perform voltage level translation. Ensure all devices operate at the same voltage level as the TCA9548A.