CJMCU TCA9548A 8-Channel I2C Multiplexer The TCA9548A is the ultimate solution for I2C address conflicts. In standard I2C networking, you cannot have two devices with the same address on the same pins. This multiplexer acts as a “gatekeeper” or a high-speed switch, allowing your microcontroller to communicate with up to 8 identical I2C devices by switching between eight separate I2C buses. Key Features Address Conflict Resolver: Connect up to 8 devices with the same I2C address (e.g., 8 OLED displays or 8 BMP180 sensors) to a single microcontroller. Bi-directional Translation: Supports voltage translation between different logic levels (e.g., 3.3V microcontrollers controlling 5V sensors). Adjustable I2C Address: The board itself defaults to 0x70, but can be changed up to 0x77 using the address pins (A0, A1, A2). This allows you to stack up to 8 multiplexers to control a staggering 64 I2C devices. Hot Insertion Support: Allows for plugging in devices without powering down the entire system. Active-Low Reset: Dedicated reset pin to clear the bus and restart the multiplexer state. Technical Specifications Specification Value Operating Voltage 3.0V – 5.0V DC Interface I2C (SMBus compatible) Default I2C Address 0x70 (Adjustable 0x70 – 0x77) Channels 8 Multiplexed I2C Channels Logic Compatibility 5V Tolerant Inputs Max Frequency Supports standard I2C speeds (100kHz / 400kHz) Standby Current Very Low Pin Configuration Power & Control Side (Microcontroller Side) VIN: Power supply (Match your microcontroller’s logic level, e.g., 5V for Arduino Uno). GND: Common ground. SCL / SDA: Connect to your microcontroller’s I2C Clock and Data pins. RST: Reset pin (Active Low). Pulled high by default; pull to GND to reset the chip. A0, A1, A2: Address selection pins. Pull high to increment the base address (0x70). Multiplexed Side (Sensor Side) SD0/SC0 to SD7/SC7: Eight independent I2C pairs. Connect one I2C device to each pair. Note: These channels do not have built-in pull-up resistors. Ensure your sensor breakout has them, or add 10kΩ resistors if needed. How to Use Connect the Hardware: Wire the multiplexer to your Arduino/ESP32 and connect your conflicting sensors to the SCx/SDx channels. Select the Channel: To talk to a sensor on “Channel 3”, you simply send a single byte (0x08 which is binary for bit 3) to the multiplexer at address 0x70. Send Commands: Once the channel is selected, any I2C commands sent by the microcontroller will only go to that specific channel. Applications Massive Sensor Arrays: Weather stations with multiple identical pressure/temp sensors. Robotics: Multiple TOF (Time of Flight) distance sensors or IMUs sharing the same address. Displays: Controlling multiple identical I2C OLED or LCD screens. Complex I2C Networks: Systems where sensors are located far apart and need bus isolation.
