4 Channel I2C Multiplexer Breakout

4 Channel I2C Multiplexer Breakout

The 4 Channel I2C Multiplexer is basically a digital switch for up to 4 I2C devices. It uses a PCA9544A multiplexer IC to allow one of four devices to be connected to the I2C bus at one time, whilst disconnecting the other three. This is really useful for I2C devices that have a fixed I2C address.

An example of such a device is the BMP180 Barometric Pressure Sensor which has a single fixed I2C address (0xEE). Therefore you can only have one such device connected to your I2C bus. The I2C Multiplexer board lifts this limitation allowing you to have 4 such devices (or a mix of other devices) connected to the I2C bus.

The Multiplexer board itself is controlled via the I2C bus so no additional microcontroller pins are required.

4 Channel I2C Multiplexer Breakout Features

• PCA9544A I2C Multiplexer IC
• 1-of-4 bidirectional translating I2C multiplexer
• I²C-bus interface logic; compatible with SMBus
• 4 active LOW interrupt inputs (pullup resistors on board)
• Active LOW interrupt output
• 3 address pins allowing up to 8 Mutiplexer boards on the I²C-bus (pull down resistors on board)
• I2C Channel selection via I²C-bus
• Power-on with all multiplexer channels deselected
• 0 Hz to 400 kHz clock frequency
• Logic level translation between 1.8 V, 2.5 V, 3.3 V and 5 V buses
• Onboard 3.3V Voltage Regulator for powering 3.3V I2C devices (default)

The multiplexer chip has in-built logic level conversion from the supply voltage / master I2C input to the I2C channel voltage. The default configuration for the board is

• Supply and Master I2C Voltage 3.3V or 5V
• I2C device voltage 3.3V

Documents

PCA9544A Datasheet
Multiplexer Breakout Schematic
Example Arduino Sketch with 4x MPL3115A sensors