Adafruit
Adafruit PCA9546 4-Channel I2C Multiplexer
Need to use multiple I2C devices that share the same address? The PCA9546 4-Channel I2C Multiplexer lets you connect up to four same-address I2C devices to a...
Need to use multiple I2C devices that share the same address? The PCA9546 4-Channel I2C Multiplexer lets you connect up to four same-address I2C devices to a single microcontroller by acting as a gatekeeper — write a single byte to select the active channel and all subsequent I2C traffic is routed to that port.
The multiplexer sits at I2C address 0x70 (adjustable from 0x70 to 0x77 via solder jumpers). With eight possible multiplexer addresses, you could theoretically control up to 8 × 4 = 32 same-address devices on one I2C bus.
Key Features
- 4 Multiplexed I2C Channels – Route I2C traffic to any of four downstream buses
- Simple Control – Write a single byte to select the active channel; all further I2C packets go to that port
- Configurable Address – Default 0x70, adjustable to 0x70–0x77 for up to 8 multiplexers on one bus
- 3 V and 5 V Compatible – Works with any logic level
- STEMMA QT / Qwiic Connectors – Solderless I2C connection on the upstream side
- Breadboard Friendly – Breakout PCB with capacitors, pull-ups, and pull-downs included
How It Works
The PCA9546 acts as an I2C switch. Your microcontroller sends a command byte to the multiplexer's address (0x70 by default) specifying which downstream channel to activate. All subsequent I2C communication passes through to the selected channel. You can enable multiple channels simultaneously if needed.
Ideal For
- Using multiple identical I2C sensors (same address) on one bus
- Isolating I2C bus segments to avoid address conflicts
- Expanding I2C capacity on address-limited projects
- Sensor arrays and multi-sensor data logging
Package Contents
- 1× Adafruit PCA9546 4-Channel I2C Multiplexer breakout, assembled
Resources
- What is STEMMA QT? – Introduction to the STEMMA QT connector system
Jargon buster
Plain-language definitions for the technical terms used above.
- breakout
- A breakout is a small circuit board that makes a tiny or hard-to-solder component easier to connect to with standard pins. It matters because this OLED module can be wired into a microcontroller project without needing to solder directly to the display’s fine contacts.
- I2C
- I2C is a two-wire communication bus used by many sensors and small modules. It matters because several I2C devices can share the same two wires, but each device needs a compatible address and your controller must support I2C.
- I2C address
- An I2C address is the number a device uses so a microcontroller can tell it apart from other devices on the same I2C bus. It matters because two devices with the same fixed address may conflict if used together.
- microcontroller
- A microcontroller is a small computer on a chip that runs your program and controls connected inputs and outputs. For this product, it is the part that reads buttons and sensors, drives the display and speaker, and communicates over Bluetooth.
- multiplexer
- A multiplexer is a chip or board that lets one controller switch between several devices that would otherwise conflict on the same bus. It matters here because multiple modules with the same I2C address cannot normally share one I2C bus without extra hardware.
- PCB
- A printed circuit board is a rigid board with copper tracks that connect electronic parts without loose wires. For this kit, the PCBs also form the airplane shape, so they are both the circuit base and part of the finished model.
- Qwiic
- Qwiic is a plug-in connector system for I2C devices that uses small 4-pin cables, so you can connect compatible sensors without soldering. It matters because your controller or adapter also needs Qwiic, or you will need a cable or breakout to wire it up.
- STEMMA
- A plug-and-cable connection system used on some maker electronics boards to make wiring simpler. If a product uses STEMMA, you need the matching cable or connector type to plug it in without soldering.
- STEMMA QT
- A small plug-in connector system for I2C boards that lets you connect compatible sensors and controllers without soldering. It matters because it can make wiring faster and less error-prone, especially when adding several small modules to a project.
- UPS
- An uninterruptible power supply is a battery-backed power system that keeps a device running when external power is unplugged or fails. For an embedded computer, it helps prevent sudden shutdowns that can corrupt files or interrupt a project.
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