Adafruit
Adafruit PCA9546 4-Channel STEMMA QT / Qwiic I2C Multiplexer
Need to use multiple I2C devices that share the same address? The PCA9546 4-Channel STEMMA QT / Qwiic I2C Multiplexer lets you connect up to four same-addres...
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Need to use multiple I2C devices that share the same address? The PCA9546 4-Channel STEMMA QT / Qwiic I2C Multiplexer lets you connect up to four same-address I2C devices with completely solderless wiring. Five JST SH connectors (1 input + 4 outputs) make it plug-and-play with any STEMMA QT or Qwiic board.
Write a single byte to select the active channel (default address 0x70, adjustable to 0x70–0x77) and all subsequent I2C traffic is routed to that port. With eight possible multiplexer addresses, you could theoretically control up to 8 × 4 = 32 same-address devices on one I2C bus. Also available as a breadboard-friendly breakout version.
Key Features
- 4 Multiplexed I2C Channels – Route I2C traffic to any of four downstream STEMMA QT / Qwiic ports
- 5 JST SH Connectors – 1 input + 4 outputs, all solderless STEMMA QT / Qwiic compatible
- Configurable Address – Default 0x70, adjustable to 0x70–0x77 via solder jumpers for up to 8 multiplexers
- Onboard 3.3 V 500 mA Regulator – Level-shift all QT ports to 3 V when using a 5 V microcontroller (jumper selectable)
- 3 V and 5 V Compatible – Works with any logic level
- Breadboard Breakout Pins – Also available for traditional wired connections
- Mounting Holes – For permanent installation in enclosures or projects
- Power LED – Indicates the board has power
How It Works
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 STEMMA QT / Qwiic sensors on one I2C 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 STEMMA QT / Qwiic I2C Multiplexer, assembled
Resources
- I2C Multiplexer Learn Guide – Overview, wiring, and example code (compatible with PCA9546)
- 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 board carries a small or fine-pitched component and brings its connections out to standard, breadboard- and header-friendly pins. Describing a part as a breakout means it can be wired into a project without soldering directly to the component's tiny 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.
- LED
- A light-emitting diode (LED) is a small electronic component that emits light when current flows through it in the correct direction. Because it only conducts one way, its polarity matters, and a through-hole LED must be soldered the correct way around to light up.
- microcontroller
- A microcontroller is a small computer on a single chip that runs a stored program and controls connected inputs and outputs such as buttons, sensors, displays and communication interfaces. In a device built around one, it is the part that executes the code and coordinates the device's behaviour.
- multiplexer
- A multiplexer (mux) is a chip or circuit that selects one of several input signals and routes it to a single shared output, with select lines choosing which input is connected; running the same idea in reverse, to send one input to a chosen output, gives a demultiplexer. Multiplexers let a single controller or line work with several signals or devices that would otherwise clash on a shared connection.
- 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.
Find this product in
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Resources & Downloads
Guides, code examples, and more
Related Tutorials
Free guides on learn.littlebird.com.au
