Adafruit
Adafruit PCA9548 8-Channel STEMMA QT / Qwiic I2C Multiplexer
Need to use multiple I2C devices that share the same address? The PCA9548 8-Channel STEMMA QT / Qwiic I2C Multiplexer lets you connect up to eight same-addre...
Need to use multiple I2C devices that share the same address? The PCA9548 8-Channel STEMMA QT / Qwiic I2C Multiplexer lets you connect up to eight same-address I2C devices with completely solderless wiring. Nine JST SH connectors (1 input + 8 outputs in two rows of four) 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 × 8 = 64 same-address devices on one I2C bus. For smaller setups, see the 4-channel PCA9546 version.
Key Features
- 8 Multiplexed I2C Channels – Route I2C traffic to any of eight downstream STEMMA QT / Qwiic ports
- 9 JST SH Connectors – 1 input + 8 outputs (two rows of four), 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
- 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(s) 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
- Large sensor arrays and multi-sensor data logging
- Expanding I2C capacity on address-limited projects
Package Contents
- 1× Adafruit PCA9548 8-Channel STEMMA QT / Qwiic I2C Multiplexer, assembled
Resources
- I2C Multiplexer Learn Guide – Overview, wiring, and example code (compatible with PCA9548)
- 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.
- LED
- A light-emitting diode is a small electronic component that lights up when current flows through it in the correct direction. In this kit, LEDs create the flashing effect, so polarity and correct soldering matter for the project to work.
- 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.
- 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.
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