# Adafruit PCA9546 4-Channel STEMMA QT Multiplexer
## Overview
You just found the perfect I2C sensor, available in a handy chainable [**Qwiic, or STEMMA QT**](https://learn.adafruit.com/introducing-adafruit-stemma-qt) package, and you want to wire up two or three or four of them to your microcontroller when you realize "Uh oh, this chip has a fixed I2C address, and from what I know about I2C, you cannot have two devices with the same address on the same SDA/SCL pins!" Are you out of luck? You would be, if you didn't have this ultra-cool **Adafruit PCA9546** **4 Channel STEMMA QT / Qwiic I2C Multiplexer**!
Finally, a way to get up to 4 same-address I2C devices hooked up to one microcontroller - this multiplexer acts as a gatekeeper, shuttling the commands to the selected I2C port with your command. [If you need to have up to 8 multiplexed devices, check out the 8-channel PCA9548 version of this board.](https://www.adafruit.com/product/5626)
**In case you're wondering why this uses the PCA9546 and not the [TCA9546A](https://www.ti.com/product/TCA9546A)**, the PCA9546 is the 'fraternal twin sister' of the TCA9546 but is easier to get during the great chip shortage of 2022-23. It works exactly the same, just can't go down to 1.8V power which is OK because QT boards are 3V or 5V only anyways. [You can still use any example code or library for the TCA9546 or TCA9548](https://learn.adafruit.com/adafruit-tca9548a-1-to-8-i2c-multiplexer-breakout/overview)
Using it is fairly straight-forward: the multiplexer itself is on I2C address 0x70 (but can be adjusted from 0x70 to 0x77 using jumpers on the back) and you simply write a single byte with the desired multiplexed output number to that port, and bam - any future I2C packets will get sent to that port. In theory, you could have 8 of these multiplexers on each of 0x70-0x77 addresses in order to control 4\*8 = 32 of the same-I2C-addressed-part.
The **Adafruit STEMMA QT / Qwiic PCA9546 Breakout - 4 Channel** has five JST SH 1mm connectors: 1 input and 4 outputs. There's one port at the end that connects to your I2C controller (there are also breadboard breakout pins if you need them). Use this breakout to add as many I2C devices to the bus as you need. Complete with mounting holes so the board can be added to any system. A small power LED lets you know that the hub board has connectivity.
There's even an onboard 3.3V 500mA regulator, so if you're using this with a 5V microcontroller like an Arduino 328-compatible, you can level shift all the QT ports to have 3V power and logic level. Simply cut/solder the jumper on the bottom of the PCB to force the power and logic level to be 3V.
Of course, because [STEMMA QT is Qwiic compatible](https://learn.adafruit.com/introducing-adafruit-stemma-qt), it will [work with any and all STEMMA QT or Qwiic boards and parts we have in the Adafruit shop](https://www.adafruit.com/?q=stemma%20qt).
Comes with only the assembled PCB, no [cables or sensors included (we have tons available though!)](http://learn.adafruit.com/introducing-adafruit-stemma-qt)
- [Next Page](https://learn.adafruit.com/adafruit-pca9546-4-channel-stemma-qt-multiplexer/pinouts.md)
## Primary Products
### Adafruit PCA9546 4-Channel STEMMA QT / Qwiic I2C Multiplexer
[Adafruit PCA9546 4-Channel STEMMA QT / Qwiic I2C Multiplexer](https://www.adafruit.com/product/5664)
You just found the perfect I2C sensor, available in a handy chainable [**Qwiic, or STEMMA QT**](https://learn.adafruit.com/introducing-adafruit-stemma-qt) package, and you want to wire up two or three or four of them to your microcontroller when you realize...
In Stock
[Buy Now](https://www.adafruit.com/product/5664)
[Related Guides to the Product](https://learn.adafruit.com/products/5664/guides)
## Featured Products
### STEMMA QT / Qwiic JST SH 4-pin Cable - 100mm Long
[STEMMA QT / Qwiic JST SH 4-pin Cable - 100mm Long](https://www.adafruit.com/product/4210)
This 4-wire cable is a little over 100mm / 4" long and fitted with JST-SH female 4-pin connectors on both ends. Compared with the chunkier JST-PH these are 1mm pitch instead of 2mm, but still have a nice latching feel, while being easy to insert and remove.
Out of Stock
[Buy Now](https://www.adafruit.com/product/4210)
[Related Guides to the Product](https://learn.adafruit.com/products/4210/guides)
### STEMMA QT / Qwiic JST SH 4-Pin Cable - 50mm Long
[STEMMA QT / Qwiic JST SH 4-Pin Cable - 50mm Long](https://www.adafruit.com/product/4399)
This 4-wire cable is 50mm / 1.9" long and fitted with JST SH female 4-pin connectors on both ends. Compared with the chunkier JST PH these are 1mm pitch instead of 2mm, but still have a nice latching feel, while being easy to insert and remove.
In Stock
[Buy Now](https://www.adafruit.com/product/4399)
[Related Guides to the Product](https://learn.adafruit.com/products/4399/guides)
### STEMMA QT / Qwiic JST SH 4-pin to Premium Male Headers Cable
[STEMMA QT / Qwiic JST SH 4-pin to Premium Male Headers Cable](https://www.adafruit.com/product/4209)
This 4-wire cable is a little over 150mm / 6" long and fitted with JST-SH female 4-pin connectors on one end and premium Dupont male headers on the other. Compared with the chunkier JST-PH these are 1mm pitch instead of 2mm, but still have a nice latching feel, while being easy to insert...
In Stock
[Buy Now](https://www.adafruit.com/product/4209)
[Related Guides to the Product](https://learn.adafruit.com/products/4209/guides)
### JST SH 4-pin Cable with Alligator Clips - STEMMA QT / Qwiic
[JST SH 4-pin Cable with Alligator Clips - STEMMA QT / Qwiic](https://www.adafruit.com/product/4398)
This cable will make it super easy to use our plug-and-play STEMMA QT boards with boards like Circuit Playground. On one end you get a Qwiic / STEMMA QT connector (technically known as a JST SH 4-pin plug) into 4 individual wires with grippy alligator clips. We're carrying these to...
Out of Stock
[Buy Now](https://www.adafruit.com/product/4398)
[Related Guides to the Product](https://learn.adafruit.com/products/4398/guides)
### STEMMA QT / Qwiic JST SH 4-pin Cable with Premium Female Sockets
[STEMMA QT / Qwiic JST SH 4-pin Cable with Premium Female Sockets](https://www.adafruit.com/product/4397)
This 4-wire cable is a little over 150mm / 6" long and fitted with JST-SH female 4-pin connectors on one end and premium female headers on the other. Compared with the chunkier JST-PH these are 1mm pitch instead of 2mm, but still have a nice latching feel, while being easy to insert and...
In Stock
[Buy Now](https://www.adafruit.com/product/4397)
[Related Guides to the Product](https://learn.adafruit.com/products/4397/guides)
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