Adafruit Teases New STEMMA QT Multiplexer, GPIO Expansion Boards

Adafruit has teased designs for a pair of new STEMMA QT breakout boards, one which works around the ongoing component shortages and another that takes a popular I2C multiplexer breakout but makes it a solder-free drop-in — creating what the company jokes is a "STEMMA QT [to] QTQTQTQTQTQTQTQT" board.

"We sell a handy TCA9584 [I2C] expander breakout," Adafruit's Phillip Torrone explains, pointing to a low-cost breadboard-friendly board which allows multiple devices to share the same I2C address. "It's great for when you want to connect eight devices of the same I2C address — but what if you want to do to it without any breadboarding, using STEMMA QT or Qwiic? Someone emailed us about it, and we gotta admit, they’re kinda right."

The solution, if you hadn't yet guessed, is a board based around the same Texas Instruments TCA9584 I2C multiplexer chip but in the STEMMA QT style — boasting a single solderless STEMMA QT port to the host microcontroller and eight for the multiplexed devices, no soldering required.

"It [also] has a level shift[er]/selector from Vin or 3.3V," Torrone continues, "which means that if you’re interfacing to 3.3V Qwiic boards from a 5V logic [Arduino] UNO it will do the conversion for you — but if you want that 5V power passed through, you can do that as well."

Torrone has also unveiled a second new STEMMA QT board design, this time a 16-pin general-purpose input/output (GPIO) expander — built to work around ongoing shortages of the Microchip MCP23017 used in Adafruit's existing board design. "[This chip] doesn’t have any address select pins (boo!)," Torrone warns, "but it does have two bank VCCIO pins so you can use it for level shifting (yay!).

"We might also take a look at the [Semtech] SX1509," Torrone adds, "which is a bit more expensive and requires 3.3V power/logic but does has PWM [Pulse Width Modulation] and keypad scanning support."

Adafruit has not confirmed when it plans to put either board into production, nor when they will be available to order on the store.