Adafruit Launches MCP23017 I2C Expander Breakout — and Teases nRF52840-Based QT Py Bluefruit

STEMMA QT projects now have an easy, low-cost way to boost their GPIO pin count — and the QT Py Bluefruit looks sure to impress.

Adafruit has launched a new general-purpose input/output (GPIO) expander, based on the Microchip MCP23017 — while teasing a shiny new Qt Py, built around Nordic's nRF52840.

"We’ve gotten a lot of requests for a MCP23017 breakout and we’ve always sorta been like 'ehh why not just use the DIP chip?'," Adafruit's Phillip Torrone explains of the thinking behind the company's latest board launch, "but with STEMMA QT we could see the use case for a plug and play version that comes with all the passives on board."

That's exactly what its new breakout board is: A compact Microchip MCP23017 and everything required to make it go, along with unpopulated breadboard-friendly pin headers and a pair of STEMMA QT connectors for addressing the device over I2C.

The breakout offers 16 general-purpose input/output (GPIO) pins, each capable of driving up to 25mA as an output; when configured as an input, all 16 pins have optional internal pull-up resistors. The device also boasts three address pins, allowing up to eight boards on a single I2C bus — for, Adafruit points out, a total of 128 GPIO pins.

At the same time, Adafruit has shown off another board, which is going through the design phase: The QT Py Bluefruit. "Now we’ve got the QT Py SAMD21, RP2040, and ESP32-S2 designed and fabricated," Torrone explains, "we're going to follow up with an nRF52840 version!"

Designed in the same compact footprint as the other QT Py models mentioned, the QT Py Bluefruit is built around the Nordic nRF52840 — meaning it comes with a 32-bit Arm Cortex-M4F microcontroller running at up to 64MHz, 256kB of RAM, and 1MB of on-board flash, plus a multi-protocol radio with Bluetooth 5.2, Bluetooth Low Energy, Bluetooth Mesh, Near-Field Communication (NFC), and 802.15.4 with support for Thread and Zigbee.

The MCP23017 I2C GPIO Expander Breakout is available on the Adafruit store now at $5.95 before volume discounts; more information on the upcoming QT Py Bluefruit is available on the company blog, but it has yet to share pricing and availability.

Gareth Halfacree
Freelance journalist, technical author, hacker, tinkerer, erstwhile sysadmin. For hire:
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