Adafruit USB Host BFF for QT Py or Xiao with MAX3421E

The Adafruit USB Host BFF adds USB Host capability to your QT Py or Xiao board, letting you connect keyboards, mice, game controllers, or USB storage devices to your tiny microcontroller projects. Built around the MAX3421E USB Host chip, it communicates via SPI for broad compatibility.

The compact BFF form factor plugs directly onto your QT Py. A Micro-B OTG connector keeps things small—use a standard OTG adapter to connect full-size USB devices. A P-FET power switch lets you control 5V power to peripherals via GPIO or the MAX3421E's built-in pin.

Key Features

• MAX3421E USB Host – SPI interface with IRQ pin
• BFF Form Factor – Plugs directly onto QT Py or Xiao
• Micro-B OTG Connector – Compact USB host port
• Power Switching – P-FET controlled 5V to peripherals
• TinyUSB Support – Native Arduino library integration

Compatible Chips

• RP2040
• ESP32-S2, ESP32-S3
• nRF52840
• SAMD21/SAMD51

Supported Devices

• Keyboards and mice (HID)
• Game controllers
• USB mass storage (flash drives)
• CDC serial devices

Package Contents

• 1× USB Host BFF board
• 1× Header set for soldering

Resources

• TinyUSB Arduino Library
• USB Host Shield 2.0 Library