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Manufacturer Adafruit (and others)
Host port USB Micro-B or USB C
Microcontroller Various
Voltage 3.3V
Digital I/O pins 20 (typically)
I/O Voltage 3.3V
Website learn.adafruit.com/adafruit-feather/overview

Feather is a form-factor for microcontroller boards created by Adafruit.

Several manufacturers make boards with different microcontrollers and feature sets.


The boards are bigger than a Pro Micro but smaller than a traditional Arduino board.

The form factor is defined in the Feather specification.

All mainboards have a JST 2-PH battery connector, capable of both running from and charging a 3.0-3.7V LiPoly battery. GPIO pins must be compatible with 3.3V logic.

All of Adafruit's boards support Arduino, and C/C++ with GCC.

An accessory board ("hat") for a Feather is called a "FeatherWing".


Adafruit Feather

There is a large number of Adafruit Feather boards.

By convention, Adafruit Feather boards have their main characteristics as part of their name.

The first part of the name often names the microcontroller:

  • Feather 32u4 boards are based on the ATMega32u4 running at 8 MHz / 3.3V, which has USB hardware and much open source firmware support.
  • Feather M0 boards are based on the Atmel/Microchip SAM D21 (ATSAMD21) with a ARM Cortex-M0 @ 48 MHz. Feather M4 boards are based on the Atmel/Microchip SAM D51 (ATSAMD51) with a faster ARM Cortex-M4F core @ 120 MHz. These boards support CircuitPython. The bootloader works as a USB storage device.
  • Feather nRF52840 boards use the Nordic Semiconductor nRF52840 which is capable of USB, BLE and NFC. They come with Adafruit's bootloader and Nordic's "SoftDevice" for BLE already installed.

Some Adafruit Feather boards with other microcontrollers do not have hardware that can run USB HID, but instead use a USB-to-serial chip that can only be used for loading firmware over USB. "HUZZAH32" or "WROOM32" boards are based on the ESP32 that support Bluetooth but not USB.

A board named Express has a microcontroller only, where other boards are named after their additional functional units: often a communications module capable of one or more of Bluetooth / BLE, WiFi or LoRa. Some boards come with SD-card reader, but one has a small SPI Flash chip instead.

Notable boards:

SparkFun Thing Plus

The SparkFun Thing Plus boards from SparkFun have a 4-pin JST connector for their "Qwiic Connect System" for I²C.

Notable boards:

Wio Lite

The Wio Lite boards from Seeedstudio all have USB-C.

Notable boards:


All Particle boards come with Nordic Semiconductor nRF52840 microcontroller which has a ARM Cortex-M4F MCU @ 64 MHz, USB device and radio capable of BLE and NFC. All Particle boards have a Micro-USB port.

Notable boards:


Note: the pinout below is the one recommended by Adafruit, and the one used for AVR ATmega32u4-based boards respectively. Boards may have more or fewer pins.

Note also that a board can be longer than standard, but are not allowed to be wider.

AVR Function GPIO ↑USB↑ GPIO Function AVR
Reset LiPo battery connector
PF7 A0 18 VBAT (from battery)
PF6 A1 19 En
PF5 A2 20 VBUS (+5V from USB port)
PF4 A3 21 13 PC7
PF1 A4 22 12 PD6
PF0 A5 23 11 PB7
PB1 SCLK 15 10 PB6
PB2 MOSI 16 9 PB5
PB3 MISO 14 6 PD7
PD2 RX 0 5 PC6
PD3 TX 1 3 SCL PD0
Ground 2 SDA PD1

The En pin disables the 3.3V output pin when connected to ground. Every board should have an internal pull-up allowing this pin to be disconnected.

Some boards have a GPIO pin in the corner instead of Ground.