# Adafruit Feather 32u4 Basic Proto > Feather-format ATmega32u4 board at 8 MHz, 3.3V with LiPo charging, native USB, onboard prototyping area, 20 GPIO, JST battery connector, and 100mA integrated charger — all in 51×23mm. ## Quick Facts - **Brand:** Adafruit - **Board Type:** dev-board - **Price:** ~$19.95 - **Product Readiness:** developer - **CPU:** ATmega32u4 @ 8 MHz - **CPU Architecture:** AVR - **CPU Cores:** 1 - **RAM:** 2 KB - **Flash:** 32 KB - **Power:** 3.7V LiPo via JST or 5V Micro USB - **Operating Voltage:** 3.3V - **Dimensions:** 51 × 23 mm - **Weight:** 4.8g ## Open Source - **Firmware:** Yes - **Schematics:** Yes - **PCB Layout:** Yes ## Compatible Firmware arduino, platformio ## Use Cases - portable - battery-powered - wearable - prototyping - iot ## Components - **ATmega32u4** (mcu): 8-bit AVR with native USB at 8 MHz, 32KB flash, 2KB SRAM — [Datasheet](https://openhardware.directory/r?to=https%3A%2F%2Fww1.microchip.com%2Fdownloads%2Fen%2FDeviceDoc%2FAtmel-7766-8-bit-AVR-ATmega16U4-32U4_Datasheet.pdf&ref=openhardware.directory&product=adafruit-feather-32u4-basic-proto&source=md-export) - **MCP73831** (charger): Microchip MCP73831 100mA LiPo/LiIon charge management IC with automatic switchover — [Datasheet](https://openhardware.directory/r?to=https%3A%2F%2Fww1.microchip.com%2Fdownloads%2Fen%2FDeviceDoc%2F20001984g.pdf&ref=openhardware.directory&product=adafruit-feather-32u4-basic-proto&source=md-export) ## Protocols - **UART**: TX: D1, RX: D0 - **SPI**: MOSI: D16, MISO: D14, SCK: D15, SS: D10 - **I2C**: SDA: D2, SCL: D3 - **USB** ## GPIO Map | Pin | Name | Type | Functions | |-----|------|------|-----------| | D0 | UART RX, External Interrupt 2 | UART | digital-input, digital-output, interrupt | | D1 | UART TX, External Interrupt 3 | UART | digital-input, digital-output, interrupt | | D2 | I2C SDA, External Interrupt 1 | I2C | digital-input, digital-output, interrupt | | D3 | I2C SCL, PWM, External Interrupt 0 | I2C | digital-input, digital-output, pwm, interrupt | | D4 | Digital I/O, Analog Input (A6) | — | digital-input, digital-output, analog-input | | D5 | Digital I/O, PWM | — | digital-input, digital-output, pwm | | D6 | Digital I/O, Analog Input (A7), PWM | — | digital-input, digital-output, analog-input, pwm | | D7 | Digital I/O, External Interrupt 6 | — | digital-input, digital-output, interrupt | | D9 | Battery voltage monitor (via voltage divider), Analog Input (A9), PWM | — | digital-input, digital-output, analog-input, pwm | | D10 | SPI SS, Analog Input (A10), PWM | SPI | digital-input, digital-output, analog-input, pwm | | D11 | Digital I/O, PWM | — | digital-input, digital-output, pwm | | D12 | Digital I/O, Analog Input (A11) | — | digital-input, digital-output, analog-input | | D13 | Onboard red LED, PWM | — | digital-input, digital-output, pwm | | D14 | SPI MISO | SPI | digital-input, digital-output | | D15 | SPI SCK | SPI | digital-input, digital-output | | D16 | SPI MOSI | SPI | digital-input, digital-output | | A0 | Analog Input / Digital I/O | — | analog-input, digital-input, digital-output | | A1 | Analog Input / Digital I/O | — | analog-input, digital-input, digital-output | | A2 | Analog Input / Digital I/O | — | analog-input, digital-input, digital-output | | A3 | Analog Input / Digital I/O | — | analog-input, digital-input, digital-output | | A4 | Analog Input / Digital I/O | — | analog-input, digital-input, digital-output | | A5 | Analog Input / Digital I/O | — | analog-input, digital-input, digital-output | ## Available Software - **[Arduino IDE]()** (open-source) - **[PlatformIO]()** (open-source) ## Description ## Overview The Adafruit Feather 32u4 Basic Proto is part of Adafruit's Feather ecosystem — a family of thin, lightweight development boards designed for portable and battery-powered projects. Built around the ATmega32u4 at 8 MHz with 3.3V logic, it combines the Arduino Leonardo's native USB capabilities with an integrated LiPoly battery charger and a small prototyping area directly on the PCB. The board provides 20 digital I/O pins (7 PWM-capable), 10 analog inputs (one dedicated to battery voltage monitoring), hardware Serial, I2C, and SPI, along with native USB support through the ATmega32u4's built-in USB controller. The integrated 100mA LiPoly charger automatically manages charging when USB power is connected, with automatic switchover between USB and battery power. The 3.3V regulator provides up to 500mA peak output, and the JST connector accepts standard 3.7V lithium polymer batteries. At 51 × 23 × 8mm and just 4.8 grams, the board is optimized for space-constrained installations. Four mounting holes and a reset button are included. The Feather 32u4 Basic Proto includes a small prototyping area with plated through-holes, enabling simple circuit additions without a separate breadboard. FeatherWing accessory boards can be stacked for additional functionality including displays, sensors, radios, and motor drivers, all sharing the standard Feather header footprint. ## Where to Buy - [Adafruit](https://openhardware.directory/r?to=https%3A%2F%2Fwww.adafruit.com%2Fproduct%2F2771&ref=openhardware.directory&product=adafruit-feather-32u4-basic-proto&source=md-export) — 19.95 ## Resources - [product](https://openhardware.directory/r?to=https%3A%2F%2Fwww.adafruit.com%2Fproduct%2F2771&ref=openhardware.directory&product=adafruit-feather-32u4-basic-proto&source=md-export) - [wiki](https://openhardware.directory/r?to=https%3A%2F%2Flearn.adafruit.com%2Fadafruit-feather-32u4-basic-proto&ref=openhardware.directory&product=adafruit-feather-32u4-basic-proto&source=md-export) ## Tags `feather`, `atmega32u4`, `lipo-charging`, `native-usb`, `adafruit`, `portable`, `breadboard` ## Images ![Adafruit Feather 32u4 Basic Proto](https://nbg1.your-objectstorage.com/openhardware-directory/entities/adafruit-feather-32u4-basic-proto/d1f2e7cb3882.jpg) ![Adafruit Feather 32u4 Basic Proto](https://nbg1.your-objectstorage.com/openhardware-directory/entities/adafruit-feather-32u4-basic-proto/b385fe5b6b59.jpg) --- [View full device page](https://openhardware.directory/devices/adafruit-feather-32u4-basic-proto)