Adafruit Feather 32u4 Bluefruit with Headers is an all-in-one Arduino-compatible + BLUETOOTH® Low Energy board with built-in USB and battery charging. The board is an Adafruit Feather 32u4 with an nRF51822 BTLE module. The Feather 32u4 features the ATmega32u4 clocked at 8MHz and 3.3V logic. This chip has 32K of flash and 2K of RAM, with built-in USB, and can also act like a mouse, keyboard, USB MIDI device, and more.
Measures 2.0" x 0.9" x 0.28" (51mm x 23mm x 8mm) without headers soldered in
Light as a (large?) feather - 5.7 grams
ATmega32u4 @ 8MHz with 3.3V logic/power
3.3V regulator with 500mA peak current output
USB native support; Includes USB bootloader and serial port debugging
You also get tons of pins - 20 GPIO pins
Hardware Serial, hardware I2C, hardware SPI support
7x PWM pins
10x analog inputs
Built-in 100mA lipoly charger with charging status indicator LED
Pin #13 red LED for general purpose blinking
4 mounting holes
On The Board
Microchip Technology ATmega32U4 8-bit MCU with USB Controller
A low-power, AVR RISC-based device featuring 32KB self-programming flash program memory.