Adafruit Feather 32u4 Bluefruit LE with Stacking Headers

Adafruit Feather 32u4 Bluefruit LE with Stacking Headers - Assembled is an "all-in-one" Arduino-compatible + Bluetooth Low Energy device with built-in USB and battery charging. The board is thin, light, and is a new standard for portable microcontroller cores. Bluetooth Low Energy is the only wireless protocol that can be used with iOS without needing a special certification, and supported by all modern smart phones. This makes it excellent for use in portable projects that will make use of an iOS or Android phone or tablet. It also is supported in Mac OS X and Windows 8+.

At the Feather 32u4's heart is at ATmega32u4 clocked at 8MHz and at 3.3V logic, a chip setup that's the same as the Flora. This chip has 32K of flash and 2K of RAM, with built-in USB. The device has built-in USB-to-Serial program & debug capability with no need for an FTDI-like chip, and can act like a mouse, keyboard, USB MIDI device, etc.

A connector has been added for a 3.7V Lithium polymer batteries and built-in battery charging to make it easy to use for portable projects. A battery is not required and will run straight from the micro USB connector. If a battery is used, it can be plugged into the USB to recharge. The Feather will automatically switch over to USB power when it's available. The battery is also tied through a divider to an analog pin to measure and monitor the battery voltage to detect when a recharge is needed.