The Bluefruit LE module is an nRF51822 chipset from Nordic, programmed with multi-function code that can do quite a lot! For most people, they'll be very happy to use the standard Nordic UART RX/TX connection profile. In this profile, the Bluefruit acts as a data pipe, that can 'transparently' transmit back and forth from your iOS or Android device. The board is capable of much more than just sending strings over the air! Thanks to an easy to learn AT command set, you have full control over how the device behaves, including the ability to define and manipulate your own GATT Services and Characteristics, or change the way that the device advertises itself for other Bluetooth® Low Energy devices to see. You can also use the AT commands to query the die temperature, check the battery voltage, and more, check the connection RSSI or MAC address, and tons more. Really, way too long to list here!

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Here's some handy specs! Like all Feather 32u4's you get: 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, comes with USB bootloader and serial port debugging You also get tons of pins - 20 GPIO pins Hardware Serial, hardware I2C, hardware SPI support 7 x PWM pins 10 x analog inputs Built in 100mA lipoly charger with charging status indicator LED Pin #13 red LED for general purpose blinking Power/enable pin 4 mounting holes Reset button The Feather 32u4 Bluefruit LE uses the extra space left over to add our excellent Bluefruit BTLE module + two status indicator LEDs.