The Micro comes with a built-in USB which makes the Micro recognizable as a mouse or keyboard.
Arduino's Microcontroller board based on the ATmega32U4
Similar to the Arduino Leonardo, but much smaller -- one of Arduino's smallest board -- making it easy to integrate into everyday objects to make them interactive.
Features 20 digital input/output pins (of which 7 can be used as PWM outputs and 12 as analog inputs), a 16 MHz crystal oscillator, a micro USB connection, an ICSP header, and a reset button
Board only - No headers
The Micro is a microcontroller board based on the ATmega32U4, developed in conjunction with Adafruit. It has 20 digital input/output pins (of which 7 can be used as PWM outputs and 12 as analog inputs), a 16 MHz crystal oscillator, a micro USB connection, an ICSP header, and a reset button. It contains everything needed to support the microcontroller; simply connect it to a computer with a micro USB cable to get started. It has a form factor that enables it to be easily placed on a breadboard.
The Micro board is similar to the Arduino Leonardo in that the ATmega32U4 has built-in USB communication, eliminating the need for a secondary processor. This allows the Micro to appear to a connected computer as a mouse and keyboard, in addition to a virtual (CDC) serial / COM port.
Item Specifics Microcontroller: ATmega32U4 Operating Voltage: 5 V Flash Memory: 32 KB (ATmega32U4) of which 4 KB used by bootloader SRAM: 2.5 KB (ATmega32U4) Clock Speed: 16 MHz Analog Channels: 12 EEPROM: 1 KB (ATmega32U4) DC Current per I/O Pins: 20 mA Input Voltage: 7-9V Digital I/O Pins: 20 PWM Channels: 7 Clock Speed: 16 MHz LEDs: 13 PCB Size: 18 x 48 mm Weight: 13 g