The Arduino Leonardo is a microcontroller board developed by Arduino. It was developed to provide an easy to use interface with the ability to perform a number of functions on a single chip. It is based on the ATmega32u4.

Arduino Leonardo Features:

• It has 20 digital input/output pins (of which 7 can be used as PWM outputs and 12 as analog inputs). These pins are enough to connect with external devices and turn your innovation into reality.
• The module supports the crystal oscillator with a frequency up to 16 MHz, enough to produce a clock pulse with a decent pace which is required for the synchronization of all the internal operations.
• Supports common communication protocols like UART, SPI, and I2C. The UART is a serial communication protocol mainly used for transferring and receiving serial data using two pins called TX and RX.
• It has a micro USB connection, a power jack, an ICSP header, and a reset button.

It contains everything needed to support the microcontroller. To get started, simply connect it to a computer with a USB cable or power it with an AC-to-DC adapter or battery.

The Leonardo differs from all preceding boards in that the ATmega32u4 has built-in USB communication, eliminating the need for a secondary processor. This allows the Leonardo to appear to a connected computer as a mouse and keyboard, in addition to a virtual (CDC) serial / COM port. It also has other implications for the behavior of the board; these are detailed on the getting started page provided by Arduino.