Arduino open source single board computer boards arduino a000057 the arduino leonardo is a microcontroller board that is based upon the atmega32u4 microcontroller it has everything required to support the microcontroller and to get started simply connect to a computer the leonardo differs from all preceding boards in that the atmega32u4 has built in usb communication which eliminates the requirement for a secondary processor this enable the board to appear to a computer as both a mouse an