High Quality Content by WIKIPEDIA articles! The AVR Butterfly , about the size of a credit card, is the cheapest self-contained, battery-powered single board microcontroller available. It runs the ATMEL AVR ATmega169PV Microcontroller IC. The board includes a liquid crystal display (LCD), joystick, speaker, serial port, real-time clock (RTC), internal flash memory, and sensors for temperature and voltage. The board is the size of a name tag and has a clothing pin on back so it can be worn as such after the user enters their name onto the LCD.