Believe it or not, this board is a small development system. It barely fits on your finger, but it features ATmega328, USB-UART, reset circuit and LED indicators. It’s compatible with standard DIP26 sockets. On-board voltage regulator allows the board to be powered directly from USB cable. It comes in two versions: 5V and 3.3V. 5V version features 16MHz SMD crystal oscillator while 3.3V version contains 8MHz oscillator. Both come preprogrammed with fast UART bootloader with 57600 bps operation, so no external programmers are needed for development.