ATMEGA 16U2 Chipset Micro USB connector 4 additional 5v and GND power pins Additional analog pins A6 & A7 The OSEPP Uno R4 USB Microcontroller is the most popular Arduino board out in the Arduino market! This board uses the 8-bit, AVR, RISC-based ATmega328P microcontroller from Atmel.The ATmega328P comes with the Arduino bootloader preloaded. There is an ICSP (In-Circuit Serial Programming) header for the ATmega328 to optionally replace the bootloader. As an added precaution, the board comes with a resettable polyfuse on the USB connection path. To prevent damage to the USB port, the fuse will trip when the current to the port exceeds 500 mA.The input and/or output pins are brought out to the headers, providing a convenient way to prototype projects without the need of soldering or desoldering. Features: 8-bit AVR RISC-based microcontroller running at 16 MHz Connects to a computer via a standard USB cable Flexible power source (USB or DC power) ICSP header for programming microcontroller Compatible with existing Arduino software libraries Compatible with all Arduino shields make for Arduino UNOs