UNO R3: Atmega16U2 instead 8U2. This update services for USB interface chip; Specification: Microcontroller: ATmega328; Operating Voltage: 5V; Input Voltage (recommended): 7~12V; Input Voltage (limits): 6~20V; Digital I/O Pins: 14 (of which 6 provide PWM output); Analog Input Pins: 6; DC Current per I/O Pin: 40 mA, DC Current for 3.3V Pin: 50mA, Flash Memory: 32 KB (ATmega328) of which 0.5 KB used by bootloader, SRAM: 2 KB (ATmega328), EEPROM: 1 KB (ATmega328); Clock Speed: 16MHz. Ethernet Shield W5100: The Ethernet W5100 network expansion module allows the Arduino to be a simple Web server; Supports reading and writing mini SD / TF card; With Micro SD card slot, supports SD card up to 2GB.