The Arduino Ethernet is a development board with the Wiznet W5100 Ethernet interface built directly onto the board — no separate shield required. It features 14 digital I/O pins, 6 analogue inputs, an on-board micro-SD card slot, a 16 MHz crystal oscillator, RJ-45 connection, power jack, ICSP header, and a reset button.

Because the Ethernet interface is integrated, there's no USB-serial driver on-board. You'll need an FTDI breakout or similar USB-to-serial adapter to upload sketches. Pins 10, 11, 12, and 13 are reserved for the Ethernet module, leaving 9 digital pins available (4 with PWM output).

Key Features

• ATmega328 Microcontroller – Running at 16 MHz with 5V operating voltage
• Wiznet W5100 Ethernet Controller – Built-in TCP/IP stack for wired internet connectivity
• Standard RJ-45 Connector – Reliable wired networking
• Micro-SD Card Slot – Store and serve files over the network (SS on Pin 4)
• 14 Digital I/O Pins – 4 reserved for Ethernet, 4 PWM-capable among the remaining 9
• 6 Analogue Inputs – For sensor readings and analogue data
• Input Voltage – 7–12V via barrel jack

Ideal For

• Compact IoT projects where a separate Ethernet shield won't fit
• Embedded web servers and network-connected data loggers
• Remote monitoring and control systems
• Headless network devices

Resources

• Arduino Ethernet Product Page
• Schematic (PDF)
• EAGLE Design Files
• W5100 Datasheet (PDF)