# Arduino Uno Ethernet

> Arduino UNO with built-in Ethernet and microSD slot based on the ATmega328P at 16 MHz — a self-contained board for networked Arduino projects without needing a separate Ethernet shield.

## Quick Facts

- **Brand:** Arduino
- **Board Type:** dev-board
- **Price:** ~$65
- **Product Readiness:** developer
- **CPU:** ATmega328P @ 16 MHz
- **CPU Architecture:** AVR
- **CPU Cores:** 1
- **RAM:** 2 KB
- **Flash:** 32 KB
- **Power:** 7-12V DC barrel jack or FTDI 5V
- **Operating Voltage:** 5V
- **Dimensions:** Arduino UNO form factor
- **SD Card:** microSD

## Connectivity

- **Ethernet:** 10/100 Mbps

## Open Source

- **Firmware:** Yes
- **Schematics:** Yes
- **PCB Layout:** Yes

## Compatible Firmware

arduino, platformio

## Use Cases

- iot
- networking
- data-logging
- home-automation

## Components

- **ATmega328P** (mcu): 8-bit AVR microcontroller at 16 MHz with 32KB flash, 2KB SRAM — [Datasheet](https://openhardware.directory/r?to=https%3A%2F%2Fww1.microchip.com%2Fdownloads%2Fen%2FDeviceDoc%2FAtmel-7810-Automotive-Microcontrollers-ATmega328P_Datasheet.pdf&ref=openhardware.directory&product=arduino-uno-ethernet&source=md-export)
- **W5100** (ethernet): Wiznet W5100 hardwired TCP/IP embedded Ethernet controller with 10/100 Ethernet support — [Datasheet](https://openhardware.directory/r?to=https%3A%2F%2Fwww.wiznet.io%2Fwp-content%2Fuploads%2Fwiznethome%2FChip%2FW5100%2FDocument%2FW5100_Datasheet_v1.2.7.pdf&ref=openhardware.directory&product=arduino-uno-ethernet&source=md-export)

## Protocols

- **UART**: TX: D1, RX: D0
- **SPI**: MOSI: D11, MISO: D12, SCK: D13, ETH_CS: D10, SD_CS: D4
- **I2C**: SDA: A4, SCL: A5
- **ICSP**

## GPIO Map

| Pin | Name | Type | Functions |
|-----|------|------|-----------|
| D0 | UART RX | UART | digital-input, digital-output |
| D1 | UART TX | UART | digital-input, digital-output |
| D2 | Digital I/O, External Interrupt 0 | — | digital-input, digital-output, interrupt |
| D3 | Digital I/O, PWM, External Interrupt 1 | — | digital-input, digital-output, pwm, interrupt |
| D4 | microSD Chip Select (SPI) | SPI | digital-input, digital-output |
| D5 | Digital I/O, PWM | — | digital-input, digital-output, pwm |
| D6 | Digital I/O, PWM | — | digital-input, digital-output, pwm |
| D7 | Digital I/O | — | digital-input, digital-output |
| D8 | Digital I/O | — | digital-input, digital-output |
| D9 | Digital I/O, PWM | — | digital-input, digital-output, pwm |
| D10 | Ethernet W5100 Chip Select (SPI), PWM | SPI | digital-input, digital-output, pwm |
| D11 | SPI MOSI, PWM | SPI | digital-input, digital-output, pwm |
| D12 | SPI MISO | SPI | digital-input, digital-output |
| D13 | SPI SCK | SPI | digital-input, digital-output |
| A0 | Analog Input / Digital I/O | — | analog-input, digital-input, digital-output |
| A1 | Analog Input / Digital I/O | — | analog-input, digital-input, digital-output |
| A2 | Analog Input / Digital I/O | — | analog-input, digital-input, digital-output |
| A3 | Analog Input / Digital I/O | — | analog-input, digital-input, digital-output |
| A4 | I2C SDA, Analog Input | I2C | analog-input, digital-input, digital-output |
| A5 | I2C SCL, Analog Input | I2C | analog-input, digital-input, digital-output |

## Available Software

- **[Arduino IDE]()** (open-source)
- **[PlatformIO]()** (open-source)

## Description

## Overview

The Arduino Uno Ethernet integrates an Ethernet jack and microSD card slot directly onto an Arduino UNO-compatible board, eliminating the need for a separate Ethernet shield. Based on the ATmega328P microcontroller at 16 MHz, it provides the familiar Arduino pin layout while adding always-present network connectivity with visual status indicator LEDs.

The board omits a USB port in favor of a 6-pin FTDI connector for programming, requiring an FTDI cable or FTDI Friend for uploading sketches. Digital pins 10–13 are reserved for the onboard Ethernet chip, and pin 4 is used for the microSD card chip select, leaving the remaining pins available for user code.

Power is delivered through the standard Arduino barrel jack, and the board maintains the R3 shield footprint with some caveats — the taller Ethernet jack may require stacking headers when using shields. The integrated microSD slot enables local data logging alongside network operations.

Designed for IoT and networked embedded applications, this board simplifies deployments where Ethernet connectivity is required without the bulk and pin overhead of stacking a separate shield.

## Where to Buy

- [Amazon US](https://openhardware.directory/r?to=https%3A%2F%2Fwww.amazon.com%2Fdp%2FB006UT97FE&ref=openhardware.directory&product=arduino-uno-ethernet&source=md-export) — $59.00

## Resources

- [product](https://openhardware.directory/r?to=https%3A%2F%2Fwww.adafruit.com%2Fproduct%2F418&ref=openhardware.directory&product=arduino-uno-ethernet&source=md-export)
- [wiki](https://openhardware.directory/r?to=https%3A%2F%2Fdocs.arduino.cc%2Fretired%2Fboards%2Farduino-ethernet-rev3-without-poe&ref=openhardware.directory&product=arduino-uno-ethernet&source=md-export)

## Tags

`arduino`, `atmega328p`, `ethernet`, `microsd`, `iot`, `networking`

## Images

![Arduino Uno Ethernet](https://nbg1.your-objectstorage.com/openhardware-directory/entities/arduino-uno-ethernet/c21a8286c268.jpg)
![Arduino Uno Ethernet](https://nbg1.your-objectstorage.com/openhardware-directory/entities/arduino-uno-ethernet/f700ff9793a0.jpg)

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