How to Run micro-ROS over Ethernet on ESP32-S3-ETH Using the W5500 Hardware TCP/IP Stack?

Summary

This project demonstrates how to connect an ESP32-S3-ETH board to a ROS 2 system using micro-ROS over wired Ethernet.

 Instead of relying on Wi-Fi, it uses the WIZnet W5500 Ethernet controller to provide a hardware TCP/IP stack and hardware UDP sockets. The ESP32-S3 focuses on executing the micro-ROS application while the W5500 handles Ethernet packet processing, providing a stable and deterministic communication path to a micro-ROS Agent running on ROS 2 Jazzy.

What the Project Does

The project implements a micro-ROS publisher on an ESP32-S3-ETH board. Every second, the firmware publishes an incrementing std_msgs/msg/Int32 message to a ROS 2 topic through a micro-ROS Agent.

Unlike many ESP32 Ethernet examples that use the ESP-IDF Ethernet driver with lwIP, this implementation communicates through the Arduino Ethernet library configured for the W5500 Ethernet controller.

The communication flow is:

rclc Executor
        │
        │ Timer Event
        ▼
timer_callback()
        │
        │ rcl_publish(std_msgs/msg/Int32)
        ▼
rcl / rmw_microxrcedds
        │
        ▼
Micro XRCE-DDS Client
        │
        ▼
Custom UDP Transport
        │
        ▼
Arduino EthernetUDP
        │
        ▼
W5500 Hardware UDP Socket
        │
        ▼
W5500 Hardware TCP/IP Engine
        │
        ▼
10/100BASE-TX Ethernet
        │
        ▼
micro-ROS Agent
UDP/IPv4 Port 8888
        │
        ▼
ROS 2 Jazzy

The micro-ROS Agent receives XRCE-DDS packets over UDP and forwards them into the ROS 2 DDS network, allowing the ESP32-S3 node to behave as a standard ROS 2 publisher.

Where WIZnet Fits

The key technical feature of this project is that it uses the W5500 as the actual networking engine, not simply as an Ethernet PHY.

The project configures the Arduino Ethernet library and registers a custom micro-ROS Ethernet transport instead of using the ESP-IDF esp_eth or lwIP networking stack.

This means:

Ethernet communication is performed through W5500 hardware sockets

UDP packets are processed by the W5500 Hardware TCP/IP Engine

The ESP32-S3 does not execute a software TCP/IP stack for this communication path

The MCU can dedicate more processing time to ROS 2 application logic

It is important to distinguish between the transport protocol and the network stack.

This project does not use TCP communication.

Instead:

Transport Protocol: UDP

Network Stack: W5500 Hardware TCP/IP Stack

Agent Mode: udp4

Communication: Hardware UDP Socket

Therefore, the correct technical description is:

micro-ROS communicates over UDP while the UDP packets are processed by the W5500 Hardware TCP/IP Stack.

This is an important architectural distinction that differentiates this implementation from ESP32 Ethernet solutions based on lwIP.

Implementation Notes

W5500 Initialization

File: src/main.cpp

SPI.begin(W5500_SCK, W5500_MISO, W5500_MOSI, W5500_CS);

Ethernet.init(W5500_CS);

set_microros_eth_transports(
    esp_mac,
    esp_ip,
    agent_ip,
    dns,
    gateway,
    agent_port
);

The firmware initializes the SPI bus, configures the W5500 chip select, and registers the W5500 Ethernet interface as the custom transport used by micro-ROS.

This is the point where Micro XRCE-DDS is connected to the W5500 UDP transport.

Creating the ROS Publisher

File: src/main.cpp

RCCHECK(rclc_publisher_init_best_effort(
    &publisher,
    &node,
    ROSIDL_GET_MSG_TYPE_SUPPORT(std_msgs, msg, Int32),
    PublisherTopic
));

The project creates a Best Effort publisher, which naturally matches the UDP transport used by Micro XRCE-DDS.

Running the Agent

The README starts the micro-ROS Agent with:

ros2 run micro_ros_agent micro_ros_agent udp4 --port 8888

The udp4 option confirms that communication uses UDP over IPv4, not TCP.

Why This Architecture Matters

Many ESP32 Ethernet projects use the following architecture:

ESP32
 └── lwIP
      └── Ethernet Driver
           └── Ethernet Controller

This project follows a different architecture:

ESP32-S3
        │
micro-ROS Application
        │
Micro XRCE-DDS
        │
Arduino Ethernet
        │
W5500 Hardware TCP/IP Engine
        │
Ethernet

The advantages include:

Deterministic wired communication

No Wi-Fi interference

Hardware socket processing

Reduced networking overhead on the MCU

Reliable communication for industrial and robotic systems

Practical Tips

Reset the W5500 before Ethernet initialization for improved startup reliability.

Verify Ethernet link status before creating micro-ROS entities.

Ensure the Agent IP address matches the local network configuration.

UDP Best Effort is ideal for telemetry but should not be used for safety-critical commands without application-level acknowledgement.

Plan hardware socket usage if additional Ethernet services (HTTP, Modbus TCP, MQTT, etc.) are added.

Keep SPI traces short and ensure proper power decoupling for reliable high-speed communication.

FAQ

Why use the W5500 instead of Wi-Fi?

The W5500 provides deterministic wired Ethernet communication that is immune to RF interference. This is especially valuable for robotics and industrial control systems where communication stability is more important than mobility.

Does this project use TCP?

No.

The communication protocol is UDP.

However, UDP packets are processed by the W5500 Hardware TCP/IP Stack, which supports both TCP and UDP in hardware.

Does the ESP32-S3 use lwIP?

Based on the project implementation, no.

The firmware uses the Arduino Ethernet library together with the custom micro-ROS Ethernet transport rather than the ESP-IDF Ethernet driver and lwIP socket APIs.

What role does the W5500 play?

The W5500 acts as the Ethernet networking engine by providing:

Hardware IPv4 processing

Hardware UDP sockets

Socket buffer management

Ethernet packet transmission and reception

The ESP32-S3 primarily executes the micro-ROS application.

Comparison with Similar WIZnet Maker Projects

Source

Original Project

https://github.com/103031430/MicroROS-Pub

Key Files

src/main.cpp

platformio.ini

README.md

Related Software

micro-ROS

Micro XRCE-DDS

Arduino Ethernet Library

ROS 2 Jazzy

micro-ROS Agent

License

No explicit LICENSE file is included in the repository at the time of writing.

Tags

W5500 ESP32-S3 ESP32-S3-ETH micro-ROS ROS2 Ethernet UDP Hardware TCP/IP Stack Micro XRCE-DDS PlatformIO Robotics