---
title: "ESP32 + W5500 Seamless Wi-Fi & Ethernet Auto-Switching"
url: "https://maker.wiznet.io/jaden/projects/esp32-w5500-seamless-wi-fi-ethernet-auto-switching/"
markdown_url: "https://maker.wiznet.io/jaden/projects/esp32-w5500-seamless-wi-fi-ethernet-auto-switching/md"
type: "UCC: User Created Content"
author: "Yarana Iot"
author_url: "https://www.youtube.com/watch?v=pT2NTDTOlFQ"
editor: "WIZnet"
editor_url: "https://maker.wiznet.io/"
original_author: "Yarana Iot"
original_url: "https://www.youtube.com/watch?v=pT2NTDTOlFQ"
published: "2026-03-03"
language: "en"
likes: 0
views: 406
comments: 0
source: "WIZnet Makers (https://maker.wiznet.io/)"
---

# ESP32 + W5500 Seamless Wi-Fi & Ethernet Auto-Switching

> ESP32 + W5500 Seamless Wi-Fi & Ethernet Auto-Switching

Original author: Yarana Iot (source: https://www.youtube.com/watch?v=pT2NTDTOlFQ)

## Article

## How to Implement Ethernet–Wi-Fi Auto Switching with W5500 on ESP32?

### Summary

This project demonstrates how to implement automatic network failover between Ethernet and Wi-Fi on an ESP32 using the WIZnet W5500 Ethernet controller. The W5500 provides wired TCP/IP connectivity, while the ESP32’s internal Wi-Fi handles wireless fallback. The firmware continuously monitors link status and dynamically switches the active interface, ensuring uninterrupted internet connectivity in an educational embedded networking setup.

---

### What the Project Does

![](https://maker.wiznet.io/upload/ckeditor5/806165202%5F1772528618%2Epng)

This project builds a dual-network ESP32 system capable of:

Connecting to the internet via **W5500 Ethernet (SPI interface)**

Falling back to **Wi-Fi** when Ethernet is disconnected

Hosting a **captive portal** to configure Wi-Fi credentials

Providing visual feedback through an LED indicator

![](https://maker.wiznet.io/upload/ckeditor5/806165202%5F1772528606%2Epng)

#### System Components

**ESP32 (or ESP8266)** – Main MCU

**W5500 Ethernet module** – Wired TCP/IP interface

**Ethernet cable (RJ45)Boot button** – Used to reset Wi-Fi credentials

**Status LED (GPIO 2)** – Indicates connection state

#### Data Flow Logic

On boot, the system attempts Ethernet first.

If Ethernet link is detected → network stack uses Ethernet.

If Ethernet link fails → system switches to Wi-Fi.

If Wi-Fi credentials are missing → captive portal opens.

Boot button (held 5 seconds) → clears saved Wi-Fi credentials.

The system therefore implements **priority-based network selection** with automatic recovery.

---

### Where WIZnet Fits

This project uses the **WIZnet W5500 Ethernet controller**.

#### Role in the Architecture

Provides hardware TCP/IP stack over SPI

Handles MAC + PHY layer internally

Offloads socket management from ESP32

Detects Ethernet link status via PHY registers

The W5500 connects to ESP32 using:

MOSI

MISO

SCK

CS (Chip Select → GPIO 5 in this project)

Because W5500 contains an internal 32 KB buffer and supports up to 8 hardware sockets, it allows the ESP32 firmware to focus on:

Link monitoring

Failover decision logic

Wi-Fi management

Captive portal configuration

In this project, W5500 acts as the **primary transport layer**, while Wi-Fi acts as the secondary transport.

---

### Implementation Notes

The original video description explains the logic but does not provide direct repository access. Therefore, the following structure is based on the demonstrated firmware architecture.

#### Conceptual integration example based on WIZnet ioLibrary

```plaintext
#include "wizchip_conf.h"
#include <SPI.h>

// SPI chip select pin
#define W5500_CS 5

void setupEthernet() {
    SPI.begin();
    pinMode(W5500_CS, OUTPUT);

    uint8_t txSize[8] = {2,2,2,2,2,2,2,2};
    uint8_t rxSize[8] = {2,2,2,2,2,2,2,2};

    wizchip_init(txSize, rxSize);

    wiz_NetInfo netinfo = {
        .mac = {0x00,0x08,0xDC,0x01,0x02,0x03},
        .dhcp = NETINFO_DHCP
    };

    wizchip_setnetinfo(&netinfo);
}
```

#### Failover Logic (Conceptual Flow)

```plaintext
if (ethernetLinkUp()) {
    useEthernet();
    WiFi.disconnect(true);
}
else {
    connectWiFi();
}
```

#### Observed Behavior from Demonstration

Ethernet cable plugged → LED ON (Ethernet active)

Ethernet unplugged → LED blinking (Wi-Fi connecting)

Wi-Fi connected → LED stable

Boot button held 5 seconds → Wi-Fi credentials erased

The firmware repeatedly checks Ethernet link state at short intervals (~500 ms window with periodic polling), enabling near-real-time switching.

---

### Practical Tips / Pitfalls

Use stable SPI wiring; long jumper wires can cause link instability.

Ensure CS pin is correctly defined (GPIO 5 in the demonstration).

Always verify PHY link status before declaring Ethernet “connected”.

Disable Wi-Fi when Ethernet is active to avoid dual-stack conflicts.

Store Wi-Fi credentials in non-volatile memory (Preferences library).

Use LED states clearly (OFF = no network, BLINK = connecting, ON = connected).

Add watchdog reset if network switching logic blocks execution.

---

### FAQ

**Q: Why use the W5500 in this project?**
A: The W5500 provides a complete hardware TCP/IP stack over SPI, allowing the ESP32 to handle network switching logic while Ethernet communication is managed internally by the controller.

**Q: How is the W5500 connected to ESP32?**
A: It connects via SPI using MOSI, MISO, SCK, and a CS pin (GPIO 5 in this project). Power and ground are also required. No external TCP/IP stack is needed.

**Q: What role does the W5500 play in this specific design?**
A: It acts as the primary wired network interface. The firmware prioritizes Ethernet, monitors its link status, and falls back to Wi-Fi only when Ethernet is disconnected.

**Q: Can beginners follow this project?**
A: Yes, if they understand basic SPI wiring and Wi-Fi configuration on ESP32. Knowledge of network concepts such as DHCP and link status is helpful.

**Q: What happens if both Ethernet and Wi-Fi are available?**
A: In this design, Ethernet has priority. When link is detected, Wi-Fi is disabled to ensure a single active transport layer.

---

### Source

**Original Video Demonstration**:
<https://www.youtube.com/watch?v=pT2NTDTOlFQ>

License: Not specified by the author.

---

### Tags

#W5500
#ESP32
#EthernetFailover
#NetworkStack
#SPI
#EmbeddedNetworking
#EducationalProject

---

Source: https://maker.wiznet.io/jaden/projects/esp32-w5500-seamless-wi-fi-ethernet-auto-switching/