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Asynchronous Web Server on ESP32-S3 (Ethernet + Wi-Fi)

This project is based on André F1ATB’s implementation of an asynchronous web server for the ESP32-S3 board, enabling both wired Ethernet (via W5500) and Wi-Fi connections on the same device.

Hardware Used

Board: T-ETH-LITE ESP32-S3 (N16R8 configuration)

Dual-core ESP32-S3, 512 KB internal RAM, 16 MB SPI Flash, 8 MB PSRAM

Connectivity: Wi-Fi (802.11 b/g/n 2.4 GHz), Bluetooth LE 5.0, Ethernet (W5500 100 Mb/s)

Other Interfaces: RJ-45 (PoE support), SPI / I²C / I²S / UART / ADC / DAC / USB

Main Implementation Details

Dual Network Support – The ESP32-S3 can operate over both Wi-Fi and Ethernet simultaneously.

Library – AsyncWebServer_ESP32_SC_W5500.h
This library is specifically designed for the lwIP + W5500 Ethernet combination, and works on both PlatformIO and Arduino IDE. It integrates Ethernet (W5500) and Wi-Fi interfaces under a unified asynchronous web-server framework.

Flash Partitioning

NVS / OTA data area

Two OTA application slots (app0, app1)

SPIFFS area for web assets

Design Considerations

SPI Bus Conflicts – If W5500 and the SD card share the same SPI bus, use a separate bus or re-map pins.

Ethernet Interface – Operates over SPI; although slightly slower than an internal MAC/PHY, it is more than adequate for IoT and web server tasks.

Programming Notes – No on-board USB interface; requires an external FTDI232 adapter (3.3 V level). Boot/reset sequence must be observed during flashing.

Why It Matters

This project demonstrates how ESP32-S3 can seamlessly combine wired Ethernet and Wi-Fi using a single codebase.
With the W5500 and the asynchronous web server library, developers can extend existing Wi-Fi-based projects to wired Ethernet with minimal changes.

Example Applications

Home automation gateway

Sensor hub / industrial IoT controller

Web content server using OTA and SPIFFS

Conclusion

The project highlights the power of the “MAC + PHY chip (W5500) + lwIP software stack” architecture.
Its asynchronous server design makes excellent use of the ESP32-S3’s dual cores and PSRAM, and offers an efficient and scalable solution for IoT systems requiring both Wi-Fi and Ethernet connectivity.