---
title: "How to Bring Up W5500 Ethernet for a DEF CON Countdown Display on M5Stack CoreS3 SE?"
url: "https://maker.wiznet.io/viktor/projects/isitdefcon/"
markdown_url: "https://maker.wiznet.io/viktor/projects/isitdefcon/md"
type: "UCC: User Created Content"
author: "DezusAZ"
author_url: "https://github.com/DezusAZ/isitdefcon"
editor: "WIZnet"
editor_url: "https://maker.wiznet.io/"
original_author: "DezusAZ"
original_url: "https://github.com/DezusAZ/isitdefcon"
published: "2026-02-19"
language: "en"
tags: ["ESP32"]
hardware: ["WIZnet W5500", "M5Stack LAN Module with W5500"]
likes: 0
views: 330
comments: 0
source: "WIZnet Makers (https://maker.wiznet.io/)"
---

# How to Bring Up W5500 Ethernet for a DEF CON Countdown Display on M5Stack CoreS3 SE?

> This project turns an M5Stack CoreS3 SE (ESP32-S3) into a DEF CON countdown display with a small HTTP server for status and a simple web UI

Original author: DezusAZ (source: https://github.com/DezusAZ/isitdefcon)

## Components

- **WIZnet W5500** x 1 ([docs](https://docs.wiznet.io/Product/Chip/Ethernet/W5500))
- **M5Stack LAN Module with W5500** x 1 ([docs](https://docs.m5stack.com/en/base/lan_base))

WIZnet parts: W5500 ([Datasheet](https://docs.wiznet.io/Product/Chip/Ethernet/W5500/datasheet?utm_source=maker&utm_medium=project&utm_campaign=w5500), [product hub](https://maker.wiznet.io/products/w5500/))

## Article

## What the Project Does

“IsItDefcon” is a maker-friendly desktop display that answers “Is it DEF CON?” and shows a live countdown to DEF CON 34 (Aug 6–9, 2026). It renders the countdown on the CoreS3 SE LCD, fetches a short news ticker from the DEF CON RSS feed (via an RSS-to-JSON service), and exposes a local web page plus JSON endpoints like `/api/check` and `/api/news` for the same data.

(Background: DEF CON is a long-running information security conference held annually in Las Vegas.)

## Where WIZnet Fits

The wired network option is the **WIZnet W5500**, packaged inside **M5Stack LAN Module 13.2**. The W5500 is a hardwired TCP/IP Ethernet controller accessed over SPI, so the ESP32-S3 can run a web server and UDP NTP without carrying a full software TCP/IP stack for the external Ethernet interface. In practice, that means fewer moving parts than “MAC+PHY + LwIP integration” when you simply want: link up → DHCP → sockets.

For this project specifically, W5500 Ethernet is used to:

- Acquire an address via DHCP and keep the lease alive.

- Serve HTTP on port 80 (web UI + JSON endpoints).

- Send/receive UDP packets for NTP time sync.

- Make outbound HTTP requests to fetch the RSS-derived news ticker.

## Implementation Notes

The firmware treats Ethernet as a first-class boot-time mode. On startup it shows a network selection menu; if LAN is selected, it brings up the W5500 path, syncs time, and starts the Ethernet web server.

### 1) W5500 bring-up sequence (SPI + reset + DHCP)

In `initEthernet()`, the sketch initializes SPI, resets the LAN module, then retries DHCP a few times before declaring failure:

```plaintext
// firmware/isitdefcon/isitdefcon.ino
SPI.begin(SCK, MISO, MOSI, -1);
LAN.setResetPin(rst_pin);
LAN.reset();
LAN.init(cs_pin);

int attempts = 0;
while (LAN.begin(mac) != 1 && attempts < 5) { attempts++; delay(2000); }
```

(From `firmware/isitdefcon/isitdefcon.ino`.)

A detail that matters on M5Stack variants: the sketch selects `cs_pin` (and related pins) based on detected board type, so the same codebase can run across CoreS3 / Core2 / older Core hardware.

### 2) “Network behavior” in the main loop (lease maintenance + periodic work)

Once LAN mode is active, the firmware keeps the interface healthy and uses it as the transport for periodic tasks:

- **DHCP lease upkeep** via `Ethernet.maintain()`

- **Hourly NTP resync**

- **RSS/news refresh** on a timer (first fetch after boot, then periodically)

- **HTTP request handling** for inbound clients

### 3) Outbound HTTP without DNS (a common embedded Ethernet trade-off)

For the news ticker, the sketch performs a plain HTTP GET to an RSS-to-JSON API. In the Ethernet path it hardcodes an IP address and calls out the reason in a comment:

```plaintext
// firmware/isitdefcon/isitdefcon.ino
// Cloudflare IP for api.rss2json.com (no DNS in M5-Ethernet library)
IPAddress apiIP(104, 26, 10, 156);
EthernetClient client;
if (!client.connect(apiIP, 80)) { return; }
```

(From `firmware/isitdefcon/isitdefcon.ino`.)

This is a realistic “wired embedded” pattern: when DNS or TLS is inconvenient on a small stack, pick an HTTP endpoint you control, or front it with a local proxy that can do DNS+TLS upstream and offer plain HTTP on the LAN side.

## Practical Tips / Pitfalls

- **Power and link first:** LAN Module 13.2 is designed as a powered module; confirm it has stable input power and that the switch port shows link before chasing firmware issues.

- **CS/reset pins are board-dependent:** this repo selects pins based on detected M5 board; if you port to another ESP32-S3 board, plan to hard-map CS/RST/INT.

- **Treat DHCP as a failure mode:** the firmware retries DHCP a fixed number of times; for unattended installs, consider adding a static-IP fallback or a longer retry window.

- **Plan around DNS/TLS constraints:** the Ethernet news fetch uses a fixed IP and plain HTTP; if your endpoint changes, that breaks. A local gateway service (DNS + HTTPS upstream → HTTP downstream) makes the device more resilient.

- **Socket budget is real:** W5500 provides 8 hardware sockets and a shared internal buffer; keep the number of simultaneous clients and outbound connections modest (especially if you add more features).

## FAQ

### Why use W5500 here instead of Wi-Fi?

For a “wall display” style device, wired Ethernet reduces variability: fewer RF issues, fewer reconnect edge cases, and a consistent local IP experience after DHCP. With W5500’s hardwired TCP/IP sockets, the firmware can focus on application logic (countdown, NTP, HTTP endpoints) rather than tuning a full external-Ethernet software stack.

### How does W5500 connect to the M5Stack CoreS3 SE in this build?

Through the M5Stack LAN Module 13.2, which integrates a W5500 and connects to the CoreS3 SE over SPI. The firmware sets the module’s chip select and reset behavior, then uses `LAN.begin(mac)` to obtain a DHCP lease.

### What role does W5500 play in this specific project?

In LAN mode it is the primary network interface: it obtains an address via DHCP, serves the on-device web UI/API on port 80, sends NTP packets over UDP for time accuracy, and performs outbound HTTP fetches for the news ticker.

### Can a beginner follow this?

Yes, if you are comfortable flashing Arduino/ESP32 sketches and understand basic LAN concepts (DHCP, IP addresses, “port 80”). The Ethernet path is relatively approachable because it is SPI + DHCP + sockets; the most common beginner friction points are power, pin mapping when changing boards, and network services like DNS/TLS.

### How does W5500 Ethernet compare with just using Wi-Fi in this repo?

Wi-Fi is convenient (no cable) and the project supports it, including an AP-based setup flow. Ethernet tends to be simpler for “always-on local web UI” use: link state is obvious, DHCP renew is explicit (`Ethernet.maintain()`), and you avoid Wi-Fi credential churn. The trade-off is physical cabling and, depending on your library stack, you may lean on plain HTTP or fixed-IP approaches for outbound requests.

---

Source: https://maker.wiznet.io/viktor/projects/isitdefcon/