---
title: "water_link"
url: "https://maker.wiznet.io/Grace_Koo/projects/water-link/"
markdown_url: "https://maker.wiznet.io/Grace_Koo/projects/water-link/md"
type: "UCC: User Created Content"
author: "IDTenev"
author_url: "https://github.com/IDTenev/water_link"
editor: "WIZnet"
editor_url: "https://maker.wiznet.io/"
original_author: "IDTenev"
original_url: "https://github.com/IDTenev/water_link"
published: "2026-03-06"
language: "en"
likes: 0
views: 506
comments: 0
source: "WIZnet Makers (https://maker.wiznet.io/)"
---

# water_link

> https://github.com/IDTenev/water_link

Original author: IDTenev (source: https://github.com/IDTenev/water_link)

## Article

## W5500 on a Multi-Protocol Embedded Board — Water-Link v1.0

### What Is This Project?

`water_link` is an **ESP-IDF based firmware SDK** for situations where RS-485, RS-232, CAN, I2C, and Ethernet need to run together on a single board.

The project provides driver and service layers that can bring up all interfaces immediately on the custom board **Water v1.1** (ESP32-S3 + WIZnet W5500), along with ready-to-run example code for each interface.

A brief overview of the board:

| Item | Details |
| --- | --- |
| MCU | ESP32-S3 |
| Ethernet | WIZnet W5500 (SPI) |
| Serial | RS-485 (UART2), RS-232 (UART1) |
| Fieldbus | CAN 2.0 / TWAI |
| Sensor Bus | I2C |
| Status Display | WS2812 RGB LED, HT16K33 FND |
| Interfaces | USB-C, Pin header (GPIO, PWM, ADC, Touch) |

---

### Role of the W5500

In this project, all network connectivity is handled by the **W5500**.

Connected via SPI, the W5500 offloads the TCP/IP stack in hardware, so the MCU can handle socket communication without implementing a software TCP/IP stack.

Within the firmware, the W5500 is abstracted into two layers:

- `**water_driver/d_w5500**` — W5500 register initialization and SPI communication

- `**water_service/s_ethernet**` — Socket-level APIs for UDP, DHCP, Ping, etc.

Application code does not need to know anything about W5500's internal registers. For example, a UDP Echo server works in three lines:

```c
s_udp_open(&udp, 0, 5000);
int32_t n = s_udp_recvfrom(&udp, &peer, buf, sizeof(buf));
s_udp_sendto(&udp, &peer, buf, n);
```

Ping works the same way:

```c
bool ok = s_ping_once(2, target, 1000, &r);
// ok: success/failure, r.rtt_ms: round-trip time
```

---

### Software Architecture

The firmware is organized into four layers:

```plaintext
app_main()
  └── water_service/    Network services — UDP, DHCP, Ping
        └── water_driver/    Chip drivers — W5500, WS2812, HT16K33
              └── water_port/    Hardware abstraction — RS-485, RS-232, CAN, I2C, SPI, GPIO
                    └── water_common/    Pin definitions, error codes, board constants
```

Each layer is an independent component. For instance, replacing the W5500 with another WIZnet chip would only require changes to `d_w5500` and `s_ethernet` — application code stays untouched.

---

### Included Examples

The SDK includes independently runnable examples for each interface:

| Example | Description |
| --- | --- |
| RS-232 | Send `hello` every 1 s, verify Loopback reception |
| RS-485 | Echo received data + append first byte |
| CAN | Receive 8 bytes, return each byte +1 on the same ID |
| I2C | Scan for devices in address range 0x08–0x77 |
| HT16K33 | Display 0–9999 counter on 4-digit FND every 200 ms |
| WS2812 | Cycle colors R→G→B→W→Fade In→Off |
| UDP Echo | Receive on port 5000, retransmit to same peer |
| Ping | Ping a target IP every 1 s, log RTT |

Each example runs independently by swapping out the `app_main()` body. UDP and Ping run as separate FreeRTOS tasks, making them a useful reference for concurrent multi-function designs.

---

### Potential Applications

The clearly separated layer structure makes it possible to apply this in various directions.

It could be used as a gateway that forwards RS-485 or CAN device data to a network via W5500, or as a reference for embedded projects that require multiple communication interfaces. Modifying the pin definitions in `water_common` may allow porting to other ESP32-S3 based boards.

---

> **Project:** [github.com/IDTenev/water_link](https://github.com/IDTenev/water_link)

---

Source: https://maker.wiznet.io/Grace_Koo/projects/water-link/