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:

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:

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:

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:

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:

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