Modbus RTU-to-TCP Gateway with W5500 and STM32

W5500 and STM32 enable seamless Modbus RTU-to-TCP conversion, bridging RS485 devices to Ethernet industrial networks.

jakelee

Published June 07, 2026

27 UCC

5 VAR

Original author: Ethernet Lab (玩转以太网) · ChinaOriginal source (new tab)

Components

Hardware components

WIZnet - W5500

x 1

WIZnet parts

W5500 Datasheet

Project description

Step 1: Understanding the Hardware This project demonstrates how to convert legacy Modbus RTU devices into Ethernet-connected Modbus TCP devices using an STM32 MCU and the WIZnet W5500 Ethernet controller. Hardware used: W5500io-M Ethernet module STM32F103VCT6 development board RS485 serial interface Ethernet connection Modbus RTU slave devices Modbus TCP master software (Modbus Poll) The W5500io-M module offers: Integrated MAC + PHY Hardwired TCP/IP stack 32KB internal buffer memory RJ45 Ethernet interface SPI host interface 8 hardware sockets Simplified Ethernet integration without porting…

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