GitHub

This project uses an Arduino Mega to read a Modbus RTU feed through RS485. This example is based on a Huawei / CHINT DTSU666-H.

From my experience it is absolutely needed to have an Arduino Mega or equivalent (needs to have at least 2 serial ports), you won't be able to read the Modbus if Serial is also used by USB Serial ...
GitHub

Modbus RTU ⇒ Modbus TCP/UDP Gateway

Modbus RTU ⇒ Modbus TCP/UDP Gateway Arduino-based Modbus RTU to Modbus TCP/UDP gateway with web interface. Allows you to connect Modbus RTU slaves (such as sensors, energy meters, HVAC devices) to ...
IEEE

Multipurpose Networked Control System Based on Arduino Uno and Modbus RTU RS-485

Abstract: This paper presents the design and implementation of a multipurpose networked control system using Arduino and Modbus RTU over RS-485 communication. The system enables robust and scalable ...