Modbus Primer

In this course about the Modbus protocol, we will begin by exploring the history of Modbus and its development over the years.

As we progress through the course, we will take a detailed look at the Modbus data model. You will learn how data is organized within Modbus devices and how different data types are accessed. The data model will be explained using practical examples to ensure that you not only understand the theory but also know how to apply it in real-world projects.

A major focus of this course is the understanding of Modbus Function Codes. Since Function Codes are at the core of every Modbus communication, we will dedicate an entire section to them. Together, we will examine the most important Function Codes, learn when they are used, and understand how they affect communication between devices. In addition, you will learn the difference between Requests and Responses and how Modbus messages are structured.

We will also cover the fundamentals of Modbus communication and explain how the Client/Server model operates. Building on this knowledge, we will discuss the differences between Modbus RTU over RS-485 and Modbus TCP over Ethernet. Furthermore, we will explore the most important Modbus RTU parameters, including baud rate, Unit ID, and biasing. By the end of this section, you will understand these concepts and know how to apply them in practice.

Finally, we will use Node-RED to put the theory into practice. Through hands-on examples, we will analyze how communication between Modbus devices works, which parameters need to be configured correctly, and how to troubleshoot common communication issues.