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How to read
Modbus data

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Serial Port Monitor

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In this article, I will tell you how to read and record Modbus data using the most advanced Modbus reader program - Modbus Analyzer. If you think about integrating the Modbus standard within your local device network or you are an active user of Modbus, this tutorial will be helpful for you.


  1. Modbus reader software
  2. How to read Modbus data
  3. What is Modbus?
  4. How does Modbus work?
  5. What is it used for?

Modbus Analyzer

Modbus Sniffer is a professional RS485 Modbus reader and data logger utility designed to decode Modbus RTU and ASCII protocol data, read it and record for its further analysis.
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The software allows sniffing the traffic coming in and going out of serial devices communicating within a Modbus network. Modbus reader app supports all types of serial ports, including RS232, RS422, and RS485.

The program is aimed at developers and testers of serial applications and hardware as well as any other specialists working with Modbus-based equipment and software. It helps to interpret or parse the messages received from or sent by your devices via serial interfaces.

One of the biggest advantages of this Modbus RTU reader is its ability to show captured data in the convenient and readable format. There are four data visualizers that the app offers: Table view, Dump view, Line view, and Terminal view. It’s up to you to decide in which mode the data will be shown. You can enable one, two or all of the visualizers at a time.

What’s also important is that Modbus RS485 reader comes with the advanced built-in search and filtering options as well as the Terminal mode that allows executing text commands.

How to read Modbus data?

Here’s how to easily capture and record Modbus messages with this dedicated app:

  1. First, download Modbus Protocol Reader and install it on your machine.

  2. Launch the app, choose “Session > New session” on the menu. Record Modbus messages

  3. In the “New monitoring session” window that will appear, select the viewing modes that will show the serial data captured during the session. New monitoring session

  4. As you are going to read Modbus data, next you need to enable the Modbus view that will display Modbus data received and sent via your system’s COM ports. Read Modbus data

  5. If needed, check the “Start monitoring now” and “Start in new window” boxes.

  6. Now, choose which events to capture: Create/Close, Read/Write, Device Control.

  7. Hit “Start monitoring” and your Modbus reading session will be activated. Modbus data acquisition

Now, in the preferences of the Modbus view, you can set the required configuration. All you need to do is go to “Session > Preferences” and select the color for date time, header, structure, details, checksum, and errors. There you can also choose whether to read Modbus data as Modbus RTU or Modbus ASCII.

Some of the other powerful features supported by Modbus Recorder Software:

  • The solution allows identifying Modbus communication issues once they appear, as the tool monitors and displays data in real time.

  • The app will also give you the way to start sniffing a COM interface even if it’s already in use by another app.

  • With this Modbus reader software you’ll be able to monitor multiple RS485 ports simultaneously. All Modbus data coming in and going out of the port will be conveniently recorded in a single log based on the first-in-first-out method.

What is Modbus?

Modbus is a serial communication protocol used for transporting data over serial channels between electronic equipment. The standard Modbus communication is set in such a way that one device, Modbus Master, writes data to or requests data from other devices, Modbus Slaves, across a serial network. As a rule, there’s one Master and up to 247 Slaves in a Modbus network. The protocol uses RS-485, RS-422, RS-232 interfaces, as well as Ethernet TCP/IP networks (Modbus TCP protocol) for data transfer.

How does it work?

As mentioned before, Modbus data can be transmitted via a serial channel connecting two COM-based devices. They communicate information as series of ones and zeros (data bits) via a standard serial cable. Each bit is sent as a voltage. Modbus connection is rather fast and the normal transmission speed is 9600 baud. The data is sent in blocks of 8 bits called bytes, each of which is represented by one of the 256 character pairs from 00 to FF.

How does Modbus work

What is it used for?

Traditionally, Modbus is applied in industry for transmitting data from control devices to the central data gathering system. This can be a system that measures humidity or temperature and forwards the results to a supervisory computer. The protocol can also serve for connecting the control computer with a remote terminal unit (RTU) in SCADA (Supervisory Control and Data Acquisition) systems. There are Modbus protocol versions for serial communications (Modbus RTU and Modbus ASCII) and for Ethernet connections (Modbus TCP).

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