How to Log RS485 Activity

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Updated on: August 29, 2026
Time to read: 7 minutes

Specialists working with RS-485 communication may need to test and log the serial interfaces in order to identify and resolve problems that may appear in RS-485 networks. More than that, programmers who develop industrial serial applications may also require a specialized tool for reading and monitoring RS-485 Modbus ports their apps communicate with.

Choosing between a hardware or software RS485 data logger 

Users can choose between hardware and software RS-485 data loggers based on their specific use case. 

RS485 data loggers are available as physical devices or software solutions. A hardware  RS485 logger is a standalone device with a power supply, memory, and an SD card for storage. It does not need to be connected to a computer to record Modbus or sensor data. A hardware Modbus data logger is necessary to record data in the field without a computer.

A software data logger is an application that runs on a computer connected to an RS485 network. Users can display, decode, and log RS485 data in real time. No additional hardware is required to decode the complete Modbus RTU/ASCII protocol. Software logging is typically the easiest solution to implement if you have a computer attached to the network and provides enhanced functionality such as protocol-level visibility.

This guide discusses how to sniff, log, and analyze RS485 and Modbus data with your computer.

Effective Software Solution: Serial Data Logger

Serial Data Logger is a software solution that makes it easy to monitor and analyze RS-485 port traffic. The application’s advanced features include the ability to monitor multiple ports simultaneously and choose the types of events you want to monitor. No additional hardware is required to log data traveling through your computer’s serial ports. 

Our comparison of Modbus software tools will help you find the right solution for sharing ports across applications, simulating Modbus TCP, and emulating slave devices.

How-to Log RS485 Activity

Whether you need to monitor a controller fitting RS-485 port, check the reaction of a particular serial device to certain data, or analyze the activity of all RS-485 interfaces your system deploys, here is how you can do this with RS-485 data logging software.

To start, download the software and install it on your computer. Launch the app in order to start a new monitoring session:

1. In the main menu of the app select Session -> New session. Alternatively, you can hit ‘New’ on the main toolbar or press CTRL+N. As a result, you’ll get the ‘New monitoring session’ window.

main menu of the app

2. Now, decide on how you’d like the captured data to be displayed and choose the desired visualizer. There are Table, Line, Dump, Terminal, and Modbus views. As an option, you can use them all simultaneously.

choose the desired visualizer

3. Next, depending on where you want your monitoring session to be started, choose between the ‘Start monitoring now’ and ‘Start in new window’ options.

choose between the Start monitoring now and Start in new window options

4. In the ‘Capture options’ select the type of events you’d like to track (Create/Close, Read/Write, Device Control.)

5. Finally, hit ‘Start monitoring’. That’s it! Now you can easily catch and analyze data transmitted via a required RS-485 port.

6. If it’s necessary to save a session, you should go to the main menu and select ‘Session -> Save session/Save session As’. Or, click ‘Save’ on the main toolbar, or press CTRL+S.

save a session

Serial Data Logger works as an RS485, RS422 sniffer and makes it possible to analyze data from several COM ports simultaneously. The solution is also useful when it’s required to connect to an RS485 port already used by another app.

Modbus Data Logging

The Serial Data Logger captures and decodes Modbus traffic over an RS485 network. It provides structured requests and responses rather than simply raw bytes. This information simplifies problem resolution for misbehaving metering devices, PLCs, or Modbus slaves.

RTU

The software serves as a Modbus RTU data logger by decoding binary frames and displaying Modbus traffic in the dedicated Modbus view. You can also filter Modbus traffic by selecting master or slave devices.

Note:  Modbus RTU frame detection and decoding have been refined over time. Build 9.5.600 fixed frame-end detection and decoding issues, while build 9.5.589 added master/slave device selection for filtering.

ASCII

The software supports Modbus ASCII monitoring through the dedicated Modbus view, allowing technicians to inspect ASCII-based Modbus traffic alongside other captured serial data.

Note:  Our Modbus vs RS485 guide provides a complete explanation of the difference between RTU and ASCII framing.

Core Functionality of RS-485 Logger Software

The RS485 logger software provides the following core functionality.

• You can connect to a COM port even if it is in use by another application.
• Data transmitted over an RS-485 interface is displayed in real time to enable fast problem resolution.
• The RS-485 analyzer and monitoring tool can monitor multiple COM ports simultaneously within a single session.
• The Send dialog lets you transmit data in string, hexadecimal, decimal, octal, or binary format to test how a device responds; Terminal view then displays the incoming data as readable ASCII text.
• Two related tools help with troubleshooting: the Compare Sessions feature highlights differences between saved sessions, while Reproduce lets you replay a previously captured session back to the serial port. 

Note:  Our RS485 communication guide provides the fundamentals you need to identify physical-layer issues that may cause problems with data capture.

Frequently Asked Questions

The EIA/TIA-485 standard is widely used in industrial applications that work over long distances and require high speeds of data transmission. The interface is particularly useful for connecting serial devices in noisy environments like process control plants, utilities sites, and factories.

RS-485 port is embedded on various devices, including low-speed modems, programmable logic controllers, computer numerically controlled machine tools, point of sale terminals, metering instruments, large special automated machines, and other equipment.

Hardware data loggers are physical devices with onboard storage and memory. They are typically used for logging unattended field equipment. A software logger runs on a computer attached to the network. They provide real-time decoding of multiple protocols, including Modbus RTU/ASCII, with no additional hardware.

Monitor RS-485 data by connecting the RS-485 interface to your computer via a serial port or a USB-to-RS-485 adapter. Start a monitoring session in the Serial Data Logger software to display and log traffic in real time without extra hardware.

You can test RS-485 communication by starting a Serial Data Logger session and using the Send dialog to transmit data to your device in the format you need. Review the device’s responses in Table, Dump, or Terminal view. This lets you verify precisely whether a problem is caused by your application or by the wiring.

Serial Data Logger can directly handle Modbus RTU/ASCII over RS-485. You may want to consult our Modbus software comparison to find the right tool for tasks such as Modbus slave simulation or TCP-heavy workflows.