If you work with Modbus protocols and have an instrument or device which you can connect to your PC's COM port, chances are you may need to collect the serial data you receive for its further analysis. Modbus Analyzer (aka Serial Port Monitor) by Eltima is a universal professional utility that can easily help you accommodate almost any serial instrument with an RS232 port. This dedicated software is an optimal way to interpret or parse the messages received from or sent by your equipment.
When a device sends a message it usually contains all sorts of extra characters and codes.
What Modbus Scanner does is helps to extract the relevant data from each message. The app is designed to decode Modbus ASCII and Modbus RTU data received and sent through the system’s COM ports.
The program allows displaying the incoming and outgoing serial messages in the most convenient and readable format. In addition, the software comes with an advanced built-in search option and unique stream filtering tools with presets.
How to parse a Modbus message:
Here’s how you can start a monitoring session and sniff a data using the simple Modbus RTU and ASCII scanner software:
- Start Serial Port Monitor on your computer.
- Select “Session -> New session” on the main menu.
- Then you’ll see the “New monitoring session” window. In this window, you can choose the visualizers that will display the serial data throughout your monitoring session.
- Select the “Modbus view” to see the received and sent Modbus data (RTU and ASCII) right on the screen.
- Then, you go to the capture options: select which events to capture – Create/Close, Read/Write, Device Control.
- Finally, click “Start monitoring” to activate a new monitoring session. That’s it!
Once you started the monitoring session with the Modbus view, you can set the required configuration in the viewer’s preferences.
To do this, you should go to “Session -> Preferences”;
Choose the color for date time, header, structure, details, checksum, and errors. Then, select whether to scan Modbus data as Modbus RTU or Modbus ASCII.
Key features of the COM port scanner app
Modbus ASCII and RTU Scanner have proved to be an efficient tool for tracking down the possible problems during the development of serial applications and drivers, testing and optimizing serial devices, etc.
This professional RS232 and RS485 sniffer offers a host of advanced features, including:
- The ability to start reading a COM port that is already in use by another program. All data received by the sniffer interface is shown in real time so that a programmer can identify any possible issues.
- The ability to monitor multiple RS232, RS422, and RS485 ports simultaneously. If you need to analyze the activity of several Modbus ports within one session, you can easily do this with the Modbus message parser app. Data flowing in and out of the port is conveniently recorded in a single log using the first-in-first-out method.
- Support for several data viewing modes: table, terminal, line, dump, and Modbus visualizers. You can use all or several of them at a time. More than that, various filters offered by this utility will also serve for precise monitoring.
- Emulation of the data transfer to a serial device in order to see the exact reaction of the device to specific commands.
How to provide communications within industrial networks
As a result of constant modernization of production, today more and more industrial automation systems are based on distribution networks working over flexible data transfer protocols.
There’s a wide variety of interfaces and data transfer protocols that provide communications within industrial networks. These include Modbus, Ethernet, CAN, HART, PROFIBUS, etc. They allow data transfer between sensors, controllers and actuators; calibration of sensors; power supply to sensor and actuators; communication between the lower and upper levels of the process control systems, and more.
The data transfer protocols are usually developed according to the requirements of a particular production and technical systems and provide a reliable connection and high accuracy of data transfer between different devices. Along with the reliability of operation in harsh conditions, ACS TP systems often require high functional capabilities, flexibility in construction, ease of integration and maintenance and compliance with industry standards.
Modbus protocol is widely used as a communication channel between automation elements in industrial data networks. There are three main implementations of Modbus protocol. Two of them are designed for serial data communication over both copper EIA/TIA-232-E (RS-232), EIA-422, EIA/TIA-485-A (RS-485), and optical (and radio) lines: Modbus RTU and Modbus ASCII. And one of them is for data transmission across Ethernet networks: Modbus TCP.
Modbus ASCII and Modbus RTU
The difference between Modbus ASCII and Modbus RTU protocols lies in the way they encode characters. In the ASCII mode, the data is encoded using an ASCII table where two bytes of data corresponding to each character. In the RTU mode, the data is transmitted in the form of 8-bit binary symbols, which provides a higher data rate. With ASCII there can be a delay of up to 1 second, unlike RTU, where messages must be continuous. Also, ASCII mode has a simplified system of data decoding and management.
Modbus protocols (Modbus ASCII, Modbus RTU, and Modbus TCP) use one application protocol to ensure their compatibility. The maximum number of nodes in the Modbus network is 31. The length of communication lines and the data transfer rate depend on the physical implementation of the interface. All elements of the Modbus network interact using a client-server model based on transactions consisting of a request and a response.
Learn more about Modbus ASCII in our advanced tutorial.
Where Modbus is used
Areas of Modbus industrial application: communication of sensors and actuators with the controller, communication of controllers and control computers, communication with sensors, controllers and corporate networks, connections in SCADA systems, etc.
The simplicity of the implementation of Modbus protocols has led to its wide application in industrial systems and not only. Today the equipment of almost all manufacturers comes with support for Modbus protocols.
Once you start benefitting with Serial Port Monitor Modbus scan feature let us know how it went in comments. Your questions are also welcome! If you have your own usage scenario that you would like to share, go here.