This is open source modbus client for Windows and Linux operation systems.

https://github.com/sanny32/OpenModScan

 

Help me out. I cannot figure out how to install "Open Modscan" in Windows 10.

- Downloaded OpenModScan-main.zip.
- Extracted zipped files to OpenModscan-main folder
- Nothing resembling a Windows executable file in the omodscan sub-folder.

What am I missing?

 

You can download installation program here

 

Very Nice package. Several improvements over Win-Tech's Modscan.

The traffic view is wonderful, which each poll and each response on its own line. Much better than the Win-tech version.

The Omodbus version adds four 32 bit integer formats that Win-Tech does not display:
- Long integer
- Swapped Long Integer
- Unsigned Long Integer
- Swapped Unsigned Long Integer

Open Modbus adds two other IEEE754 32 bit floating formats with its LE button which selects between Big Endian and Little Endian.
Win-tech two standard FP formats correspond to the LE Byte Order button selection "Little Endian":
- Win-Tech's "Float MSRF" corresponds to OModscan's "Swapped FP" + "Little Endian" (TV Modbus-X FP B)
- Win-Tech's "Float LSRF" corresponds to OModscan's "Floating Point" + "Little Endian" (TV Modbus FP LB)

So there's two other 32 bit float formats available with the selection of "Big Endian"

A very useful, useable piece of software

 

There seems to be a bug in the scanner: finding the wrong Device ID (node address).

Case in point: The server's IP address is 192.168.1.42; the server's Device ID is 3.

Here's the setup for the scan:


Here's the results when the scanner found the server at 192.168.1.42, but at Device ID 10, not Device ID 3.

 

There seems to be a bug in the scanner: finding the wrong Device ID (node address).

Case in point: The server's IP address is 192.168.1.42; the server's Device ID is 3.

Here's the setup for the scan:
View attachment 3759

Here's the results when the scanner found the server at 192.168.1.42, but at Device ID 10, not Device ID 3.

View attachment 3760

Can u show me finded devices at result list on the right side of the MODBUS Scanner dialog?

 

I have been trying this with a Modbus RTU device. I agree it is very useful and usable software; thanks for your contribution!

Register addresses seem to be off by one though, e.g., to write register 3008 you use register 3009 in Open ModScan.

 

Register addresses seem to be off by one though, e.g., to write register 3008 you use register 3009 in Open ModScan.

You must be used to using 0-based addressing. This software appears to use 1-based addressing, just like WinTECH's ModScan.

Take a look here for more details:
https://control.com/forums/threads/modbus-register-numbering.49844/

 

There seems to be a bug in the scanner: finding the wrong Device ID (node address).

Case in point: The server's IP address is 192.168.1.42; the server's Device ID is 3.

Here's the setup for the scan:
View attachment 3759

Here's the results when the scanner found the server at 192.168.1.42, but at Device ID 10, not Device ID 3.

View attachment 3760

Are you sure you're not confusing the scanning status (i.e. what device ID it's currently trying to scan) with the actual discovered devices? In your screenshot, the scanning is 100% complete and the Device Id shows 10 because that was the highest Device Id you configured it to scan, not because it necessarily found a device at Device Id 10.

@SaNNy, if this is indeed the case, perhaps it would be less confusing to remove the values for the scanning fields (Address, Port, Device Id, Scan Time) after, or shortly after, the scan has completed. This would then be consistent with how it looks prior to starting the first scan.

 

You must be used to using 0-based addressing. This software appears to use 1-based addressing, just like WinTECH's ModScan.

Take a look here for more details:
https://control.com/forums/threads/modbus-register-numbering.49844/

["human-readable" register number and is 1 more than the "on-the-wire" address"] to me, that just seems to create confusion...

Thanks for the explanation.

 

to me, that just seems to create confusion...

Yep, just one of the many quirks of Modbus. You're not the first to be confused by this, and certainly won't be the last. This "off by one" addressing issue is one of the most common mistakes made when configuring Modbus devices.

 

Isn't the point of scanning to report what's been found? Otherwise, what's the point of scanning?

The scanner function does report the IP address properly. I suspect that it found the correct Device ID, too, but for whatever reason, it did not report the found address, rather it reported what ID it ended the with.

 

Here's a screen shot of the scanner with the scan results: no results. I figured the 'scanning' values on the left was the reported result because there's nothing in the results window. Repeating the scan produces the same null result.

 

I would interpret your screenshot as OpenModScan did not find any Modbus devices.

Perhaps your computer and the Modbus/ TCP server are on different subnets. I see you're scanning for devices on the 192.168.1.xxx subnet. Is your computer's IP address also on this subnet (i.e. does it start with 192.168.1 and use a subnet mask of 255.255.255.0)?

Can you connect to the Modbus device and read register values using the main screen in OpenModScan?

 

The test of the OpenModbus scanner function is being done with a known target server box.

The server is connected with the laptop running either Modscan or OpenModscan. Both Modscan and OpenModscan communicate as expected with the server.



The scanner starts at 192.168.1.1, runs for 42 seconds before displaying 192.168.1.42 (the correct target IP) and then the Device ID counts up from one to whatever value is the the end-of-range for the Device ID. The Scan Results is never populated, remaining blank.

 

I decided to try Open Modscan with RTU over RS-485.

I can't get the 'Connections' to display the COM ports for a serial connection. It's stuck on Remote TCP/IP server, as the screen shot shows. How do I get it to display "Direct Connection to COMx" ?

 

I'm able to see both my FTDI-chip USB to RS-485 converters in Open ModScan's connection window.

Does Window's Device Manager show your converter under the Ports category?

Do you know what type of chip is in the your converter you're using? It's possible Open ModScan is not able to detect your chip type.

 

@SaNNy It seems that the Slave Response Timeout setting in the Modbus Protocol Selections window has no effect (I was only able to test using a serial connection). With no slave devices connected, the Number of Polls counter increments at the rate dictated by only the Scan Rate setting, regardless of the Slave Response Timeout setting (I tried setting it to 250, 1000, and 10000 with no difference).

 

@SaNNy, if this is indeed the case, perhaps it would be less confusing to remove the values for the scanning fields (Address, Port, Device Id, Scan Time) after, or shortly after, the scan has completed. This would then be consistent with how it looks prior to starting the first scan.

It is possible to implement in future version.

@SaNNy It seems that the Slave Response Timeout setting in the Modbus Protocol Selections window has no effect (I was only able to test using a serial connection). With no slave devices connected, the Number of Polls counter increments at the rate dictated by only the Scan Rate setting, regardless of the Slave Response Timeout setting (I tried setting it to 250, 1000, and 10000 with no difference).

Slave Response Timeout setting only affects the connection to device, not the polling of the device.

 

Slave Response Timeout setting only affects the connection to device, not the polling of the device.

I don't understand this. What is a "connection" when using Modbus RTU?

So then what setting in Open ModScan should be increased if you have a Modbus RTU slave that takes a long time before responding to requests and Open ModScan"s requests are timing out?