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It doesn't appear that the USR-TCP232-410s is capable of communicating to more than 1 device as a TCP client. Can your PLC's be configured to be the Modbus TCP client? Of course, the USR-TCP232-410s would then need to be configured as a TCP server. While this may work, it's possible that the...

You need to change the configuration of the USR-TCP232-410s when you swap the connections. Specifically, you need to change the Work Mode setting between TCP Client and TCP Server. When the Ethernet side is connected to ModSim (which is a server), the Work Mode of the USR-TCP232-410s should be...

You have 33 total devices on your network (32 slaves and 1 master). If all devices are 1 Unit Load devices, you are exceeding the 32 Unit Load limit of RS-485. The RS-485 spec only allows up to 32 Unit Loads. Additionally, a 100 ohm termination puts more load on the bus than the typical 120 ohm...

Can you clarify what you mean by Fieldbus? Fieldbus is a generic term, and in fact, PROFIBUS is a type of fieldbus. https://en.wikipedia.org/wiki/Fieldbus

You're receiving an exception response (0x83 0x2) which is 02 - ILLEGAL DATA ADDRESS. This means that one or more registers contained in your request do not exist on the slave. Note that pymodbus uses 0-based addressing. You may have to subtract 1 from the register number. If you're still...

Have you tried using a terminal emulator on your computer to test communications with the ZK830 and see the exact response message for the command(s) you're trying to send from your PLC? Wouldn't that only apply when "Print" is selected for the protocol under Admin->Ports->Protocol?

Using a USB to RS-485 adapter is very different from using an Ethernet to RS-485 adapter. The problem here is that there are many different (and incompatible) versions of Modbus depending on whether RS-485 or Ethernet is used. There are two Modbus versions that run on RS-485: Modbus RTU and...

I found the device: https://www.fonrich.com/static/dcb009b26ccfd808a22b4f197c380396/FR-DCMG-MMPP_UM_EN_V1.0.pdf It seems that the FG terminal is used as the RS-485 common-mode reference for these devices. Is this the terminal you have grounded to the building's grounding system for each device...

Regardless of whether the voltage is AC or DC, a voltage higher than the specified maximum applied to an RS-485 transceiver can damage it. While not ideal, using earth ground as the RS-485 common-mode reference is a configuration that can be made to work. However, earth ground is a very noisy...

It sounds like there may be improper grounding on the RS-485 network and that you may be measuring voltages with respect to incorrect references. If you truly had over 100V difference between A or B and the common-mode reference, your devices would not survive that (RS-485 allows for only -7 to...

I think the source of the confusions is because you are looking at documentation for the wrong protocol. The image you show seems to be from the product's PROFIBUS documentation: https://lamtec.su/download/Etamatic/BUS/BA-Profibus-DLT6100-EN.pdf Try the Modbus documentation here...

You're going to need to provide a little more detail for anyone to have any chance of helping you with this request. What TCP port is being used? Where did you run into this protocol? Do you know what device(s) are sending these packets? Do you have any additional packet examples or only the one?

What protocol is the ZM405 configured to use under Admin->Ports->Protocol? It appears the ZM405 supports several different protocols and supports both serial and Ethernet communication. It seems the intended method of communicating to a PLC is using the Ethernet port and either the Modbus/TCP...

XON/XOFF is software flow control. Using it would require you to send XON and XOFF control characters. XON would turn on transmission, while XOFF would stop transmission. https://en.wikipedia.org/wiki/Software_flow_control There's also hardware flow control (RTS/CTS, DTR/DSR), but this can only...

Well I found a service manual here: https://usermanual.wiki/Manual/ZM401405sen501334.673270420.pdf According to that, those settings should be in the ADMIN level menu under Ports->Serial.

Thank you for clarifying. Did you ever resolve the issue from your original post? Do you have any documentation available on the ZM405 about its RS-485 communication? The manual is very sparse with details in its communication section, but I'm guess it continually streams ASCII characters in...

OK, I understand this is frustrating, because yes, it should not be that hard. But let's make sure you're focusing in the right places. You previously stated you've successfully used the ZM405 scale many times with a virtual COM port. Was this with the RS-485 option card and using a USB to...

I think you've answered your own question here. How useful would a Modbus device be if, after you've configure its device address, it reverts to a default address some time later? There's no way you'd be able to have any other devices on that network and not have issues. So yes, device...

Many weight scales with RS-232 output use their own, simple ASCII protocol for communication. This protocol should be documented in the scale's user's manual. I recommend first trying to communicate to the scale using your computer, a USB to RS-232 adapter, and a terminal emulator such as PuTTY...

I am in no way affiliated or can provide support on the Modbus libraries that I linked in my previous post. I was merely providing them as examples of the results I got when performing an internet search for "Modbus .NET compact framework WinCE" . I suggest you contact the developers of those...