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How many wires are being used in the RS-485 cabling between the devices? Are you using a reference wire? Is termination installed/enabled on the RS-485 bus? If so, are network idle biasing resistors also installed? If this network has termination without idle biasing, it's possible it has...

Thank you for the additional details. Unfortunately I can't find any documentation online for the ST129CP-50HV other than a datasheet. Do you have a manual with the Modbus registers you can share? The results from your stop/start test are interesting. The fact that the blue dot moves to the...

Hello and welcome to the forum! Can you provide the Sungrow model number of the BESS and/or a user's manual? Is the web app your own creation, being served by the CM4 or is it from the Sungrow system? When the battery fails and there is a fault, how do you remove the fault condition and clear...

How are you determining that the slaves do not send a response back? Could the slaves instead be sending an exception response? What is your RTU's timeout time? In other words, how long does it wait for a response from each slave? Are all 15 devices the same (i.e. same vendor and model)? If...

That meter communicates using the IEC 62056-21 protocol. https://en.wikipedia.org/wiki/IEC_62056#IEC_62056-21 Therefore, I don't think you can use Termite and simply send ASCII commands. Take a look at these software tools/libraries instead...

No, RS-485 is not compatible with Ethernet! That is NOT an RS-485 Ethernet port, it's an RS-485 RJ-45 port. This distinction matters. It is an RS-485 port that just happens to use the same connector (RJ-45) as the standard Ethernet port connector (RJ-45). At best, connecting this RS-485 port...

This question doesn't have anything to do with Modbus itself. It is an application-level problem, so of course you will not find any recommendations in any communication specification. This is a question that every engineer creating a Modbus device must consider. There is not a single correct...

As this seems to be a homework assignment, I'll tell you what I just told your classmate. https://control.com/forums/threads/modbus-tcp-ip-communication-suggest-good-platform-for-that.54140/ For assignments such as this, we are not going to do your work for you. We can, however, review the work...

OK, this must be a homework assignment. https://control.com/forums/threads/how-can-two-pcs-communicate-without-any-hardware-using-modbus-tcp-ip-protocol-and-also-by-using-stm32-ide.54114/ Are we going to see posts from the whole class asking for answers to this same homework problem? For...

Please clarify, is your intention to develop Modbus applications for an STMicroelectronics STM32 microcontroller? You need to clearly explain what equipment/devices you are using and what you are trying to accomplish in order for us to be able to help you.

Your question is a bit confusing, as there are details that don't seem to make sense. I understand you have two PC's (one should be a master and the other a slave) and you want them to communicate to each other using the Modbus/TCP protocol. The confusing part is your stipulation that the PC's...

I'm glad to hear you got it working with your Pi as the server and the HMI as the client. Although, if that is successful, it should be possible to have the Pi be the client and the HMI be the server. It's likely that there are still some incorrect configuration settings on the HMI when...

I recommend testing each piece of equipment individually using a computer and a USB to RS-485 adapter to determine where the problem lies. There are several Modbus software tools available, for example: WinTECH ModScan and ModSim http://win-tech.com/ Simply Modbus master and slave simulators...

Well I don't know what to tell you then. If you have the CRC order at Low to High and all of your communication settings match (baud rate, parity, stop bits, slave address), then communications should work. Maybe you need to power cycle the controller for the settings to take effect.

If communication was working previously, both the software and the controller must have had their CRC bytes in High to Low order. You need to change this ordering on both the software and the controller, not just the controller. Changing that setting to Low to High order on the controller...

Both of those captures simply show the same request packet over and over (no responses). The packet is 01 03 10 00 00 66 20 C1 which is a request to slave address 1 to read 102 holding registers starting at address 0x1000. Now while a CRC value of 0x20C1 is the correct CRC for the packet, I...

Thank you for clarifying. I don't know anything about the capabilities of the Weintek HMI, other than the images you show and what I can find online, but in general, this may be able to be accomplished two ways. 1. Read the data (tags, registers, etc.) from the HMI directly from the HMI's...

Can you take a raw hex capture of the Modbus data between the Mebay software and the controller and post the results? Here are some terminal emulator programs that could be used to do this: Termite with the "Hexadecimal View" filter https://www.compuphase.com/software_termite.htm CoolTerm...

Can you elaborate on what exactly you're trying to do, the equipment involved, and the type of Modbus connections (Ethernet, RS-485, RS-232, etc.) between each device? Do you have 3 pieces of equipment (HMI, "a board", and Raspberry Pi)? Is the HMI is connected to "the board" via RS-232 (or is...

Those images of the monitoring software don't seem like it's decoding the packets properly. The lengths are all wrong and it's only showing requests, no responses. A Modbus RTU request to read holding registers is always 8 bytes in length. Also from the connection settings image it seems to...