Post by mbmik on IoDrvModbusTCP_Diag not defined when using MODBUS ^{CODESYS Forge talk (Post)}
Thanks alot for your time and help! I quickly tested the suggestion, as it makes a lot of sense. Unfortunately the erros still appear as before. The settings was already set before, and i tried turning it off.. no effect..
Last updated: 2024-04-16

Post by hyet on IoDrvModbusTCP_Diag not defined when using MODBUS ^{CODESYS Forge talk (Post)}
Currently seeing the same issue here, with a project moved from 3.5.19. Diving into it too to see if i can find the cause
Last updated: 2024-05-01

Post by guilhermeleao on How to communicate 2 pcs that are using CODESYS ^{CODESYS Forge talk (Post)}
I need to connect 2 computers on the same network that are running codesys, so that they can receive and change variable values from each other. This connection must preferably be made using Modbus.
Last updated: 2024-05-06

Post by zer0g on Modbus Client Request Not Processed ^{CODESYS Forge talk (Post)}
Hi, I have the same problem as the guys above. Any solution or hint in the right direction is appreciated. Codesys version 3.5.19.2, Lib version: 4.4.0.0. Thank you!
Last updated: 2024-05-29

Post by timvh on Modbus TCP Server connection is ESTABLISHED but all holding registers are value 0? ^{CODESYS Forge talk (Post)}
Are you sure you need to read holding registers? Have you tried reading input registers?
Last updated: 2026-01-07

Post by salvatorethomas on Port instantiation of serial interface in WAGO PLC using Modb_L05.lib in CoDeSys v2.3 ^{CODESYS Forge talk (Post)}
Hi — good description of the problem. A few suggestions / questions that might help narrow this down: Since your first serial port (COM2) works fine but the second (COM4 + MODBUS_EXT_MASTER) never opens, check whether the two ports are truly independent — some WAGO modules share internal resources, so COM4 might conflict with other functions or modules. Make sure that the physical wiring and module configuration for the second port (baud rate, flow control, RS-485 vs RS-422, etc.) exactly match what the library expects — a mismatch in flow control or wiring could prevent port opening even if the LED signals seem OK. Try using a plain SERIAL_INTERFACE on COM4 first (like you did for COM2) without Modbus logic — if that opens, you know the hardware + port config is fine, so the issue is more likely with modb_L05.lib. If the port opens but Modbus still fails, enable debug/logging (if available) to inspect whether the port opening fails or the subsequent Modbus negotiation fails. If you like — I can share a minimal example project I used with WAGO + COM4 + Modbus that worked; you could adapt that to test your setup. Wacky Flip
Last updated: 2025-12-01

Post by nulltrace on How change Unity-ID in TCP Modbus Slave ^{CODESYS Forge talk (Post)}
Hey Husarz. i don't forget you, the Thing is, to give you my answer, i have to wait for Answer from Codesys/E. Schwellinger. i suspect Mr. Schwellinger is on in Vacations that week. so please, be patient at moment
Last updated: 2026-04-10

Post by fleaplc on Modbus TCP Server connection is ESTABLISHED but all holding registers are value 0? ^{CODESYS Forge talk (Post)}
Did you check the communication with a sniffer ? (ex. Wireshark) to check if the holding get to zero by a wrong writing (client initialization?) o something else?
Last updated: 2026-01-27

Post by risele on Modbus connection via Qronox PCD3 M6893 ^{CODESYS Forge talk (Post)}
First, if you don't need to change conversion rules in runtime, take a look at "Unit conversion" module (Application -> add object -> UnitConversion). You can specify there biderectional conversion with different units, limits and so on. Second, since MODBUS don't have "real" types but only general 16-bit registers and Real is 32-bit, generally you need a byte-was conversion Real <> two Words. Note, that depending on the devices on both sides, there are two options: Real-> Word1, Word2 or Real-> Word2, Word1, where Word1 is minor register in Modbus register pair and Word2 is major. You can use simple union: TYPE u_Real : UNION rVal:REAL; wVal:ARRAY[0..1] OF WORD; dwVAL:DWORD; //same as previous, may be easier to specify the MB register END_UNION END_TYPE and convert it as following: VAR myUnion:u_Real; rValue_TO_SEND:REAL; rValue_TO_GET:REAL; END_VAR myUnion.rVal:=rValue_TO_SEND; rValue_TO_GET:=myUnion.rVal; Note, that WORD-order should be properly set in MODBUS registers, otherwise you will get strange values. This tool is helpful: https://www.scadacore.com/tools/programming-calculators/online-hex-converter/ Alternative, you can use functions as REAL_TO_DW and DW_TO_REAL from OSCAT_BASIC, for example.
Last updated: 2026-02-19

Post by husarz17 on How change Unity-ID in TCP Modbus Slave ^{CODESYS Forge talk (Post)}
I need the same issue. In my application TCP server on raspberry (codesys) should have UnitID 1. But it only works when I am requesting with UnitID 255. And my application can't work with this parameters...
Last updated: 2026-03-31

Post by nulltrace on How change Unity-ID in TCP Modbus Slave ^{CODESYS Forge talk (Post)}
Hey Husarz, thanks for your Message, now i understand your Problem, also able to reproduce that. Pls. give me a Short Time to Check some stuff on this, i'll come back to this Topic with news ASAP. Greetings
Last updated: 2026-04-03

Post by nulltrace on How change Unity-ID in TCP Modbus Slave ^{CODESYS Forge talk (Post)}
Hey, I also waiting for feedback from Mr. Schwellinger @eschwellinger, please send me an answer, i would appreciate it. The clue is, i know the solution, but have to check if it's allowed to share.
Last updated: 2026-04-14

Post by husarz17 on How change Unity-ID in TCP Modbus Slave ^{CODESYS Forge talk (Post)}
Good to know there's a solution to this problem. I hope you'll be able to share it with me. I can't wait to hear about it.
Last updated: 2026-04-20

Post by lepewe4ka on Sysmac Studio to Codesys ^{CODESYS Forge talk (Post)}
Could you send me an example? I would like to generate a data structure using XML files.
Last updated: 2023-09-20

Post by lepewe4ka on Sysmac Studio to Codesys ^{CODESYS Forge talk (Post)}
Could you send me an example? I would like to generate a data structure using XML files.
Last updated: 2023-09-20

Post by vladimirsmall on Send data to USB ^{CODESYS Forge talk (Post)}
Hello/ Need send some file ( for example Array of string) to USB. Which library need used for this. Thank you
Last updated: 2024-07-20

Post by damian177 on Problem with downloading OPC UA tags by Data Source Manager ^{CODESYS Forge talk (Post)}
After 3 hours is some progress - please find in attachment - progress1.jpg
Last updated: 2024-09-04

Post by lsislsis on RPI Serial port connects with no errors but not data being transmitted or received ^{CODESYS Forge talk (Post)}
Is there any solution because we have the same problem with other hardware?
Last updated: 2024-09-30

Post by dkugler on Reading a negative number ^{CODESYS Forge talk (Post)}
why not simply converting data type UINT to INT? Then avoid negative values with ... := MAX(0 , intTest); Good luck!
Last updated: 2025-05-28

Post by levih on FbHTTPs_Get how to get data from a website and use it in codesys ^{CODESYS Forge talk (Post)}
You get an array of DWORD into your receive buffer. You need to process this into usable data, before you can fit it into your DUT. I've made it work using FbWrite_ToIEC_ByRule in stead of Fb_JSON_ParseAndModify. I've attached images of the code. You receive the data into ARRAY[0..1023] OF DWORD. Then you use that array as the input for fbWrite_ToIEC_ByRule. To get the output from this you define a rule to fit the expected data structure including nesting levels. The you feed the rule into FbWrite_ToIEC_ByRule and then you can set the output to be of your DUT type.
Last updated: 2025-06-16

Post by tonyadrem on update data/tim ^{CODESYS Forge talk (Post)}
Hello How to update the dates from timestamp to the actual time? THX!
Last updated: 2025-08-25

Post by tonyadrem on update data/tim ^{CODESYS Forge talk (Post)}
Hello How to update the dates from timestamp to the actual time? THX!
Last updated: 2025-08-25

Post by trycyclepower on How to transfer data from DINT to Union(16 Bools) which I need to use in Few FBs ^{CODESYS Forge talk (Post)}
Thanks a lot, it worked.
Last updated: 2023-12-14

Post by ph0010421 on How to transfer data from DINT to Union(16 Bools) which I need to use in Few FBs ^{CODESYS Forge talk (Post)}
In the Struct, change the 'BOOL' to 'BIT'
Last updated: 2023-12-14

Post by eschwellinger on Data Transferring between 2 PLCs in a same PC ^{CODESYS Forge talk (Post)}
.. this will not work on the same pc
Last updated: 2024-02-06

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