Post by irshad on Modbus TCP/IP slave communication errow ^{CODESYS Forge talk (Post)}
While reading the value of a slave device, it shows error frequently and i need to restart my PLC for getting the communication back. In codesys it shows the slave in Red color with error status. How to solve the above
Last updated: 2024-02-03

Post by nano on Dynamic setting of the modbus tcp/ip slave ip address ^{CODESYS Forge talk (Post)}
habe a look to this faq, this should work for u https://faq.codesys.com/plugins/servlet/mobile?contentId=24510471#content/view/24510471
Last updated: 2024-02-17

Post by timvh on Timeout Error in Modbus Communication with WAGO PFC200 and iEM2050 Meter using 750-652 Module ^{CODESYS Forge talk (Post)}
I'm not sure, but maybe you have to configure the 750-652 first with the WAGO-IO-CHECK software to set it in RS485 mode?
Last updated: 2024-02-27

Post by ph0010421 on Sending Sequential Modbus TCP Packets ^{CODESYS Forge talk (Post)}
Hello You'll need to write a proper sequence to send, then wait for confirmation, and then move on to the next step. Use the CASE statement in ST. It's perfect for creating a sequence.
Last updated: 2024-03-08

Post by dawidr on Timeout Error in Modbus Communication with WAGO PFC200 and iEM2050 Meter using 750-652 Module ^{CODESYS Forge talk (Post)}
Did you manage to solve the problem with time out? I got the same issue and I've no idea what I'm doing wrong.
Last updated: 2024-04-07

Post by dawidr on Timeout Error in Modbus Communication with WAGO PFC200 and iEM2050 Meter using 750-652 Module ^{CODESYS Forge talk (Post)}
Did you manage to solve the problem with time out? I got the same issue and I've no idea what I'm doing wrong.
Last updated: 2024-04-07

Post by vincentger on v3.5 SP19 - Modbus TCP Devices - Channel Limit? ^{CODESYS Forge talk (Post)}
Any resolution on this? I have currently 75 channels in my project that i brought up from SP18, which means i am 65 Channels above the new limitation?
Last updated: 2024-04-09

Post by marcolim on Slow modbus digital input response ^{CODESYS Forge talk (Post)}
Hi francoinf, I've the similar problem and similar configuration. I did with an Arduino Board loaded by a ModbusRTUServer application on it. What I've notice is the slowly acquisition when release the digital signal (e.g. pin2) when it gets off. Anyone have suggestion?! Thanks
Last updated: 2024-04-13

Post by marcolim on Slow modbus digital input response ^{CODESYS Forge talk (Post)}
[Update]. My issue's solved, I applied the resistors in Pull-down configuration on each digital input. In thus configuration never happened "floating or delaying" acquisition on SoftPLC/Arduino Board.
Last updated: 2024-04-15

Post by timvh on IoDrvModbusTCP_Diag not defined when using MODBUS ^{CODESYS Forge talk (Post)}
Most likely related to the Device Diagnostics functionality. Double click on your device (PLC), go to the tab "PLC settings". Enable the advanced option "Enable diagnosis for devices". Build your application again.
Last updated: 2024-04-15

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 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: 6 days ago

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

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