Post by mariacugnier on Modbus TCP/IP having problems with global variables ^{CODESYS Forge talk (Post)}
Are these variables already declared in the IO list? It looks like it's trying to create new variables instead of mapping them to the existing ones.
Last updated: 2025-05-22

Post by ph0010421 on Dynamically enabling/disabling Modbus slave devices in runtime (performance issue with timeouts) ^{CODESYS Forge talk (Post)}
Hello If you uncheck 'Auto restart Communication', it will try once and never again. You can manually reset the slave if needed : Slave.xReset (or something similar) Or I have a ModbusRTU library if you want to try it.
Last updated: 2025-08-12

Post by mavitia on Application based license problem - Modbus TCP ^{CODESYS Forge talk (Post)}
raspberry pi is running ubuntu, so it has the codesys control for linux arm 64 bit, IDE is 3.5.19, both were installed last week from the latest versions online, im currently out of the PC but will upload some evidence ASAP
Last updated: 2023-12-18

Post by yelshebani on Add device greyed out ^{CODESYS Forge talk (Post)}
Hi Add device is greyed out, havent connected to the PLC yet. what do I need to do to have ability to add devices, I want to add a Modbus TCP Master device
Last updated: 2023-12-19

Post by marekxc on Little endian to Float from Modbus RTU ^{CODESYS Forge talk (Post)}
Maybe try going back to step one and: Var Reg1: WORD; Reg2: WORD; Reg12: DWORD; Value: REAL; end_var // program Reg1:= 4096; Reg2:= 14884; Reg12:= (reg2 * 65536) + reg1; Value:= DWORD_TO_REAL(Reg12);
Last updated: 2023-12-28

Post by forest on SM Drive license error ^{CODESYS Forge talk (Post)}
Hi, when it comes about license, I used INVTmatic Studio, which uses Codesys, for programming INVT plc. I bought Codesys Modbus license, it was not expensive, and then realised that INVT didn't have License Manager option (greyed out in program) which is needed for using of Codesys License. I contacted support from INVT, but developers told me that option is still not available. So depending on environment for programming Codesys, you can or not use Modbus license. Good thing about this version of Modbus TCP it works both direction. I could send commands and receive feedbacks from drive. But communication stops after 30 mins. So I used simple version of ethernet modbus which is somewhere in INVT or Condesys library (I can check tomorrow) which works only one way. I could send cmd to drive, and control it, but didn't have any feedback, like some readings back in PLC. which is bad, but at least I could start it and it didn't fail after 30 mins.
Last updated: 2024-01-10

Post by mozburg on v3.5 SP19 - Modbus TCP Devices - Channel Limit? ^{CODESYS Forge talk (Post)}
Has there been any progress on this issue? Currently running sp19 patch 5 with all packages updated but unable to add more channels...
Last updated: 2024-01-18

Post by dim54 on MBChannel ^{CODESYS Forge talk (Post)}
Hello! I am interested in the Modbus Slave channel parameter uiReadLength to use in the ST-program (see picture). How to read the value of uiReadLength in a ST-program? Only Edwin the Great and Terrible can answer this question.
Last updated: 2024-01-22

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 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 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

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