Post by danwoodlock on Rpi zero w lost license after 4.11 update ^{CODESYS Forge talk (Post)}
Hello all, Encountered an issue with my zero which seems to have happened after the 4.11 update. It now runs in demo mode (2hr) and I am trying to see what the appropriate steps are prior to contacting codesys directly. Background: I recently did a fresh install of w11 on my pc, so it seems "c:\ProgramData\CODESYS\Licenses\" only has information related to my pi5, which I licensed just this past Friday. I have all my license documentation about my rpi zero as far as the emails received, but when I try to claim using the ticket number it says its already been used, or something to that effect, which it was. Currently trying to perform device license reader, which is taking some time.
Last updated: 2024-04-14

Post by robpqs on Program from one PLC to other WAGO 750-8204 ^{CODESYS Forge talk (Post)}
Hello, You use the WAGOUpload tool. You can download it on the download center of WAGO. Make a backup and restore it on the new device. (if can check the remanent data to copy the persistent variables if necessary) You can also use a SD card, go to the WBM copy it the image to the SD card and restart the other controller on the SD card. In the WBM, copy it back to the internal flash. If you contact your local Wago office, they will more than probably help you. There is also a WAGO forum. RP,
Last updated: 2024-05-27

Post by adaffern on Runtime on Raspberry pi5 stops after 15 seconds ^{CODESYS Forge talk (Post)}
Hi Guys, I'm new to CODESYS on the pi and I'm struggling to get it working. My issue is that the runtime keeps stopping after approximately 15 seconds. I have installed the runtime package 4.11.0.0 on the pi, trying on both a 64 bit and 32 bit OS. Looking at old forums it all references the 4B and the fact they used 32 bit Debian bullseye (the last version of raspberry pi os) however the pi 5 doesn't offer this version when I try select it in the imager. Has anyone managed to get running using the pi 5? Any help would be greatly appreciated. Thanks, Adam
Last updated: 2024-06-10

Post by timothyzalusky on Strange Behavior on Raspberry Pi ^{CODESYS Forge talk (Post)}
Hello, I am seeing some weird runtime behavior related to the EQ function on a rapsberry pi based system. I have attached a screenshot showing the strange latching I am seeing on the EQ function, and I have not seen this behavior before. I tried freshly restarting the runtime and it has this same behavior. Anyone seen this? I am on 3.5.20 with the latest runtime installed. Basically, as soon as it hits one of those EQ's in the program, it latches effectively locking the output on. Any input from the Codesys team would be appreciated as well as anyone that might know what I am seeing.
Last updated: 2024-06-18

Post by ron-rp on Errors with VisuUserManagement library ^{CODESYS Forge talk (Post)}
Hi all, I've played a bit with the VisuUserManagement library, and some other security option in my project, and I started getting this error when logging in - see attached pic. something to do with a specific screen in the library - VUM_Login. Also, Codesys started to ask me to log in to the library when logging in, asking to log in as user of the groups Maintainer or Owner, which I dont know either users (attached pic). when I close the login screen and try to log in to the PLC again, everything works again until I close and open Codesys. I do use user and password to login to the PLC, and this login screen is fine I know the user and pass I setup. anyone know what did I do wrong here and how to fix it?
Last updated: 2024-06-25

Post by davidbo on How to stop dhcpcd and use SysSockSetIpAddressAndNetMask to set address? ^{CODESYS Forge talk (Post)}
It is stated: "Dynamic ip address, provided by DHCP, BOOTP, etc. Cannot be changed by SysSockSetIpAddressAndNetMask()" Therefore I try to stop dhcpcd and flush the eth0 like this VAR CONSTANT flushIP:STRING:='sudo ip addr flush dev eth0'; stopDHCP:STRING:='sudo systemctl stop dhcpcd'; END_VAR SysProcessExecuteCommand2(pszCommand:=stopDHCP, pszStdOut:=stdout,udiStdOutLen:= SIZEOF(stdout),pResult := ADR(Result)); SysProcessExecuteCommand2(pszCommand:=flushIP, pszStdOut:=stdout,udiStdOutLen:= SIZEOF(stdout),pResult := ADR(Result)); Besides losing the connection when flush occurs the CODESYS halts, seen on the display and I cannot see why, because I have lost the connection from my IDE. Why does the flush command halt the execution of the application?
Last updated: 2025-11-04

Post by imdatatas on Codesys IDE initialization error from a new Sandbox image ^{CODESYS Forge talk (Post)}
Hello everyone, I created a new sandbox image on the D drive with Codesys Installer. However, when I launch the IDE from this image, it gives the error shown in the attached image. -- Codesys V3.5 SP19 Patch7. -- The installer is the latest (2.5.0). -- All packages in the installer were updated to the latest version as of today when creating the sandbox. -- The originally installed IDE on the C drive does not give this error when launched. -- I last upgraded it to Softmotion 4.20.1.0 through the installer. Has anyone encountered the same or a similar issue? Will this issue be fixed in the next update? Best regards, Imdat
Last updated: 2025-12-05

Post by bigwhig on Could not write options file at... ^{CODESYS Forge talk (Post)}
Using Codesys 3.5.21.5. Tried installing both by full .exe file and using codesys installer. Installation requires elevation and completes just fine. However when running Codesys and closing the IDE, options-files are not written: Seems regular users are only given read-access to these files: Running Codesys as admin works as admins have full access. Haven’t been necessary before to run as admin. Don’t think I have the issue on my work-laptop, but have experienced this on a number of other computers. Above screenshots are from my private stationary running Windows 11 Pro: Anyone else experiencing this? Is this by design or a known issue?
Last updated: 2 days ago

Post by mattkaree on Mapping values with etherCAT mailbox communication ^{CODESYS Forge talk (Post)}
I am using a WAGO PFC200 PLC as an etherCAT master and a Keyence IV3-G120 with DL-EC1A attached as an etherCAT slave. I am using CODESYS V3.5 SP21 Patch 3. I was able to set up mailbox communication and can see values changing accordingly, but I want to know how I can map these values and reference them in my program. I am able to map the process data objects in the 'EtherCAT I/O Mapping' tab, but there is no where to map the mailbox values in the 'CoE Online' tab. Is there a way I can reference one of these values in my code?
Last updated: 2026-01-27

Post by gseidel on Absolute movement controlled by an external encoder. ^{CODESYS Forge talk (Post)}
Hi polyautomacao, basically, there are two ways to approach this. My first choice would be to check whether your servo drives supports an external encoder, connect the encoder to the servo and configure the servo accordingly. In this case, you would not need to change anything in the CODESYS application. If that is not an option, you could use SM_DrivePosControl, a drive that closes the position loop in the PLC, and feed it with the external encoder positions. See (0). You can switch your servo drive to velocity control mode (SMC_SetControllerMode) and use SMC_FollowVelocity to apply the fSetVelocity of the SM_DrivePosControl to your servo. The MC_MoveAbsolute can then be performed on the SC_DrivePosControl Hope that helps. (0) https://content.helpme-codesys.com/en/CODESYS%20SoftMotion/_sm_example_poscontrol.html Best regards, Georg
Last updated: 2026-03-04

Post by cd-tt on cannot connect ot linux runtime: device does not answer the scanrequest ^{CODESYS Forge talk (Post)}
I have the following setup: Proxmox PC with a debian 13 VM running CODESYS Control Linux SL and Edge Gateway. Installation method was through the Deploy Control SL and went rather smoothly. In my Device Tab I find the gateway and when scanning my network I also find my runtime. I want to connect and get promted that I should add a user. After setting up the user I get an error saying, that the device is not responding my scanrequest. Deploy Control SL Operation saying everythings up and running. I can confirm that from the terminal on the VM with "systemctl status codesyscontrol" and "systemctl status codesysgateway". I am running out of ideas how to fix that issue. Can anybody help? Screenshots attached.
Last updated: 2026-06-11

Post by domebruce on TCP communication and TCP Streams ^{CODESYS Forge talk (Post)}
Hello, I'm doing some tests with TCP communication using Reader, Writer and TCP_Process components from NBS 4.0. I'm having a really hard time finding documentation and examples on these components. I found a very simple and incomplete example here: https://forge.codesys.com/prj/codesys-example/nbs/home/Home/. The documentation is also insufficient: it only provides the names of the FBs, Methods and their parameters, but no descriptions about how to use them. Do you have any suggestions on where to find more support? More generally, why is the free online CoDeSys documentation so poor? What do you think? Thanks Domenico Canavero
Last updated: 2026-06-16

Post by ophelia on Phantom Test Slot Preventing Suite Completion ^{CODESYS Forge talk (Post)}
Hi all, I'm working with a CODESYS 3.5 unit test framework on an embedded Linux PLC and running into an issue where a phantom test slot appears in the results that never completes, preventing the full test suite from ever finishing. The symptom: A blank-named test entry appears in the results table with an ever-increasing action count. It stays as "Testing" or "Failing" indefinitely. Because it never closes, bAllFinished never goes TRUE and the final report is never generated. Question: Has anyone seen this kind of phantom slot issue in a CODESYS unit testing setup? Thanks
Last updated: 2026-07-09

Post by tyronnosaurus on ReceiveWatchdog FB not working on J1939 P2P PGNs ^{CODESYS Forge talk (Post)}
Hi guys. I've got a device that sends a status message over J1939 and a PLC running Codesys to receive it. This message uses a P2P PGN (as opposed to a broadcast PGN). Codesys can only read it if I mark the J1939_ECU as "Local" (see screenshot 1). The message is received correctly, that is not the problem. The problem is detecting if the message stops being received. Local ECUs have no Watchdog checkbox to detect if the message has been received in the last X seconds. In order to implement a watchdog, I've used a ReceiveWatchdog FB. The same code works well for any non-P2P message, but doesn't work for this particular P2P message I'm trying to monitor. Even if I physically disconnect the device, ReceiveWatchdog.xBusy stays True, and ReceiveWatchdog.xError never triggers due to a timeout error. Is there any caveat in the ReceiveWatchdog FB that makes it unable to monitor P2P PGNs in Local J1939_ECUs?
Last updated: 2024-07-11

Post by lbartik on J1939 TX/RX PDU1 ^{CODESYS Forge talk (Post)}
Is it possible to transmit a PDU1 PGN using the J1939 manager and local device? What if I need to transmit a PGN RQST via 0xEA00 (PGN 59904)? How would I do this P2P (Destination < 0xFF) or broadcast (Destination 0xFF)? I don't think this is possible for any destination type. I don't think it's possible to receive broadcast PDU1 messages either. For example, an address claim PGN 60928 (0x18EEFF80) is addressed to all nodes (0xFF) and not any specific local device so it will be filtered out. These are major oversights in the IoDrvJ1939 library to not support every PDU1 RX/TX scenario. IoDrvJ1939 supported scenario: 1. Receive (RX) PDU1 (P2P) destination-specific (PDU-specific < 255) to local device with matching address IoDrvJ1939 unsupported scenarios: 1. Receive (RX) PDU1 (P2P) global (PDU-specific = 255) 2. Transmit (TX) PDU1 (P2P) global (PDU-specific = 255) 3. Transmit (TX) PDU1 (P2P) destination-specific (PDU-specific < 255)
Last updated: 2024-09-23

Post by struccc on Bibliothek: floatingpointutils ^{CODESYS Forge talk (Post)}
The issue s the byte order typically in this case. Can be especially problematic with floating point numbers - even more tricky if transferred with a word based protocol. It is a peasant way to try out the alternatives, dword order can be a-b-c-d, b-a-d-c, c-d-a-b, d-c-b-a where a is the most significant, d is the least significant byte. So all you need is to swap the bytes in your dword, until you get the expected result. If you don't want to mess writing code for this, I'd recommend CAA_Memory library for that: MEM.ReverseBYTEsInDWORD and MEM.ReverseWORDsInDWORD functions would definitively do the trick. Otherwise, can do like this: VAR dwIn : DWORD := 16#11223344; dwOut : DWORD; rOut : REAL; pIN : POINTER TO BYTE; pOUT : POINTER TO BYTE; END_VAR pIN := ADR(dwIn); //pOUt := ADR(dwOut); pOUt := ADR(rOut); pOut[0] := pIN[3]; pOut[1] := pIN[2]; pOut[2] := pIN[1]; pOut[3] := pIN[0]; Ugly, but does the job...
Last updated: 2024-11-19

Post by r-c-r on SM3RaspiStepper 0.0.0.6 issue ^{CODESYS Forge talk (Post)}
Ok, so i made some tests in the meantime and i have some conclusions. It apears that the enable bit is activated only when a motion function is executed. I implemented a very simple program with MC_Power and MC_Jog. If i enable everything on MC_Power, the enable GPIO pin stays off. However, as soon as the MC_Jog function is used the enable GPIO pin turns ON and remains ON. In version 0.0.0.4 this is not happening. The GPIO enable pin turns on or off when the MC_Power is enabled or disabled. From this behaviour i understand that in version 0.0.0.6 the GPIO enable bit is activated together with pulse and dir pins when motion starts. When motion stops, enable bit remains with the last state (on in this case) and you cannot turn it off for example. For me this bit is useful because i can turn on and off the stepper drive with MC_Power function. Now i can turn it on, but never off.
Last updated: 2025-04-04

Post by rene-h on ClientFilter used the same Client ID 2 times - Bug? ^{CODESYS Forge talk (Post)}
Hello, like the topic name says, i have a problem on one Visu which i cannot reproduce on another Visu. We filter buttons with input locks and visible items with [CURRENTCLIENTID] on different WebVisu's with different ID's, and one time the itfClient used the same Client ID for 2 Clients, so the Visualization on the first ID was wrong, because that one which connected after did not have the same permissions like the first, so the first one was blocked. We read the Clients with the VisuClientIteration project: //count active clients gCli.iNumberOfClients:=gCli.iNumberOfClients+1; // if client is active write data to global struct IF gCli.iNumberOfClients > 0 THEN gCli.astClientInfo[gCli.iNumberOfClients-1].iClientID:=itfClient.ClientId ; gCli.astClientInfo[gCli.iNumberOfClients-1].stCurrentVisu:=itfClient.CurrentVisuName; gCli.astClientInfo[gCli.iNumberOfClients-1].wsUserName:=itfClient.UserName; gCli.astClientInfo[gCli.iNumberOfClients-1].sIpAddress:=itfClient.GetIPv4Address(); gCli.astClientInfo[gCli.iNumberOfClients-1].ClientType:=itfClient.ClientType; END_IF Runtime from the device: 3.5.19.20 Codesys we use: 3.5.20.10 I added a screenshot where the same ID exists 2 times. Thanks for your answers.
Last updated: 2025-05-14

Post by giackanto on Eoe issues with Windows and Linux ^{CODESYS Forge talk (Post)}
Hello, I've been trying to use EoE for communication between a Windows PC and an M753 drive from Control Technique. Despite following some online guides (https://content.helpme-codesys.com/en/libs/EtherCATStack/4.3.0.0/Ethernet_over_EtherCAT/fld-Ethernet_over_EtherCAT.html) I haven’t had any success. Both are connected to a Debian device where RTE is running: The PC is connected via the Ethernet port. The drive is connected via the EtherCAT port. I'm unable to ping the drive from my Windows PC. Here is my configuration: On Debian: (See attachments 1, 2, 3) enp1s0 = Ethernet port enp2s0 = EtherCAT port tap2 = TAP device IP forwarding and routes are both configured. On Windows: (See attachments 4, 5) On Codesys: (See attachments 6, 7) Version: Windows 11 Debian GNU/Linux 11 Codesys 3.5.17 Control for Linux SL 4.7.0 EtherCAT 4.4.0 With this configuration, I can ping the TAP device, but not the drive (See attachment 8). Could someone explain how to properly configure all these settings? Thank you, GA
Last updated: 2023-12-19

Post by rabaggett on CODESYS control for Raspberry Pi 64 SL errors ^{CODESYS Forge talk (Post)}
Hi, I am trying to create a project using a raspberry pi, I have added the modules for the Pi and MCP3008. I have encountered som errors that I don't know how to track down. 1. The GPIOs give preprocessor errors, but I read that this does not prevent compiling. This seems to be true. I can build the empty project with no errors. 2. After adding a SPI master and MCP3008, the preprocessor errors double, but seem similar and the project again builds with no errors. 3. I add a DUT and GVL, with a function, and I get the following errors. They remain even if I delete these things. ------ Build started: Application: Device.Application ------- Typify code... [ERROR] crr: C0032: Cannot convert type 'Unknown type: 'ADR(GVL_Io_17160064_c083_41f8_9e53_208be7537753_HPS_7.Io_17160064_c083_41f8_9e53_208be7537753_HPS_7)'' to type 'POINTER TO IoConfigParameter' [ERROR] crr: C0077: Unknown type: 'GVL_Io_17160064_c083_41f8_9e53_208be7537753_HPS_7.Io_17160064_c083_41f8_9e53_208be7537753_HPS_7' [ERROR] crr: C0046: Identifier 'GVL_Io_17160064_c083_41f8_9e53_208be7537753_HPS_7' not defined Compile complete -- 3 errors, 0 warnings I attach the project. What am I doing wrong? Thanks!
Last updated: 2024-05-02

Post by nixola on CmpCharDevice blocks gpiochip access on Raspberry Pi 5 since update from SP18 to SP21 ^{CODESYS Forge talk (Post)}
Hi, I added the following lines to /etc/codesyscontrol/CODESYSControl_User.cfg: [CmpCharDevice] PermittedPath.0=/dev/i2c* PermittedPath.1=/dev/spidev* PermittedPath.2=/sys/class/gpio/* PermittedPath.3=/dev/gpiochip* However, I'm still unable to read or control GPIO pins from any CODESYS application. Specifically, setting the pin direction (and, thus, the IoDrvGpioSysfs driver configuration) fails, with a rather non-descript error in the logs: Description Component Setting direction failed for GPIO pin 586 IEC Update configuration failed from driver IoDrvGPIOSysfs CmpIoMgr I'm running CODESYS Control for Linux ARM64 SL version 4.21.0.0; it's running in rootless mode, as the codesyscontrol user, but said user is in the gpio group and can otherwise normally interact with GPIO, both via gpioset/gpioget and via the sysfs driver in /sys/class/gpio/. The system is a custom 64-bit Raspberry OS based distro, running on a Raspberry Pi CM5 on kernel 6.18.34 with PREEMPT_RT scheduling.
Last updated: 2026-07-21

Post by animesh on SoftPLC (CODESYS Control x86 RTE V3 x64) OPC UA binds only to 127.0.0.1 — Not binding to LAN IP ^{CODESYS Forge talk (Post)}
Hello everyone, I am facing a persistent issue with the OPC UA Server on Advantech Soft PLC with hard realtime for Win64 (V3_5_2010_3) and need help from the community. Device Information Name: Advantech Control x86 RTE V3 x64 Vendor: Advantech Co., Ltd. Categories: PLCs Version: 3.5.20.10 Description: Advantech Soft PLC with hard realtime for Win64 (V3_5_2010_3) Problem Summary The OPC UA Server works perfectly when accessed via: opc.tcp://localhost:4842 opc.tcp://<hostname>:4842</hostname> But it does NOT work when using the LAN IP: opc.tcp://192.168.0.XX:4842 In UAExpert I get: Discovery FindServers on opc.tcp://192.168.0.XX:4842 failed (BadCommunicationError) Port is LISTENING in windows Firewall.. Tried with turning off the firewall completely. System Information Windows 10 x64 Advantech CODESYS RTE Soft-PLC (hard real-time) Network IP: 192.168.0.XX Hostname: WINDOWS-XXXXX Need your Support
Last updated: 2025-11-24

Post by megasilver on Cannot download program to CR1074 – Version mismatch error ^{CODESYS Forge talk (Post)}
Hello, I am having a problem downloading my application to an ifm CR1074 using CODESYS. When I try to download the program to the controller, I get the following errors: [FATAL ERROR] Version mismatch at: 'KEYBOARD_SET_MAPPING' Requested version: 2.0.0.12 Implemented version: 3.4.0.0 [FATAL ERROR] Version mismatch at: 'SYSCFG_SPLASH_SET_SPLASH_SCREEN_VISIBLE' Requested version: 2.0.0.12 Implemented version: 3.4.0.0 [FATAL ERROR] Version mismatch at: 'SYSTEM_IO_BACKLIGHT_SET_CURRENT_BACKLIGHT_BLOCKING' Requested version: 2.0.0.12 Implemented version: 3.4.0.0 [FATAL ERROR] Version mismatch at: 'SYSTEM_IO_BACKLIGHT_SET_CURRENT_BACKLIGHT' Requested version: 2.0.0.12 Implemented version: 3.4.0.0 [FATAL ERROR] Version mismatch at: 'KEYBOARD_RESET_LEDS_BLOCKING' Requested version: 2.0.0.12 Implemented version: 3.4.0.0 [FATAL ERROR] Version mismatch at: 'KEYBOARD_SET_LED_COLOR' Requested version: 2.0.0.12 Implemented version: 3.4.0.0 [FATAL ERROR] Version mismatch at: 'SYSCFG_DEVINFO_GET_KEYBOARDS_INFO' Requested version: 2.0.0.12 Implemented version: 3.4.0.0 The controller is running an OS version that should be compatible with CODESYS 3.5 SP16, and I am using the latest available ifm/ecomatDisplay package for this OS version. Therefore, I do not think this is simply a CODESYS or OS compatibility issue. It looks like the application expects system functions with version 2.0.0.12, while the controller implements version 3.4.0.0. Could this be caused by an incorrect or outdated library, device description, package installation, or a mismatch between the libraries used in the project and the libraries installed on the CR1074? What would be the correct way to identify which component is requesting version 2.0.0.12 and how can I resolve this version mismatch? Thank you for your help.
Last updated: 2026-08-21

Post by matteodigani on Error using function block "Write alias address" ^{CODESYS Forge talk (Post)}
Hi, I've got a problem using the function block "Write alias address" (ETCStack library 4.9.0.0). this is the code: EtherCAT_1(); IF EtherCAT_1.ConfigRead AND enable THEN CASE seq OF 0: exec := FALSE; T.IN := TRUE; T.PT := T#10S; T(); IF T.Q THEN seq := 1; T.IN := FALSE; END_IF ; 1: T.IN := FALSE; T(); //THIS ONE WORK CORRECTLY! WrAliasAdd.xAbort := FALSE; WrAliasAdd.usiCom := DWORD_TO_USINT(EtherCAT_1.InstanceNumber); WrAliasAdd.wSlaveAddress := 1002; WrAliasAdd.xAutoIncAdr := FALSE; WrAliasAdd.uiAliasAddress := 19; WrAliasAdd.udiTimeOut := 3000; IF start THEN exec := TRUE; ELSE IF NOT error THEN start := TRUE; END_IF END_IF IF WrAliasAdd.xDone THEN start := FALSE; done := TRUE; error := FALSE; exec := FALSE; seq := 5; END_IF IF WrAliasAdd.xError THEN start := FALSE; done := FALSE; error := TRUE; exec := FALSE; END_IF ; 5: exec := FALSE; T.IN := TRUE; T.PT := T#1S; T(); IF T.Q THEN seq := 10; END_IF ; 10: T.IN := FALSE; T(); //THIS ONE GIVES ME AN ERROR! WrAliasAdd.xAbort := FALSE; WrAliasAdd.usiCom := DWORD_TO_USINT(EtherCAT_1.InstanceNumber); WrAliasAdd.wSlaveAddress := 1006; WrAliasAdd.xAutoIncAdr := FALSE; WrAliasAdd.uiAliasAddress := 25; WrAliasAdd.udiTimeOut := 1000; IF start THEN exec := TRUE; ELSE IF NOT error THEN start := TRUE; END_IF END_IF IF WrAliasAdd.xDone THEN start := FALSE; done := TRUE; error := FALSE; exec := FALSE; seq := 99; END_IF IF WrAliasAdd.xError THEN start := FALSE; done := FALSE; error := TRUE; exec := FALSE; END_IF ; ELSE ; END_CASE WrAliasAdd(xExecute := exec); END_IF The first one slave ethercat works correctly, but the other one gives me an error. Attached the ethercat configuration of the devices. All the devices are set "Optional". So my idea is to enable only the first one (1002) and the fifth one (1006).
Last updated: 2025-10-01

Post by olehmann03 on PFC200 - WAGO 750-8202 - MODBUS RTU ^{CODESYS Forge talk (Post)}
Hello, I’m working on implementing Modbus RTU communication with a Carel controller (CPCO). I want to use the front RS485 interface through the DB9 connector. The issue is that I can’t get the communication working correctly. Below are the steps I’ve done so far: Connected pins 3 and 8 from the DB9 connector to the +/- RX/TX terminals on the Carel side. In the PLC shell, I set serialmode to RS485. In WBM under Administration > Serial Interface > Assign owner of serial interface, I set the port to unassigned. In the device tree, I created Modbus_COM with the following settings: COM port: 1 Baud rate: 19200 Parity: None Stop bits: 1 Created a Modbus client on this COM interface in RTU mode. Under the status tab, I can see it is in running state. On the client, I created a Modbus server and set the Modbus address of my unit to 1. Defined a few channels as FC03 to read holding registers according to the Carel register map. I checked the communication with the Carel controller using a USB-to-RS485 converter connected to my PC, and communication works correctly there. In the status tab, I can see that the Modbus server is polling, but there is no response from the controller. I also tried multiple times swapping A/B lines on the Carel side, but it did not help. Do you have any suggestions on what else I should check?
Last updated: 2026-05-22

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