UC20-M4000 Redundancy – Application is not automatically synchronized and redundancy breaks after online change
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UC20-M4000 Redundancy – Application is not automatically synchronized and redundancy breaks after online change
Last updated: 2026-03-16
Post by mrkm-dic on UC20-M4000 Redundancy – Application is not automatically synchronized and redundancy breaks after online change
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Hello, I am currently testing redundancy using two UC20-M4000 controllers with CODESYS Control SL. The basic redundancy functionality (Active/Passive switching and failover) works, but I am experiencing problems when updating the application. Environment Controller: Weidmüller UC20-M4000 OS: u-OS Runtime: CODESYS Control SL 4.12.1.0-1 Redundancy link: dedicated Ethernet connection between the two controllers Time synchronization: NTP configured, time difference between controllers is about 1–2 seconds Current behavior Application synchronization When I download a modified application to PLC1 (Active controller), the application is not automatically copied to PLC2 (Passive controller). However, when I perform a path swap, the application download to PLC2 starts automatically. My expectation was that the Passive controller would automatically receive the updated application after downloading to the Active controller. Online change When performing an online change, redundancy is lost and the controllers switch to Standalone mode. Typical log messages include: RedundancySynchronize called Redundancy failover itself works correctly. The application boot project exists on both controllers (Application.app and Application.crc). Network interfaces are up and correctly configured. Question Is this behavior expected when updating the application in a redundant UC20-M4000 setup? Should the Passive PLC automatically receive the updated application, or is manual synchronization required? Any advice or recommended configuration for stable redundancy during online change and application download would be greatly appreciated. Thank you.
Last updated: 2026-03-16
Post by bdschnapp on OPC-UA ApplicationUri / ProductUri
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Were you able to figure out if it is possible to change the Application/Product URI of your server? I am having the same problem.
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Post by bdschnapp on OPC-UA ApplicationUri / ProductUri
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From Codesys support: The format of the URN is always the same. It's always urn:<vendor>:<product>:OPCUA:Server. What I think you can influence the vendor and product (DeviceName) through settings in the runtime cfg file:</product></vendor> [SysTarget] VendorNameUnicode="T\00E\00S\00T\00" DeviceNameUnicode="t\00e\00s\00t\00" Note that these are 16-bit strings, thus the ASCII padded with nulls
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OPC-UA ApplicationUri / ProductUri
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Transparent wireless serial bridge for Modbus RTU – experience with LoRa/WiFi RS-485 link to CODESYS runtime
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Transparent wireless serial bridge for Modbus RTU – experience with LoRa/WiFi RS-485 link to CODESYS runtime
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Post by dafalin-codesys on Transparent wireless serial bridge for Modbus RTU – experience with LoRa/WiFi RS-485 link to CODESYS runtime
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Post by tvm on Discussion for Home page
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@lucawu @risele for some reason I don't get notifications of new posts on this thread so I just noticed them now. We switched from Schneider to Beckhoff a few years ago, and Beckhoff has their own JSON handling library. I haven't had time to do any development on PRO_JSON since last year, and it's unlikely that I will any time soon. If you or anyone else is interested in being added as an admin to this project let me know. It was an interesting project for me, and I learned a lot. I know there's people all over the world using it in different applications, but there are also a lot more options than there were when I first developed this. Maybe it's time to pass the torch to someone who's actively using it.
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