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code:dqmh:realtime-workaround

Real-Time Workaround

DQMH 5.0 and later supports both Singleton and Cloneable modules in LabVIEW Real Time. DQMH 5.0 modifies how the DQMH modules are launched. DQMH now uses Start Asynchronous call instead of the Run VI Server Method. The workaround described below is no longer needed.

This is a workaround to the problem described here, concerning DQMH up to version 4.2.1.

A bug in LabVIEW breaks the Control Value.Set VI server function for references to non-reentrant VIs when executed on Linux RT with Embedded UI enabled in the run-time engine.

As this bug does not apply to VI references to reentrant VIs (Clonable DQMH modules do actually work), the solution seems to be to also load Singleton DQMH modules reentrant (Use “Application Control → Load VI Reference” with options 0x08).

A template for the VI shown in the screenshots below can be found in our hse-dqmh libraries in hse-dqmh.lvlib:DQMH Load Main VI Reference.vi. Because of scope restrictions, the VI needs to be duplicated and made part of the corresponding module's .lvlib.

code/dqmh/realtime-workaround.txt · Last modified: 2020/04/06 09:37 by joerg.hampel