PVAccess Library for LabVIEW Development Insights
Explore the collaboration meeting between Ross Titmarsh and EPICS in April 2025, focusing on the creation of a PVAccess Library for LabVIEW. Discover the motivation, challenges, and development progress in integrating LabVIEW with PVXS to enhance data acquisition systems.
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Presentation Transcript
PVAccess for LabVIEW Ross Titmarsh EPICS Collaboration Meeting April 2025
Background Ross Titmarsh Software Engineer in the ISIS Accelerator Diagnostics Software section We design, build and maintain DAQ systems for beam diagnostics Almost all of our systems use National Instruments hardware -PXI or cRIO
Background Each DAQ system is linked to a centrally hosted Vista database DAQ system uses LabVIEW Webservices to provide an HTTP endpoint This returns an XML document mapping channel names to values Adapted this with a P4P IOC to cut Vista out
Motivation It cannot see any PVs not hosted on the DAQ No alarms Limited metadata Dated API, bad developer experience Extra complexity with IOC for each DAQ system
The solution? - A PVAccess Library for LabVIEW Initial idea Reality Build PVXS into a DLL LabVIEW doesn t understand C++ DLLs Call it from LabVIEW LabVIEW doesn t understand C++ datatypes Success LabVIEW requires some special memory management functions
The solution? - A PVAccess Library for LabVIEW Write a LabVIEW compatible C interface for PVXS Build that into a DLL Create a LabVIEW API around these functions
Development so far - C/C++ lv_interop.hpp Definitions and functions for interfacing with LabVIEW memory exceptions.hpp Translating C++ exceptions into LabVIEW error codes utils.hpp Functions for transferring data between LabVIEW and PVXS server.cpp C interface for PVXS server client.cpp C interface for PVXS client value.cpp C interface for PVXS value manipulation
Development so far - Server Hosting of NTScalar and NTScalarArray PVs Posting Fetching Different types handed with malleable VIs
Create a server Stop and close the server Add an NTScalar (float64) PV initialised as 0 Start the server Fetch the latest value Post it Increment it
Development so far - Client Getting NTScalar and NTScalarArray PVs Putting NTScalar and NTScalarArray PVs Different types handed with malleable VIs
Development summary All development so far has been targeting Windows Current at the alpha stage Duncan Abbott is working on targeting NI Linux Real-Time Release an alpha VIPM package soon
Future Support optional metadata: units, timestamp, alarm, limits, etc Support NTEnum, other normative types Develop a test suite LabVIEW event based put handling and monitoring Read only PVs Improve the build system
Check it out https://github.com/ISISNeutronMuon/pvaccess-labview
