Instrument Control (GPIB, Serial, VISA, IVI)

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Locking a GPIB instrument

I have situation where three computers share the same ENET-GPIB/100 controller. The applications on the PCs use the NI-VISA .NET VISA Library to access the instruments on the GPIB.

Is it possible for 1 PC to exclusively lock one particular instrument on the, preventing the other 2 from using it without locking the whole ENET-GPIB interface?

The other 2 PCs should still have access to other instruments on the ENET-GPIB.

On one PC, I tried LockResource(..) in a GpibSession with 1 instrument, but that didn't prevent one of the other PCs from using that instrument.


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(This is the same response that I e-mailed you earlier today)

At this time it is not possible to do what you want with our driver and GPIB-ENET/100. The ENET/100 does support interface locking to where one computer can lock out others who are trying to access it via viLock or IBLCK, and VISA supports locking an instrument (resource) and not allowing any other processes on a single computer to access the resource (via viLock), but there is currently no implementation of locking a particular resource so that no other computer can access it.

Depending on what you are trying to do, it may be appropriate to force all the computers to "go through" a single VISA server, which could use viLock to lock other computers out, but each computer would be going
through this "gateway" computer to access the instruments. Another solution is to use multiple GPIB-ENET/100's. A third solution is to use some sort of network semaphores that can be held and released by each computer; the implementation of this solution would probably be up to the operating system if it even exists.

Hope this helps.

Scott B.
Applications Engineer
National Instruments
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