How to create a virtual gpib instrument

[jens]

Hi there,

I need to create an application which will act like a GPIB instrument.

The purpose is to use existing GPIB Test suite and to have a virtual instrument which reroutes the commands sent to a specific gpib address to a DDE interface. So the DUT Host software running on the same PC can be controlled in the Automated test setup like a GPIB instruemnt.

In pictures :

PC - runs a GPIB test suite & A host interface for the DUT controlled over Serial or USB.

I want to add a 1 address gpib reroute application, which looks like a gpib instrument to the Test Suite, but converts those send and read commands into DDE commands that are pased onto the Host interface.

So all three programs will be running on one and the same PC. Exterally there is the DUT(Serial) and Instruments (GPIB)

Does anybody have some tips. I need some starters on how to go about this. Do I use the NI-488 DLL for this ?

Any examples maybe ? Maybe someone has written GPIB spy routines ?

Thanks

Jens

[ryanm]

NI-Device provides source code, so users can create simulated GPIB devices. The help manual for NI-Device is located at:
http://digital.ni.com/manuals.nsf/websearch/ECACBDF5788A6C3486256E6D005187F7?OpenDocument&node=132100_US.
This should help you determine if NI-Device will fit your needs.

[jens]

Thanks Ryann,

I not sure this is what I need.

I hope to redirect a call to a GBIP instrument, instead of going out onto the bus it is rerouted to a application that monitors or spys what is happening on the GPIB card.

Example.

The application has address 21, while the physical instruments on the bus are 10,11&12.

When a ATE Program tries to communicate with 21, the messages are intercepted to this special application while all other instrument calls to 10,11&12 are communicated via the physial GPIB bus.

The ATE program should not notice if the address 21 is real or a virtual/simulated instrument.

I can't change the ATE, but I can add more instruments to it. I need that instrument to be a software app. running on the same PC.


Jens

[ryanm]

Hi Jens,

Your right. NI-Device will not allow the command to stay within the same computer. Since the driver is setup to interface with the hardware, the best solution would be to create a wrapper for the driver. The wrapper would then control which commands are passed to the GPIB driver and which commands are passed to the DDE interface.

[jens]

hi Ryann

Yip thats sounds like a method, but I have never doen something like this before. Can you point me in any directions to learn more about wrappers ?

The driver you probably mean the 488.2 driver or the Hardware driver ?

Jens

[ryanm]

Hi Jens,

There are several examples of wrappers on the Developer Zone. I have attached a very simple one to help get you started. Please discard the .vi file. This shows the wrapper being called in LabVIEW, which is irrelevant in this case.