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Fail to find AP2700 in VISA resource through APIB

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Hello All,


Thank you for your taking look first.


I am trying to build a AP2700 automation project through APIB (Audio Precision's own GPIB protocol). I do have APIB USB adapter to get USB-A plug into my laptop. The driver is installed well since I could use AP2700 software to connect my SYS-2722 and query data in picture 1. However, I can not find this instrument in VISA resource which is really wired. Could somebody help me to find out what I did wrong? Thank you.







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Message 1 of 3
Accepted by topic author PeterjwWu

It's not weird. The APIB device driver implements its own proprietary USB protocol. The Audio Precision application of course knows how to talk to this proprietary driver but that is the only software who does.


As such you could only access it through VISA USB Raw but you do not want to do that.

1) in order to do that you would need to deinstall the Audio Precision driver and then can't use the APWin software anymore to talk to the device.

2) You would need the low level USB protocol description from Audio Precision and implement the entire protocol using VISA USB Raw methods. And if the device uses some special USB features such as isochronous transfers (no idea why a measurement device would need that) or interrupt transfers you a can't do that with VISA USB Raw. Well interrupt transfer go in some limited way but isochronous transfer definitely not.


There are several problems with this last point: 

1) It is unlikely that Audio Precision will give you the protocol description. Without it you could just try to talk to a Klingon instead and have as much success. Without a good protocol description you can NOT implement an USB protocol!


2) Even if you could get a hopefully decent protocol description, implementing an USB Raw protocol on your own is a very work intense and error prone task. Unless you like to tinker with bits and bytes on the lowest level, it's simply not something you will ever get to work in a decent way.


There are about 3 possible options:


1) Asking Audio Precision to provide you with a so called VISA passport (that is a VISA software plugin driver) for their APIB interface hardware,

2) Asking Audio Precision to provide you with a shared library (DLL) with according LabVIEW VIs to access it

3) Get a GPIB interface hardware and connect your AP device over GPIB to your computer


And yes the problem lies entirely with Audio Precision. They choose to use a proprietary communication bus with a proprietary software driver and a proprietary software application for their hardware.

Rolf Kalbermatter
My Blog
Message 2 of 3

Hello Rolf,


Thank you for your timely reply which is really helpful to me. You are right. LabVIEW can't control AP2700 through APIB due to AP's private protocol. I got some information from AP website that if we only have APIB, then the only way to connect is through ActiveX. Hope this topic could help someone who have the same problem in the future.


Thank you again!


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