GPIB error 28 with vi but no error in MAX communication

[jcrooke]

I am communicating to a GPIB device through the NI USB-GPIB-HS unit. I get an error 28 trying to communicate with my vi. I read that the error 28 is due to the USB power not being sufficient, but my device communicates fine through the MAX GPIB communication interface and through the interactive control, which means that the device and the interface are actually working fine.

What else could be causing my VI to fail?

By the way, resetting the host PC re-established communication through the VI.

Communication was always possible through MAX and through the interactive control.

Would this problem be fixed by directly calling the 488.2 library functions?

[Jonathan_S1]

This could also be happening if your interface is losing power at any time.  This could happen if either the system or computer enters a standby state.  It seems to me like the power to the device may be getting interupted at some point.  Does any of this seem as though it may be applicable?

Jon S

[jcrooke]

It is possible that the computer or the device (SRS SR780 Dynamic Signal Analyzer) has gone to sleep and then awakened again. But why, then, would the GPIB functions in the VI fail after a sleep event even though I never lose communication through the NI MAX communication tool?

[JÞB]

jc-

This sounds like Windows is shutting down the USB power In fact the default setting for USB Hub power management is to allow Windows to shut off the port (Its a "Green thing"). 

To disable this fine feature go to the control panel>Hardware manager,  Expand the USB controllers select and right-click each USB Root Hub, Chose Properties.   From the Property pop-up choose the Power Management Tab and UNCHECK the box shown below