How to generate the zero packet on the Bulk-OUT pipe by NI-VISA?

[yytseng]

I can generate the Bulk-OUT "*IDN?"on this USB RAW Class device by using write. But, how to generate this zero packet(Short packet) on the Bulk-OUT pipe? YY

[Intaris]

Have you tried a normal Bulk out transfer with an empty string as an input?  Seems the logical choice.

Shane

[yytseng]

I tried, but failed.

[Intaris]

Failed?

Error message? Just no functionality? What?

Shane.

[yytseng]

no action, no error. 

[yytseng]

I add write "" to this device.

But, no effect. no error.

[Intaris]

What program did you use to show the USB comms?

There is a single difference between the two transfers in the iomage below.  The T on the left of the "number of Bytes" is different but I don't know what that means.  YOu should check the software you used to find out what this means.

I would post a Bug report that VISA is ignoring zero-byte transfers.

Shane.

[Justin_E]

It'd be helpful to see USB port sniffer captures from successfully sending a zero packet transfer with your program, and from unsuccessfully sending this packet with VISA.

[yytseng]

Successfully

the difference with unsuccessfully is the red part.

even, I try to write an "" nothing happened.

no warning, nothing happened.

[yytseng]

Hi Shane,

  Do you get any response from Ni?

YY