Mac VISA/USB : STB timeout bug?

[pkeller]

Hi,

I appear to have run into a bug in the Mac USB implementation of the VISA STB (Read Status Byte) function. If I set a long session timeout, the VISA STB function waits that long to return, even if the instrument returns the status quasi-instantaneously. With the default timeout value, all is well.

This is not the behavior under Windows. 

As a work-around, I restore the default timeout before reading the STB.

-- Philip 

[Marco_Brauner]

Hi,

sorry for the late reply! 

Can u post your code please?

Which VISA-Version are you using?

regards

Marco Brauner NIG

[pkeller]

Dear Hans,

Thanks for the reply. Just so you know: in the meantime, I have also posted a support request by e-mail (Reference#7209437), which went to NI Switzerland (Laurent Pollara-Brevart) who has forwarded the question to the US.

I am using LabVIEW 8.5.1. I am attaching our low-level VI that writes a command and reads the response and any errors, plus its sub-VIs. If you use the default command (*IDN?), it should work for any IEEE 488.2 compatible instrument. In this version, I change the timeout value on the VISA session just before calling the VISA STB function; by default, I have it at 10 ms. You can play with this value, and observe that the VISA STB takes exactly that amount of time to return.

Thanks again,

-- Philip