GPIB Read.vi has timeout error even though data is received

[Stella]

Hi,

Hope someone out there can help me. Here's my problem.

I'm using LabVIEW 6.0i to communicate with the HP34401A DMM (addr 22) and the Cornerstone 130 Monochromator (addr 4) in a star config (both devices are connected to the PC) on my PCI-GPIB in a W2K Pro environment.

There is a problem with receiving data from the Cornerstone after the HP finishes communication. It seems that the HP does something to the GPIB that makes the NI-488.2 think that the transmission is not finished so the Read command times out, but all the data is received.

I'd noticed in NI-Spy that when the HP was finished, the interface is in LOK. Something is sending the LLO and I can't seem to find that co
mmand in the HP. I've managed to disable the LOK by unasserting the REN. Since the Cornerstone requires the REM state to operate, the REN is reasserted.

The drivers used for both devices are originals from the companies (Oriel makes the Cornerstone) but the HP uses the VISA and the Cornerstone uses the NI-488.2 commands (send, receive).

Is there any way of getting rid of the timeout errors? They are adding quite a bit of delay to the process (about 7.5 sec addition per scan). Has anyone had similar problems?

Thanks a lot. 🙂

Stella

[Ryan_M]

If you're receiving both the complete data set and a timeout error, I would imagine that you have termination improperly set. You may need to make sure that you are looking for the correct EOS byte or that the EOI line is being asserted. If these terminal conditions are not met, the receive will not finish even though it has read all of the data thus resulting in a timeout.

[Stella]

Thanks Ryan.

This confirms my suspicions about the incorrect termination of the transmission. The correct EOS byte is being sent but I'm not too sure about the EOI line. I'll check that out. Thanks once again.