How do I call VISA Read multiple times without a timeout?

[Trendor]

Using a termination character will not be an option. Most of the data is binary, and as such, any bit pattern is possible. The first 2 bytes will be ASCII and some number of bytes (determined by the value of the second byte) after that will ASCII. The remaining data is then binary.

I have tried this same vi on a standard PCI GPIB controller and found it to work fine. However, using a GPIB USB B controller seems to fail with multiple reads from an instrument query. I wish I knew what was going on.

Thanks

[LoganS]

I've tried to get similar code to work with both a PCI-GPIB board as well as a GPIB USB-B, and have not had any success with either using VISA. I do have success using the GPIB function calls rather than VISA function calls. Could you attach a SPY capture to your next post of where you application works with the PCI-GPIB interface, and one where it does not work with GPIB USB-B? I'm trying to find out more from R&D, however the R&D technical conference started today, so I am no sure how quickly I'll be able to get a response for you. Anyhow, please attach the files if possible, and we will go from there.

Logan S.