How do I capture data (in CVI) from GPIB when I am not the controller (data being read by controller)?

[Greg01]

I need to capture and act on position data and the serial poll status being read by a controller (other than my machine) in a CVI program. Kind of like NI-Spy. Is this possible?

[craigherdman]

Greg01,

This sounds like a job for our PCI-GPIB+ boards that have extra hardware to allow GPIB bus monitoring. The GPIB Analyzer software (that comes with the board)works in tandem with the hardware components of the PCI-GPIB+ board allowing one to monitor bus, data, and handshaking lines. Here is the link to the PCI-GPIB+ product page:

PCI-GPIB+ Product Page

...and here is information on the GPIB Analyzer:

GPIB Analyzer Information

NI-SPY cannot monitor driver level calls on multiple machines. Hope this helps!

Craig H.
NI Applications Engineering

[Greg01]

I don't think that answers my question. I have PCI-GPIB+, but I need to react to the information on the bus in my CVi program. What I would like to do is monitor the serial poll of a particular piece of equipment and react to a change in a particular bit in the status byte.

[craigherdman]

Greg01,

*STB? will return the value of the Status Byte. Of course the bit values are read-only at this point. Feel free to post additional questions if I failed to understand the question. Good luck!

Craig H.
NI Applications Engineering

[Greg01]

No, it does not help at all! I don't need a sales pitch. I would like to know if my program (written in the LabWindows IDE) can monitor the lines (and react to what it finds). I have the PCI-GPIB+ card. My question is "how do I monitor the lines using LabWindows CVI?

[craigherdman]

Greg01,

If I understand correctly the desired functionality is to mimick the behavior of the GPIB Analyzer in software. Is this correct? If this is what is desired then there really isn't a proven solution. There have been other requests for similar functionality (mimick the Analyzer in software to allow an in-between to read bus data) but nothing has been implemented at this point.

At this time one can read the results between two devices passively on the PCI-GPIB+ board using the Analyzer software. There isn't a way at this time to do this in CVI.

If your controller is receiving the status byte then you could possibly modify the controller code to share the data with whatever other program that you need.

I would also recommend making a
product suggestion here (tracked in our R&D database):

http://digital.ni.com/applications/psc.nsf/default?OpenForm&temp1=&node=

Again, let me know if I've missed anything.

Craig Herdman
NI Applications Engineering

[Greg01]

What I need to do is listen to a display unit which is providing position information of an antenna pedestal to another controlling computer as it moves the position. The display unit has a record increment bit in the serial poll byte. When that bit goes high, I need to get the position (as it is being reported to the controlling computer). Can I do that?

[craigherdman]

Greg01,

So is the code running on the controlling computer or are you attempting to have a third computer read the serial poll byte? If your application is running on the controlling computer then we can perform a ReadStatusByte command or an ibrsp command (to return the serial poll byte allowing us to act on certain bits). If a third entity is involved to actually handle the monitoring (a third computer that 'looks' at the serial poll byte and triggers a reaction in code) then we won't be able to accomplish this.

Craig H.
NI Applications Engineering