Delay after reading ibrsp(), if two process uses the gpib-32.dll

[Sathish]

Hi all,

I have a delay problem after ibrsp(), let me explain my application first.

I am usin AT-GPIB/TNT(PNP) NI's GPIB card. It is connected to 3 R&s instruments (signal generators) and a prober (TSK prober). In my application, there is a probercontroller which will keep on polling the SRQ line for data from prober which uses ibrsp() call in a while loop in a thread. When the first ready command (0x67) came it will start the sequence and then give the control to Test application which will start doing testing. The test application also uses the GPIB dll to communicate with R&S instruments.

After receving the first command from prober there is a delay of 1.5 secs in sending the next sequence com
mand to prober.

My observations:
I suspected the probercontroller, so wrote a small testprogram to simulate the functionality of probercontroller dll. It is very fast. I run another application which uses gpib-32.dll to communicate with R&S instruments and run my small sample testprogram, it behaves slow (takes 1.5 secs or more to send the response after getting command from prober). The sample application also uses serial polling for SRQ status and calls ibrsp(). I found the slow is happening when two process access the gpib-32.dll. I doubt whether the delay is due to context switching or something else.

Kindly, give me your valuable suggestions to solve this delay.

Sathish

[Randy Solomonson]

There may be instrument drivers available for these instruments at ni.com/idnet. If not, the NI-Spy utility is very helpful in identifying such problems. The thread may be starving the gpib-32.dll by locking it with ibrsps. Note that the gpib-32.dll is thread-safe in that only one call can happen at a time. The ibnotify or ibInstallCallback can help by installing an SRQ interrupt handler. See gpib32.hlp for more details. Another alternative is to make the thread sleep for a short time between polls.

Randy Solomonson
Application Engineer
National Instruments