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Execution times using USB-DIO96H




As you know we use the USB-DIO96H with the latest Instacal 6.73 libraries. The application was developed using C++ and the related libraries. We found that the application is fairly slow in its execution.

These are the values we got after profiling as a 32bit application running on Win11.

cbDOut using cbw32.dll        
Number of times called: 78,193    
Execution time per call: 2.99 ms
Total time elapsed for the full run of the app: 3.896617833 mins

cbDIn  using cbw32.dll
Number of times called: 24,829    
Execution time per call: 3.01ms
Total time elapsed for the full run of the app: 1.245588167 mins

The total duration for running the app from start to finish is short of 6 mins and the above two calls consume 5.14 minutes

Is this the expected speed of operation of the I/O access for this DAQ?

Is there something we are missing by which we can speed this up?

A quick reply with suitable suggestions would be great.


Anand C J

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The USB-DIO96H is not a speedy device, and my test indicates that a single 8-bit port can be updated about 2600 times per second.  I used a 32-bit C program with a while loop to write ones & zeros continuously for my test. To determine the update rate, I measured the output square wave which was about 1300 Hz (2600 updates).

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Question 1: Do the National Instrument PCI/e DAQ's use the same libraries as the Instacal?

Question 2: We profiled the f/w running the PCI and the UDB DAQ units. We seem to get PCI transactions under 10uS while the USB accesses seem to be around 2.9 ms? Could your libraries be using wait times on USB calls that account for such dergadation?

- Anand C J

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