CPU load increases when running AI Buffer Read

[sergey 671]

Platform: Win2K, LabView 6.02i, NI-DAQ 6.9.2, PCI 6071E sampling board.

I have an application with a loop containing an AI Buffer Read VI. When I run the application, the Task manager shows that the CPU load steadily increases (like there is a "CPU leak" 🙂 ) until it reaches 100% and then no other module (like application GUI) can work. The profiling shows that the only "heavy" VI is the AI Buffer Read.

One more strange thing: if I open another window (like Windows Explorer) or move some windows on the screen, while running AI Buffer Read, the CPU load jumps by 20-30% and does not decreases afterwards.

Any help will be appreciated.

Sergey.

[Filipe A.]

Hello;

You are seeing that behavior because the AI Buffer Read.vi is a synchronous vi, meaning that the CPU execution pointer will be stuck inside that VI until the datapoints are ready to be read.

The way to overcome the CPU to be overheaded, is to make asynchronous calls. You can get examples of Analog Input acquisition VIs using asynchronous VIs, at Search Examples->I/O Interfaces->Data Acquisition->Analog Input->DAQ Occurrences.

Hope this helps.
Filipe A.
Applications Engineer
National Instruments