LabVIEW

PWM wave data Transferred by DMA FIFOs are not ideal

I am using DMA FIFO for transferring PWM data to Host Target, and the Target host saves the data in c:\DI Log Data. But the saved data is not the original PWM wave data.

Hardware: PXI-7841,PXIe-8133,PXIe-1065

Software: LABVIEW 2013 VERISTAND2013

At the FPGA part, the action of writing into FIFOs works, the Boolean control ‘EnableRecordHighTime’ works at controlling the function writing into the FIFOs or not, so that a host VI (the FPGA bit file used in VeriStand2013) can enable or disable this function. ‘DI41’&’DI42’ control can acquire the PWM wave produced by signal generator, the write FIFO action is executed one time every 1 us.

And I have developed a Custom Device for VeriStand2013, in the custom device I opened the 7841’s reference, then read the 7841’s DMA FIFO, at last saved the FIFO data in RT Target, in which the path is ftp://10.10.3.30/DI Log Data.

But the saved PWM wave data is not ideal. Such as 10K PWM wave, there should have 50 points ‘0’ and 50 points ‘1’, but sometimes the number of the points is not as ideal as expected, like under piecture.