fpga / Windows syncronization

[aerochem]

Two questions about accessing an FPGA app from a Windows Labview App:

A) After several development cycles, I get two "insane object" errors every time the Windows App containing two FPGA references gets compiled. Functionality, however, does not seem to be compromised. Any ideas what this means?

B) The FPGA App uses an IRQ inside a timed loop to let the Windows App know when to retrieve data. However, it seems that the loop timer stops counting while the FPGA board waits for the windows App to acknowledge the interrupt. As a result, the loop is about 3 ms longer than it should be. Is there any way to prevent this, or should the acknowledge interrupt method not be used together with a loop timer?

Thanks in advance.

[Bassett_Hound]

Hi areochem,

To answer the first question the insane message  you get is a known issue with LabVIEW FPGA 8.0 and the block diagram grid alignment option. It will typically happen after placing the VI on the diagram and selected a FPGA VI for the reference that has a bitfile compiled. When enabled, the grid alignment causes the scripted LabVIEW code generated by the FPGA Open VI Reference.vi to throw insane object errors.

Workaround: Turn off the diagram grid alignment option:

Tools » Options » Alignment Grid » Enable diagram grid alignment (uncheck)

For the second question  you should be able to use a Loop Timer in a while loop with a IRQ.  There is an example ( Interrupt Method for synchronization ) shipped out with with the FPGA module that does this exact setup.  Its possible your host may not be acknowledging the IRQ fast enough causing the delay.  Another option you might have is to make use of DMA transfers back to the host.  You might also check out the following link.

What is the Best Method For Synchronizing a LabVIEW FPGA and a Host Interface VI?
http://digital.ni.com/public.nsf/websearch/5930DB001A07F988862570BB001DF031?OpenDocument

Hope this helps,

Steven B.