Preprocessing Steps Exceeded error appeared

[Wolley]

Hello, I have been working on a VI and I recently got it functional. I had it functional and I had been using it for an hour or so to trouble-shoot some hardware - not making ANY changes to the VI.

One of the times I started it though, it didn't work. It first returns error:

   Code: -1074118647

   niScope multi Read Cluster.vi:1<ERR? A previous acquisition is still in progress. If you are attempting to change an attribute, note you can only fetch attributes while an acquisition is still in progress.

After showing this briefly, it returns another error:

   Code: -1074126846

   niScope Add Waveform Processing.vi:1<ERR> Unable to perform desired measurement operation. The maximum number of preprocessing steps (100) has been exceeded.

Again, this VI worked fine fo a considerable while, and these errors appeared out of nowhere. Any suggestions on how to remedy them would be very much appreciated.
Thank you,

Wolley

[nathand]

Did the error occur only once, or now it happens every time, or you see it only occasionally?

I don't know if this will fix the problem, but I recommend moving the scope initialization and close outside the main for loop; there is no reason to close and reopen the device on every loop cycle. The trigger setup can go outside the loop too.

From a LabVIEW style point of view, the sequence structure is unnecessary, except for the final frame with the wait in it. Otherwise you can use error wires to determine order of execution.

Do you want the Start and Reset for loops to run at some random time, possibly in parallel? There's nothing setting the order in which they execute relative to each other and the main loop, so they could run at any time.

[Wolley]

Hi,

I think it was just an error with the CPLD that this program depends on - after removing power to the CPLD and then repowering it, and playing with it in the soft panel to ensure that it works, it ran in the VI fine.

The reason the open and close are inside the loop was that through experimenting I found that the integrals that are being calculated are only cleared when the scope is closed down for each iteration - as each loop is a measurement for a different physical line, it's necessary that each line has its own integral.

Also, I would like the Start and Reset loops to run at the same time before the main loop, yes - though the two needn't be exactly the same time, it would be nice. Suggestions for that? More sequence structures? Heh.

Thanks,

Wolley

[Wolley]

Actually, best-case would be to have the two start at the same time in the beginning, but to also have the Reset iterate once more after everything is done - a redundancy, but not one without value. I couldn't set up two outputs to the same channel though, so I wasn't sure how I would do that.

Thanks,

Wolley

[nathand]

I can't figure out what you're doing with the Start and Reset signals. Why bother with Simulate Signal when all you want is to turn on, then off (or vice versa) a digital output? Just build a constant boolean array with two elements, one true and one false. You might want some timing there, too, if you need some delay between the two states. If you want the reset and start for loops to run in parallel, put the writes in the same for loop instead of two separate loops.

You can write to the same output from multiple locations; just keep the task open, and wire it through the for loop. You need the wire to go through the for loop to get the correct execution order. Write to the Reset channel, wire that to the acquisition for loop (which will prevent the acquisition from running until the reset completes), then wire it out of the for loop to another write, which won't execute until the acquisition loop completes.

[Wolley]

It's my first time playing with DAQ digital i/o, don't judge. Haha. 

Thanks for your tips!

Wolley