Datafeed with or without gaps?

wiggie · Post by **wiggie** » Fri Jan 11, 2008 12:16 pm

I'm not sure how silly this question is, but here it goes:

Is the datafeed from the amplifier being picked up continuously? Is it being picked up in frames? How is it being picked up in relation to the triggers?

This information is importan to me, because, for example, I want to compute averaging x ms before the trigger to y ms after the trigger.

My assumption is, that the data comes in and is being sampled right away with no gaps whatsoever.

Cheers,

Paul

Post by **Coen** » Fri Jan 11, 2008 7:03 pm

The AD-box always sends all samples to the PC, and the PC processes all samples. If for some reason, ActiView cannot keep up with the incoming data-stream, an error is detected and the program stops with a popup message. So, the data in the BDF file always contains ALL samples, you can be 100% sure that there are no gaps.

Best regards, Coen (BioSemi)

wiggie · Post by **wiggie** » Mon Jan 14, 2008 1:09 pm

Super, thanks!

wiggie · Post by **wiggie** » Tue Apr 08, 2008 2:03 pm

One more thing pertaining to the above question:

Looking at the Data coming out of Downsample-5th.vi, is it trickling out sample after sample or does it come in some sort of frames, i.e. chunks of data?

The way I understand it is, for example, when averaging is computed relative to the trigger: the trigger word is found and buffering starts, and by that I mean the samples that are coming in are buffered in a matrix, one sample after the other, until the trigger starts again, and then the word if found again, and that is the second run for buffering which gets averaged with the ones before.

Is that correct?

Post by **Coen** » Fri Apr 11, 2008 1:39 pm

The 2D output arrays from Downtsample-5th.vi have a constant number of rows (number of channels, dependent on the speedmode), and a variable number of columns (successive samples, amount of samples in an array depends on the value of the "display block size", which is constantly adjusted according to the backlog)

The average buffer starts top fill with samples after a trigger is detected. The buffer fills until the "sweep length" is reached (new triggers are ignored until during the sweep).

Best regards, Coen (BioSemi)