FIFO loop

[nos]

I am using an RT FIFO to pass data from three analogue channels in a timed loop, sampling at 32Hz, to a secondary loop for writing to disk, see attached jpg. The vi appears to work correctly except that the first row of data in each data file is repeated, see attached txt file.

Any comments/suggestions on the possible cause of this behaviour would be appreciated.

Best regards,

nos

[Ben]

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@nos wrote:

I am using an RT FIFO to pass data from three analogue channels in a timed loop, sampling at 32Hz, to a secondary loop for writing to disk, see attached jpg. The vi appears to work correctly except that the first row of data in each data file is repeated, see attached txt file.

Any comments/suggestions on the possible cause of this behaviour would be appreciated.

Best regards,

nos

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Check the error cluster from the FIFO before saving it to file.

Ben

[xseadog]

Hi nos,

you jpg does not provide a lot of info. Do you actual need afull time stamp? if not i would just log the loop time so you can see when the loop is updated.

Can not determine if the time loop runs simultanously with the next loop?

Text file does not indicate that the data is a previous copy ( note channel 2 & 3)

how have you initialise your FIFO.

just my 25 øre's worth

xseadog

[nos · Accepted solution]

Thank you both for your responses.

It seems that using a FIFO like I am doing is not the best method of passing data from a sampling loop to writing loop, even though I got the idea from a NI tutorial, see http://zone.ni.com/devzone/cda/tut/p/id/11198. The problem being synchronization between the two loops.

A different approach is to use a queue, which has now been implemented, and seems to give data in the required format.

Best regards,

nos