Hello:
Thank you very much for responding.
As you have guessed, I use LabView RT with a PC target.
I was actually executing the VI from the “main”. I do not know why, but I have tried again the DAQmx Create Timing Source/ Frequency with the new timebase (you can see in the attached doc called CTS) and the previous errors do not appear anymore.
Anyway, the reason why I want to change the timebase is to try to resolve one problem: I’m developing a real time application that acquires and processes two signals. The processing is performed to provide a diagnostic. The main specification of my application is that the maximum time interval admitted between one sample in “the real world” and the diagnostic emission is 15 ms (this is the real deadline).
The signals are acquired by the NI-6115 at 5 MSamples per second and channel. This DAQ only supports buffered acquisition.
In order to achieve the real deadline what I do is to limit the input buffer by the VI Configure Input Buffer to 80000 samples per channel, which is equivalent to 15 ms (in other words, the real deadline).
The acquisition and processing is performed in a Timed Loop with a period of 10 ms. The key thing is that the complete application is able to execute for various minutes (10 minutes, even more time) without overwriting error (error -200279). Independently of the execution time (2 seconds, 2 minutes, 5 minutes, 10 minutes…), the available samples per channel in the last iteration of execution range from 4000 to 5000 samples. Since the timed loop period (10 ms) plus available samples per channel (the worst case is 5000 samples, that is 1 ms of samples) yields 11 ms (10ms+1ms=11ms) I understand that the deadline is fulfilled because 11ms<15ms.
However, when I quantify the number of Finished Lates, it varies depending on the clock used in the timed loop. Since the acquisition uses the 20MHz timebase available in the Ni-6115, I wanted to check if the Finished lates are related to the bad synchronization of the clocks or something like that. But, after using the 20 MHz timebase in the timed loop (In DAQmx Create Timing Source/ Frequency: Frequency=100 Hz; and the period of the timed loop=1tick), all the iterations still yield Finished Lates. I have registered the “expected end” and “actual and” of only 200 iterations of the timed loop and, due to a delay in the second iteration, all the iterations appear delayed 1 tick (10 ms). I have tried to process nothing (only read the samples) in the first and the second iteration, but the delay still appears, this time in iteration 4 (I have attached a Vi with the arrays corresponding to Expected end, actual end…).
Maybe I’m misunderstanding everything and all this is stupid thinking.
Thank you very much for your help.
