Pretrigger Samples minimum 2 for DAQmx Reference Trigger ?

[Steve_TDiode]

DAQmx Trigger with Reference Analog Edge seems to require a minimum value of 2 for pretrigger samples per channel.

If correct, I do not see that mentioned in LabVIEW version 2017 Help nor DAQmx version 19.0

Steve

[Kevin_Price]

I can't directly confirm the minimum=2 you seem to observe, but have seen several other areas around DAQmx where 2 is the minimum legal value.  So it sounds plausible that might be a real limit even if not clearly documented.

Do you get an error when you ask for 1 or does the task silently coerce you to 2?

-Kevin P

[Steve_TDiode]

Other situations of requiring a minimum value of 2 that I have experienced are related to clock ticks usage, for example with counter output pulse generation.

https://knowledge.ni.com/KnowledgeArticleDetails?id=kA00Z000000P6i5SAC&l=en-US

I wouldn't think that pretrigger samples would require clock tick usage in this manner or at least think the DAQmx driver could accept a value of 0 and then adjust or configure the hardware and possibly the acquired data to accommodate values less than 2.

The task does not coerce to 2.

Steve