I am using an M series 6281 DAQ board and would like to read 8 AIN channels. I would like to read 1000 samples/channel. I have a 15hz analog trigger at APFI0 to trigger the data acquisition. Once the trigger is received the data is read and analyzed and a DOUT is performed then I wait for the next trigger. This sequence is performed about 200 times.
I am running OSX which unfortunately means I have to use Daqmx Base.
The problem I am having, as described in many other posts, is that in order to detect the analog trigger you must start and stop the task for each iteration. Starting and stopping the task slows the acquisition time and triggers are missed.
The fix as I have read is to use a counter which is retriggerable as the sample clock. An example is provided for Daqmx (Multi-Function-Ctr Retrigg Pulse Train Generation for AI Sample Clock.vi) but is not available in Daqmx Base.
Looking into the code it appears that you cannot use an analog trigger to trigger the counter in Daqmx Base. Is there a way to get around this?
I do not have an available AIN channel to read the trigger from and do not want to perform continuous acquisition.
Knowing how slow the Start and Stop Task functions are, has NI attempted to trim the overhead in these functions so that only the functions needed to rearm the trigger etc. are performed, eliminating the need to Start and Stop the task within the loop? Perhaps it could be called Rearm Trigger. hummm… Has anyone out there done this?
My problem on the forefront appears to be a very basic DAQ process (and it is with other vendor’s boards and software). I am attempting to replace a windows based PC using a Data Translation board and LabView drivers with a Mac and an NI board. My thought was that since we use LabView exclusively that an NI DAQ board was the obvious chose. Because of Daqmx Base it is painfully apparent that I made a mistake.
I have spent many many hours trying to hack through Daqmx Base. The overhead in these vi’s is absurd (try searching for a text string through a couple thousand loaded vi’s of which 100 are password protected, it takes about 5 minuets and 100 clicks of the mouse!) the documentation is poor (the RLP’s are a black box) and it limits the functionality of the DAQ board.
With that said, I love programming in LabView and would hope that NI would bring Daqmx Base for the Mac up to speed soon!
