DAQmx Base AI start trigger delay

[LarryO]

   I am new to using DAQmx Base for OSX.  Unfortunately it is far from intuitive and the help files and examples are lacking to say the least.  I must say that I am very disappointed in NI for putting these drivers out in this state.  The Task Configuration Utility does not even work for crying out loud!

I have spent days trying to figure out how to write what would appear to be a very simple program.  I am running OSX 10.4.7, LV 8.0 and using the M series 6281 DAQ Board.

I have a control signal that latches 8 sample and hold circuits.  I would like to use this signal as an external trigger to read the S/H data.  I need to have a delay after the trigger is received prior to reading the data.  After a read is performed the data needs to be analyzed.  Depending on the analysis a Dout may need to be performed then the AIN channels need to be read again.  This loop runs through approximately 100 iterations.  The trigger runs at 15hz.  I would like to use the APFI terminal for the trigger input.

Any help or examples would be very much appreciated.

[stilly32]

HI LarryO,

Specifying a trigger delay is not supported in DAQmx base, but you can easily work around this by acquiring the full data set and parsing out a known number of samples. Based on the number of samples and sample rate, you can calculate a delay. I modified the Acq&Graph Voltage-Int Clk-Dig Start.vi (Dynamic) by setting it to continuous,  adding a while loop and implementing a delay with the Delete from Array.vi. You can change to sample size to fit your needs.

On subsequent reads when you don't want to remove the delay, you can use a case structure to bypass the delete from array. For your digital, I would combine the Write Dig Port (Dynamic) example with this to output based on your analysis. 

Hope this helps, please post back if you have additional questions on how to implement this or if I need to clarify any of my suggestions.

Cheers,

Andrew S

National Instruments

Message Edited by stilly32 on 02-02-2007 11:34 AM

Message Edited by stilly32 on 02-02-2007 11:49 AM