simulateneous digital and analog triggering

[clintons]

Hi,

I have an experiment which is very similar to this posting:

http://forums.ni.com/t5/LabVIEW/How-do-I-reset-the-Arm-Trigger-with-DAQmx/m-p/2006639/highlight/fals...

Like in the posting, I need to trigger off of the logical AND of a low frequency (3 Hz) and a high frequency signal (100 Hz).  However, my experiment differs in that my low frequency signal is an analog input (AI0) and I need the experiment to trigger off of every edge change of the high frequency signal while the analog input is high.  To do this, I have created an AI trigger which starts a counter whose high and low state are similar to that of my analog input signal.  I then export the counter output event to a port (PFI8) and pass that signal and the other high frequency signal through an AND gate as in the linked posting above. 

Up to this point, everything works.  I have included a VI which does just this part.

However, I then connect the output of that AND gate to a PFI0 port and use that as a digital trigger to read an AI0,1 channel.  When I perform this final step, my entire system stops working, but yields no errors.  To troubleshoot, I have measured that the counter output to the PFI8 port has stopped functioning and the PFI8 port remains in the low state.  For some reason when I add the additional AI channel (either AI0 or AI1, it doesn't matter) with digital trigger (PFI0), everything grinds to a halt.  I have also included the VI for this case. 

Any ideas??

Thanks much!

[JaredRo]

Hi clintons,

Are you using an external AND gate like the other thread described?  Have you verified that the output of this external AND gate is giving you correct values?  What model hardware are you working with?  If you provide me this information I may be able to offer you some advice for your application.

[clintons · Accepted solution]

Hi Jared,

I am indeed using an external AND gate as described in the thread.   Further searching actually led me to find out that "You can't have two analog input tasks running at the same time" from this thread:

http://forums.ni.com/t5/Multifunction-DAQ/Multiple-analog-inputs-by-multiple-digital-triggers/td-p/1...

As a result I had to build a circuit to convert my analog signal to a TTL signal (for triggering).  I then AND'ed the two signals in the same was as described in the thread already mentioned earlier.  

-Clinton