error 42 DAQmx Base DMA overflow

[Tanzella]

A quick update.  The AO and AI processes are reproducibly out of phase while running.  Now, I need to figure out how to get both processes to start within 1ms of each other.  Now they start from 1.6 to 1.85s apart with the error lines on the starts connencted together.

[Paul_C. · Accepted solution]

Hey Francis,

How are you able to verify that they are out of phase?  In addition, I've compiled some code to demonstrate how it should work.  Basically, you need to ensure that your analog output task is starting from the start trigger of your analog input task.  Please take a look at the code.  Again this was done with the device "Dev1" so you may need to change a few things on the block diagram such to reflect your device name.

Regards,

Paul C. 

[Tanzella]

Thanks Paul,

    I'll test the vi right away.  I determine the phase by outputting a sequence of 225 ramps from 0 to 4v in 4s and plot the first point in the AI data.  The first point changes from 1.6 to 1.85v.  However on each subsequent scan the first point is always the same valtage as in the first scan.  I'm using the triggers to make sure the AO and AI are on the same 1000Hz signal so that works fine.  By using a timing delay between Starts I can get the offset to below 250ms, which I might live with.

     You said that I want to trigger the AO from the AI, I'm doing the opposite right now.  I got an error when I tried to program the CTR0 to trigger the PFI0 on the same board.  Is this correct?  I'll let you know how your suggestion works out.

Francis 

[Tanzella]

Hi Paul,

    An update.   The 6733 AO card can not be triggerred using the mxBase Trigger vi, and does not automatically generate pulses on the CTR0 line when running.   So I generate pulses on the CTR0 line (at the same rate as the AO) and used them to trigger the 6143.  Attached is the modified vi.  Again, the AO and AI waves were slightly out of phase but remained dead-stable during the run.  For now, I'll live with the small initial offset since it's always the same from scan to scan.

Francis