02-18-2008 02:46 PM
02-19-2008 06:21 PM
02-20-2008 08:54 AM
Hi Kristen,
I have tried two main approaches, neither worked.
1. Modify the Cont Gen Voltage Wfm-Int Clk.vi found in the DAQmx example vis by copying everything upto the start task vi, to which I then added an indicator in the task out parameter. I then put the remaining "is task done" and clear task blocks in a separate vi. The idea was to be able to generate the voltage, get the task name and then pass the task name back to the clear task vi so that it can be stopped. I dont have to necessarily do this in Teststand, as I can simply use the variable for task name passed to me. I know we use this method for other instrumentation control. Anyway, the problem, I found with this was that the wave was only generated once! I discovered this by probing with a scope probe on the DAQ break out box for the analog out line. Although the display on the vi shows the waveform it generated, it just seems to do it once. Unfortunately, to keep it going, I would have to put it in some kind of a while loop, which would then not allow me to resume control after starting this wave generation. Oh yes, I also modified this vi in various ways, such as using stop task and clear task instead of using the is task done.
2. Create task on MAX. I was able to test it successfully, since my options at that point were to start and stop. While its started, the wave generation is constant, I saw it on the probe. However, the same issue when I call it using a created vi that starts the task, gets the task name as a variable, which I then pass onto another vi to clear the task. It only generates once, which is easier to see if you highlight the execution.
Also, looking at the help files and associated documentation, the continuous generation does require the daq assistant vi or other express vis to be run inside a loop. So that wasnt an option either.
So, I have tried what you recommended, but perhaps I was working off a less applicable example vi. Maybe you can advise me on which vi was your starting point.
02-21-2008 11:50 AM
02-21-2008 12:10 PM
Hi Kristen,
Thank you for looking into this. I tried with the examples you and Matt sent and actually I have been in touch with him. I was not able to generate the same behaviour as you did. When the control returns from start.vi, I find that the output stops. I also tried it on the DAQ breakout box SCB-68 by connecting the analog output to the analog input and watching on the DAQmx test panel.
So I believe, he is now working on trying it with hardware specific to us, the 6289 pxi.
Thanks for your response.