Checking Status of Analog Output operation on DAQ6731

Question

I am using the DAQ6731 board to output an analog signal. My program reads in a file which contains pre-calculated data values, and uses the following series of NIDAQ functions to do the outputting:
WFM_Group_Setup
WFM_Load
WFM_Rate
WFM_ClockRate
WFM_Group_Control/START
This is followed by a do-while loop which is supposed to check whether the output is done yet. I am trying to use WFM_Check to determine when the data is finished. As an added function, I want to let the user spontaneously stop the operation at any time by pressing any key. To do this, I am using an if statement which checks whether getch()==NULL, and if NOT, then I break out of the do-while loop. I could also put the getch()==NULL condi
tion inside the while argument and have it check there.
The loop is followed by WFM_Group_Control/CLEAR.
My problem is as follows. It seems like the WFM_Check function isn't doing anything. The getch()==NULL condition works (if I press a key at any time, the DAQ will stop waveform generation). However, if I do not press any keys, and the waveform generation finishes on its own, the program hangs there. It won't proceed until I press a key. I would like the program to stop if EITHER I press a key OR the waveform generation finished on its own. The key is, the wfmStopped parameter seems to remain 0 no matter what happens. In the Traditional NI-DAQ Function Reference Help, Version 7.1, it says for WFM_Check that "If the generation is continuous (including pulsed waveform generation), the parameters wfmStopped and itersDone are always 0". So it seems like WFM_Check is not doing anything when I call it.
Is there any way (like other NI-DAQ functions) that I can use which wil
l act as a flag and tell me when my operation is complete?

Answer 1

Hello,
It seems to me that our goal should be to output the data, and check for a key press. I have attached a sample program that will output data in small chunks. You should be able to modify this program to output your data from the disk. You can also add key press checking code inside of the while loop. Whenever you are done writing data, or get a key press, just exit the while loop.
Let us know if you have any follow questions on how to use this program.
Best regards,
Justin T.
National Instruments
Attachments:
WFMdoubleBuf.C ‏9 KB