Analog output still active after quitting program

[BLowery]

I'm running the VoltUpdate.prj example to output a constant voltage level on a PXI-6723.  It works as expected, except when I quit the program, the output is still active at the lsat voltage setting.  I tried the code in a project of my own (without all the UI code, just DAQmx) and the same thing is happening.  This is happening despite calls to StopTask() and ClearTask().  I wouldn't think you would need to stop or clear the task prior to closing the program, anyway.  It should stop any measurement/generation when the program ends.  Anyone know what's going on here?

Edit to include some code:

	float64 data = 1.756;
	DAQmxErrChk (DAQmxCreateTask("Voltage Out", &myTask));
	DAQmxErrChk (DAQmxCreateAOVoltageChan(myTask,"Analog/ao0","",-9.0,9.0,DAQmx_Val_Volts,""));
	DAQmxErrChk (DAQmxStartTask(myTask));
	DAQmxErrChk (DAQmxWriteAnalogF64(myTask,1,1,10.0,DAQmx_Val_GroupByChannel,&data,NULL,NULL));
	DAQmxErrChk (DAQmxStopTask(myTask));

 The last line doesn't stop the output and neither does a StopTask then ClearTask call in the "panelCB" EVENT_CLOSE event.

[AnalogKid2DigitalMan · Accepted solution]

Do an AnalogWrite of 0.0V prior to stopping the task.

-AK2DM

[BLowery]

I understand that would work, but is it normal for AO boards (mounted in a PXI chassis) to stay active after closing the program that's controlling them?  That just doesn't make sense to me.  It seems like that fix would be masking a problem.  It also suggests that DAQmxStopTask() and DAQmxClearTask() don't actually do anything except maybe throw away the task handle.

[crossrulz]

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@BLowery wrote:

is it normal for AO boards (mounted in a PXI chassis) to stay active after closing the program that's controlling them?

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Yes it is.  I'm not saying I agree with that, but every analog output (including Arbitrary Waveform Generators) I have used does this.

[BLowery]

Fair enough.  Thanks and fhqwhgads!

[Kevin_Price]

FWIW, I believe the DSA devices revert to 0 output on their own very shortly after the task is stopped.   They work differently from the "regular" D/A converters found on most of the DAQ boards.   I kinda remember observing this when trying to align a DSA output with a non-delayed "regular" AI output.  It was quick-and-dirty code to figure out the clocking delay needed, but I remember how the regular AI started at seemingly "random" voltages based on whatever phase its sine wave happened to be at when I stopped the last trial run.  However, I think I recall that the DSA always started from 0 volts.

-Kevin P