function generation from Create AO Channel

[walter-donovan]

I'm trying to output a sine wave through a USB-6211 using this Create Channel task. I cannot find a single example of how to use this function after the task is created. All 17 examples provided by NI use the Create AO voltage setting and the must use an external function generator. Do any examples exist on how to use this thing? BTW USB-6211 specs list "AO waveform modes:"

"Non-periodic waveform"

"Periodic waveform regeneration mode from onboard FIFO"

"Periodic waveform regeneration from host buffer including dynamic update"

I have no idea what the preceding means other than it seems to indicate that the board is capable of outputting waveforms, unlike the other queries that came up during my pre-question search.

[Dennis_Knutson]

I don't understand your problem with the"17 examples" that you found. Yes, you would use one of the create waveform functions in order to generate the data that the card will output. It does not have any internal waveforms stored in it.

I'm not sure of the dfference in the regeneration modes but with regen enabled, the card will continuously output a waveform you have provided a single time. Without regen, you have to keep passing the waveform to the DAQmx Write. If you want to change the waveform, with regen disabled, you can update the signal without having to stop/start the task.

[walter-donovan]

I am trying to use the "function generation" setting of the Create analog output channel. It has wires for "type" which I have set to "sine", also wires for amplitude and frequency. Using this, why would you have to use a standalone function generator as used in all the 17 examples? If it asks for a type of wave output along with frequency and amplitude it sort of implies that it is in itself a wave generator or at least sets up a task to generate a sine wave to the analog output. I cannot however, find a subsequent DAQmx task to implement the signal generation.

[Brad_K · Accepted solution]

Hi walter-donovan,

Only two devices support DAQmx Create Channel (AO-FuncGen).vi: NI ELVIS II and NI ELVIS II+, which have a dedicated function generator in hardware. You can't use the AO Function Generation channel type with any other devices. Sorry about the confusion.

Brad

[Dennis_Knutson]

edit - already answered

[tbob]

ooops, I had writen something but now I see the answer is already there.  The help screen for this polymorphic function should specify which cards have the capability to use this function.

[walter-donovan]

Thanks all for the guidance. I am surprised that it let me write this into a vi and did not give error or other warnings. It just silently did not operate. FYI Someone mentioned that there "should be" a list of hdwr in the help file. I went back and reread every word of the help file and couldn't find anything.

[Dennis_Knutson]

You do get an error (-200432) when you run it and the error message says you can't select that output type.

[walter-donovan]

Excuse me? I posted "...and did not give error or other warnings" but you are telling me that I did? I assure you I have no reason to lie to you or anyone else about this condition. Maybe a little more patience and less bitterness is in order here. Frankly I don't understand your seeming contempt and animosity for all those who know less than you about Labview. For clarification (and proof that I am not lying) I have attached the vi.

One more thing. If all that National Instruments offers for programming support is nasty answers and condescending remarks, I may want to call MMC or find another source. I don't really need this kind of garbage in my life or job.

[Brad_K]

Hi walter-donovan,

There is a list of supported DAQmx properties for each device in the LabVIEW Help. Does that sound like what you heard about? It doesn't cover the VIs, though, just the properties.

Edit: the reason you're not seeing any errors is because your VI has automatic error handling turned off (probably because it's based on a DAQmx example VI which also did?) and nothing is wired to the error cluster of DAQmx Clear Task.vi. Try connecting a General Error Handler.vi and see what happens.

Brad