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Independent programming of channels?

Hi Everyone!

I am trying to program the two analog output channels on my DAQ card
independently in such a fashion that when one channel is being changes
the output value of the other continues the way it was (no glitches).

Ideally I would like to be able to do this as a buffered operation (i.e.
only have to feed the card every so often) but if that's not possible
single point updates might work as well. Can anyone give me a brief
description of the VIs I'll need and how what the important parameters are?

I looked at the Advanced Output VIs but it appears that whenever I wish
to change the output data for buffered writes I need to call AO Control
with a 'clear' setting which will clear ALL channels, right?

R
udolf
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Hello Rudolph,

I depends on the HW and the driver. If you have a National Instruments E-Seies board, and a newer DAQ driver. You should not have any problems.

You can choose from many example programs from National Instruments' web site. Here is a link to the Example Program Database (EPD): http://www.ni.com/support/epd/. In the search field I used the search phrase: +"analog output" (with the quotes and plus sign) and got 56 hits. Browse through these and see if any of them do the trick. You can also check the shipping examples with LabVIEW (Help >> Examples >> I/O Interfaces >> DAQ Examples >> Analog Output, in LabVIEW 6.x) and see if anything helps.

If you have additional questions about settings and parameters, I recommend that you post on National Instrumen
t's DAQ site: natinst.public.daq.general.

Have a great day!

Joel Andersen
Applications Engineer
www.ni.com/ask
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Hi Rudolf,

Please Call Edit >> Preference >> Performance & Disk and
check on "Multithread" in your VI. I have not experienced
it with DAQ board yet, but I think what you want to do as
described might be possible. Please try this simple way.
(Or does anybody else know in detail?)

Hope to help you any way.

Thanks,
--Tom (Tomoya ITO)
--Mechanical Engineer


Rudolf Potucek wrote:

> Hi Everyone!
>
> I am trying to program the two analog output channels on my DAQ card
> independently in such a fashion that when one channel is being changes
> the output value of the other continues the way it was (no glitches).
>
> Ideally I would like to be able to do this as a buffered operation (i.e.
> only have to feed the card every so often) but if that's not possible
> single poin
t updates might work as well. Can anyone give me a brief
> description of the VIs I'll need and how what the important parameters are?
>
> I looked at the Advanced Output VIs but it appears that whenever I wish
> to change the output data for buffered writes I need to call AO Control
> with a 'clear' setting which will clear ALL channels, right?
>
> Rudolf
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Hmmm ... I am still working on this. But so far the best way I have found
(good thing I have a scope to see what's *really* coming out of the card)
is to set up both output channels at the start to do continuous writing
(set no, cycles to 0) and then just update the write buffer using the
AOWrite VI. This works (though on a PII/300 I can't do more than about 3
buffer updates/s without glitches) but it's very inconvenient if the two
generators have a different time-base because of buffer-sizes and
step-heights.

I would very much appreciate if anyone could tell me whether it's
possible to do an AOInit call (or whatever) that only affects ONE channel
without touching the other, i.e. leaves the other looping as before.

Rudolf

Tomoya ITO tec.com> wrote:
: Hi Rudolf,

: Please Call Edit >> Preference >> Performance & Disk and
: check on "Multithread" in your VI. I have not experienced
: it with DAQ board yet, but I think what you want to do as
: described might be possible. Please try this simple way.
: (Or does anybody else know in detail?)

: Hope to help you any way.

: Thanks,
: --Tom (Tomoya ITO)
: --Mechanical Engineer
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