Subject: 2 VIs access 1 DAQ card?
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Hi Jim,
Due to thread confusion, not sure if someone already pointed this out.
You probably need to make one vi, maybe we could call it a servlet,
to read all the data from the AI, and separate it into two queues or
buffer vi's that are then read by the client vi's. Can't be much help
with wizards or assistants, since I've never used them. Suspect they
only work for uncomplicated jobs. Also just noticed you asked the
question a month ago. Oh well, did the typing already, hope it helps.
--
Bill Gilbert, EM Tech
Univ of MN Physics
Phone 612 624 4870
Fax 612 624 457


On Fri, Nov 16, 2012 at 3:58 PM, Neville Dholoo <ndholoo at yahoo.com> wrote:
> Jim,
>
> DAQ Express VI's, or DAQ Assistant or Wizard etc. all use underlying calls to DAQmx VI's. As Nathan mentioned, you can't have two tasks accessing the same hardware resource (i.e. the analog channels). So it won't work, whatever method you choose to use.
>
> The reason for this is there is only one timing engine per channel group. I am assuming you are using hardware timing?
>
> Sample them all at the higher rate, and then downsample a group of that to your lower sampling rate.
>
> It might be possible using software timing (obviously not as repeatable as hardware timing).
>
> Two separate loops with the same task ID, reading all channels at different loop rates. Sorry I don't have any desktop hardware to confirm this.
>
>
> Neville Dholoo
> Advanced Measurements Inc.
> Calgary AB
> Canada
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