Simulated CompactDAQ 9188 with (3) 9225 modules

[univater]

Hi,

I'm debugging a project in Visual Studio 2010 (C#, .net 4) and have NI-DAQmx 9.4 installed.  I don't yet have the actual hardware so I'm using a simulated CompactDAQ 9188 chassis with 3 simulated 9225 modules.  I'm trying to create 3 tasks, 1 for each module.  When debugging, I can start all three tasks but shortly thereafter one task will stop providing data and provide the error -20022 (Resource is already in use).  If I only use 2 tasks, I get no errors.  Also, if I change the 3 simulated modules to be 9205 modules, I can successfully run all 3 tasks.  So it appears there is a difference between using 9225 modules (simultaneous sampling modules) and 9205 modules (scanned modules).  This error can even be simulated in Measurement & Automation Explorer.  A single CompactDAQ 9188 chassis is supposed to be capable of 7 simultaneously hardware timed tasks.

Is this just a bug with using simulated 9225 devices?

If not, how do I configure and run 3 tasks with 3 9225 modules (1 task per module) on a CompactDAQ 9188?

Any help would be greatly apreciated.

[MarkGrot]

Hi univater,

The cDAQ-9188 chassis has 3 analog input timing engines so you can have 3 hardware timed AI tasks running simultaneously.  There is an additional restriction that only 2 of those 3 tasks can contain sigma-delta modules, such as the 9225.  I'm not exactly sure where we call that out in the specs but I'll take a look.  The 3 9205 modules do not error because they are not sigma-delta modules and do not have the same restriction as the 9225.

Is there a reason you don't want to include multiple modules in the same task?

[MarkGrot]

The 2 task restriction is mentioned in the chassis manual Chapter 2: Analog Input: Analog Input Timing Signals: AI Convert Clock Signal Behavior For Analog Input Modules: Sigma-Delta Modules 1st paragraph.  Page 2-4 in the current version of the manual.

I realize that might not be the most obvious location.

[univater]

Thanks for pointing that out.  I typically like dividing tasks by either module or board function (on multifunction DAQ cards) so that if a task errors out or times out, I know which module or card is the culprit.  I guess I wouldn't have even known that the 9225 is a sigma-delta device.  It does not state that when using the configurator and selecting your modules.  You have to look at the 9225 manual to find that out.

Is there a way to set up the 3 9225 modules to use 3 tasks but share a single clock?

Are all simultaneous sampling devices sigma-delta devices?

Thanks again for all your help!

[MarkGrot]

Probably most straightforward listing of analog input module types is in the DAQmx help under C Series Device Groupings.

There is no way for you to synchronize three tasks containing sigma-delta modules because the chassis only supports two.  If you put two modules in two tasks and share clocks, the slave task still uses the scarce timing resources so it doesn't enable you to have more tasks.

Also, the modules are a little different than other modules.  Instead of sharing a sample clock, you would need to share a synchronization pulse and sample clock timebase.  Another thing to consider is that you probably need to account for the module input delay.

Not all simultaneous modules are sigma-delta.  The 9215, 9222, and 9223, for example, are not.