Multi channel read operation. How does it work?

[tmunsell]

Hi again,

I have been using the Daytronic Corp. Single Channel Read sub-VIs to read each channel from the DAQ individually to display them on the front panel.

I can't quite figure out how to use their Multi-channel Read VI to display data from several channels on different instruments on the panel.  I'm hoping to get this figured out so I can eliminate the 30+ seperate single channel sub-VIs that I'm using now.  It would make for a less cluttered block diagram!  I've attached Daytronic's LLB file.  Could someone take a few moments and check them out and see if what I want to do is possible?  The fellow at Daytronic who created them isn't working there anymore (hence the latest version being for LV 7.0).  Thanks in advance!

[MikeS81]

Hi Todd,

did you try to use a loop for your calls? I´m sure it´s possible and it is definitifly easier than using 30 vi´s side by side.

Mike

[tmunsell]

Hi Mike,

Here's a link to an attachment of the app I created: http://forums.ni.com/ni/board/message?board.id=170&thread.id=343134&view=by_date_ascending&page=2

Actually, the entire app is enclosed in a While Loop.  I ended up having to do this to have it update the data in real-time.  I'm still learning loops (and LV in general), so I'm limited in what I can do at the moment.  I'm still going through the online tutorials about the LV basics.  Do you know where there is an example of what you suggest that I can study?  I tend to learn more quickly from reverse-engineering things than from reading the books, although I do use both methods. 🙂

I'm still hesitant about using case structures, since no one else in the company knows anything about Labview.  I'm trying to make the block diagram as simple to understand as possible for them in case I'm not there and they have a problem.  Reading structures confuses even me at the moment.  My current app looks more like a simple 2D wiring diagram (albiet a large one), which I'm hoping will make it easier for the others to interpret it if they need to.  They all have knowledge in reading basic drawings and schematics.

PS.  I'm also anxiously awaiting delivery of version 8.6.  The new feature of automatically cleaning up the block diagram looks like a fantastic addition to the software!  Do you know if a zoom feature for the diagram has been added yet?  I've chatted with a few people who would like to see that option available, rather than having to scroll up/down and left/right.

Thanks again!

[tmunsell]

By the way... as I learn more about LV, I'll be re-creating the entire app as I learn, step-by-step.  I've already started experimenting.  Since the current app is functioning well enough for now, I'll have time to make improvements and hopefully clean up and streamline it's operation significantly.  Any suggestions would be greatly appreciated!

[Brinoceros]

Hi Todd,

First, you mention the driver only updated as of 7.0.  It seems that this is the same driver, which was updated as of 8.0.

The best resource for these instrument drivers is usually example VIs included with the driver.  In this case, you can see that the Simple Datalogger Example.vi demonstrates the use of the IO Multi Channel Read.vi (in the 4 frame of the main sequence structure, and in the 1 frame of the inner sequence structure).  The code is a challenge to follow, but should demonstrate the use of this VI.  Also, be sure you have the context help open (Ctrl-H), and put your mouse cursor over the IO Multi Channel Read.vi.  This gives a very helpful description of the I/O for this VI.

I hope this helps!