Examples for good programming practice with multiple DAQmx tasks

I'm writing a program to continuously log data from 8 counters, 8 encoders, and 8 voltages. The proof of concept VI with a single counter was simple and elegant, but scaling up to all signals resulted in a wiring mess. I've been working through the Labview Core courses, and am currently on Core 3. I still haven't come across a discussion on how to work with multiple DAQmx tasks without making a mess of the block diagram. Can anyone point me in the right direction?
Also, say I have a state machine that has a configure, idle, and logging states. I need to set the initial values of the encoders during configuration, and keep up with their changes while in the idle state so I have appropriate starting values when entering the logging state. Can anyone point to an example that shows how this might be accomplished?
Thanks

I'm very familiar with AE's/Functional Globals - but I have struggled in the past with handling multiple DAQmx tasks - particularly when you're using multiple devices and using different types of measurements which require seperate tasks/handling (e.g. such as thermocouples which require extra compensation).
I'm not even sure I know whare the requirements are for needing multiple tasks - I know you can need multiple tasks for a single device if the type of measurement is different but can you share an Analogue Input task amongst multiple devices?
I think in hindsight (and without too much thought now) it looks like a good case for Object Oriented LabVIEW - with a base DAQmx class (initialise, configure, start, acquire, stop, close etc.) and then child classes for each type of measurement (with one task associated with each - and private data unique to that specific class). You then hold an array of objects (one for each task) and iterate through each one with dynamic despatch to get the data.
I don't know your particular experience level of using LabVIEW (and as such, OO may not be appropriate) - but as a wider discussion of 'best practice' it seems like an appropriate method I would use going forward.
Certified LabVIEW Architect, Certified TestStand Developer
NI Days (and A&DF): 2010, 2011, 2013, 2014
NI Week: 2012, 2014
Knowledgeable in all things Giant Tetris and WebSockets

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Good programming practice - Abstract class

Hi all,
I have been trying to help another soul in this forum, and came to the conclusion that I don't know good
programming practice when it comes to abstract classes.
Is this correct?
You CAN implement methods in an abstract class, but it's not recommended.
I have NEVER done this...when is there possibly a need to?
Regards.
/ k

Yes, absolutely, you can implement methods in an abstract class. Any method that all subclasses will perform in the same way can be implemented in the abstract base class. If subclasses perform similiar functions depending on their type you declare those as abstract in the base class. Here is a contrived example that I have seen on job interviews.
Suppose your developing an application that draws on a panel. We want to provide some canned shapes such as a circle, a square and a triangle. We want to be able to draw the shape set or get its color and calculate its area.
Let's define an abstract base class Shape
public abstract class Shape{
    private Color myColor;
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public void setColor(Color newColor){
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// however, drawing the shape and calculation its area are depending on the actual shape.
public abstract void draw();
public abstract double getArea();
// so then Square would be something like
public class Square extends Shape{
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      return sideLength * sideLength // assumes somehow we know sideLength
public void draw(){
              // concrete implementation
}we can do the same things for Circle class and Triangle class.
And, if you think about it you'll notice that we could have made a Rectangle class and then Square would be a subclass of Rectangle where both dimensions are equal.
I hope that somewhat strained example helps answer your question.
DB

Do IOS app developers follow any good program practices?

I've had my iPad (original) a little over two years now, and I can say without a doubt, it is the most unstable platform I've used in nearly 30 years of using computers. Most apps crash routinely, usually while at least one other app is running in the background. Unloading the crashed app from memory and reopening uually works, but is a huge nuisance (and reason enough to me why iPads are not business-ready, except for specific task applications requiring mobility). As one trained in both software and systems engineering, with 20 years IT experience mostly in engineering, I have to conclude that IOS app developers use "code and fix" development, with little testing before release. Of course, in theory it could be that IOS itself isn't well designed to handle multitasking and doesn't provide adequate process isolation. Either way, it makes for a frustrating experience as a user.
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Good programming practices:   creating Iterator objects

Hi,
This is a question about Good programming practices for creating Iterator objects of ArrayList objects. The following line of code works fine in my program (as ridiculous as it may sound):
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AJ-Phil wrote:
Hi,
This is a question about Good programming practices for creating Iterator objects of ArrayList objects. The following line of code works fine in my program (as ridiculous as it may sound):
        Iterator cheesesIterator = cheeses.iterator();but I was wondering whether Java is automatically inserting the <Type> and new code to make:
        Iterator<String> cheesesIterator = new cheeses.iterator();and therefore whether it is good practice to use these everytime? TFirst, new chesses.iterator() won't compile.
iterator() is just a method that returns an iterator. It constructs an instance of a private or nested class that implements iterator, and returns a reference to it.
As for the <T>, when you declare List<String>, that parameterizes that list with type String. The iterator() method returns Iterator<T>. You can look at the source code for yourself. It's in src.zip that came with your JDK download.
Separate from that is your declaration of that variable as type Iterator, rather than Iterator<String>. Regardless of what you declare on the LHS, the iterator() method returns Iterator<T>. Your bare Iterator is essentially Iterator<Object> or Iterator<? extends Object> (not sure which, or what the difference is), which is assignment compatible with Iterator<T>. If you had declared it Iterator<String>, you wouldn't have to cast after calling next().
Edited by: jverd on Nov 23, 2008 11:33 AM

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Any usefull examples of good coding practice in large programs

Hi, ive been writing code for about 10 years now. Know a good bit about labview now lmao! But want to get to know good code practices e.g. in creating large programs, code templates, avoiding race conditions, use of multiple loops and to be able to write code for clients as a contractor. Any one help me??
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Solved!
Go to Solution.

Check out thelargeapp community and this KB article
Message Edited by Jeff Bohrer on 06-14-2010 04:49 PM
Jeff

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Thanks for the input. With regards to the file format, the decision has been made by my superiors not to use TDMS - unfortunate, but NI hasn't provided the information to write a MatLab file reader, which is a requirement. So, I've created a custom file format tailored to the needs of my application, but generic enough to be used for other apps. With it, I've been able to stream 8 channels at 800KHz (4 channels each from 2 PXI-6120s) without breaking a sweat. However, the performance varies greatly depending on which slots the cards are in (but that's a whole different discussion - see the PXI forum for that one). Once NI solves that one, I'll feel a lot more comfortable.
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Holger,
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Best practice for TM on AEBS with multiple macs

Like many others, I just plugged a WD 1TB drive (mac ready) into the AEBS and started TM.
But in reading here and elsewhere I'm realizing that there might be a better way.
I'd like suggestions for best practices on how to setup the external drive.
The environment is...
...G4 Mac mini, 10.4 PPC - this is the system I'm moving from, it has all iPhotos, iTunes, and it being left untouched until I get all the TM/backup setup and tested. But it will got to 10.5 eventually.
...Intel iMac, 10.5 soon to be 10.6
...Intel Mac mini, 10.5, soon to be 10.6
...AEBS with (mac ready) WD-1TB usb attached drive.
What I'd like to do...
...use the one WD-1TB drive for all three backups, AND keep a copy of system and iLife DVD's to recover from.
From what I'm reading, I should have a separate partition for each mac's TM to backup to.
The first question is partitioning... disk utility see's my iMac's internal HD&DVD, but doesn't see the WD-1TB on the AEBS. (when TM is activity it will appear in disk utility, but when TM ends, it drops off the disk utility list).
I guess I have to connect it via USB to the iMac for the partitioning, right?
I've also read the benefits of keeping a copy of the install DVD's on the external drive... but this raises more questions.
How do I get an image of the install DVD onto the 1TB drive?
How do I do that? (install?, ISO image?, straight copy?)
And what about the 2nd disk (for iLife?) - same partition, a different one, ISO image, straight copy?
Can I actually boot from the external WD 1TB while it it connected to the AEBS, or do I have to temporarily plug it in via USB?
And if I have to boot the O/S from USB, once I load it and it wants to restore from the TM, do I leave it USB or move it to the AEBS? (I've heard the way the backups are created differ local vs network)>
I know its a lot of question but here are the two objectives...
1. Use TM in typical fashion, to recover the occasion deleted file.
2. The ability to perform a bare-metal point-in-time recovery (not always to the very last backup, but sometimes to a day or two before.)

dmcnish wrote:
From what I'm reading, I should have a separate partition for each mac's TM to backup to.
Hi, and welcome to the forums.
You can, but you really only need a separate partition for the Mac that's backing-up directly. It won't have a Sparse Bundle, but a Backups.backupdb folder, and if you ever have or want to delete all of them (new Mac, certain hardware repairs, etc.) you can just erase the partition.
The first question is partitioning... disk utility see's my iMac's internal HD&DVD, but doesn't see the WD-1TB on the AEBS. (when TM is activity it will appear in disk utility, but when TM ends, it drops off the disk utility list).
I guess I have to connect it via USB to the iMac for the partitioning, right?
Right.
I've also read the benefits of keeping a copy of the install DVD's on the external drive... but this raises more questions.
Can I actually boot from the external WD 1TB while it it connected to the AEBS, or do I have to temporarily plug it in via USB?
I don't think so. I've never tried it, but even if it works, it will be very slow. So connect via F/W or USB (the PPC Mac probably can't boot from USB, but the Intels can).
And if I have to boot the O/S from USB, once I load it and it wants to restore from the TM, do I leave it USB or move it to the AEBS? (I've heard the way the backups are created differ local vs network)
That's actually two different questions. To do a full system restore, you don't load OSX at all, but you do need the Leopard Install disc, because it has the installer. See item #14 of the Frequently Asked Questions *User Tip* at the top of this forum.
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Examples for good programming practice with multiple DAQmx tasks

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