what is an xnode?

[SteveChandler]

Ok silly question but what is an xnode? I have seen them mentioned and I know they have something to do with scripting. The LabVIEW help search returned nothing that was very useful.

[altenbach]

There's an ongoing discussion over at lava.

[Darin.K · Accepted solution]

I have been playing with these guys a bit lately, and will offer a few insights I have gained.  An XNode is roughly the BD equivalent of an XControl.  It is organized much like a normal Library, and a .xnode file is basically XML just like a .lvlib file.  

XNodes have certain "abilities" which you control by writing Ability VIs.  These range from drawing the image, to specifying the terminals to generating the actual code.  There is great flexibility, you can adapt to wire types, resize the nodes horizontally and vertically, have configuration screens, text fields.  The downside is that there is a lot of baggage, ie. all of these ability VIs have to be around, so a simple VI with a single XNode may require dozens of subVIs.  No problem when they ship with LV, a bit of a drag for home built ones.

I have been an instigator of late in regards to XNodes, and I am soon (I hope) to unleash my XNode Wizard onto the community.  It deals with the creation of XNodes and the addition of Ability VIs and SubVIs.  It also simplifies the process for most of the basic abilities.  My favorite part is that it eliminates the scripting in many cases.  You write a template VI, use my tool to tag terminals on the BD by clicking on an image, and then simply generate a list of wiring rules to match XNode terminals to BD terminals.  I also have simple tools to bundle/unbundle inputs/outputs for the ever-popular expandable nodes.

The old claim was that XNodes would be too complex and not the type of "customer experience" that LV users want.  I intend to prove them wrong, stay tuned.  They once said similar things about scripting....

In the meantime, let me know if you can make sense of this

http://forums.ni.com/t5/LabVIEW/Truth-Table-Node/m-p/1293680

[BartSchroder]

Yes but what is an XNode? What is it used for? Please don't say in terms of some other thing such as an X Control (what is that, and what is BD).  I have been trying to figure this out as well.

I find that quite a bit of Labview documentation lacks the step back and define 'What is it used for and what does it do' sort of description. It would be really useful if a short introductory paragraph for major features did this.

Thanks for any help!

[tst]

XNodes aren't part of the LV documentation, because XNodes aren't officially a part of LV. They're an incomplete feature which can be accessed if you dig, but it's at your own peril.

In any case, an XNode is a block diagram object which has code behind it. You write VIs which get called when certain events occur (the node is dropped, the node is double clicked, etc.) and you also need to write VIs which control what the node looks like and what it actually does. They're an advanced subject, and not only because they are incomplete and undocumented.

If you don't know that BD is short for block diagram (or what an XControl is), you should definitely NOT be dealing with XNodes. If you're having trouble with a new concept, you should try looking through tutorials and examples. I know that NI has some for XControls, for example, although those are also a relatively advanced subject.

[adhikari]

Hallo,

I am trying to get some knowledege about Xnode, but i feel difficulty to understand it. Attached is a summation node which i tried to make xnode similar to it. This has to be multiple selectable inputs which adds and substracts the input signal. where and how could i start to make it ? Thanks in advance.

[crossrulz]

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adhikari wrote:This has to be multiple selectable inputs which adds and substracts the input signal.

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What's wrong with just using the Compound Arithmetic Node?  It does everything you described here.

[adhikari]

i just wanted to learn about how to build x-node.

[altenbach]

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@adhikari wrote:

i just wanted to learn about how to build x-node.

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... and how would it be useful for anybody reding this to look at an image of it?

The important feature is in the function, which a picture cannot show.

[adhikari]

I am trying to make my first xnode which has to do exactly like attached vi. But I want to change its BD appearance as a circle using xnode abilities .This has to be multiple selectable inputs which adds and subtracts the input signal. how could i start for doing this? Attached is a compound arithmetic VI and picture as a circle which i wanted to have as a xnode.