Newbie Question: Control DO on Exit

[jb313]

Hello,

I am brand new to LabVIEW and need to get a small project done quickly.  I have only really used Express VI's...

I do, however, have a DAQ and control system up and running (I'm sure it could be done much more efficiently, and I plan to refine as I learn)...

What I really need to know are two things:

1) How to ensure a pair of digital outputs are off on start-up (I have them default to off on power-up in DAQmx) but I mean on start-up of my VI.

2) How to ensure they're off on exit of the VI (no matter what the state of the toggle in the on screen, if they stop it, I need the outputs to go off).

Please can anyone give me some help, or an example?

-Jeff

[crossrulz]

You could just simply write falses to the digital lines at the very beginning of your program and again in your shutdown code.

[KeenanJohnson]

It sounds like you really need some sort of state machine architecture. This way you can have certain tasks that happen on start up, shutdown and anywhere in between. 

https://www.ni.com/en/support/documentation/supplemental/16/simple-state-machine-template-documentat...

[jb313]

Cross,

Thank you, for the reply.

That's exactly what I'd do in language I was familiar with.  I literally just don't understand the graphical syntax yet.  The express VI's are all I've touched--even the loop and exit criteria were auto-generated by LabVIEW.

I just need to understand (may be an example), of DO control on start-up / shutdown...

-Jeff

[jb313]

Keen,

Thank you too, a state machine might really be the thing I need.  Not sure how best to implement one in LV, but the concept is very familiar.

Even if I figure out the init, run and exit states (would add-in other states too, later, e-stop, limit, etc.) still not sure how the code can set a digital output.  I'm that new to LabVIEW!

-Jeff

[crossrulz]

Might I recommend taking some tutorials:

LabVIEW Basics

And be sure to read up on the state machine:https://www.ni.com/en/support/documentation/supplemental/16/simple-state-machine-template-documentat...

[jb313]

I get that, but thank you.

I was hoping there was a "stick this control in here, set output state, link to stop button" kind of answer, or "here's an example of that with a DAQ Assistant!"

I appreciate the links.

[JÞB]

Just because you have a great set of initials...

Here would be one way to do DO with set-up and exit

The Sub.vi is simply this

[jb313]

Jeff B,

They are strong initials, aren't they!?

Ok, I think I understand some of what's going on in there.  I will study it and try to make some sense.  Would you happen to have the actual .VI of that I can play with?

Thank you, Jeff, much appreciated!

-Jeff B.

[Yamaeda]

Under Help menu you can find examples of both state machines and daqmx, you just need to combine those two. 🙂