control references within subvis

[PA-Paul]

Hi all,

I have a small problem I'm not sure how to deal with. I've written a subvi to control the movement of a stepper motor. The subvi sends the appropriate command to make the motor perform a movement and then monitors the stepper driver until the movement is complete (it's marginally more complex than that - it deals with limit switches on the drives and a hardware E-Stop implementation as well). What I want is for the top level VI which calls this subvi to know when the drive is in motion. I have a boolean control within the subvi, but obviously, the top level vi can't see that. I created a (boolean typed) control reference and property node within the subvi and hooked it up to the connector pane. This works as I expected, but I want this functionality to be optional - and if I don't connect a control reference to the subvi, I get an error saying "invalid reference".

How do I make it not worry if I don't wire a reference in?

Thanks in advance!

Paul

[silmaril]

There is a function called "Not a Number/Path/Refnum?" on the comparison palette.

Use this to check if the reference is invalid (which will be the case if the reference input is unwired).

[PA-Paul]

Brilliant, had forgotten about that.

Thanks!