How many ways to read and write a local variable in a called VI?

[aRCo]

Ciao!

I'm producing my first TestStand sequence. It is called "FirstAttempt" and it is made by a single step which calls a VI. One of the first dilemmas i encountered realizing this sequence is how to read and write a local variable (created going in Variables -> Locals ('FirstAttempt') -> <right click to insert local>) in the called VI.

The first way (the only one i tried) is to create a control and an indicator on the VI front panel, connect them to their respective terminals in the connector pane and then specify (going in Step Settings -> Module) that these connectors (shown in the Parameter Name column) are linked to the local variable (selected in the Value column).

The second way (not tried) consists in using TestStand API: create a Sequence Context reference on the VI front panel, link it to a property node in the block diagram, select the property "Locals" and extract from this the local variable name and value which, i think, can be readable and writable.

So...

Are the shown ways correct?

Are there other ways?

Knowing that a "local" variable can be considered "global" within the whole sequence, is there the possibility to simply create a reference to the local variable and use the reference in the called VI block diagram in order to save space in the connector pane (if using method 1) or in the block diagram (if using method 2)?

Thanks!

Message Edited by aRCo on 09-17-2009 05:09 AM

[RayFarmer]

Hi,

Before TestStand 3 you would use the second way you quoted as its the only way.

But now you would use the first way you quoted. You may still what to pass the SequenceContext if you were going to use the TestStand API. For TestStand 3.x and above you would use this way as the first chose. (Personnelly, I would not pass the SequenceContext into a VI if I know it was never going to be used in that VI.)

Not sure I understand your final comment, maybe you are liking it to passing the reference of a control to a subVI so that the control can be updated from within the subVI.

If this is the case and you had a situation where you had a step that was running in parallel with the rest of the steps in the sequence either as a separate thread or execution and were dependent on the contents of the  local variable changing from that parallel running step, then you would have to use the API SetVal method to change the local.

Hope this is clear.

Regards

Ray Farmer