LabVIEW
How to test if a connection is wired in a subvi
Hi,
The only way to do this, is to set the default values to something special
(NaN, -1, etc.).
In the VI you have to test the input, if it is default, the control is not
wired. If a connection is not used, LV uses the default value (but only if
the control is wired as a connector).
Regards,
Wiebe.
"Joolz" wrote in message
news:506500000008000000C7590000-1027480788000@exchange.ni.com...
> If a VI calls a subvi, some connections may be not be required. Is it
> possible to find out (within the subVI) whether the optional
> connections are connected or not?
The only way to do this, is to set the default values to something special
(NaN, -1, etc.).
In the VI you have to test the input, if it is default, the control is not
wired. If a connection is not used, LV uses the default value (but only if
the control is wired as a connector).
Regards,
Wiebe.
"Joolz"
news:506500000008000000C7590000-1027480788000@exchange.ni.com...
> If a VI calls a subvi, some connections may be not be required. Is it
> possible to find out (within the subVI) whether the optional
> connections are connected or not?
Search LabVIEW like a graph! 
Hi all,
one method of checking the default value is to take a copy of the control value as it has come in, and then perform a re-initialise to default method on the original control. You can then compare - if they're the same then it's a default (though it might be a coincidence that you wired a value into the sub.vi that matched - maybe it's something NI could add in a future release - a property of a control to say it got it's data elsewhere). This method makes sure that you're not going to run into a block diagram / front panel mismatch if you ever update the program (i.e. you set a control's default value, then you have to remember to change the constant on the block diagram too.
It's a little more cumbersome - I use a sub.vi to do the che
cking. Because the data isn't important, you can do the comparison based on the variant data.
The attached files are in LabVIEW 6.1.
Just my 2 cents worth.
S.
one method of checking the default value is to take a copy of the control value as it has come in, and then perform a re-initialise to default method on the original control. You can then compare - if they're the same then it's a default (though it might be a coincidence that you wired a value into the sub.vi that matched - maybe it's something NI could add in a future release - a property of a control to say it got it's data elsewhere). This method makes sure that you're not going to run into a block diagram / front panel mismatch if you ever update the program (i.e. you set a control's default value, then you have to remember to change the constant on the block diagram too.
It's a little more cumbersome - I use a sub.vi to do the che
cking. Because the data isn't important, you can do the comparison based on the variant data.
The attached files are in LabVIEW 6.1.
Just my 2 cents worth.
S.
