Reference to control on main front panel fails when subvi front panel is closed?

Hi All,
I'm experiencing an odd bug. In my code, I use a subvi to control a piece of hardware. This subvi has controls for all of the functions of my hardware.
I'm changing the value of one of these controls from my main front panel by running a reference to a knob on my main front panel into the subvi, grabbing the value of the knob with a property node, and then updating the value of the subvi control using a signaling property node.
This works fine when my subvi front panel is open but fails to work at all when the subvi front panel is closed.
I'm new to labview , so any help is appreciated.
Thanks,
Arpan
Solved!
Go to Solution.

What is your LabVIEW version?
Front panels that are not shown are typically not updated and might not even be loaded into memory.
The presence of certain code elements (e.g. property nodes) often forces the front panel to be in memory even if it is not shown, but I haven't studied it in a long time so there might be subtleties. Maybe somebody from NI can give more details.
If it does not work unles the FP is open, open the front panel minimized to avoid distraction.
Can you attach some code? Maybe there are better ways to do all this anyway.
LabVIEW Champion . Do more with less code and in less time .

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> How can I get a reference to all controls on a front panel of one type
> )for example of the type Text Ring?
>
> I'd like to set the strings[] property of all the Text Ring controls
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Solved!
Go to Solution.

This is a basic issue on which you can find tons of forum posts
The online help for the function recitates:
int SetCtrlVal (int panelHandle, int controlID, ...);
Parameters
Input
Name
Type
Description
panelHandle
int
Specifier for a particular panel that is currently in memory. You obtain this
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controlID
int
The defined constant, located in the .uir header file, that you assigned to the control in the User Interface Editor, or the ID returned by NewCtrl or DuplicateCtrl.
value
New value of the control. The data type of value must match the data type of the control.
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int SetCtrlVal (int panelHandle, int controlID, ...);
Purpose
Sets the value of a control to a value you specify.
When you call SetCtrlVal on a list box or a ring control, SetCtrlVal
sets the current list item to the first item that has the value you
specify. To set the current list item through a zero-based index, use SetCtrlIndex.
When you call SetCtrlVal on a text box, SetCtrlVal appends value to the contents of the text box and scrolls the text box to display value. Use ResetTextBox to replace the contents of the text box with value.
Note This function updates the displayed value immediately. Use SetCtrlAttribute with ATTR_CTRL_VAL to set the control value without immediately updating the displayed value. For this reason, SetCtrlAttribute with ATTR_CTRL_VAL is generally faster than SetCtrlVal. However, if the control in which you are setting the value is the active control in the panel, SetCtrlAttribute with ATTR_CTRL_VAL displays the value immediately.
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Parameters
Input
Name
Type
Description
panelHandle
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controlID
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value
New value of the control. The data type of value must match the data type of the control.
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Reference to control on main front panel fails when subvi front panel is closed?

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