15 You can change the configuration of a local variable so that it acts as a control, or a read local . To do this, right-click the variable and select Change To Read . On the block diagram, a read local icon behaves just like a control. When this node executes on the block diagram, your program reads the data in the associated front panel control or indicator. To change a read local to a write local, right-click the variable and select Change To Write . The local variable will change its data direction so that it receives data instead of providing data. On the block diagram, you can visually distinguish read locals from write locals. A read local has a thick border, emphasizing that it is a data source, similar to a control. A write local has a thin border, because it acts like a data sink, similar to an indicator. As a conclusion, an indicator (or a control) can have multiple local variables which might be read local or write local for the same node (Figure 22). Figure 22 Read Local- Write local 3.8 PROPERTY NODES Property nodes allow users to set or read properties or qualities of a front panel object. The properties include foreground and background color, data formatting and precision, visibility, descriptive text, size and location on the front panel, and so on. To create a property node for an object on the front panel, right click on the object and select Create Property Node. Similar to local variables, property nodes can be changed to read or write depending on the application. Multiple property nodes for the same object can be created where different properties can be manipulated. There are many properties available for the various front panel objects in LabVIEW. Some are common to all front panel objects, while others are specific to some controls and indicators. Property nodes will not be discussed in details in this section since there are many different properties, for more details, you can refer to the LabVIEW Help and built-in examples. 4. KEYSTROKE SHORTCUTS LabVIEW has many keystroke shortcuts that make working easier. The most common shortcuts are listed below. Keystroke Shortcuts <Ctrl-H> : Activate/Deactivate Context Help Window <Ctrl-B> : Remove Broken Wires From Block Diagram <Ctrl-E> : Toggle Between Front Panel and Block Diagram <Ctrl-Z> : Undo (Also in Edit Menu) <Ctrl-U> : Re-routes all existing wires and rearranges objects on the block diagram automatically
16 5. SAMPLE VI In this section, you will develop a simple VI to use various modules and structures from the Functions palette. To insert objects in the Block Diagram window, right-click anywhere on the white color window. By doing that, the Functions Palette will appear as shown in Fig. 23. It contains all functions (VIs) that you may need to insert in the Block Diagram to develop an application. You can also click on the thumbtack (upper left corner) to tack down the palette, i.e. keep it open even if you clicked anywhere else on the block diagram.
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- Fall '16