LabVIEW basics

Automatic Tool Selection:  When the tool selection window at the top of the tool palette is lit green, LabVIEW will select whichever tool appears to be the correct one. When the tool selection window is dark, the user must select the appropriate tool. The tab key can be used to cycle through the four most common tools: the operating tool, the positioning tool, the wiring tool, and the labeling tool. The shift key toggles between the positioning tool and the wiring tool.

Main Application Instance/NXT: LabVIEW programs can be run targeted to the computer or to the NXT. The label in the bottom left corner of the LabVIEW window indicates whether the program is targeted to the computer (Main Application Instance in white) or targeted to the NXT (NXT in orange). To switch, choose Target to NXT/Target to Computer from the File menu. If you want to run the program on the NXT separate from the computer, you must be targeted to the NXT. If you want to use controls or indicators on the front panel or run in debug mode, you must be targeted to the computer.

Context Help:  Context help gives information and examples for each icon. To turn on the context help, click on the question mark in the upper right corner. A new window will open. To see information about a particular icon, place your cursor over it. Information (and links to examples) will appear in the context-help window.

Wiring: Wires are used to connect icons within a program. The wire color indicates the type of data carried by the wire: blue for integer, orange for floating point, green for Boolean, pink for string. Opening the context help will allow you to see the input and output terminals for an icon, which is very useful for wiring. To anchor a wire to a particular spot on the block diagram, click on the spot as you drag the wire. To remove broken wires, use control-B (command-B on the Mac) or choose Remove Broken Wires from the Edit menu.

Constants, Controls, Indicators: Constants and controls can be used to specify parameters or inputs. To create a constant at an icon terminal, right-click (control-click on a Mac) on the terminal and choose Create Constant. A box will appear, wired to the appropriate spot. You can then enter a value for the constant. To change the value later, use the operating tool. Instead of creating a constant, you can also choose to create a control. The control will be displayed on the front panel and can be modified on the front panel as well. Just as a control shows an input, an indicator shows an output. Like a control, it is displayed on the front panel.

Highlight Execution:  To help debug a program, run it targeted to the computer with highlighting execution turned on. As the program runs, each step will be highlighted as it is reached. To highlight the execution in a program, click on the light bulb icon at the top of the block diagram before running the program.

Clean Up Diagram:  To make a program neater, click on the button labeled Clean Up Diagram at the upper right of the block diagram.

Align Objects and Distribute Objects: To align or evenly space the icons in your program, select the icons and click on the button labeled Align Objects or Distribute Objects.


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Barbara Bratzel

Barbara Bratzel

Barbara teaches at the Shady Hill School in Cambridge, Massachusetts and works at the Center for Engineering and Education Outreach at Tufts University. She is the author of several LEGO robotics activity books for teachers, most recently STEM by Design.
Barbara Bratzel

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