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Unformatted text preview: Connexions module: m12201 1 DEBUGGING TECHNIQUES Version 1.1: Jul 16, 2004 2:54 pm GMT—5 National Instruments This work is produced by The Connexions Project and licensed under the
Creative Commons Attribution License * Abstract
In this section, you will learn about LabVIEW debugging techniques. If a VI does not run, it is a broken, or nonexecutable, VI. The Run button often appears broken,
shown at left, when you create or edit a VI. If it is still broken when you ﬁnish wiring the block diagram, the
V1 is broken and will not run. Generally, this means that a required input is not wired, or a wire is broken. 1 Finding Errors Click the broken Run button or select Windows>>Show Error List to display the Error list window, which
lists all the errors. Double-click an error description to display the relevant block diagram or front panel and
highlight the object that contains the error. 2 Execution Highlighting View an animation of the execution of the block diagram by clicking the Highlight Execution button,
shown in this media. Execution highlighting shows the ﬂow of data on the block diagram from one node
to another using bubbles that move along the wires. Use execution highlighting in conjunction with single-
stepping to see how data move from node to node through a VI. NOTE: Execution highlighting greatly reduces the speed at which the VI runs. 3 Single—Stepping Single—step through a VI to View each action of the VI on the block diagram as the VI runs. The single—
stepping buttons affect execution only in a VI or subVI in single-step mode. Enter single-step mode by
clicking the Step Over or Step Into button. Move the cursor over the Step Over, Step Into, or Step Out
button to View a tip strip that describes the next step if you click that button. You can single—step through
subVIs or run them normally. If you single-step through a VI with execution highlighting on, an execution glyph, shown in this
media, appears on the icons of the subVIs that are currently running. *http://creativecommons.org/licenses/by/1.0 http://cnx.org/content/m12201/1.1/ Connexions module: m12201 2 4 Probes Use the Probe tool, shown in this media, to check intermediate values on a wire as a VFI runs. When
execution pauses at a node because of single-stepping or a breakpoint, you also can probe the wire that just
executed to see the value that ﬂowed through that wire. You also can create a custom probe to specify which indicator you use to view the probed data. For
example, if you are viewing numeric data, you can choose to see that data in a chart within the probe. To
create a custom probe, right-click a wire and select Custom Probe>>New from the shortcut menu. 5 Breakpoints Use the Breakpoint tool, shown in this media, to place a breakpoint on a VI, node, or wire on the
block diagram and pause execution at that locatiFon. When you set a breakpoint on a wire, execution pauses
after data pass through the wire. Place a breakpoint on the block diagram workspace to pause execution
after all nodes on the block diagram execute. When a VI pauses at a breakpoint, LabVIEW brings the
block diagram to the front and uses a marquee to highlight the node or wire that contains the breakpoint.
LabVIEW highlights breakpoints with red borders for nodes and block diagrams and red bullets for wires.
When you move the cursor over an existing breakpoint, the black area of the Breakpoint tool cursor appears
white. Use the Breakpoint tool to click an existing breakpoint to remove it. http://cnx.org/content/m12201/1.1/ ...
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