CS320n

1
CS320n Visual Programming

• More LabVIEW Foundations

2
What We Will Do Today

• Look at some more features of LabVIEW
• Work on exercises involving debugging and
  creating sub VIs

3
VI Libraries

• VIs can be saved as individual programs
• A group of VIs can be saved together as a VI
  library
• creating -gt an option in the save window
• opening -gt open as regular file, then select
  which VI to open from library

4
From Last Time

• Some functions have a variable number of inputs
• The string concatenation function
• When opened notice blue dots on top and bottom
• function can be expanded for more inputs
• note visual cue on order of inputs in result for
  three input function

5
Debugging

• VIs that are broken cannot be run
• analogous to syntax error in text based
  programming languages
• Most common mistakes
• required input missing on function terminals (for
  example, add)
• type mismatch on data (wire double when integer
  was expected
• loose, unconnected wires
• sub VI is broken
• multiple inputs into a single indicator

6
Broken Programs

• Clicking on the broken arrow brings up a list of
  errors
• Clicking on an error displays more information
  about the error

7
Stepping Through a Program

• Sometimes you want to observe a program step by
  step, not all at once
• Click on the single set button instead of the run
  button
• Press the single step button to see the flow of
  the program

8
Execution Highlighting

• Another excellent debugging tool is Execution
  Highlighting
• aside why no debugging tools in Alice?
• Select Highlight Execution and data values and
  movement shown as program runs. Very useful
• Can be used as program runs or combined with
  stepping through program

9
Probes

• To view the value on a wire or result of a
  function you can either set up an indicator or
  use a probe
• With a running program, probe is auto selected
  when putting the cursor near a wire
• When the program is not running probes can be
  added.
• choose the Window menu
• select Show Tools Palette
• click on the probe tool to add probes
• be sure to change Tool back to auto select when
  finished

probe
10
Breakpoints

• Suppose you want to stop the program at a single
  point, deep into the execution
• using the step by step control is a pain
• set a breakpoint
• right click or use breakpoint tool
• program will run normally until it hits that
  point

break point on wire and function
11
Creating sub VIs

• If you create a program and want to use that in
  other program you can create a Sub VIs
• steps in creating a sub VI
• assign VI controls and indicators to wire
  terminals on its connector pane so that data can
  be passed into and out of the VI
• create an icon for the VI

12
C to F

• Create icon
• right click on icon in upper right corner and
  select Edit Icon

13
Assign Connectors

• Defining parameters
• like in Alice
• Right click icon on the front panel. (Not the
  block diagram.)
• Select Show Connector
• two terminals
• input / control on left
• output / indicator on right
• click in left hand terminal / box on icon and
  select front panel control to set
• repeat for right hand side terminal