EET 2259 Unit 2
Virtual Instruments



Read Bishop, Chapter 2.
Lab #2 and Homework #2 due next
week.
Quiz #1 next week.
Floyd, Digital Fundamentals, 10th ed
Virtual Instruments


Remember, LabVIEW programs are
called virtual instruments, or VIs for
short.
Recall that every VI has a front panel
(user interface) and a block diagram
(program code).
(Bishop, p. 53)
Floyd, Digital Fundamentals, 10th ed
Items on Front Panel



The front panel contains controls and
indicators.
Controls are inputs that let the user enter
data, such as switches, knobs.
Indicators are outputs that display data
to the user, such as graphs, numeric
displays.
(Bishop, p. 62)
Floyd, Digital Fundamentals, 10th ed
Controls Palette

Use the controls
palette to place
controls or indicators
on the front panel.
(Open palette by View
> Controls Palette or
by right-clicking a
blank area on front
panel.)
(Bishop, p. 62)
Floyd, Digital Fundamentals, 10th ed
Finding Controls & Indicators

On the controls palette, under Modern, the
most commonly used controls and indicators
are grouped into three categories: Numeric,
Boolean, and String & Path.
Floyd, Digital Fundamentals, 10th ed
Search Button on Controls Palette

Search button lets you find controls or
indicators by name.
(Bishop, p. 64)
Search
Floyd, Digital Fundamentals, 10th ed
Items on Block Diagram

The block diagram contains items connected
by wires. Most items on the block diagram fall
into one of four categories:




Built-in functions (such as multiplication)
SubVIs (A subVI is a smaller program contained
within a bigger program.)
Express VIs (a special type of subVI)
Terminals representing front-panel controls or
indicators, or constant values
Floyd, Digital Fundamentals, 10th ed
(Bishop, pp. 68-69)
Distinguishing Functions from
SubVIs (Part 1)

On block diagrams, built-in functions
have a pale yellow background, while
subVIs usually have a white background
(except for Express VIs, which have a
blue background).
(Bishop, p. 70)
Floyd, Digital Fundamentals, 10th ed
Distinguishing Functions from
SubVIs (Part 2)



When you double-click a function, nothing
happens.
When you double-click a standard subVI, the
front panel for the subVI opens. (Remember,
a subVI is a complete program with its own
front panel and block diagram.)
When you double-click an Express VI, a
dialog box opens to let you configure it.
(Bishop, p. 70)
Floyd, Digital Fundamentals, 10th ed
Functions, SubVIs, and Express
VIs



Functions: Can’t be customized.
Standard subVIs: You can rewire the block
diagram to customize.
Express VIs: You use dialog box to
customize.
Floyd, Digital Fundamentals, 10th ed
Icons vs. Expandable Nodes


Standard subVIs and Express VIs can be
displayed either as icons or as expandable
nodes.
To change display, right-click and select (or
deselect) “View As Icon.”
(Bishop, p. 70)
Floyd, Digital Fundamentals, 10th ed
Example

Same VI, viewed three different ways.
Icon
Floyd, Digital Fundamentals, 10th ed
Expandable Node
Expanded Node
Colors for Data Types

Terminals and wires are color-coded to show
what type of data they carry:






Blue = integer
Orange = floating point number
Green = Boolean (true/false)
Pink = String (text)
Blue & White Dashed = Dynamic (for Express VIs)
Usually two terminals can be connected
together by a wire only if they’re the same
data type.
(Bishop, p. 72)
Floyd, Digital Fundamentals,
10th
ed
Terminals

A terminal on a block diagram is a
connection point for a wire. There are
several kinds of terminals, including:




Constants
Control terminals for inputs from front panel
Indicator terminals for outputs to front panel
Node terminals on functions or subVIs
(Bishop, p. 71)
Floyd, Digital Fundamentals, 10th ed
Control Terminals




A control terminal has an arrow pointing out to
the right.
There’s a control terminal on the block
diagram for each control on the front panel.
On front panel, can right-click and choose
“Find Terminal.”
On block diagram, can right-click and choose
“Find Control.”
(Bishop, p. 72)
Floyd, Digital Fundamentals, 10th ed
Indicator Terminals




An indicator terminal has an arrow pointing in
from the left.
There’s an indicator terminal on the block
diagram for each indicator on the front panel.
On front panel, can right-click and choose
“Find Terminal.”
On block diagram, can right-click and choose
“Find Indicator.”
(Bishop, p. 72)
Floyd, Digital Fundamentals, 10th ed
Icons vs. Data Type Terminals


On the block diagram, control terminals and
indicator terminals can be displayed either
as icons or as data type terminals.
To change display, right-click and select (or
deselect) “View As Icon.”
(Bishop, p. 72)
Icon
Floyd, Digital Fundamentals, 10th ed
Data Type Terminal
Terminals on Functions or SubVIs
(Part 1)


Functions and subVIs also have terminals
where wires can connect to them.
By convention, inputs are placed on the left
and outputs are on the right.
Floyd, Digital Fundamentals, 10th ed
Terminals on Functions or SubVIs
(Part 2)

To show terminals more clearly, right-click
and select “Visible Items” > “Terminals”
Floyd, Digital Fundamentals, 10th ed
Dataflow Programming


In traditional text-based programming
languages, the order of the statements
determines the order in which they’re
executed.
In LabVIEW’s graphical language, the layout
on the page does not tell you the order of
execution. Rather, a node executes
whenever all of its inputs are available.
(Bishop, pp. 82-83)
Floyd, Digital Fundamentals, 10th ed
Highlight Execution Button

To watch the order in which nodes are
executed in the block diagram, click the
Highlight Execution button on block
diagram’s toolbar and then run the VI.
(Bishop, p. 84)
Click on Highlight Execution button; data
flow is animated using bubbles. Values are
displayed on wires.
Floyd, Digital Fundamentals, 10th ed