Transcript EET 159 PowerPoint Slides

EET 2259
Programming for
Electronics Technology
Professor Nick Reeder
Reminders
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Please turn off cell phones.
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No food or soft drinks in the classroom.
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Stow water bottles at floor level.
EET 2259 Unit 1
LabVIEW Basics
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Read Bishop, Chapter 1.
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Lab #1 and Homework #1 due next
week.
LabVIEW
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Stands for Laboratory Virtual Instrument
Engineering Workbench.
It’s a software package created by
National Instruments (www.ni.com). This
company bought Multisim a few years
ago.
(Bishop, p. 3)
National Instruments
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Company founded about 30 years ago in
Austin, TX.
In addition to Multisim, LabVIEW, and
other software packages, they sell data
acquisition boards and other hardware for
using computers in engineering, science,
and industry.
(Bishop, pp. 3-4)
Some of LabVIEW’s Uses
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General-purpose programming
Instrument control
Data acquisition
Data analysis
Data presentation
Automated testing
General-purpose Programming
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Writing programs to perform calculations,
process information, play games, etc.
Examples:
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Checkbook balancer
Calorie counter
Baseball statistics calculator
This is not really what LabVIEW is meant
for, but you can use it to do these things.
Instrument Control
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Using computer to control multimeters,
oscilloscopes, function generators, etc.
Data Acquisition (DAQ)
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Connecting the computer directly to circuits or
sensors to measure voltage, current, temperature,
pressure, light intensity, chemical composition, etc.
Need to have either:
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a special data-acquisition board
installed in your computer,
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or an external data-acquisition
device such as an NI myDAQ.
Data Analysis
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Performing statistical analysis, curve
fitting, signal processing, or other kinds of
mathematical calculations on the data
that you’ve gathered from a DAQ board
or from measuring instruments.
Similar to what you can do with Microsoft
Excel or other spreadsheet programs.
Data Presentation
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Using tables, charts, and graphs to
present the results of your data analysis.
Again, similar to what you can do with
Microsoft Excel or other spreadsheet
programs.
Automated Testing
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Using computers to automatically test
circuit boards or other manufactured
parts as they leave an assembly line.
G
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LabVIEW is built around a programming
language called G.
Most of this course will be devoted to
learning how to write programs in G.
(Bishop, p. 4)
Graphical vs. Text-Based
Language
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Most other programming languages
(Assembly, VisualBasic, C, C++, Java,
etc.) are text-based languages. You
write programs by typing text.
G is a graphical language. You write
programs by placing icons and
connecting them with wires.
(Bishop, p. 4)
Example Program in C
#include <stdio.h>
int main()
{
float value1, value2, product;
printf("Enter first number => ");
scanf("%f", &value1);
printf("Enter second number => ");
scanf("%f", &value2);
product = value1 * value2;
printf("The product is %f", product);
Same Program in LabVIEW
“Virtual Instruments”
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LabVIEW programs are called virtual
instruments, or VIs for short.
When you save a program file in
LabVIEW, its extension is “.vi”
(Bishop, p. 4)
Front Panel & Block Diagram
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Every LabVIEW program has two parts,
which appear in two different windows on
your computer screen: the front panel
and the block diagram.
You don’t have to save these two parts
separately; whenever you save, they’re
both saved in the same file.
Front Panel
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The front panel is the user interface for a
program. It contains controls (inputs)
and indicators (outputs).
Controls let the user feed data into the
program.
Indicators let the program give data back
to the user.
Sample Front Panel
Block Diagram
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The block diagram shows the program’s
underlying logic. It shows how the user’s
data (entered through controls) is
manipulated to give the results that are
fed back to the user (through indicators).
The block diagram contains components
“wired” together.
Sample Block Diagram
Toolbar
Run Button
Continuous Run Button
Abort Execution
Additional Buttons on
the Diagram Toolbar
Pause/Continue Button
Execution Highlighting
Button
Text Settings
Step Into Button
Align Objects
Step Over Button
Distribute Objects
Step Out Button
Reorder
Resize front panel
objects
(Bishop, pp. 10-14)
Controls Palette & Functions Palette
Controls Palette
(Used to place controls &
indicators on Front Panel)
Functions Palette
(Used to place functions
on Block Diagram)
(Bishop, pp. 24-26)
Menus
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LabVIEW has pull-down menus and
short-cut menus (pop-up menus) that
give you many options.
Sections 1.6 and 1.7 in textbook discuss
the menus.
(Bishop, pp. 14-23)
Help
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LabVIEW’s context help window is very
useful. It automatically shows help for
functions and other objects when you roll
your mouse over those objects.
More detailed help is also available
through Help menu.
(Bishop, pp. 33-34)
Context Help Window
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Ctrl + H
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Detailed help
Lock help
Simple/Complex Diagram help
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Saving Your Control Values
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When you save a VI, values that you
have set on the front panel are not
saved.
But you can make them be saved by
selecting Edit > Make Current Values
Default before you save.
Or you can do this with a single control by
right-clicking it and selecting Data
Operations > Make Current Value
Default.
Example Programs
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LabVIEW comes with many example VIs,
which you can access by clicking Help >
Find Examples… in LabVIEW’s menus.
More examples are in the textbook’s
Learning Directory files, which you’ll
download from the Web as part of
Homework #1.
(Bishop, p. 5)