Download while - RoboJackets

2011 TE Sessions Supported by:
Basic Concepts of Programming
November 3, 2012
www.robojackets.org
Before you begin…
Good programs:
• Take time
• Can be easily read
• Are easy to improve upon
The best way to make a good program is to
break the project up into smaller tasks.
General LabVIEW Info
• Dataflow is from left to right – the wires show
the order the code is run
• If two different blocks of code are not
connected in any way, they will run at the
same time when the VI starts
• Pressing ctrl+h in labview shows a dialog box
that briefly summarizes each icon function as
well as wire data.
Function Palette
• This box contains the operations that will be
used while coding.
• The programming header contains the
operations that will be used most frequently.
Picture of Function Palette
LabVIEW Constants
Basic Constant Types
• Numeric
• Strings (usually words)
• Boolean (true or false?)
Controls
• Usually trigger parts of a program
• Come in many forms such as buttons, knobs
and dropdown boxes (known as ring controls
in LabVIEW)
Indicators
• Show outputs
• Examples: graphs, gauges, slide fills
Loops
2 main types in programming: “while” and “for”
Biggest difference: while can be infinite, for is
always finite
While Loop
For Loops
While Loops
Called “while loops,” because the code keeps
running while a condition is met (while x < 5,
while x ≠ 7, or while a = “false”)
NOTE: Your code runs until the while loop
condition is met.
Index
Stop
Stopping While Loops
Stopping While Loops (cont’d)
Timing Changes
Normally, while loops run as fast as your
computer can allow them to run. However, that
may be too fast for your program.
Timing Changes (cont’d)
Shift Registers
• Shift registers remember the value that
occurs at the end of the loop and bring it
back to the beginning of the loop.
• Shift registers can be found in both while and
for loops.
• Shift registers usually have to be initialized
(this means, set the first value).
Example without Shift Registers
Initialize
Example with Shift Registers
Shift Registe
While Loop Example
• Make a while loop that does the following
– Increments an integer by 1 every loop iteration
– Multiplies a double by 2 every loop iteration
• Displays both of these numbers
– Waits .5 seconds for each loop iteration
– Has a stop button to terminate the loop
Solution
For Loops
For loops are a special type of while loop that
can only be stopped when it has run a set
number of times.
For Loops Usage: Arrays
For loops are great for making arrays in LabVIEW
Array- indexed list of similar elements
[4, 7, 12, 16, 25] : an array of numbers
[dog, cat, bird, fish] : an array of animal words
For Loop Array Example
Array Indicator
Count
Random
Numbers
Index
Case Statements
You can divide your code to run when certain
conditions are met. Case statements should be
used in while loops.
This code adds 1 every second the
button is pushed down.
Case Statement Example (False)
Case: False
Case Statement Example (True)
Case: True
Activity
• Write code to simulate an input device
– Using a while loop, two case structures, and two
buttons, have two counters that increment by 1
for each unit of time that each button is pressed
– If button 1 is pressed, counter 1 will increment
– If button 2 is pressed, counter 2 will increment
– If both buttons are pressed, both counters will
increment
Solution