Introduction to LabVIEWChris Thompson

Introduction

• What is LabVIEW?

• Project Explorer

• VI Front Panel

• Block Diagram

• Icon and Connector Pane

• Data Types

• While Loops

• For Loops

• Case Structures

• Arrays

• Clusters

• Polymorphism

What is LabVIEW?

• LabVIEW is a graphical programming language.

• LabVIEW programs are called Virtual Instruments; VI’s.

• The user interface is the Front Panel.

• The Block Diagram contains the graphical programming code.

• LabVIEW uses graphical dataflow programming.

Project Explorer

• The Project Explorer is a container for all of the VI’s and other resources required for a LabVIEW application.

VI Front Panel

• The Front Panel contains controls and indicators to operate the program and provide a display of data or information generated by the program.

VI Block Diagram

• The Block Diagram is the code that executes when the program runs.

Exercise 1

• Lets create a simple VI to create and display a random number between 0 and 10.

• Start a new VI: FILE>NEW VI…

• Place a Numeric Indicator on the Front Panel

• On the Block Diagram, add a Random Number and a Multiply function from the Numeric Palette.

• Right click on one input of the Multiply function and select CREATE>CONSTANT, and type 10 to set the value.

• Wire the rest of the diagram and run the program.

Icon and Connector Pane

• The VI Icon can be customized for your application.

• The Connector Pane allows you to connect your VI to other VI’s.

Commonly Used LabVIEW Data Types

• Numeric• Floating Point Single, Double, Extended precision

• Signed Integer Byte (8 bit), Word (16 bit), Long (32 bit)

• Unsigned Integer Byte (8 bit), Word (16 bit), Long (32 bit)

• Boolean – True or False

• String – one or more ASCII characters

• Enums – Enumerated preset list

While Loops

• A While Loop is a code structure that executes repeatedly until a condition is met.

• The Iteration Terminal provides a count of the number of times the loop has executed.

Exercise 2

• Let’s modify our Random Number program to generate a number once every second.

• On the Block Diagram, place While Loop enclosing all of the previously added functions.

• Right click Condition Terminal input and select CREATE>CONTROL.

• Place a Wait function inside the While Loop from the Timing Palette.

• Right click the input terminal to the Wait function and select CREATE>CONSTANT.

• Type 1000 to set the value of the constant to 1000 milliseconds.

For Loops

• A For Loop is a code structure that executes a defined number of times.

• The Count Terminal determines how many times the loop executes.

Exercise 3

• Let’s make a VI that averages 10 random numbers.

• Start a new VI, place a Numeric Indicator on the Front Panel.

• Create a For Loop and wire a constant to the Count Terminal set to 10.

• Place a Random Number, Multiply, and Add functions inside the loop.

• Add a Shift Register by right clicking on the For Loop border and selecting ADD SHIFT REGISTER.

• Wire everything to generate a number between 0 and 10 every time the loop runs and add it to the previous iteration.

• Add functions outside the loop to divide by 10 and display on the Front Panel Indicator.

Case Structures

• A Case Structure contains two or more sub-diagrams.

• The Case Selector label contains the name of case.

Arrays

• An Array is a data structure consisting of elements and dimensions.

• Elements are the data that make up the array.

• Dimensions are length, height, or depth of the array.

• An Array can have one or more dimensions.

Clusters

• A Cluster is a data structure that contains data elements of mixed types.

• The Error Cluster is commonly used in most VI’s for error handling.

• This cluster contains a Boolean (status), a numeric (code), and a string (source).

Polymorphism

• A VI can be designed to do different functions depending on the data that is wired to them.

• The FRC has a number of these types of VI’s, so in most cases you will need to select the correct variation for your application.

What to do Next

• Practice Coding!!

• Download LabVIEW from the FRC site, activate it with the team code.

• Purchase a LabVIEW Home license from Digilent for $50.

• Use LabVIEW to write programs for Arduino or Raspberry Pi.• Go to LabVIEW MakerSpace and download the LINX toolkit.

• LabVIEW Physical Computing kit from Digilent has license and a Pi, USB, and SD card for $89.