Navigating LabVIEW

Wires

• Wires transfer data between block diagram objects.

• Wires are different colors, styles, and thicknesses,

depending on their data types.

• A broken wire appears as a dashed

black line with a red X in the middle.

Floating-point

Integer

String

Boolean

Scalar

1-D Array

2-D Array

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Context Help

• Displays basic information

about wires and nodes when

you move the cursor over an

object.

• Can be shown or hidden in

the following ways.

− Select Help»Show Context

Help from the LabVIEW menu.

− Press <Ctrl-H>.

− Click the following button on the

toolbar:

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LabVIEW Help

• Contains detailed descriptions and instructions for most

palettes, menus, tools, VIs, and functions.

• Can be accessed by:

− Selecting Help»

LabVIEW Help from the

menu.

− Clicking the Detailed help

link in the

Context Help window.

− Right-clicking an object

and selecting Help from

the shortcut menu.

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Examples

• LabVIEW includes

hundreds of example

VIs.

• Use NI Example Finder

to browse and search

installed examples.

− Select Help»Find

Examples in the menu.

• Click the example buttons in LabVIEW Help topics.

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Controls Palette

• Contains the controls and

indicators you use to create

the front panel.

• Navigate the subpalettes or

use the Search button to

search the Controls palette.

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Functions Palette

• Contains the VIs, functions,

and constants you use to

create the block diagram.

• Navigate the subpalettes or

use the Search button to

search the Functions palette.

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F. Searching for Controls, VIs, and

Functions

Palettes

Quick Drop

NI Global Search

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Searching for Controls, VIs, and Functions

Ways to find controls, VIs, and functions:

• Search or navigate the palettes.

− Controls palette

− Functions palette

• Search by name of object.

− Quick Drop dialog box

• Search palettes, LabVIEW Help, and ni.com.

− Search text box in toolbar

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Searching with Quick Drop

• Lets you quickly find controls,

functions, VIs, and other

items by name.

• Press the <Ctrl-Space> keys

to display the Quick Drop

dialog box.

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Lesson 2

Creating your First Application

TOPICS

A. Dataflow

B. Labview Data Types

C. Tools for Programming, Cleaning and Organizing Your VI

D. Building a Basic VI

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A. Dataflow

LabVIEW follows a dataflow model for running VIs

– A node executes only when data are available at all of

its input terminals

– A node supplies data to the output terminals only when

the node finishes execution

DISCUSSION

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B. LabVIEW Data Types

Shortcut Menu and Properties Dialog Box

Numeric Types

Boolean Types

String Types

Enums and Other Types

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DISCUSSION

LabVIEW Data Types

Terminals visually communicate information about the data

type represented

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DISCUSSION

Shortcut Menus

– All LabVIEW objects

have associated

shortcut menus.

– Use shortcut menu

items to change the

look or behavior of

objects.

– To access the shortcut

menu, right-click the

object.

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DISCUSSION

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Properties Dialog Box

– All LabVIEW objects have

properties.

– To access properties, right-

click the object and select

Properties.

– Property options are similar

to shortcut menu options.

– Select multiple objects to

simultaneously configure

shared properties.

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DISCUSSION

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Numerics

Various data type

representations:

– Floating-point

– Unsigned integers

– Signed integers

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DISCUSSION

Numeric Conversion

Coercion Dot

– Coercion dots indicate that LabVIEW

converted the value passed into a

node to a different representation.

• Occurs when a node expects an input

with a different representation.

– LabVIEW chooses the representation

that uses more bits.

– Avoid coercion by programmatically

converting to a matching data type.

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DISCUSSION

Exercice 1:

1: le type de données est réel

2: changer le type des entrées à entier sur 32bit

3: Changer les contrôles à des constantes de type entier

DISCUSSION

Booleans

– Behavior of Boolean

controls is specified by

the mechanical action.

– Boolean have only

TRUE/FALSE values.

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DISCUSSION

Exercice 2:

1: créer un nouveau VI

2: Editer les équations suivantes:

A and B

A or B

A nand B

A and B and C

3: Ajouter un voyant LED à chaque entrée

DISCUSSION

Strings

– A string is a sequence of ASCII

characters.

– Strings have various display

styles.

• Backslash codes

• Password

• Hex

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DISCUSSION

Enums//Ring

– Enums give users a

list of items from

which to select.

– Each item represents

a pair of values.

• String

• 16-bit Integer

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DISCUSSION

Other Data Types

– Dynamic

• Stores the information generated or acquired by an Express VI.

– Path

• Stores the location of a file or directory using the standard

syntax for the platform you are using.

– Waveform

• Carries the data, start time, and dt of a waveform.

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DISCUSSION

C. Tools for Programming, Cleaning and

Organizing Your VI

– Create, modify, and debug VIs

using the tools provided by LabVIEW

– A tool is a special operating mode of the

mouse cursor

– The operating mode of the cursor corresponds to the

icon of the tool selected

– When using the Automatic Tool Selection, LabVIEW

chooses which tool to select based on the current

location of the mouse

DISCUSSION

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DISCUSSION

D. Building a Basic VI

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DISCUSSION

Acquire Express VIs

– DAQ Assistant Express VI

– Instrument I/O Assistant Express VI

– Simulate Signal Express VI

– Read from Measurement File Express VI

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DISCUSSION

Analyze Express VIs

– Amplitude and Level Measurements Express VI

– Statistics Express VI

– Spectral Measurements Express VI

– Tone Measurements Express VI

– Filter Express VI

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DISCUSSION

Present Express VIs and Indicators

– Display Message Express VI

– Play Waveform Express VI

– Report Express VI

– Write Measurement File

Express VI

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DISCUSSION

Building and Running a VI

Place Express VI on the block diagram.

1.

2. Configure the dialog box that opens.

3. Wire Express VIs together.

Save and run the VI.

4.

The Run button appears broken when the VI you

are creating or editing contains errors.

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DISCUSSION

DISCUSSION

Lesson 3

Troubleshooting and Debugging VIs

TOPICS

A. Correcting Broken VIs

B. Debugging Techniques

C. Undefined or Unexpected Data

D. Error Handling

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A. Correcting Broken VIs

Broken Run arrow  VI cannot be compiled  VI cannot be executed

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DISCUSSION

Common Causes of Broken VIs

– Broken wires exist on the

block diagram.

• You wired a Boolean control to

a String indicator.

• You wired a numeric control to

a numeric control.

– A required block diagram

terminal is unwired.

– A subVI is broken.

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DISCUSSION

B. Debugging Techniques

Execution Highlighting

Single-Stepping

Probes

Breakpoints

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DISCUSSION

Debugging Techniques

What to look for if a VI produces unexpected data or behavior:

– Are there any unwired or hidden subVIs?

– Is the default data correct?

– Does the VI pass undefined data?

– Are numeric representations correct?

– Are node executed in the correct order?

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DISCUSSION

Execution Highlighting

– Use execution highlighting to watch the data flow

through the block diagram.

– If the VI runs more slowly than expected, confirm that

you turned off execution highlighting in subVIs.

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DISCUSSION

Single-Stepping

– Single-step through the VI to view each action of the VI

on the block diagram.

– Suspend the execution of a subVI to edit values of

controls and indicators, to control the number of times it

runs, or to go back to the beginning of the execution of

the subVI.

• Open subVI and select Operate»Suspend When Called from

the shortcut menu.

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DISCUSSION

Probes

– Use the Probe tool to observe intermediate

data values and check the error output of VIs

and functions, especially those performing I/O.

– Specify to retain the values in the wires so

that you can probe wires for data after

execution.

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DISCUSSION

Breakpoints

– When you reach a breakpoint during execution,

the VI pauses and the Pause button appears red.

• You can take the following actions at a breakpoint:

− Single-step through execution using the single-stepping buttons.

− Probe wires to check intermediate values.

− Change values of front panel controls.

− Click the Pause button to continue running to the next breakpoint

or until the VI finishes running.

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DISCUSSION

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C. Undefined or Unexpected Data

Check for unexpected Inf values or NaN values in your

mathematical operations:

– ∞ (Inf)

• Infinity

• Produced by dividing a number by zero.

– NaN

• Not a number

• Produced by invalid operations, such as taking the square

root of a negative number.

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DISCUSSION

D. Error Handling

Automatic and Manual Error Handling

Merge Errors Function

Error Clusters

Warnings

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DISCUSSION

Error Handling

Error Handling – Anticipation, detection,

and resolution of warnings and errors

– You cannot predict every problem a user can encounter.

– Without a mechanism to check for errors, you know only

that the VI does not work properly.

– Error handling tells you why and where errors occur.

• Automatic error handling

• Manual error handling

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DISCUSSION

Manual Error Handling

– You control when dialog boxes appear.

– Propagate errors by wiring the error out cluster to error

in cluster of next node to execute.

– Terminate the error chain with a call to Simple Error

Handler VI.

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DISCUSSION

Merge Errors

– Propagate errors along wires.

– Merge errors from different wire paths.

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DISCUSSION

Merge Errors Function

– Merge Errors function returns the first error found. If no

error is found, it returns the first warning.

– The Merge Errors function does not concatenate errors.

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DISCUSSION

Error Clusters

– Use the error cluster controls and indicators to create

error inputs and outputs in subVIs.

• The error in and error

out clusters include the

following components

of information:

− Status

− Code

− Source

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DISCUSSION

Errors and Warnings

Status = TRUE

Status = FALSE

Code = Non-zero

Error

Warning

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DISCUSSION

Errors and Warnings Recommendations

– Report errors and warnings with the Simple Error

Handler VI

• Modify Type of Dialog to detect warnings.

– Call the Simple Error Handler VI from the top-level VI.

– Avoid error dialogs in subVIs.

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DISCUSSION