Language - LabVIEW

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Language - LabVIEW

Windows with LabVIEW

Welcome to using Phidgets with LabVIEW! By using LabVIEW, you will have access to the complete Phidget22 API, including events. We also provide example code in LabVIEW for all Phidget devices.

LabVIEW is a development environment for a graphical programming language created by National Instruments.

Language - LabVIEW

Windows with LabVIEW

Welcome to using Phidgets with LabVIEW! By using LabVIEW, you will have access to the complete Phidget22 API, including events. We also provide example code in LabVIEW for all Phidget devices.

LabVIEW is a development environment for a graphical programming language created by National Instruments.

Requirements

First, make sure you have the following:

● Phidgets Drivers for Windows installed(see Part 1 of this user guide)

Phidget LabVIEW Library downloaded


Note: The LabVIEW Library also contains example VI trees, which we'll cover later in this guide.

Using Our Examples

One of the best ways to start programming with Phidgets is to use our example code as a guide.

Unpack the Phidget LabVIEW Library and rename the unpacked folder to Phidgets.

Using Our Examples

Navigate to the following directory:

● For 32-bit LabVIEW, C:/Program Files (x86)/National Instruments/LabVIEW 20xx/instr.lib

● For 64-bit LabVIEW, C:/Program Files/National Instruments/LabVIEW 20xx/instr.lib

Place the renamed folder at this location:

Using Our Examples

Next, open LabVIEW and create a new VI:

Using Our Examples

In the new block diagram window, open the functions palette (View -> Functions Palette).

Next, go to the Phidgets palette (Instrument I/O -> Instrument Drivers -> Phidgets):

Using Our Examples

Next, select a palette that will work for your Phidget and drag VI Tree.vi onto your block diagram:

Using Our Examples

Right-click on VI Tree.vi and select Open Front Panel:

Using Our Examples

From the front panel, navigate to the block diagram (Window -> Block Diagram):

Using Our Examples

The VI Tree Block Diagram lists all VIs available for its Phidget Class, and which subpalette to find them under. The examples are located near the bottom of the block diagram. Right-click the example you would like to use and select Open Front Panel:

Using Our Examples

When you are ready, press Run and the application will demonstrate the Phidget's functionality.

Here is an example of an Accelerometer channel on a Spatial Phidget:

You should now have the example up and running for your device. Play around with the device and experiment with some of the functionality. When you are ready, the next step is configuring your environment and writing your own code!

Configure Your Environment

First, we recommend enabling the Show constant labels setting in LabVIEW. This setting will reduce complexity when developing, and is especially recommended for beginners.

To enable the setting, first navigate to Tools -> Options on your block diagram:

Configure Your Environment

Select the Environment category and enable Show created constant labels at the bottom:

Configure Your Environment

To begin working with Phidgets, you will need both a StartPhidget VI and a ClosePhidget VI:

Configure Your Environment

Select a class that will work with your Phidget from the drop-down menu for each VI:

Configure Your Environment

You can now add device information or any initialization parameters to the StartPhidget VI. Using your mouse, hover over each of the connection nodes to see information about it:

Configure Your Environment

If you would like to add device information or initialization parameters, right-click the connection node and navigate to one of the following:

Create -> Constant

Create -> Control

Configure Your Environment

Creating a constant will allow you to modify device information from the block diagram:

Configure Your Environment

Creating a control will allow you to modify device information from the front panel:

The environment now has access to Phidgets. Next, we'll walk through writing your own code.

Write Code

Along with this guide, your main resources for writing LabVIEW code will be:

● The examples

● The Phidget22 API

● The VI help files

Examples of more complex general topics such as using multiple Phidgets and connecting to a Phidget over the Network Server can be found under the VI Tree for the Phidget Common palette.

Example Flow

Most LabVIEW examples follow the same basic flow: starting a Phidget, reading some data, and closing the Phidget.

Step One: Initialize, Open And Wait For Attachment Of The Phidget

The entire process of opening and initializing a Phidget can be done by using the version of StartPhidget.vi that corresponds to your device. In most cases, StartPhidget.vi will also attempt to wait for the first data to become available from the device for 5 seconds after initialization.

If you'd prefer to initialize the device manually, you can use OpenPhidget.vi for your device and call the individual functions to set up the device.

Step Two: Do Things With The Phidget

You can read data and interact with your Phidget both by polling it for its current state (or to set a state), or by catching events that trigger when the data changes.

To poll devices, simply place the corresponding blocks:

To use events, there are three main blocks for each type, to create, execute, and close the event handler. When creating the event, all devices using an event of the same type must be grouped into an array to ensure the events get processed correctly.

Step Two: Do Things With The Phidget

Once created, the events will be processed by [Name]EventExe.vi. When an event occurs, the pertinent information will be output, as well as information to reference which device caused it.

After a program has run its course, the event handler must be closed.

Step Three: Close And Delete

Closing a Phidget is done by using the appropriate version of ClosePhidget.vi

That's all the basic building blocks you need to create a LabVIEW program using Phidgets.

Help and Documentation

For more information on the use of any VI and its parameters, right-click the VI and select Help

Help and Documentation

This will take you to an HTML page outlining the function of the VI. This includes a list of all its parameters, which devices support them, their range of acceptable values, and their default values, where applicable:

What's Next?

Now that you've set up Phidgets in your programming environment, you should read our guide on Phidget Programming Basics to learn the fundamentals of programming with Phidgets.

Continue reading below for advanced information and troubleshooting for your device.

Scroll down for device-specific troubleshooting, or go to the next slide for LabVIEW troubleshooting.

LabVIEW Troubleshooting

I cannot attach to an object any more after running my program once

What this means is you probably aborted the VI which stopped the program before the Phidget could be closed. Aborting execution will not release the Phidget device properly and will consequently make it unusable until the Phidgets library (or LabVIEW) has been restarted.

To resolve this, you may open a new VI, place PhidgetResetLibrary.vi, and run it. This will completely reset the current Phidget library, making it possible again to connect to all Phidgets.

Note that this action will close all Phidgets that are currently open in LabVIEW, and should not be used while other Phidgets-related LabVIEW VIs are running.

Phidget Reset All Palette.png

Phidget Reset All.png

In order to prevent this from happening you should use a software stop button when possible instead of halting operation. That way the Close subVI gets called and the Phidget will be released.

I cannot find my error code on this website

All Phidgets-based error codes in LabVIEW are offset by 7000 to avoid conflicting with LabVIEW's own error codes. To get the equivalent Phidget return code from the LabVIEW error code, simply subtract 7000. For instance, error code 7003 in LabVIEW translates to Phidget Return Code 3.

To find the meaning of all Phidget Return Codes, you can go to the Phidget22 API page, and open the PhidgetReturnCode section under Enumerations.

Events Can Occasionally Cause Issues, Especially When There Are Multiple Of The Same Type Of Event

In other words, if you open 2 of the same device and have a sensor change event for each one your system can behave unpredictably. This problem is a quirk in the way that LabVIEW handles passing events to and from C. There are a few solutions to this issue, either:

  • Stop using events and simply poll the device. Events work similarly to polling in LabVIEW anyway and should not cause substantial performance changes to your application.
  • Implement a simple fix to the events which are causing the problem. The pointer is identical in the case where two events of the same type are passed from a single function. This causes the events in C to output to the same event in LabVIEW. To get around this you need to copy the offending subVI, then change the name of the cluster object in it from "Event" to something else (your choice), change the name of the .vi to something else and then use those two different subVIs in your program. You would need to repeat this for each subsequent event of the same type you wish to have.
  • Make an array of all the devices you intend to use with the event, and feed the array into a single EventCreate vi, and use a single EventExe handler for all the events. When using this method, it might be tempting to add multiple event handlers, but keep in mind that events only occur once, in whichever handler sees them first. When running multiple Phidgets through the single event handler, you can determine which one caused the event by comparing the phid terminal from the EventExe VI to the Phidget IDs (Device In/Device Out) of your Phidgets.

We recommend using either of the the first two solutions where possible. The first is a bit cleaner, but the second will work just as well. We only recommend using the third method in cases where it is not practical to manually create individual event handlers.

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