Language - Flex AS3

Flex AS3 is no longer maintained by Phidgets.

Assessment for use with Phidgets

Our honest opinion on how well this language is suited to controlling Phidgets. If it is a poor choice, suggest and link similar (better) languages.

Support

Flex AS3 has a complete API and code samples for all Phidgets devices.

For a complete list of our supported languages and their support status, click here.

Restrictions

In this section, list any restrictions or limitations that this particular language may impose. For example, incompatibility with certain operating systems.

Development Environments and Compilers

Describe each major compiler and notable differences or important information. (eg. framework versions) If there are known issues/workarounds mention them and link to the corresponding issue at the bottom of the page.

Quick Downloads

Before you can run your program, you need to set up the proper environment and get the necessary files off the Phidgets website. Visit the drivers section at www.phidgets.com and get the latest:

• Phidget Framework

You will need the Phidget Framework to use and to program with Phidgets. We also recommend that you download the following reference materials:

• API Manual
• API Reference
• Flex AS3 Sample Code
• You can find a high level discussion about programming with Phidgets in general on the General Phidget Programming page.
• The Device Functionality page explains the general operational information for your device.

You may want to have these pages open while working through these instructions.

Getting Started

The Phidget examples were written using Actionscript 3.0 under Adobe Flex Builder 3 and this tutorial assumes its use. Other development environments should work provided they support Actionscript 3.0, and each would be set up in a similar manner. First launch Flex and generate a new project with a descriptive name such as PhidgetTest. You will then need to add the Phidget Library to your project library path. This can be done under Project | Properties | Flex Build Path on the Library tab, by clicking the “Add SWC” button and selecting the Phidget21Library.swc from the Flex examples. As an alternative, you can copy the “com” folder that is located in the Flash AS3 examples into your project source directory and it should work as well.

Coding For Your Phidget

Before you can use the Phidget, you must import references from the library to the device in the main body of code. In MXML and Actionscript 3.0:

  <?xml version="1.0" encoding="utf-8"?>
  <mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" layout="absolute">
  <mx:Script>
     <![CDATA[
        import com.phidgets.PhidgetInterfaceKit;
        import com.phidgets.events.*;
        //More code goes here
     ]]>
  </mx:Script>
  </mx:Application>

Afterwards, the Phidget object will need to be declared and then initialized. For example, a start function is set to execute on initialization, and then an instance of a PhidgetInterfaceKit is declared and then set inside with:

  public var phid:com.phidgets.PhidgetInterfaceKit;
  public function start():void{ 
     phid = new PhidgetInterfaceKit();
     //More code goes here
}

The object name for any type of Phidget is listed in the API manual. Every type of Phidget also inherits functionality from the Phidget base class.

Connecting to the Phidget

Next, the program needs to try and connect to the Phidget through an open call. Open will continuously try to connect to a Phidget, based on the parameters given, even trying to reconnect if it gets disconnected. This means that simply calling open does not guarantee you can use the Phidget immediately. We can handle this by using event driven programming and tracking the AttachEvents and DetachEvents, or checking the isAttached property.

  phid.open("localhost", 5001);

The API manual lists all of the available modes that open provides. In Flash, the parameters can be used to open the first Phidget of a type it can find or based on its serial number. One important thing to remember is that when working with Phidgets, a local connection will reserve the device until closed. This means other programs that open the Phidget may end up preventing other instances from retrieving data. The one connection per device limit does not apply when exclusively using the Phidget WebService, and the Actionscript libraries by extension.

Event Driven Programming

We recommend the use of event driven programming when working with Phidgets. In Actionscript 3.0, we hook an event handler with the following code:

 
  phid.addEventListener(PhidgetDataEvent.SENSOR_CHANGE, onSensorChange);

The onSensorChange method will get executed every time the PhidgetInterfaceKit reports a change on one of its analog inputs. The values from the report can be accessed from the PhidgetDataEvent object.

  private function onSensorChange(evt:PhidgetDataEvent):void{
     //Insert your code here
}

Some events such as Attach and Detach belong to the base Phidget object and thus are common to all types of Phidgets. Please refer to the API manual for a full list of events and their usage.

Working directly with the Phidget

Some values can be directly read and set on the Phidget and used as an alternative to event driven programming. Simply use the instance properties or call member functions such as getSensorValue(index: int) or setOutputState(index: int, val: Boolean) for PhidgetInterfaceKits.

Working with multiple Phidgets

Multiple Phidgets of the same type can easily be run inside the same program. In our case, it requires another PhidgetInterfaceKit instance to be defined and initialized. The new instance can then be set up, opened and used in the same process as the previous one. If the application needs to distinguish between the devices, open can be called with the serial number of a specific Phidget.

Flash Security Settings

During debugging or after publishing the project, you may encounter some difficulties with Flash network security settings either inside or outside of the development environment with Phidgets. Permissions for your project folder can be added through the settings manager at here, under “Always trust files in these locations” | “Edit locations...” | “Add location...”.

Other Phidgets

The design given in this document can also be followed for almost all Phidgets. For example, if you were using a PhidgetRFID instead of an PhidgetInterfacekit, you would declare a RFID object instead of a InterfaceKit object. The methods and events available would change but they can be accessed in a similar manner.

Building your Project

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Common Problems and Solutions/Workarounds

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