Language - Visual Basic 6.0

Preamble about the language's origin and its main characteristics.

Support

Visual Basic 6.0 has a complete API and sample code for all Phidgets devices.

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

• 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.
• 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
• VB6 Sample Code
• You can find a high level discussion about programming with Phidgets in general on the General API 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 Microsoft Visual Basic 6.0 and this tutorial assumes its use. To begin, launch VB6 and create a Standard EXE for our project. Then, place a TextBox (Text1) in the form designer for the purpose of capturing some simple output.

Coding For Your Phidget

Before you can use the Phidget, you must include the Phidget ActiveX objects in your project. This can be accomplished from the components controls screen (Project | Components...) by checking the box beside “Phidget Library 2.1”, or by browsing to the location the framework was installed and choosing the Phidget21COM.dll.

Afterwards, the Phidget ActiveX object will need to be declared and then initialized. The simplest method is to place the Phidget ActiveX object from the palette directly on to your form.

Alternatively, you can dynamically create the ActiveX object in the code using Controls.Add(). You may need to uncheck ‘Remove information about unused ActiveX Controls’ in Project Options when using this if the form does not have the corresponding control placed.

  Public WithEvents PhidgetInterfaceKit1 As PhidgetInterfaceKit
  Set PhidgetInterfaceKit1 = Controls.Add("Phidget21COM.PhidgetInterfaceKit","PhidgetInterfaceKit1")

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

The program can try to 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 account for a connection by using event driven programming and tracking the AttachEvents and DetachEvents, or by calling WaitForAttachment. WaitForAttachment will block indefinitely until a connection is made to the Phidget, or an optional timeout is exceeded.

  Private Sub Form_Load()
    PhidgetInterfaceKit1.Open
    PhidgetInterfaceKit1.WaitforAttachment (3000)
  End Sub

The different parameters and open calls can be used to open the first Phidget of a type it can find, open based on a serial number, or even open across the network. The API manual lists all of the available modes that open provides. One important thing to remember is that when working with Phidgets, a local connection will reserve the device until closed. This prevents any other instances from retrieving data from the Phidget, including other programs. The one connection per device limit does not apply when exclusively using the Phidget Webservice.

You can call Close any time outside of the Phidget’s own event handlers to end the connection.

Event Driven Programming

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

    Private Sub PhidgetInterfaceKit1_OnSensorChange(ByVal Index As Long, ByVal SensorValue As Long)
         Text1.Text = Index & ":" & SensorValue
    End Sub

With this method, the code inside onSensorChange will get executed every time the PhidgetInterfaceKit reports a change on one of its analog inputs. You can let the editor generate the procedure prototypes for you through the drop down menu at the top of the code window.

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 inside polling loops used as an alternative to event driven programming. Simply use the instance properties such as SensorValue(Index as Long) or OutputState(Index as Long) for PhidgetInterfaceKits.

  phid.OutputState(4) = True

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.

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 place a PhidgetRFID ActiveX object instead of a PhidgetInterfaceKit. The methods and events available would change but they can be accessed in a similar manner.

Building your Project

Describe the different ways a project could be built using this language.

Common Problems and Solutions/Workarounds

Windows: My application does not compile when a function contains more than one parameter.

In Visual Basic 6.0, the common way to handle this issue is to not enclose the parameters with brackets. For example, instead of:

Object.getProperty(Parameter1, Parameter2)

You should write:

Object.getProperty Parameter1, Parameter2

The example programs uses the MATLAB timer() call, which relies on the Java Virtual Machine. Since Rosetta does not support Java, the examples will not operate as expected.