Language - MATLAB

MATLAB has a supported API for all Phidgets devices, and code samples for some devices. For a complete list of our supported languages and their support status, click here.

MATLAB does not allow any form of event driven programming. Most of our other supported languages do, we recommend choosing a language that does.

If this is your first time working with a Phidget, we suggest starting with the Getting Started page for your specific device. That page will walk you through installing drivers and libraries for your operating system, and will then bring you back here to use MATLAB specifically.

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.

Drivers, Libraries and Resources

Before you can run your program, you need to set up the proper environment and get the necessary files off the Phidgets website. The functionality through MATLAB essentially means calling functions in the C library through MATLAB. Hence, you will need the C/C++ libraries below, and you will probably find the C/C++ API documentation below useful.

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:

• C/C++ API Manual
• API Reference
• MATLAB 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 MATLAB m-files and this tutorial assumes its use. Your project will need to be able to find the phidget21Matlab.h from the MATLAB examples.

Coding For Your Phidget

Programming with Phidgets will make extensive use of the calllib() function. Before you can use the Phidget, you must include a reference to the library in the code in the main body of code. Copy phidget21Matlab.h to your project directory and then in MATLAB:

  function phidgettest(n)
     loadlibrary phidget21 phidget21Matlab.h;
      % More code goes here
  end

Afterwards, the Phidget object will need to be declared and then initialized. For example, we can declare a PhidgetInterfaceKit with:

  ikptr = libpointer('int32Ptr',0);
  calllib('phidget21', 'CPhidgetInterfaceKit_create', ikptr);
  ikhandle = get(ikptr, 'Value');

The ikptr is converted to ikhandle as a handle of the PhidgetInterfacekit, and is used for all the C function calls where CPhidgetHandle phid is used. 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 handle this by calling waitForAttachment. WaitForAttachment will block indefinitely until a connection is made to the Phidget, or an optional timeout is exceeded.

  calllib('phidget21', 'CPhidget_open', ikhandle, -1);
  if calllib('phidget21', 'CPhidget_waitForAttachment', ikhandle, 2500) == 0
     % Insert your code here
  end

The different types of open can be used with parameters to try and get the first device it can find, open based on its 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. At the end of your program, don’t forget to call close to free any locks on the Phidget.

  calllib('phidget21', 'CPhidget_close', ikhandle);
  calllib('phidget21', 'CPhidget_delete', ikhandle);

Working directly with the Phidget

MATLAB does not support event handling, so all data must be read and sent directly. Simply use the C API functions such as CPhidgetInterfaceKit_getSensorValue() or CPhidgetInterfaceKit_setOutState() for InterfaceKits.

  while n<10
    dataptr = libpointer('int32Ptr',0);
    calllib('phidget21', 'CPhidgetInterfaceKit_getSensorValue', ikhandle, 0, dataptr)
    disp(get(dataptr, 'Value'));
    n=n+1;
  end

Here a pointer is created to mark a value from the InterfaceKit inside a polling loop, and then its value is displayed to screen.

Working with multiple Phidgets

Multiple Phidgets of the same type can easily be run inside the same program. In our case, it requires another pointer and handle initialized for a PhidgetInterfaceKit. The new instance can then be set up, opened and used in the same fashion 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 Interfacekit, you would call CPhidgetRFID_create instead of CPhidgetInterfaceKit_create. The functions 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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