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As a Software Engineer I'm interested in how tightly coupled that one piece of code is to another. Coupling is the amound of dependencies that one entity has on another and tightly coupled code tends to be less portable and adaptable. But the concept of coupling doesn't stop at software. Coupling is also applicable to the relationship between hardware and software and I'm interested in avoiding tight coupling between the hardware and software for my code too.

With real implementations of Windows Phone 7 devices floating around it would be easy for some one to attempt to write an application that is tightly couple to that implementation. In some cases these low risk associated with doing this; for example if one tightly couples to screen resolutions (and there will only be two screen resolutions) it could be some time before some one needs to address another screen resolution. I'm writing a piece of code that is going to be sensative to the sampling rate of the accelerometer. And easy but tightly coupled way to handle this would be to measure the sample rate of the accelerometer and then write my code accordingly. But if I do this then I assume quite a few things. I would be assuming that other phones have the same sample rate. I would assume that the same phone will always have the same sample rate. I don't know that either of these assumptions are true.

The time information returned in the from DateTime.Now is precise enough for me to perform the measurements that I needed. So I wrote a quick application that would measure the accelerometer sample frequency and display it in a text box.

Here is my initial code

       private Accelerometer _accelerometer;

        // Constructor
        public MainPage()
        {
            InitializeComponent();
            this.DataContext = this;

            _accelerometer = new Accelerometer();
            _accelerometer.ReadingChanged += new EventHandler(_accelerometer_ReadingChanged);
            _accelerometer.Start();
        }

        void _accelerometer_ReadingChanged(object sender, AccelerometerReadingEventArgs e)
        {
            DateTime previousUpdate = LastUpdate;
            LastUpdate = DateTime.Now;
            double period = LastUpdate.Subtract(previousUpdate).TotalSeconds;
            double frequency = 1.0/period;
            if (frequency > HighestFrequency)
                HighestFrequency = frequency;

        }

        
// LastUpdate - generated from ObservableField snippet - Joel Ivory Johnson
  private DateTime _lastUpdate;
  public DateTime LastUpdate
  {
    get { return _lastUpdate; }
      set
      {
          if (_lastUpdate != value)
          {
              _lastUpdate = value;
              OnPropertyChanged("LastUpdate");
          }
      }
  }
 //-----      
// HighestFrequency - generated from ObservableField snippet - Joel Ivory Johnson
  private double _highestFrequency;
  public double HighestFrequency
  {
    get { return _highestFrequency; }
      set
      {
          if (_highestFrequency != value)
          {
              _highestFrequency = value;
              Dispatcher.BeginInvoke(() => { OnPropertyChanged("HighestFrequency"); });
            
          }
      }
  }
 //-----


        void OnPropertyChanged(string propertyName)
        {
            if(PropertyChanged!=null)
            {
                PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
            }
        }

        #region INotifyPropertyChanged Members

        public event PropertyChangedEventHandler PropertyChanged;

        #endregion
    }

Ofcourse there may be those that are curious as to what value a real device will currently returned. Of course publishing that type of information could result in more tightly coupled code being written. I'll post more once the code I am writing is done.

Tags: Windows Phone, Programming

Samsung released an updated version of their Windows Mobile SDK today.  The updated SDK contains new APIs that will let you access the proximity sensor and the compass in devices such as the Omnia II. You can get more information on the updated SDK from the Samsung Mobile Innovator site.

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An off subject observation.  In looking over my CodeProject articles I can't help but notice a trend. If I write something that is of productive value (EX: Windows Mobile development without Visual Studio)it seems to get good ratings over time. But if I write something with no apparent productive values (like the Zune HD Level article) it gets ratings at a faster rate. What does that mean?  It sounds like it means people are more interested in articles about fun things than productive things.  I may take this into consideration in mu future articles. It's already influenced the direction of my next article.

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If you are just getting started with Windows Mobile development then you will want to check out a page that Mike Francis has posted on his site.  It gives a a rather complete list of software you'll need/want, community resource, example code, guidance documents and other resources to get you started.  Check it out at http://blog.mjfnet.com/blog/FormatPage.aspx?path=content/projects/resources/resources.format.html

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I posted a code sample on CodeProject a few moments ago.  It is a remake of a simple game.  Best of all if the game is run on a compatible Samsung device it will take advantage of the hardware via the Samsung Mobile SDK. For more information see the article at the following link:

http://www.codeproject.com/KB/mobile/WiMoBubblePuzzle.aspx

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I've heard criticisms of the Windows and Windows Mobile environment because of the way that the default message pump is implemented and the performance cap that it puts on applications that require constant refreshing of the UI (such as games).  The problem is that the default message pump is geared towards business applications and minimizing CPU usage.  If you need to make a high performance application or game then you should use a different message pump implementation. You should not be waiting on WM_PAINT message.  You should just go ahead and repaint the screen.   Given that many developers will never alter the default message pump implementation it is preferable to have one that has low CPU usage by default.  If you want to do performance graphics you need a loop similar to the following:

	
bool keepRunning = true;
while(keepRunning)
{
	if(PeekMessage(&msg,NULL,0,0,TRUE))
	{
		if(msg.message==WM_QUIT)
			keepRunning=false;
		if (!TranslateAccelerator(msg.hwnd, hAccelTable, &msg)) 
		{
			TranslateMessage(&msg);
			DispatchMessage(&msg);
		}
	}
	else
	{
		//Execute Game Logic Here and rendering here
	}
}

The default message pump handling would be blocked when there are no messages to process and the WM_PAINT message (being low priority) would always be the last thing on the queue. In the message pump above the application will be able to concentrate on the game logic and give attention to messages on the queue when they arrive.  We'll talk about  other things that you would need to do for a game in coming posts.

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In my experience identifying the DirectDraw driver on the device is difficult to impossible.  According to documentation the IDIRECTDRAW::GetDeviceIdentifier method should be used to retrieve the driver information.  At the time that I am writing this the Windows Mobile 6 documentation shows that this method has one parameter of type  LPDDDEVICEIDENTIFIER.  But when you try to use the method you’ll find there is a second parameter needed of type DWORD.  When I first came across this I was a little confused because there was no mention of it in the documentation.  But I finally came across documentation for Windows CE 3.0 that mentioned the second parameter as being a flag and DDGDI_GETHOSTIDENTIFIER was the only possible value.  I tried to use the flag but then I found that it wasn’t defined in my header file.  After a bit of searching on the Internet I found this flag has a value of one.  I added a conditional #define to my source code.  It is conditional so that if I ever do get a correct header file it won’t break my code with redundant definitions.

#ifndef DDGDI_GETHOSTIDENTIFIER
#define DDGDI_GETHOSTIDENTIFIER 0x00000001L
#endif

I ran my code an error informing me that the argument was invalid.  I considered the possibility that 1 wasn’t the correct value. So I tried calling the function in a for loop testing out all possible values.  For the value of 0 I received  E_NOTIMPL. For all other values I received E_INVALIDARG.  As a final test I ran this against an emulator image with identical results.  So as far as I am concerned this method cannot be called in confidence.

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I recent had to take into consideration the APIs available in Windows Mobile for something I was working on recreationally. As per usual I added my notes and conclusions to my OneNote notebook and thought I would share some of it for those that may need to look up the same information.

I think I may have to go through all of these APIs and write a general introduction like what I did for Windows Mobile Power Management.

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I had the need to identify the driver being used in a set of Windows Mobile devices a little earlier and have a very simple program for doing so.   I grabbed some code that Mark Prentice had written to do so. Getting the string that identifies the driver is a couple of lines of code.

AdapterListCollection al = Manager.Adapters;
string driver = al.Default.Information.DriverName.ToString();

If you run this code the one thing you want to watch out for is a driver named "d3dmref.dll".  If you have this driver then that means you OEM didn't create/license a driver for your device and the graphics will render in seconds per frame.

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Samsung's Lab.dev has come out of beta.  What is Lab.dev?  It is a service offered by samsung that allows you to test your code on real Windows Mobile hardware remotely.  If you don't have a physical device but wanted to see how your code would behave on a Somsung device this is the perfect way to test out your software if you can't afford to purchase multiple physical devices. For more information see http://bit.ly/ds8gN or open up a Samsung Mobile Innovator account at http://innovator.samsungmobile.com

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You can now download the Windows Mobile 6.5 SDK from Microsoft.

http://www.microsoft.com/downloads/details.aspx?displaylang=en&FamilyID=20686a1d-97a8-4f80-bc6a-ae010e085a6e

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Are you waiting for the Windows Mobile 6.5 SDK before developing your application for the marketplace?  There's no need to wait as most of the functionality is already available in the Windows Mobile SDK now.  The only thing you can't access with it are Widgets.  But according to Steve Bell of Microsoft this summer a Developer Resource Kit will be release to update the SDK. It will include guidance on writing widgets and accessing other WM6.5 features.

 via MSDN Marketplace Forums

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Windows Internals 5th Edition was released to the presses today.  If you've ever been curious of the low level details of Windows you'll want to check this book out.  It should be about 70 USD when it goes on sale.  Here's a description of the book:

Get the architectural perspectives and inside details you need to understand the Windows kernel!

Delve inside the Windows kernel with noted internals experts Mark Russinovich and David Solomon, in collaboration with Alex Ionescu and the Microsoft Windows product development team. This classic guide—fully updated for Windows Vista and Windows Server 2008, including 64-bit extensions—describes the architecture and internals of the Windows operating system. You’ll find hands-on experiments you can use to experience Windows internal behavior first hand, along with advanced troubleshooting information to help you keep your systems running smoothly and efficiently. Whether you’re a developer or a system administrator, you’ll find critical architectural insights that you can quickly apply for better design, debugging, performance, and support.

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New developers to Windows Mobile often ask the question "What language should I use to get started with Windows Mobile development."  Paul Yao has written a nice guide for developers trying to decide on a language.  If those developers decide on the .Net path then he also has free books available on his website to get them started.

Microsoft Article: http://msdn.microsoft.com/en-us/library/dd630621.aspx
Site with Free Books: http://www.paulyao.com/res/code/login.aspx?ReturnUrl=%2fres%2fcode%2fdefault.aspx

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The "24 Hours of Windows Mobile" series is back! In the next presentation Nick Landry talks about WCF on Windows Mobile on 22 April 2009.  The following week Chris Craft is presenting on Mobile Databases.

• Mobile WCF
• Mobile Databases

BTW: If you've missed any of the "24 Hours of Windows Mobile" series I've got the links to all of them below.

Source: blogs.msdn.com/croman

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