Visible Light Communications - Lumia 920 Windows Phone + Galaxy S5 Android

While i wait for the components to arrive i am trying some new stuff using the existing setup. Here is how i implemented a VLC data transmitter using the Windows Phone 8.0 - A Nokia Lumia 920....

--- A few eons later ---

Well this just did not turn out to be good. I tried to modulate the flash of the camera on both the Lumia 920 Windows phone and Android Galaxy S5 with similar results - It Does Not Work !! The maximum modulation frequency i got was around 33 Hz for both the devices. I believe achieving higher data rates using onboard timer mechanisms of the OS just does not work. If you are reading this and are an expert on Android or Windows Phone Operating systems, i would be glad if you could give this a try or even sugesst me how to achieve high resolution timers that operate without giving any distortion / timing errors if i use them to modulate the camera flash. The image below shows the application. Turn On / Turn Off just switch the flash ON/OFF using the torch mode. Timed button activates a timer based on the DispatchTimer class. The time duration is taken from the Textbox. Similarly the Pool Timer button activates a timer created using the ThreadPoolTimer class.

As an example here is the code from my windows phone program. P.S - This code was adapted from several examples i found on the internet and after doing a brief study on the WP8 How Tos. I do not major in WP8 programming ;) So if you spot something wierd please let me know...

	using System;
	using System.Collections.Generic;
	using System.Linq;
	using System.Threading.Tasks;
	using System.Windows;
	using Microsoft.Phone.Controls;
	using Microsoft.Phone.Shell;
	using FlashKontrol.Resources;
	using System.Windows.Media;
	using Windows.Phone.Media.Capture;
	using System.Windows.Threading;
	using Windows.System.Threading;
	namespace FlashKontrol
	{
	public partial class MainPage : PhoneApplicationPage
	{
	private AudioVideoCaptureDevice _captureDev;
	private const CameraSensorLocation _sensorLoc = CameraSensorLocation.Back;
	private IReadOnlyList<object> supportedCameraModes;
	private bool torchMode = false;
	private DispatcherTimer dispTimer;
	private ThreadPoolTimer periodicTimer;
	private bool flashFlag = false;
	// Constructor
	public MainPage()
	{
	InitializeComponent();
	InitializeCaptureDevice();
	SelectCaptureDevice();
	flashOff.IsEnabled = false;
	tspan.Text = "500";
	// Sample code to localize the ApplicationBar
	//BuildLocalizedApplicationBar();
	}
	private async void InitializeCaptureDevice()
	{
	_captureDev = await GetCaptureDevice();
	}
	private async Task<AudioVideoCaptureDevice> GetCaptureDevice()
	{
	AudioVideoCaptureDevice captureDevice = await AudioVideoCaptureDevice.OpenAsync(_sensorLoc, AudioVideoCaptureDevice.GetAvailableCaptureResolutions(_sensorLoc).First());
	return captureDevice;
	}
	private void SelectCaptureDevice()
	{
	try
	{
	supportedCameraModes = AudioVideoCaptureDevice.GetSupportedPropertyValues(_sensorLoc, KnownCameraAudioVideoProperties.VideoTorchMode);
	torchMode = supportedCameraModes.ToList().Contains((UInt32)VideoTorchMode.On);
	if (torchMode)
	{
	_captureDev.SetProperty(KnownCameraAudioVideoProperties.VideoTorchPower, AudioVideoCaptureDevice.GetSupportedPropertyRange(_sensorLoc, KnownCameraAudioVideoProperties.VideoTorchPower).Max);
	}
	}
	catch (Exception ex)
	{
	}
	}
	private void BitOn()
	{
	_captureDev.SetProperty(KnownCameraAudioVideoProperties.VideoTorchMode, VideoTorchMode.On);
	}
	private void BitOff()
	{
	_captureDev.SetProperty(KnownCameraAudioVideoProperties.VideoTorchMode, VideoTorchMode.Off);
	}
	private void Button_Click(object sender, RoutedEventArgs e)
	{
	if (torchMode)
	{
	BitOn();
	flashOn.IsEnabled = false;
	flashOff.IsEnabled = true;
	}
	}
	private void Button_Click_1(object sender, RoutedEventArgs e)
	{
	if (torchMode)
	{
	if (this.dispTimer != null)
	{
	this.dispTimer.Stop();
	timerOn.IsEnabled = true;
	BitOff();
	flashOn.IsEnabled = true;
	flashOff.IsEnabled = false;
	poolTime.IsEnabled = true;
	}
	else
	{
	BitOff();
	flashOn.IsEnabled = true;
	flashOff.IsEnabled = false;
	}
	if (periodicTimer != null)
	{
	periodicTimer.Cancel();
	flashOn.IsEnabled = true;
	flashOff.IsEnabled = false;
	poolTime.IsEnabled = true;
	}
	_captureDev.Dispose();
	}
	}
	private void timerOn_Click(object sender, RoutedEventArgs e)
	{
	if (this.dispTimer == null)
	{
	this.dispTimer = new DispatcherTimer();
	this.dispTimer.Interval = TimeSpan.FromMilliseconds(Convert.ToDouble(tspan.Text));
	this.dispTimer.Tick += new EventHandler(dispTimerEventHandler);
	}
	flashOn.IsEnabled = false;
	flashOff.IsEnabled = true;
	timerOn.IsEnabled = false;
	poolTime.IsEnabled = false;
	this.dispTimer.Start();
	}
	private void dispTimerEventHandler(object sender, EventArgs e)
	{
	if (flashFlag == false)
	{
	if (torchMode)
	{
	BitOn();
	flashFlag = true;
	}
	}
	else
	{
	if (torchMode)
	{
	BitOff();
	flashFlag = false;
	}
	}
	}
	private void poolTime_Click(object sender, RoutedEventArgs e)
	{
	if (periodicTimer == null)
	{
	flashOn.IsEnabled = false;
	flashOff.IsEnabled = true;
	timerOn.IsEnabled = false;
	poolTime.IsEnabled = false;
	periodicTimer = ThreadPoolTimer.CreatePeriodicTimer(PoolTimerHandler, TimeSpan.FromMilliseconds(Convert.ToDouble(tspan.Text)), DestroyPoolTmrHandler);
	}
	}
	private void PoolTimerHandler(ThreadPoolTimer timer)
	{
	if (flashFlag == false)
	{
	if (torchMode)
	{
	BitOn();
	flashFlag = true;
	}
	}
	else
	{
	if (torchMode)
	{
	BitOff();
	flashFlag = false;
	}
	}
	}
	private void DestroyPoolTmrHandler(ThreadPoolTimer dTimer)
	{
	dTimer.Cancel();
	}
	// Sample code for building a localized ApplicationBar
	//private void BuildLocalizedApplicationBar()
	//{
	// // Set the page's ApplicationBar to a new instance of ApplicationBar.
	// ApplicationBar = new ApplicationBar();
	// // Create a new button and set the text value to the localized string from AppResources.
	// ApplicationBarIconButton appBarButton = new ApplicationBarIconButton(new Uri("/Assets/AppBar/appbar.add.rest.png", UriKind.Relative));
	// appBarButton.Text = AppResources.AppBarButtonText;
	// ApplicationBar.Buttons.Add(appBarButton);
	// // Create a new menu item with the localized string from AppResources.
	// ApplicationBarMenuItem appBarMenuItem = new ApplicationBarMenuItem(AppResources.AppBarMenuItemText);
	// ApplicationBar.MenuItems.Add(appBarMenuItem);
	//}
	}
	}

view raw MainPageXAML.cs hosted with ❤ by GitHub

	<phone:PhoneApplicationPage
	x:Class="FlashKontrol.MainPage"
	xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
	xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
	xmlns:phone="clr-namespace:Microsoft.Phone.Controls;assembly=Microsoft.Phone"
	xmlns:shell="clr-namespace:Microsoft.Phone.Shell;assembly=Microsoft.Phone"
	xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
	xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
	mc:Ignorable="d"
	FontFamily="{StaticResource PhoneFontFamilyNormal}"
	FontSize="{StaticResource PhoneFontSizeNormal}"
	Foreground="{StaticResource PhoneForegroundBrush}"
	SupportedOrientations="Portrait" Orientation="Portrait"
	shell:SystemTray.IsVisible="True">
	<!--LayoutRoot is the root grid where all page content is placed-->
	<Grid x:Name="LayoutRoot" Background="Transparent">
	<Grid.RowDefinitions>
	<RowDefinition Height="Auto"/>
	<RowDefinition Height="*"/>
	</Grid.RowDefinitions>
	<!-- LOCALIZATION NOTE:
	To localize the displayed strings copy their values to appropriately named
	keys in the app's neutral language resource file (AppResources.resx) then
	replace the hard-coded text value between the attributes' quotation marks
	with the binding clause whose path points to that string name.
	For example:
	Text="{Binding Path=LocalizedResources.ApplicationTitle, Source={StaticResource LocalizedStrings}}"
	This binding points to the template's string resource named "ApplicationTitle".
	Adding supported languages in the Project Properties tab will create a
	new resx file per language that can carry the translated values of your
	UI strings. The binding in these examples will cause the value of the
	attributes to be drawn from the .resx file that matches the
	CurrentUICulture of the app at run time.
	-->
	<!--TitlePanel contains the name of the application and page title-->
	<StackPanel x:Name="TitlePanel" Grid.Row="0" Margin="12,17,0,28">
	<TextBlock Text="Rishi Franklin" Style="{StaticResource PhoneTextNormalStyle}" Margin="12,0"/>
	<TextBlock Text="Flash Kontrol" Margin="9,-7,0,0" Style="{StaticResource PhoneTextTitle1Style}"/>
	</StackPanel>
	<!--ContentPanel - place additional content here-->
	<Grid x:Name="ContentPanel" Grid.Row="1" Margin="12,0,12,0">
	<Button x:Name="flashOn" Content="Turn On" HorizontalAlignment="Left" Margin="10,41,0,0" VerticalAlignment="Top" Click="Button_Click" Width="178"/>
	<Button x:Name="flashOff" Content="Turn Off" HorizontalAlignment="Left" Margin="268,41,0,0" VerticalAlignment="Top" Width="178" Click="Button_Click_1"/>
	<Button x:Name="timerOn" Content="Timed" HorizontalAlignment="Left" Margin="10,144,0,0" VerticalAlignment="Top" Width="178" Click="timerOn_Click"/>
	<TextBox x:Name="tspan" HorizontalAlignment="Left" Height="72" Margin="0,250,0,0" TextWrapping="Wrap" Text="TextBox" VerticalAlignment="Top" Width="456"/>
	<Button x:Name="poolTime" Content="Pool Timer" HorizontalAlignment="Left" Margin="268,144,0,0" VerticalAlignment="Top" Width="178" Click="poolTime_Click"/>
	</Grid>
	<!--Uncomment to see an alignment grid to help ensure your controls are
	aligned on common boundaries. The image has a top margin of -32px to
	account for the System Tray. Set this to 0 (or remove the margin altogether)
	if the System Tray is hidden.
	Before shipping remove this XAML and the image itself.-->
	<!--<Image Source="/Assets/AlignmentGrid.png" VerticalAlignment="Top" Height="800" Width="480" Margin="0,-32,0,0" Grid.Row="0" Grid.RowSpan="2" IsHitTestVisible="False" />-->
	</Grid>
	</phone:PhoneApplicationPage>

view raw MainPAGE.xaml hosted with ❤ by GitHub