Python

JSON (De)Serialization of nested objects

During my first encounter of handling JSON (de)serialization in Python, I faced the problem of (de)serializing objects that have properties that are instances of another class. Using the json module, one has to write two methods, a complex_handler and a class_mapper that are fed to json.dumps and json.loads respectively. The design problem here is that the class_mapper needs to compare a dict that is to be deserialized with the properties of potential classes in order to find the matching type. In the first level of deserialization one could potentially provide the type as a parameter to the deserialization-function, but as soon as there is a child property, the type may be unknown. Therefore each class that is to be deserialized has to be registered into a collection of (properties) -> class mappings. To simplify the handling, I wrote the following JsonConvert class: Now we can define some classes and make…

Arduino, C#, Hardware, Root, Windows 8, WinRT

Arduino as a MIDI/Bluetooth Relay for Windows 8.1 Apps

In my last post I described how a Bluetooth connection between Arduino and a Windows 8.1 device can be established. The next step for me was to connect the Arduino to my electronic drum kit which has both, a MIDI-IN and a MIDI-OUT jack, but any other electronical instrument will do as well. The wiring diagram for an Arduino Uno R3 with MIDI-IN/OUT and the JY-MCU Bluetooth module is shown in Fig.1. NOTE: Occasionally there are MIDI shields available for Arduino, so you might not have to build it on your own. The Arduino code to relay MIDI>Bluetooth and Bluetooth>MIDI is actually quite simple. //======================================================authorship //by Michael Osthege (2013) //======================================================includes #include “SoftwareSerial.h” //======================================================constants const int TX_BT = 10; const int RX_BT = 11; const int MIDI_TX = 1; const int MIDI_RX = 0; //======================================================bluetooth setup SoftwareSerial btSerial(TX_BT, RX_BT); //======================================================initialization void setup() {     Serial.begin(31250);     btSerial.begin(9600);     Serial.println(“Bluetooth initialized”); }…

Arduino, C#, Hardware, Windows 8, WinRT

Bluetooth communication between Arduino and Windows 8.1

Introduction Recently, after being inspired by this video of Arduino Bluetooth communication with Windows Phone 8 by Marcos Pereira, I got myself some new devices to play with: Arduino Uno R3 in a starter kit (link) JY-MCU Bluetooth module (link) and a few extra cables The thing is: I don’t have a Windows Phone 8 yet and the Windows Phone 7.8 APIs do not support this kind of Bluetooth communication. But: I have a Surface RT and with Windows 8.1 the RFCOMM API can be used to establish a serial link to the Arduino. Arduino and Visual Studio It happens that my developing skills are quite limited to C# and when I had to develop some Kinect software with Processing in early 2012, I almost freaked out. Arduino code is written in C++  and the standard Arduino IDE is derived from the Processing IDE. Fortunately there’s the Visual Studio extension…

C#, Root, UI, Windows Phone

A Custom (Async) MessageBox for WPF and Windows Phone

The System.Windows.MessageBox provided by .NET is limited to a very small set of MessageBoxButtons (Yes/No/OK/Cancel) which do not allow for custom Button texts. The System.Windows.Forms.MessageBox also blocks the UI thread, which can be an annoying disadvantage as well. The MessageBox on Windows Phone has the same disadvantages. Custom buttons in a MessageBoxe simplify the decision for the user, because they can describe the results of the action: However you need to do this with a custom control, so for WPF as well as Windows Phone I designed a simple method for asynchronously showing a MessageBox with custom buttons. (The WPF implementation based on this control by Evan Wondrasek) So let’s bring some sample code.In WPF you can use multiple custom buttons: And on Windows Phone you’re limited to 2 buttons: To use CustomMessageBox, you need to get TCD.Controls from NuGet: And on Windows Phone 7.x you also need async support,…

C#, Metro, Windows 8, WinRT

In-App Donations for Windows 8 Apps

Recently I wanted to offer my customers the opportunity to donate some money. No extra features, just a clean donation option. In-app purchases seemed to be the best option. The idea is to have a list of products which have a price and contain “donate” in their product ID (Fig. 1). In the app the list of products can be retrieved and shown when a donate button is tapped. If donations have been given can be checked by enumerating the existing licenses and looking for the “donate” term (Fig. 2). Reasonably simple right? Well the principle is simple, but in-app purchases are a bit tricky to develop, debug and get through certification. (It took me 7 submissions to get it right..) Those are the things that can result in certification failure: no internet connection -> exception store does not respond properly -> exception error message looks to much like a…

C#, Root, UI, Windows 8, WinRT

Localizing Enums (in a ComboBox)

Enums have many useful applications and are often used in CoboBoxes to let the user select things. In the code behind the enum values are often defined using more or less cryptic text, because neither spaces, special characters, or leading numbers can be used in enum values (for good reasons!). Therefor it is necessary to change the text to something more understandable (language-localized in some cases). One way to achieve this is to create the ComboBox items manually, but it’s much more comfortable to fill the ComboBox items directly with the enum values, because you can get/set the SelectedItem without converting it back and forth from/to the enum value. You can’t override the .ToString() method of the Enum type, so we have to come up with another solution. Just like any other control, the ComboBox uses a Template to create its items. We will replace the default template with one…

C#, UI, Windows 8, WinRT

Keyboard Dismissing ComboBox

In the last few days I came across a design issue with the touch keyboard on Windows 8. The keyboard dismissal logic (documented here) defines a list of controls which do not cause the keyboard to dismiss when they get focused. The purpose is to prevent the keyboard from opening and closing all the time when the user fills out a form and is likely to switch between keyboard-editable controls such as TextBox and other controls like AppBar, Checkbox, RadioButtons the ComboBox and some more. While that works fine with the other controls, ComboBox expands when interacted with and might get covered by the touch keyboard. And unfortunately you can’t change that behavior, or manually dismiss a deployed touch keyboard. (The user is in complete control over the keyboard.) While on the MSDN forums it was suggested to alter the layout such that the ComboBox is less likely to collide with the…

C#, Windows Phone

TCD.Web.NotiConn – communicate between handsets without a server

Two days ago, when I was cycling, suddenly I had the answer: Imagine you have two Windows Phone 7 devices and want to establish a two-way connection between them. For example to play a game of Tic-Tac-Toe. You can do this either with a server on the internet, that connects the clients with each other, or the multicast protocol on WiFi-networks. The same WiFi network may not always be available to both users, but you don’t want to set up a server either (maybe, because you’re only doing this for fun, or you don’t have the resources). The only way to send messages to a WP7 app via the internet is to use push notifications. But how do you exchange the channel addresses between the devices? One way is to use a QR code: Establish a push notification channel on both devices Encode the channel URI into a QR code…

C#, Kinect, Windows 8, WinRT

TCD.Mathematics

UPDATE: Source and samples for WinRT and WPF are now on GitHub: https://github.com/michaelosthege/TCD.Mathematics This is just a quick post to introduce you to TCD.Mathematics, which is a NuGet package that adds several extension methods to the System.Windows.Media.Media3D namespace. If you’re unfamiliar with this namespace, it contains Point3D, Vector3D, Line3D and Plane3D classes which can be used for three-dimensional calculations. EDIT: I just submitted an update to the NuGet package, wich adds support for WinRT. Please not that WinRT does not have neither Point3D, Vector3D, nor the System.Windows.Media.Media3D namespace. So in WinRT all classes, including substitutes for Point3D/Vector3D are located under TCD.Mathematics. EDIT: Since version 1.2.0 TCD.Mathematics is a Portable Class Library that targets everything: Silverlight 4+, .NET4+, .NET for Windows Store, Windows Phone 7+, Xbox360 – make sure you’re running version 2.1+ of NuGet Package Manager! The extension methods, which are added to the mentioned Point3D/Vector3D classes are: Vector3D.AsPoint3D() Point3D.AsVector3D() Vector3D.Normalized() Point3D.CenterOfClusterWithOtherPoint3Ds () Point3D.ProjectOnLine3D() Point3D…

C#, Kinect, UI, Windows 8

TCD.Kinect

EDIT: If you’re interested in Skeleton tracking and calculating 3D stuff, take a look at TCD.Mathematics too^^ EDIT: There’s a WPF application that I once wrote, featuring SkeletonPainter3D: Kinect Sword. There’s a Youtube video of it (http://youtu.be/2j6GCd4M1bA) and that’s the source code: http://dl.dropbox.com/u/7813771/Blog/CodeSamples/KinectSword.zip   Hello there, I’ve created another UserControl, this time for Kinect and .NET 4.5, which hopefully has the potential to save you a lot of time. It can be used to draw three-dimensional Skeletons and explore the virtual space around them in real-time. A picture may be more appropriate: The control can be constructed in XAML: xmlns:kinect=”clr-namespace:TCD.Kinect.Controls;assembly=TCD.Kinect.Controls” <kinect:SkeletonPainter3D x:Name=”painter” Background=”Black” IsAnaglyphEnabled=”False” CameraFieldOfView=”70″ CameraPosition=”0,0.5,-1″ CameraLookAt=”0,0,2″ /> And populated with Skeletons using painter.Draw(skeletons), where skeletons is an Skeleton[] from inside the SkeletonFrameReady event. You can either get the TCD.Kinect package from NuGet, or refer to the sample implementation: http://code.msdn.microsoft.com/Implementation-of-f175b025 Let me know if you have any questions or suggestions, and by the way: SkeletonPainter3D has an experimental…