Monday 13 October 2008

Digi Connect ME JumpStart Kit Hardware Emulation + Demo Code

Here is a small demo application running on a Digi Connect ME JumpStart kit, and an emulator of the kit:

I've started a new open source project for Digi Connect ME sample code, hosted on the TFS servers at CodePlex: 

The Pure Robot - Digi Connect ME project demonstrates the basics of interaction with the Digi Connect ME module, as well as emulation of the JumpStart kit hardware.

Emulating Hardware
One of the main features of this project is the Digi Connect ME JumpStart kit emulator. This was an interesting exercise for me since Digi do not supply their own emulator along with the kit and I've never attempted to build an emulator before. I've created one in the solution, in a project named PureRobot.Emulators.Digi.ConnectME.JumpStart. The code is in a beta stage: it's ready to look at with the LightFun sample code being discussed; however the serial emulation UI is not complete so the other sample projects in the solution may not work as expected yet.

The emulation features of the Microsoft .NET Micro Framework (.NET MF) are very easy to work with. Essentially all you need is a few lines of .NET code, an XML configuration file and some kind of UI. You can then execute your .NET MF code against the emulator and (in theory) see the same results as you would on the actual hardware.

I've made a basic attempt at defining the hardware in the emulator XML configuration file:

This file outlines the Input / Output (IO) capability of the Digi Connect ME module, and the memory characteristics as defined in the documentation:

Processor: 55MHz NS7520 (Digi Part no. NS7520B-1-I55)
Memory: 2 MB of Flash, 8 MB of SDRAM
IO: 5 GPIO pins, TTL (CMOS 3.3V) serial

For the user interface I used an image of the JumpStart kit board and added some overlaid bitmaps for the LEDs in the on state.

The emulator framework provides a nice set of objects to listen out for GPIO state changes. The only complexity in the UI code is that IO events will occur on another thread, so you need to synchronize with the UI thread before modifying the Windows Forms components to represent changes. When I first tried this, I used the InvokeRequired/BeginInvoke pattern of Windows Forms controls, but found the performance sucked. Instead I went for a synchronized set of integer variables which are modified by the IO thread using .NET thread synchronisation objects, then read on a timer from the UI thread - this seems to give a more realistic emulation experience.

The code for the UI form is here:

Running the Demo Code
To run the sample code:

  • Download the Visual Studio 2005 source and open the solution
    • You might have to cancel a few dialogs that attempt to access the source control server, then choose to 'Permanently remove source control association bindings'
  • Build the solution
    • When you build the solution the emulator will be added to the registry
  • Open the Project Properties of PureRobot.Digi.ConnectME.JumpStart.LightFun -> Micro Framework tab, and set the Transport to Emulator and the Device to 'PureRobot.Emulators.Digi.ConnectME.JumpStart'
  • Set the PureRobot.Digi.ConnectME.JumpStart.LightFun to the startup project
  • Run (hit F5)
    • If everything has been successful you should see the lights flashing away on the emulator application as they do in the video above.

Please feel free to play with the code and if you have any bugs, problems or improvements please don't hesitate to contact me through comments to this post or through the CodePlex site.


Unknown said...

Keep up the good work Luke!
I would like to be in touch with you and do Digi programming together.

Luke Thompson said...

Sure, I would be happy to work with you. I'm still doing work with the Digi modules and would value your input. Why don't you join the CodePlex project and we can share code and communicate through that?