Bailey O.H.Embedded systems.Desktop integration.2005

To fully understand how to access a USB device please review the code listings in the Chapter 11\USB folder available from the download sites. Each listing is very detailed and the C++Builder project files are included so you can get a feel for how to implement true cross-platform libraries in code.

Comparing Delphi/Kylix to C++BuilderX

This topic both concludes developing our middle-tier interface software and serves to lead into developing the user application layer. The products that we’ve used up to this point are all excellent products in their own right. Choosing code development over using a visual editor is not an easy decision to make. Several factors weighed heavily in using C++BuilderX over Delphi/Kylix for the middleware device interface.

The first item was the fact that Kylix does not generate native machine code that can be executed at the device driver level. Kylix has quite a few support libraries that make it an excellent user application development tool. Those same libraries, however, can wreak havoc when attempting to develop kernel or device driver level code.

The second compelling reason for selecting C++BuilderX for the device layer was the ability to add additional compilers along with the numbers of native compilers supported out of the box. The Borland code generators produce code that is of excellent quality. In my years of experience I’ve found Borland’s code quality and execution speed is second to none. But the ability to add other third-party compilers like GNU and even Microsoft Visual C and Intel make it a very versatile product. The flexibility in the C++BuilderX IDE in adding cross-compilers and scripts make it very attractive for the developer who is doing exactly what we are — developing cross-platform libraries from a sin- gle-source code base.

Mono and the .NET Framework

This is a brand new approach to development. Mono 1.1 is currently available, and I have successfully compiled C# code ported from the .NET framework without modifications. A lot of care has to be taken, however, in the use of the available .NET framework features available under Linux. This is a good approach but the framework isn’t quite ready for us.

wxWidgets and DialogBlocks

The wxWindows cross-platform development library for application development was recently renamed wxWidgets. DialogBlocks is a GUI application designer. The output from DialogBlocks can be compiled on any platform that supports the wxWidgets libraries. wxWidgets are strictly C++ so if you’re uncomfortable with C++, don’t use wxWidgets or DialogBlocks.

As you build the user interface with DialogBlocks the header and C++ source files are updated to reflect your changes. An application class is created (sound familiar?) and once your design is finished all that is left is to fill in your event handler code. DialogBlocks is a very powerful designer and is much improved over many commercial products. DialogBlocks runs on the same platforms that wxWidgets supports, including the IBM S390 mainframes.

It’s Time to Develop the User Application

Well, we’re down to the final task of creating the user application. Here is where the payoff of separating the device interface layer from the user application really shows. We are going to take two approaches to the user interface application. One will use the Kylix/Delphi/C++ Builder approach and the other will use the DialogBlocks/wxWidgets/C++BuilderX approach. With the Delphi/Kylix approach we will write a small application using the CLX component libraries. We will demonstrate how to build and distribute an application using this method for both Windows and

This will add the text in the edit box to the memo box and update the count of lines on the status bar.

7.Now it’s time to run the application. Add some text to the edit box and press Add. You should see the text added to the memo box and the line count incremented in the status bar. Figure 11-5 shows the Windows version.

Figure 11-5

8.Copy (or save) the project to a Linux machine with Kylix 3 installed. Start Kylix and open the project. You will receive an error that Unit1.pas cannot be located in the path. Ignore the error and manually open Unit1.pas. If there is a path in the uses clause, eliminate the path so the line for Unit1 simply says Unit1.

9.Next, compile and run the program. The following should be displayed.

Figure 11-6

The program should run unchanged and look similar to the above output. Add text to the memo box and the program should function identically to the Windows version. Remember earlier we created a Windows DLL and Linux shared library for the device interface layer. To access the hardware layer we will add the shred objects to the project along with the definition files if required and write the logic to access the serial, Ethernet, and USB ports.

The wxWidgets Development Effort

Now, we will develop a simple application using wxWidgets and DialogBlocks. To begin we will design the user interface in DialogBlocks.

1.Start DialogBlocks and select Sample Projects from the main screen. A list of projects will be displayed. I chose the NoteBook dialog project shown in Figure 11-7.

Chapter 11

Figure 11-7

The far left window pane in Figure 11-7 shows the available components in our current project, the middle pane is our designer, and the right pane contains properties associated with the currently selected design element. The tabs across the top hold the editor, header, source code file, variable definitions, and event handlers. Anything defined within the DialogBlocks context will be in the source files. To add source and header files you need to generate the associated classes; otherwise you will not see any code created. The next step in the process is to create a C++BuilderX project and add the source and header files we just created as shown in the following figure.

Figure 11-8

To compile and build the program with C++BuilderX, we need to also add the wxWidget libraries and add any remaining code and source files. When the project is complete, compile the project and link to the native wxWidget libraries for the chosen platform. wxWidgets takes a slightly different approach to development from Delphi/Kylix. I like to work with both and find Delphi and Kylix excellent products for developing solid

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