Introduction to Writing Windows CE Display Drivers

Introduction to Writing Windows CE Display Drivers(1)

IntrodUCtion

For many developers, writing display drivers can be an intimidating task. Windows CE, Microsoft's operating system targeted toward embedded devices, is no exception. Fortunately, Microsoft provides C++ classes that can be used to simplify writing display drivers. As convenient as these classes are, there are improvements than can be made to them that can further simplify display driver development and make display drivers more portable across Windows CE devices.

Increased portability provides additional value for display drivers as Windows CE moves to different platforms with various display requirements, such as Internet appliances, video conferencing systems, and game consoles. Even within a product family, such as HPCS, this portability is valuable as each generation of product adds more features and functionality and moves to different display hardware.

This article reviews the fundamentals of graphics, display hardware, and Windows CE display driver development, including the display driver C++ classes. It then eXPlores improvements to the C++ classes that will simplify display driver development. At the end, you will have a set of improved display driver classes that should be simple enough to quickly and easily get running on any device, yet complete enough to support any additional hardware features. Of course, this doesn't prevent you from making your own improvements as well.

Fundamentals of Graphics and Display Hardware

For those developers not familiar with the principles of graphics hardware, it is worth providing a quick overview of the fundamentals of graphics and display technology in the context of a typical Windows CE display device. Graphics hardware is primarily composed of a display controller, a frame buffer and a DAC. The display controller handles Access to the frame buffer by the CPU, generates the video timing for the current display mode, and fetches the display data from the frame buffer to be displayed. The frame buffer stores the display data. The DAC, or digital to analog converter, converts the digital display data to an analog format to be sent to the monitor. This is necessary since most monitors expect analog voltage levels that represent the intensity of each color channel. The diagram below demonstrates the relationship among these components. It should be noted that as a result of the high level of integration achieved in today's silicon, all three components can be found in a single chip from some manufacturers.