Study Of The I/O Device Driver Model And Framework Based Embedded System

Embedded System applies to industry control, multimedia, communication and so on widely. I/O Device Driver-one of Embedded Operating System structure, plays a pivotal role in the application area of Embedded Operating System. As a rule, two methods are used for doing I/O device driver. One is process structure system; another is single system. On I/O device driver structure of Embedded Operating System, Implementing I/O device driver has another two approaches-kernel-level I/O Technology and user-level I/O Technology. I/O device driver is one of Operating System and lie in priority level in kernel-level I/O Technology. Kernel-level Technology supports device driver program remove embedded operating system kernel; Devices are directly controlled, written, red and device buffers are managed on user-level; because it is simple to be implemented in micro-kernel operating system, user-level I/O gets increasingly important for embedded applications.Embedded operating system implements software called device drivers, whose purpose is to manage, or drive, hardware devices. A device driver links an operating system and a device, making it possible for the operating system to recognize the device and to present the device's services to applications. It is difficult to obtain easily-implement and real-time at one time by means of single method in implementing I/O device driver.To resolve the problem, this thesis discusses user-level I/O Technology of process structure combining with layered structure model. Layered device drivers split the code into an upper layer called application layer and a lower layer called hardware device driver layer. It is legible and easily-implement for I/O devicedriver structure; it is convenient for Debug and concealing hardware driver detail. To support user-level I/O of process structure for embedded system, signal mechanism is adopted. To ensure real-time demand, this thesis discusses signal mechanism combining with external interrupt to implement user-level I/O. According to real-time demand, user selects some way. To achieve Interrupt response procedure in times, special I/O device cache is used in signal mechanism. User-level I/O Technology of process structure combining with layered structure model needs bigger internal RAM and ROM. But, with the development of MCU performance and price fall increasingly, RAM and ROM influence gets more and more unimportant for the implementation of user-level I/O Technology of process structure combining with layered structure model.The implementation of stream device management with USB device in Sx3000 real-time embedded operating system adopts user-level I/O Technology of process structure combining with layered structure model.