| The development of computer architecture is shifting from the "center of CPU" period to the "center of BUS" period. In the "center of CPU" period , the development of computer centered on the CPU and instituted related standards for CPU. The design of peripheral equipment and the extending of architecture are restricted within narrow limits .whereas the "center of BUS" period , just as its name implies, it constituted different bus standards to be applied in different situations, for different bus system has its unique standard protocol and peripheral equipments . The appearance of every new bus standard is either for solving the flaw of old bus , or for optimizing the computer's performance based on some given consideration. The appearance of USB bus standard is no other than the reason, for solving the shortcoming of traditional bus and leading the trend of the development of computer. Furthermore, the research and design of embedded USB system will broaden the applied field of USB interface technology, and bring the brand-new world of the design of embedded system.In PC, along with the maturation of USB technology , the exchange and storage of mobile data has recently become a hot focus in IT fields. USB is the medium of data mobiling as well as the kernel. Along with the spread of USB application , the industry has introduced USB to the non-PC field ,namely embedded system, actualizing the point-to-point communication . But for USB's topologic architecture, based on the host, has various restrictions to all kinds of handy equipments, the applications of USB Host in embedded system become a hot topic in nowadays electronic world. In theory , the realization of USB Host in embedded system need loading and interpreting USB protocols, establishing related equipment class protocols ,and implementing especial embedded USB Host application. But the primary difficulty is that USB protocol needs high degree memory and operating speed which 8/16 MCU is difficult to match. How to solve the contradiction between the limited resource of MCU and complex USB protocols is the key of embedded USB Host system of MCU. This paper is based on the point of seeking and solving the embedded USB Host system of MCU with a optimal means.Both theory and practice are included in this paper. The part of theory is the development, condition, trend, demand and skill of embedded system, USB protocols and equipment class protocols, the data traffic framework of USB, the structure of MCU ,and so on. The part of practice is mastering developing means, designing thestructure of embedded USB Host, fabricating hardware circuit, writing program which based on W77E58 and SL811HS ,reducing USB protocols, loading USB protocols, using the developing tools to compile, run and debug code, testing, improving and maintaining the application system, finally ,bringing the USB Host model into a practical application.Five chapters are involved in this paper. In chapter 1, the history and trend of embedded systems, the characteristics of embedded technology and the researching significance and contend of this paper are introduced. In chapter 2, USB protocols which are closely related to the programming of embedded USB Host are introduced. In chapter 3, Firstly, the current solutions of embedded USB Host system are depicted, secondly a basic design thought of embedded USB Host system based on MCU is provided. In chapter 4, the inner-structure and using methods about the SL811HS chip, the hardware and software architecture of a kind of embedded USB Host are depicted, how to use the SL811HS chip to realize the data communication based on USB protocols about MCU is discussed. This helps to design cheap and powerful function embedded devices, and can be widely used in information device and controller. In chapter 5, the practical application of embedded USB Host in embedded system. |
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