Research Of USB Host Interface On Digital Set-Top-Box

This paper discussed on how to design and implement embedded USB host interface in digital Set-Top-Box , and also how to use it in digital TV field. First of all, studies on the newest progress of the designing of embedded USB host interface and relevant products at present was carried out, on this foundation, schemes of two kinds of realization of USB host interface were probed into: (1) USB host controller + CPU, (2) (USB host controller + MCU) + CPU. After considering the pluses and minuses of the two kinds of schemes synthetically, scheme (1) was adopted to implement our USB host interface, and chose USB host controller chip SL811HS, which satisfied USB 1.1 specification, to design the hardware circuit. And then, the realization of USB protocol stack system was probed into, which is the difficult and key point of the whole system design. On the structure of USB protocol stack, every kind of realization scheme is similar, including such PC systems as windows and linux, they generally adopted the layered structure. Considering the convenience of design, this implementation referred to the USB driving system in the kernel source of earlier version linux, and made some changes and improvement to fulfill the need of embedded real time system. In addition, because initial purpose of the design is to support removable memory equipment on digital Set-Top-Box, so there is no support driver for other device classes (such as HID devices) other than Mass-Storage devices, and no support for ISO transmission too, but as a result of the perfect modularization of the whole system implementation, these functions are very easy to expand. Finally, on the basis of the USB host interface hardware circuit and corresponding driving system that are designed out, relevant upper strata applications were discussed, such as file broadcast controlling and receiving system based on DVB-S standard, design of MP3 player based on USB file storage, and the update of Set-Top-Box software based on USB removable memory equipment, etc. At the same time, its relevant performances were tested, and also compared in two different implementations, various kinds of parameters reached the anticipated designing requirement. To the problems appeared during designing, such as babble conditions, this paper also analysed them in details, and listed the corresponding solutions to these problems while implementation.