| The technology sector of the 21th century economy is one of the largest sectors in many first world nations. With the rapidly development of the information age, USB have gained worldwide recognition and USB products have become a public commodity. As noted above, there are many products on the market today that incorporate USB connectivity for those very reasons. Because of its ease of use and popularity, this has also spun off a side effect to USB's already impressive list of features: functionality. Compared to legacy ports such as parallel and serial RS-232, USB has the largest product base out of all PC connectivity options. We can now have access to USB modems, scanners, digital cameras, storage, networking, printers, and wireless standards in a single PC interface. This allows us to add almost any type of functionality that exists to a computer, or even to an embedded system. The release of the On-The-Go (OTG) supplement to the USB2.0 Specification changed the USB world. For the first time, spec-compliant USB devices can talk to each other without requiring the services of a host computer. It is necessary to study the architecture and the development method of the USB OTG. By adapting a virtually limitless connectivity option to an embedded system, we can port all of that functionality from a PC to a more application specific or lower level microprocessor. We can create an image recognition security device, or a digital seismograph, or any specific use application by using existing end user USB peripherals connected to an embedded system. However, embedded microcontrollers are notorious for limited interfacing options, and adaptation of special application devices can prove costly and inefficient. By creating a viable, low cost solution for USB connectivity, we can expand the functionality of an application specific integrated circuit without detrimental costs and other inhibitive measures. Our Embedded USB Host/Slave Application Module tries to using USB embedded chip SL811HS , on basis of the latest technology USB OTG, a multifunction embedded host/slave system module conforming to USB1.1 was developed. The module can support FAT simplified file system, automatically identify ordinary flash memory disk, and configure a device as a standard disk drive in order to realize data collection and store when it is on host mode. If the module is on slave mode, it can be regarded as a general USB interface to conduct data collection, data communication and transmission with PC. The testing results show that the module can be widely used in various portable and embedded data system, and implement USB OTG functions safely. This thesis, according to the thinking of the item development, gives detailed expound in five sides as follows: the development of USB OTG will be described firstly. It tries to give developers and users a snapshot of USB OTG. Secondly, the thesis discusses the architecture and features of USB, including the bus attributes, electrical specification for the USB, the protocol definition, types of transactions, and so on: in chapter 3, the USB embedded system hardware development will be described, using SL811HS chip; Then, the emphasis turns to problems as follows: how to develop USB software according to USB bus protocol. The modularizing layered architecture is been adopted, which makes it easy to realize, port, reuse, test and modify; when it is on host mode We also sum up and use some specification such as USB1.1, Bulk-Only transport and UFI command specification; a user...
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