The Realization Of Host/Slave USB Interface

USB (Universal Serial Bus) has been developing rapidly in recent years, having the attributes of low-cost, rapid-speed, ease-of-extend, plug-and-play, so it is applied widely. USB Specification compartmentalizes the data transfer system to two parts: host computer and peripheral device. At present, PC acts as the host computer, the market's USB products act as the peripheral device. But the embedded systems which use microcomputer such as MCU as the core lack the direct interfaces to USB products. As a result, the host USB interface applied the embedded systems becomes the focus of USB field. MCU reads and writes flash memory disk directly, furthermore the technology can be applied on instruments to realize portable instrument. On the basis of the host USB interface, the system with the slave USB interface which can be used as peripheral device is more popular. This paper follows the new idea to design and practice the host/slave USB interface.The system selects Winbond's W78E54B to act as the CPU, and selects Cypress's SL811HS to act as USB host/slave interface chip to buildup the interface module. The hardware of the system possesses the virtue of cheapness, speediness, etc. From the point of the host USB software, the system integrates USB Driver, USB host controller driver and user software, it enumerates and configures flash memory disk well. Moreover, the system follows mass storage class protocol and establishes FAT(File Allocation Table) file system so that it can read and write flash memory disk. The slave USB software includes device end's firmware and PC end's device driver which is exploited using VC++, DDK and DriverStudio as well as PC end's user software to realize the module acting as universal device to communicate with PC.According to the method introduced in this paper, the host/slave USB interface module is established successfully. The experiments proved that this system is reliable, extendable and can be transplanted to other embedded system.