Design And Implementation Of Embedded File System Based On NAND Flash

With the development of information technology and wide usage of digital products, nowadays embedded system becomes hotspot in computer technology research and application. NAND Flash is one of storage devices which are widely used in embedded field. However, embedded file system based on NAND Flash was applied to some professional fields in the past, without considering much of desktop system. This makes it more complex to support digital products for desktop system.In this paper, an embedded file system based on NAND Flash is designed and implemented. FAT is used here to realize good compatibility between the NAND Flash embedded file system and the desktop system. Nevertheless, because of the physical structure in NAND Flash, we could not use FAT directly on NAND Flash. So FTL is used for wear-leveling and dynamic address mapping. Details are as follows:(1) Basic theory and development status in embedded file system are researched and various file system formats are compared. Basic theory and various technologies in flash memory are researched and two key flash technologies are compared.(2) After researching FAT principle, we build FAT frame as a whole. Structure and operation is designed based on system management, directory management and file management. We also allocate cache according to embedded system resource. Finally we implement all kinds of common functions in embedded file system.(3) FTL is added between FAT and NAND Flash. FTL divide NAND Flash's logic space according to wear value and design multiple structures and mechanisms to record updating data. FTL implement wear-leveling and address transition. In addition, a NAND Flash driver is also designed.This embedded file system based on NAND Flash enhances both the system compatibility and universality: provide a suit of standard API, design based on groupware independent of embedded operating system, support all series of FAT and support many kinds of NAND Flash device. In addition, a fast file seek method is put forward and implemented for enhancing the system performance in this paper.