Design Of Log Structure File System Based On μC/OS-Ⅱ

File system, as an important part of the operating system, plays a key role bothin the operating system or data processing and user information stored on the media.With the continuous development of embedded systems, it is dealing with more andmore volume. In nowadays, the vast majority of embedded systems use Flashmemory to store data and codes, especially NAND Flash which often used to storeusers’ data files. As establishing file system in Flash do exist problems such asaverage wear-leveling, but log type file system can solve the security problem, andcan realize the Flash of load balance.This paper first introduces Flash memory, especially physical structure ofNAND Flash, and then elaborates the importance of embedded file system, especiallyYAFFS, introduces C/OS-IIkernel’s organization and management structure.After the further understanding of NAND Flash storage characteristics and workmechanism theory of log structure file systems, based on the μC/OS-II real-timeoperating system kernel, this thesis designs a successful file system which called UCShas implemented simple functions like file reading and writing. This file system isdivided into four levels: API layer used to provide users with function interface, filesystem layer serving data inspection to make sure data accuracy and validity, logicaladdress layer used for tnode tree made by transformation between physical addressand logical address structure, hardware layer which directly transfer data to thebottom of the hardware. All documents of this file system have a special page to storehead files, which preserved the basic information of files. These data informationwere displayed and transferred in use of data structure like Ucs_Handle,Ucs_ObjectStruct, Ucs_DeviceStruct, Ucs_ChunkCache, Ucs_Spare, Ucs_Tags. Filestructure can be set up only by scanning head files.Through ARM92410development platform experiment, UCS file system hasachieved file operations such as open, read, write, close and other basic processing. Itis the great significance for improving widely used real-time file system μC/OS-II, atthe same time this has a strong promotion for autonomous researching and developing of the file system.