uC/FS详解(开发文档)

features of µC/FS are: 

·  MS-DOS/MS-Windows compatible FAT12 and FAT16 support. 

·  Multiple device driver support. You can use different device drivers with µC/FS, which allows           you to access different types of hardware with the file system at the same time. 在该文件系统中可同时支持多个设备驱动

·  Multiple media support. A device driver does allow you to access different medias at the same            time. 

·  OS support. µC/FS can easily be integrated into any OS. In that way you can make file operations        in a multithreaded environment. 

·  ANSI C stdio.h like API for user applications. An application using standard C I/O library can             easily be ported to use µC/FS. 

·  Very simple device driver structure. µC/FS device drivers need only very basic functions for                 reading and writing blocks. Therefore it is very simple to support your custom hardware. 

·  Generic device driver for SmartMedia cards, which can easily be used with any kind of card                  reader hardware. 

·  Generic device driver for MultitMedia & SD cards using SPI mode, which can be easily integrated.

上面的图是FATFS,但与UC/FS的是一样的

   1：API层类似于linux的VFS层

      The API layer is the interface between µC/FS and the user application. It does contain a library of ANSI C oriented file functions, such as  FS_FOpen, FS_FWrite etc. The API layer does transfer these calls to the file system layer. Currently there is only a FAT file system layer available for µC/FS, but the API layer can deal with different file system layers at the same time. So it is possible to use FAT and any other file system at the same time with µC/FS.  

    API层是µC/FS 提供给用户使用的接口层（fs_api.h），API层将各种调用传输到file system layer（文件系统层），目前对µC/FS（文件管理实现机制）来说 只有一个 FAT文件系统层被使用，API层可以处理不同的文件系统层，因此µC/FS可同时支持多种文件系统（API层类似于linux中的虚拟文件系统VFS，他的功能是提供给童用户标准的系统调用接口，VFS层下面才是具体实际的文件系统层，有FAT、EXT2等等，这个根据硬件的情况（格式化时使用什么文件系统）来调用具体的文件系统）。

   2：File System Layer 文件系统层这层与linux是一样的，是具体的管理文件所用的文件系统

   The file system layer translates file operations to logical block operations. After such a translation, the file system calls the logical block layer and specifies the corresponding device driver for a device.

   文件系统层将文件操作转换为逻辑块操作，之后，具体的文件系统调用逻辑块层函数并指定设备相应的驱动；linux中，文件系统将各种系统调用转换为各种IO请求（系统请求即是对底层相应的扇区、柱面、等操作），IO请求被放到对应设备的IO请求队列中去，再由一个系统内核线程一直读取请求队列中的请求，没有请求时就睡眠，拿到请求就通过设备驱动实现具体的操作

    uC_FS\FSL\fat\ 下面就是FAT文件系统的各个文件。

   3：Logical Block Layer 逻辑块层

   the main purpose of the logical block layer is to synchronize accesses to a device driver and to have an easy interface for the file system layer.  The logical block layer does call a device driver to make a block operation. 

   逻辑块层的主要目的是同步访问设备驱动与文件系统的简易接口，逻辑块层调用设备驱动来实现设备的块操作。

   4： Device Driver Layer 设备驱动层

 

   下面的流程是参考uC/FS用户手册上的例程来写的，可以参考。

   1:调用FS_Init()初始化文件系统，在使用uC/FS的任何功能函数之前须要首先调用该函数进行初始        化；

   2：进入MainTask()

           1：调用FS_IoCtl()格式化：使硬件按指定的文件系统来管理文件

              This call is used to format your RAM disk in order to be able to write data to                     it. Formatting your RAM disk should not cause any problem.

           2：调用应用程序中的函数_write_file()非uc/fs的函数

                 _write_file()中又依次调用： FS_FOpen()， FS_FWrite()，FS_FClose()

              FS_FOpen()：在这个例程中FS_FOpen()创建了一个叫default.txt的文件，如果创建成功，函数                           将返回一个FS_FILE结构体的指针，如果出错将返回0

              FS_FWrite()：文件创建成功之后，将一串字符串写入该文件中，如果写入时出错，例程中调                              用FS_FError()处理错误。

              FS_FClose()：关闭上面打开的文件，返回主任务中

     读： FS_FOpen()->FS_FRead()->FS_FClose()

   1：Create a simple project without µC/FS 

      We recommend, that you create a small “hello world” program for your system. That project should already use your OS and there should be a way to display text on a screen or serial port. 

   2: Add your µC/FS configuration

      In order to configure  µC/FS for your system, you should create a new sub-directory in µC/FS’s config directory and copy the files  fs_conf.h  and fs_port.h from one of the other sub-directories to your directory. For the following chapters, we assume that you have created a directory FS\CONFIG\myconfig. Usually, the only file  you have to modify is fs_conf.h. For an easy startup, we recommend, that you disable all drivers except the RAM disk driver. Please check out the chapter “Configuration of µC/FS” for detailed information about the configuration.  

   3: Add µC/FS generic source code 

     Add all source files in the following directories:

     and their sub-directories to your project.  

   4: Configure the search path[为开发环境添加所以代码的路径]

        FS\API 

        FS\CONFIG\myconfig 

        FS\LBL 

        FS\OS

   5: Add generic sample code

       For a quick and easy test of your µC/FS integration, you should use the code 

       found in FS\sample\main.c.  

 

     This is the main configuration file for the file system. You define which drivers you want to use and, the configurations for these drivers.

      用户手册中列出了一个配置样本，包括下面的各个配置项目

    1：OS support 

      You can specify whether you are using uC/OS-II, embOS, Windows or no OS support at all.  Please set  FS_OS_UCOS_II,  FS_OS_EMBOS, FS_OS_WINDOWS to 1, respectively. For no OS support at all, set all of them to 0. If you need support for an additional OS, you will have to provide functions described in the chapter “OS integration”. 

    2：Time/Date support 

      If you want to be able to add date and times to your files, you will need to set 

FS_OS_TIME_SUPPORT  to 1. 

    3：File System Layer Support

      µC/FS can support different file system at the same time. You can enable them by setting FS_USE_XXX_FSL, where XXX is the name of the file system layer. The current version of µC/FS only supports the FAT file system, so you will need to set FS_USE_FAT_FSL to 1.

   4：Device Driver Support and configuration

I      RAM Disk:       to  1

       Windows Driver:    FS_USE_WINDRIVE_DRIVER to 1