NIOS2 Essay--fat32 File system

1. Overview

FAT32 is one of the Windows system hard disk partition formats, with a maximum single file size of 4GB.

The FAT32 consists of the following 3 parts:

• Mbr:master Boot Record, 512KB, physical 0 address of the hard disk to 0X55AA end partition;

• Fat:file Allocation table, 512*2kb, 32-bit file allocation table, maximum single file size 4GB, to 0X55AA end partition;

• File and directory data: a directory area.

For example, a 42B file would occupy 2k=4 Sector (512KB).

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2. Introduction of Fatfs Source code

FATFS is a free, open-source FAT file system that is especially suitable for small embedded devices andFATFS supports fat12/fat16/fat32.

FATFS File system structure:

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Fatfs source files are as follows:

	function
ffconf.h	Fatfs module profile	need to configure parameters as required
ff.h	Fatfs and Application module Common header file	not modified
FF.C	Fatfs module source code	not modified
diskio.h	Fatfs and disk I/o module common header file	not modified
diskio.c	Fatfs and disk I/o module interface Layer file	platform-related code, required to write functions based on media
Integer.h	data type definition	related to compiler
Option folder	Optional external features	For example, to support kanji needs to be modified

3. Fatfs Source Porting

Three steps for Fatfs transplantation

• Data type: Define the type of data in Integer.h

• Configuration: Configure Fatfs related functions via ffconf.h

• function writing: In DISKIO.C to write the underlying driver, generally need to write 5 function disk_status, disk_initialize

Disk_read, Disk_write, Disk_ioctl, Get_fattime

In Ffconf.h, the main modifications support the full extent of functions, supported font formats, and so on.

#define  _FS_MINIMIZE0/* This option defines minimization level to  Remove some basic api functions.//   0: all basic functions  are enabled./   1: f_stat (),  f_getfree (),  f_unlink (),  f_mkdir (),  f_truncate ()  and f_rename ()/      are removed./    2: f_opendir (),  f_readdir ()  and f_closedir ()  are removed in  Addition to 1./   3: f_lseek ()  function is removed in  addition to 2. */#define  _CODE_PAGE1/* This option specifies the  oem code page to be used on the target system./   Incorrect setting of the code page can cause a file open  failure.//   1   - ascii  (no extended character. non-lfn cfg. only)/    437 - U.S./   936 - Simplified Chinese  (DBCS) */ #define_USE_LFN0 #define_max_lfn255#define_lfn_unicode0/* this option switches character  encoding on the API.  (0:ansi/oem or 1:utf-16)/  to use  unicode string for the path name, enable lfn and set _ lfn_unicode = 1./  this option also affects behavior of  string i/o functions. */

In diskio.c, modify the corresponding driver (SPI Low-level driver View Blog "NIOS2 essay--SD card SPI operation

"), the modified code is as follows:

filename: diskio.c//author:   shugen.yin//date:     2016.12.22/ /function: fatfs lower layer api#include  "Diskio.h"/* fatfs lower  layer api */#include   "sd_spi.h"//Initialize Disk dstatus disk_initialize  (byte pdrv) {U8  res=0;    res = sd_initialize ();//sd_initialize () if (res) return   sta_noinit;else return 0; //initialization succeeded}  //get disk status dstatus disk_status  (BYTE  pdrv/* physical drive nmuber  (0..)  */) { return 0;}  DRESULT disk_read  (byte pdrv,/* physical drive nmuber  (0 ...)  */BYTE *buff,/* Data buffer to store read data */DWORD  sector,/* sector address  (LBA)  */UINT count/* Number of sectors  to read  (1..128)  */) {U8 RES=0; &Nbsp;   if  (!count) Return res_parerr;//count cannot be equal to 0 or return parameter error   res=sd_readdisk ( Buff,sector,count);    //handles the return value, spi_sd_driver.c the return value to FF.C return value     if (res== 0x00) return res_ok;     else return res_error;   } #if  _USE_WRITEDRESULT disk_write  (byte pdrv,/* physical drive nmuber  (0 ...)  */const BYTE *buff,/* Data to be written */DWORD sector,/*  sector address  (LBA)  */uint count/* number of sectors to write   (1..128)  */) {u8 res=0;      if  (!count) return RES_ Parerr;//count cannot be equal to 0, otherwise the return parameter error   res=sd_writedisk ((u8*) buff,sector,count);     // Processes the return value, turning the return value of SPI_SD_DRIVER.C to the return value of FF.C     if (res == 0x00) return res_ok;      Else return res_error;} #endif #if _use_ioctldresult disk_ioctl  (Byte pdrv,/* physical drive nmuber   (0 ...)  */byte cmd,/* control code */void *buff/* buffer to send/receive  control data */) {dresult res;       switch (cmd) {     case ctrl_sync:sd_cs_set;        if (SD_ Waitready () ==0) res = res_ok;         else res  = RES_ERROR;  SD_CS_CLR;        break;      case get_sector_size:        * (WORD*) Buff  = 512;        res = RES_OK;         break;     case get_block_size:        * (word*) buff = 8;         res = RES_OK;        break;      case get_sector_count:        * (DWORD*) buff = SD_ Getsectorcount ();        res = res_ok;         break;    default:         res = RES_PARERR;        break;     }    return res;} #endifDWORD  get_fattime  (void) { return 0;}  //dynamically allocates Memory void *ff_memalloc  (uint size) {return  (void*) size;} Free memory void ff_memfree  (VOID* MF)  {}

4. Build the hardware and software environment

Here is the "NIOS2 essay--SD Card SPI operation" in the project, the TF card (2GB) borrowed SD card sleeve inserted into the SD card holder, as shown in:

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Write the main function and run the final compilation: The terminal displays the file write success

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5. Final results

Use the card reader to open the TF card, HELLO. TXT file is generated and the contents of the open file are written correctly.

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NIOS2 Essay--fat32 File system