Understanding of common API functions of FATFS file system in STM32

First of all, this is the first time I have opened a blog on CSDN. This is also my first blog post. If there are any shortcomings, please feel free to correct me . I am currently a sophomore student. The reason why I chose to use a blog here is that I was inspired by an embedded expert. If I share my learning with my friends, I believe I can learn more.

Without further ado, let’s get to the point.

First of all, FATFS is a completely free and open source FAT file system module, designed specifically for small embedded systems, written in standard C language, with strong independence, and can be easily ported to 8-bit, 16-bit, and the 32-bit ARM series STM32 that I am using. That is, FATFS is a scalable file system. This is particularly important.

The hierarchical structure diagram of the FATFS module is as follows. Here, some information from Zhengdian Atom is referenced. Thanks to Atom

The bottom layer interface, including the storage media read/write interface (disk I/O) and the real-time clock that provides file creation and modification time, requires us to write porting code according to the platform and storage media. The
middle layer FATFS module implements the FAT file read/write protocol. The FATFS module provides ff.c and ff.h. Unless necessary, users generally do not need to modify them. When using, just include the header file directly. The
top layer is the application layer. Users do not need to pay attention to the complex FAT protocol and internal structure of FATFS. They only need to call a series of application API interface functions provided by the FATFS module to users.

So, let me introduce my understanding of the commonly used API interface functions of the FATFS file system. (The following is what I wrote directly in WPS, so I copied it directly to understand it)

/* FRESULT f_open function mode all open mode description

-------------------------------------------------- ----------------------------------

FA_READ | Read mode, (read and write modes can be effective at the same time)              

FA_WRITE | Write mode, (read and write modes can be effective at the same time)

FA_OPEN_EXISTING | Default opening method

FA_OPEN_ALWAYS | Open the file and create a new file if it does not exist;

  | In this way, you can use f_lseek to append data to the file

                  |

FA_CREATE_NEW | Create a new file. If the file already exists, the creation fails.

FA_CREATE_ALWAYS | Create a new file. If the file already exists, overwrite the old one.   

                      |

-------------------------------------------------- ----------------------------------

*/

/*------------------------------------------------ ----------------------------------

/①The following test f_write writes data through the program, that is, a new txt document is created through the program and there is data

  res=f_open (&fil,"0:/write.txt", FA_CREATE_ALWAYS|FA_WRITE); //Create a new file and write operation

f_write (&fil, "This is a new file, the data is just written in!", 48, &bww); //The prerequisite is to open the file in the form of writing

f_close(&fil);//Close the file, must appear in pair with f_open function, same as below

res=f_open (&fil,"0:/write.txt", FA_READ);

  f_read (&fil, buf,48,&bww);

f_close(&fil); //Whether you open or create a new file, remember to close it

LCD_ShowString(10,210,280,24,24,(u8 *)buf);//

①The following test writes data through the program, that is, a new txt document is created through the program and there is data

-------------------------------------------------- ---------------------------------- */

/*------------------------------------------------ ----------------------------------

②The following test FRESULT f_lseek() moves the file pointer. This function can move the current pointer position when reading or writing an open file, that is, it can add or subtract some unnecessary data.

     res=f_open (&fil,"0:/write.txt", FA_WRITE);

 res = f_lseek (&fil , 25); ////The pointer points to the 25th byte

 res = f_write (&fil , "40" ,2 , &bw); //2 means the written data is 2 bytes

    // res = f_lseek (&fil , fil.fptr + 10); ////The pointer moves forward 10 bytes

 res = f_lseek (&fil , 28); ////The pointer points to the 28th byte

     res = f_write (&fil , "forward" ,8 , &bw);

    // res = f_lseek (&fil , fil.fptr - 20); ////The pointer moves backward 20 bytes

 res = f_lseek (&fil , 37); ////The pointer points to the 37th byte

     res = f_write (&fil, "backward", 9, &bw); //Write 9 bytes of data

     res = f_lseek (&fil , fil.fsize); ////The pointer points to the end of the file

     res = f_write (&fil , "end" ,3 , &bw);

     res = f_close ( &fil );

-------------------------------------------------- ---------------------------------- */

/*------------------------------------------------ ----------------------------------

③The following test FRESULT f_truncate() truncates the file. This function can truncate the file at the current pointer or extend the file length.

      res = f_open (&fil ,"0:/write.txt", FA_WRITE); //Open file and write operation

      res = f_lseek (&fil , 60); ////The pointer points to the 60th byte

      res = f_truncate (&fil ); ////Truncate the file here, all data after 60 bytes will disappear, that is, truncate the file

      res = f_sync ( &fil ); ////Close the file

-------------------------------------------------- ------------------------------- */

/*------------------------------------------------ ----------------------------------  

④ Refresh cache information FRESULT f_sync (FIL* FileObject ) function, * FileObject == pointer to the file object structure

For example: res = f_sync (&fil);

Function description: This function is compatible with f_close. The difference between it and f_close is whether the current file is valid after execution.

          After calling this function, the current file is still readable, writable and searchable.

Usage: When the file is in write mode for a long time, such as data logging, call this function regularly, or call it immediately after writing data.

          This function can reduce data loss caused by unexpected situations such as power outages, which is a bit like the regular background save in WORD.

-------------------------------------------------- ---------------------------------- */

/*------------------------------------------------ ----------------------------------   

⑤Create a new folder FRESULT f_mkdir (const TCHAR* DirName) function, *DirName == pointer to the name of the folder to be created

Function Description: Create a new folder,

Note: The file name should comply with the fatfs standard and cannot contain illegal characters.

      The length of the file name cannot be greater than 8, otherwise the new creation will fail.

Example: f_mkdir("new"); //Create a new folder named new       

-------------------------------------------------- ------- */

/*------------------------------------------------ ----------------------------------   

⑥ Delete files and folders FRESULT f_unlink() function, *FileName: pointer to the name of the file or folder

Function Description: This function can delete a file or folder

Notes for use:

           When deleting a folder: 1. It cannot be the current folder

               2. It cannot be a non-empty folder

When deleting a file: 1. The file cannot be opened

                         2. Cannot be a read-only file

For example: f_unlink("new"); //Delete the folder "new"

      f_unlink("TEXT/write.txt"); //Delete the "write" txt text in the "TEXT" folder

When deleting files, you must pay attention to the following points: all the tails must end with png.txt

-------------------------------------------------- ------- */

/*------------------------------------------------ ----------------------------------   

⑦Rename\move file or folder FRESULT f_rename (const TCHAR* OldName, const TCHAR* NewName)

Function Description: This function can move or rename a file or folder

Parameter description: *OldName: pointer to the old file name

          *NewName : pointer to the new file name

Notes for use:

           1. This function can rename a file or folder, regardless of whether the folder is empty.

 2. This function can move files or folders, regardless of whether the folder is empty.

For example: res = f_rename("Test.txt","Test1.txt"); //Rename the test.txt file,

           res = f_rename("Test 1.txt","PAINT/Test 2.txt");

 //Move the test1.txt file to the folder PAINT and rename it to test2.txt

-------------------------------------------------- ------- */

/*------------------------------------------------ ----------------------------------   

⑧Get file information FRESULT f_stat(const TCHAR* FileName,FILINFO* FileInfo)

Function description: This function can obtain the latest modification time, attributes and other information of the file. The obtained information is stored in the fileninfo structure

Parameter description: *FileName: pointer to the file name

          *FileInfo: Pointer to the structure that stores file information. The type must be FileInfo

Notes for use:

           1. If the target is a folder, the size is 0.

 2. This function is invalid for the root directory.

 3. Both time and date are two bytes, and the storage format is as follows:

 a) Date:

                    i. bit15…bit9: The decimal number after the year calculation should be added with 1980

                    ii. bit8 … bit5: month

                    iii. bit4 … bit0: day

           b) Time:

                    i. bit15…bit11:

                    ii. bit10…bit5: points

                    iii. bit4 … bit0 : The decimal number calculated for seconds should be *2

Example:

         i. Date: 0000001 0001 00001, which means January 1, 1981

         ii. Time: 00001 000001 00001, which means 1:01:02.

Example: res = f_stat("TEXT/write.txt", &filinfo); //Read the information of the newname.txt file in the folder directory

if( res )

printf("newname.txt err : %d\r\n", res); //Failed to read the file information successfully

else

{

printf("newname.txt size : %lu\r\n",filinfo.fsize);//Read the length of the file, that is, how many bytes it occupies

printf("fdate : %d\r\n",filinfo.fdate); //Read the file's most recent modification date and convert it into binary.

printf("ftime : %d\r\n",filinfo.ftime); //Read the last modification time of the file and convert it into binary

printf("fattrib : %d\r\n",filinfo.fattrib);//Display the properties of the file, that is, what file

//#define AM_RDO 0x01 //Read-only file

//#define AM_HID 0x02 //Hidden file

//#define AM_SYS 0x04 //System file

//#define AM_VOL 0x08 //Volume label file

//#define AM_LFN 0x0F //

//#define AM_DIR 0x10 //Program directory

//#define AM_ARC 0x20 //Archive file

//#define AM_MASK 0x3F //

}

-------------------------------------------------- ------- */

/*------------------------------------------------ ----------------------------------   

⑨Change file attributes: FRESULT f_chmod (const TCHAR* FileName,BYTE Attribute,BYTE AttributeMask)

Function Description:

          1. This function can modify the attributes of a file or folder

          2. The properties that can be modified are only one or a combination of the following. Other properties are invalid.

AM_RDO //Read-only file

AM_ARC //Archive file

AM_SYS //System files

AM_HID //Hidden files

Parameter Description:  

a) *Filename: pointer to the name of the file or folder

b) Attribute: The attribute to be set, that is, what the file or folder attribute needs to be changed to

c) AttributeMask: The attributes that need to be changed (including the attributes to be set and the attributes to be cleared), that is, the original attributes and the attributes that need to be changed

Instructions:

a) Attribute must be a subset of AttributeMask

b) The function processes the attribute set in AttributeMask. If the attribute is contained in Attribute, it is set, otherwise it is cleared.

Example: Write to the file TEXT/.txt, set the HID and SYS attributes, and cancel the ARC and RDO attributes

         res = f_chmod("TEXT/write.txt", AM_HID | AM_SYS, AM_ARC | AM_RDO | AM_HID |AM_SYS);

         if( res )

 printf("err :%d\r\n", res);

 else

 {

 res = f_stat("TEXT/write.txt", &filinfo);

   printf("fattrib : %d\r\n",filinfo.fattrib);//

         }

-------------------------------------------------- ------- */

/*------------------------------------------------ ----------------------------------   

⑩Change file timestamp FRESULT f_utime (TCHAR* FileName, FILINFO* TimeDate)

Function Description:

1. This function can change the last modification time of a file

Parameter Description:

a) Filename: pointer to the file

b) Timedate: pointer to the file information structure

Usage: In this function, we can write a regular date and time, and then this function integrates the data according to the date storage format (see above) and calls f_utime.

FRESULT set_timestamp (char *obj,int year, int month, int mday, int hour, int min, int sec);//

{

FILINFO fno;

fno.fdate = (WORD)(((year - 1980) * 512U) | month * 32U | mday);

fno.ftime = (WORD)(hour * 2048U | min * 32U | sec / 2U);

return f_utime(obj, &fno);

res = set_timestamp("123.txt",2001,06,05,02,03,34);//Modify 123.txt time

printf("%d\r\n",res);

This example fails because the prototype of the function FRESULT set_timestamp(); is not found  .

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Well, the above is my understanding of the commonly used API functions of the FATFS file system. I hope it can help some friends quickly understand