I want to use FatFS library using STM32F303 internal flash memory. I created user_diskio.c file and described necessary functions USER_write, USER_read and USER_ioctl for reading and writing data to/from internal flash

  if (FATFS_LinkDriver(&USER_Driver, USER_Path) == 0)
    result = f_mount(&FATFS_Obj,(TCHAR const*)USER_Path, 1);

f_mount gets FR_NO_FILESYSTEM error. Using function f_mkfs((TCHAR const*)USER_Path, 0, 512); gets FR_NOT_ENABLED error. I don't understand, how should I format disk sector to use FatFS library.

  • \$\begingroup\$ Format of your f_mount call does not seem to correspond to documentation elm-chan.org/fsw/ff/00index_e.html \$\endgroup\$
    – Anonymous
    Commented Jun 6, 2017 at 8:06
  • \$\begingroup\$ I would recommend stepping in the code to find the actual function calls that the FatFS lib is making towards your implementation file. Either your parameters to the f_mount function call are not correct or the functions in your diskio.c file is not correctly implemented. \$\endgroup\$
    – MathiasE
    Commented Jun 6, 2017 at 9:03

2 Answers 2


I want to use FatFS library using STM32F303 internal flash memory.

That's not going to work very well. I would recommend that you reconsider.

FatFS expects to be working with a block device where it's possible to write any 512-byte sector of the disk at any time. This is not how flash memory works on STM32 devices -- on the STM32F3 series, flash memory is organized as a set of 2 KB sectors (not the 512-byte sectors assumed by FAT!), each of which can only be written to as part of a program/erase cycle.

Writing to a single 512-byte subsector of the 2 KB flash sector will require an expensive, slow operation where you erase the entire flash sector, then re-write it with one sector modified. This will wear the flash memory very quickly, resulting in premature failure of the device.

That all being said, based on the FatFS code I looked at, FR_NOT_ENABLED does not appear to be a valid return value from f_mkfs(). Either you've read the error code wrong, or you're running into a bug in the version of FatFS you're using.


You should format your flash as FAT32 or exFAT. Since your flash is internal to the MCU, you'll have to get that f_mkfs call right (otherwise you could have formatted it externally).

Right now it seems to have the wrong argument count (refer to this example) and FR_NOT_ENABLED is not a valid return code for this function anyway, so you're probably not even calling it in your code.

  • \$\begingroup\$ Currently i'm using older version of fatfs and that func has only 3 arguments \$\endgroup\$ Commented Jun 6, 2017 at 12:15
  • \$\begingroup\$ @Igor1488 First, good luck getting help with the library version you didn't even bother to specify. Second, when you're struggling getting a lib working, the first thing to try is to upgrade to the current stable release: this will solve a whole bunch of bugs and dramatically increase the relevance of whatever guidance you may get. \$\endgroup\$ Commented Jun 6, 2017 at 13:58

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