Electronic – Using FatFS on internal flash of STM32f303 microcontroller

fatflashstm32

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.

Best Answer

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.

Related Solutions

How to write on SD card smaller than sector size (512 bytes)

Read, modify and Write the sector in the file allocation table to update cluster indexes.

You must do that only when the number of clusters for a file changes. A usual cluster size is 32 KB.

Read, modify and Write the sector in the file new allocated cluster.

No, you only have to write the changed data sectors. You could omit the read cycle when you write the data to card in 512 byte steps.

Read, modify and Write the sector where the file entry reside.

Most FAT implementations write this once on file create, and once on file close (to update the size when written to).

Electronic – FatFs: Why am I not able to properly read sector 0

Turns out the answer had to do with the way I was implementing the SPI transactions using the Nordic SDK.

My rcvr_mmc function looked like this:

static
void rcvr_mmc (
    BYTE *buff, /* Pointer to read buffer */
    UINT bc     /* Number of bytes to receive */
)
{
    nrf_drv_spi_transfer(&spi, NULL, 0, buff, bc);
}

I assumed my rcvr_mmc was working since I was correctly parsing command responses. However, sector reads weren't working at all. I didn't even see a full 512*8 clock cycles.

Once I realized that was happened, I looked more closely at the Nordic SDK SPI driver and discovered this:

https://devzone.nordicsemi.com/question/66434/nrf_drv_spi_transfer-larger-transfer-size/

Since sector reads pass bc=512, this resulted in nothing really being read. My very inefficient hack for now to get this work is:

int i;
uint8_t small_buf[1];
for (i = 0; i < bc; i++) {
    nrf_drv_spi_transfer(&spi, NULL, 0, small_buf, 1);
    buff[i] = small_buf[0];
}

Best Answer

Related Solutions

How to write on SD card smaller than sector size (512 bytes)

Electronic – FatFs: Why am I not able to properly read sector 0

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