I want to know the number of bytes per sector in the FAT file system.

[kkuma256]

I want to know the number of bytes per sector in the FAT file system, but the get_free function in FatFs returns the number of sectors. How can I determine the number of bytes per sector?

It would be ideal to inspect the ssize member of the FATFS structure, but it may not exist depending on the value of the _MAX_SS macro.

Is it possible to retrieve the sector size by sending the GET_SECTOR_SIZE command through disk_ioctl? However, how can I call this function from a user application?

[Turbo J]

Sector size is fixed 512 bytes, and I have never seen a disk where that was not the case. SD cards have that sized fixed in the spec IIRC.