That depends on what partition schema do you use. If MBR then first 512 bytes are the partition table and the boot code (like on PC), there is a limit of 4 partitions (that on PC was solved by makind "extended partition" and then first 512 bytes of that partition enabled another partitions). GPT for instance does not have this limitation and it contains backup table at the end of device. Also you may use MBR disk schema with no partitions that is pretty common with some unformatted pendrives and simple USB MSC emulation on tiny MCUs with USB device.
Also FAT does not seem perfect solution for embedded storage because of 1 possible data corruption on power loss and 2 memory wear leveling because some locations are used far more often than the others (i.e. atime that can be disabled). There are other filesystems designed with embedded application by design :-) Are you sure that partition table is okay and you are formatting / mounting the correct partition? :-) Tomek On Tue, Oct 29, 2024 at 7:00 PM Tim Hardisty <timhardist...@gmail.com> wrote: > > Whilst FAT on a NOR flash may generally be seen a not such a great > idea...please ignore that and confirm if... > > ...I am right in deducing that I can't simply make a FAT file system on > (say) the third mtd partition (with 512 byte sector emulation) > (partitions 0, 1 and 2 are "raw" data) since FAT will treat the entire > flash devices as a "volume" and so fail to find a partition table at the > bottom end of the flash device? If so, it no doubt explains why I can > format a FAT FS but not mount it. > > I could - perhaps should - re-jig my partitions so partition 0 is used > for FAT, rather than partition 3, but before I do that are there any FAT > FA/NuttX gurus who can let me know if there is a way to do this (and > save me the hassle of reworking my bootstrap and MCUboot locations etc. > for now)? > -- CeDeROM, SQ7MHZ, http://www.tomek.cedro.info
