I am using an SD card accessed using the SdFat library to store resources (image files for a UI screen) and as part of improvements to help manage versions I would like to be able to read the volume label/name of the SD card (which has a version number in the volume label or name). The SD card is FAT32 formatted. I can see that the volume name used to be stored in the boot sector on the SD card but that there is reference to it being a special file under FAT32. I haven’t been able to find any SdFat library related way to read the volume label. Has anyone got an idea how to do this?
I can’t answer from the top of my head, but in such a case I’d usually try to locate a tool that allows me to investigate the FAT, partition table and root directory of the medium on the byte level.
Armed with that and maybe some documentation (e.g. wikipedia) about the FAT32 structure, you may be able to work your way throught the structure and see what tools SdFat provides you with in order to get to that specific info.
One Windows tool that I found to be helpful in that endeavour might be
DiskInvestigator http://www.theabsolute.net/sware/dskinv.html
also hosted be reputable heise.de, which I tend to trust most with freeware downloads
https://www.heise.de/download/product/disk-investigator-25771
(unfortunately this tool seems to lack exFAT support, but that should not keep you from getting your puzzle solved)
@ScruffR, Thanks for the pointers. I had done a bit of digging in Wikipedia and it seems that with FAT32 the volume label is held in a special file on the root directory as well as in the extended boot sector (this isn’t the correct name). I can see with tools the special file but can’t read it. I have now tried a different approach which is to put my own file with the resource version and this is working fine. Thanks again for your help.
It's not the file you need to read but only the directory entry of that file which is the first root entry and provides the volume name.