Re: Mass storage for Wichit Sirichote 1802 kit #Wichit



First assume the pc is like any other computer, it can be programmed to address anything.

Also current PCs if there is a limitation its due to the OS not any specific file system.  An example
of that is Win10 does NTFS or FAT but does not have a user utility to read or write a sector.
Linux has dd that does that as part of the distribution but its a dangerous tool as you can corrupt
the system disk very easily.  In both cases its possible to have tools that are both smart and not
tied to the native file system and can address a non-system (typically not drive C: and D: in
windows parlance) device like a USB disk, USB memory dongle, a CF or SD/uSD in
an adaptor.

Yes you can, and no sorta.  The first is any tag and bag file system its easy to read the catalog
and see where a specific file is.  Due to its simple nature it also does not allow for fragmented
files as they are by default sequential.   The basic structure is a file starts at block nnnn and
continues for nnnn blocks.  Everything you need to find the file is in the catalog/directory.

File systems like NTFS, HPFS, FAT, CP/M, ELFOS all allow for fragmented files as its efficient
use of space.  All of those directory systems are more complex but finding a specific file and
the blocks it uses can be done, with greater overhead.  To find a file and its pieces is harder
as the directory entry requires you to access several tables on the disk to assemble the
needed information.

The bottom line is a low overhead file system for a simple (bounded) computer like
ELF, SCAMP, or whatever is a handy thing if mass storage is needed.  While it is
possible to have a more sophisticated file system one often needs more ram and
EE/Eprom to support it.

While none of this talks about how to actually interface or do it we have the Arduino and
it interfaces to SD via SPI (it has that) and also has serial.  With its 30 some K of flash
its possible to put a Fat file system (there is a library for that) in the Arduino as is
commonly done and be able to access files on a PC using an USB to SD adaptor.
Then the ELF can use a serial IO to talk to the Arduino and read/write/delete a file
by name and conduct transfer to the SD.  This makes for simple things that can
send data to the PC or get data or programs from the PC.  That lowers overhead
but the expense(DC power, added code) is also a lot of MPU (arduino) doing the
heavy lifting.  While that works its kinda upside down, the powerful system [PC]
with all the IO should put stuff on the portable devices (SD) in a form that the
ELF can use directly and any filesystem work is placed on the PC.

Just me, but I see it as a way to have fun and apply stuff I've learned over the
last 50 or so years.


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