[En-Nut-Discussion] UROM file system and RAM vs Flash allocation on AT91SAM

[Harald Kipp]

Henrik Maier wrote:

> been designed initially, the 32-bit ARM version is not yet able to directly
> read the file contents
> from flash memory.

...

> Does this draw-back still exist or do newer UROM drivers support reading
> from Flash in-place?

It still exists. The solution would be to place the UROM arrays in a
different linker segment. Note, that this requires .hex or .elf files.
Pure binary images, often used by boot loaders, cannot handle memory gaps.

I'm very near to a flash file system named UFLASH, specifically designed
for Atmel's Dataflash. It works great in general, but in later tests
file entries got vanished after reboot. :-( It will take a few weeks
more to publish it.

I also tried
http://www.sics.se/contiki/developers/coffee-contikis-flash-file-system.html
The tests provided by the author worked fine, but all tests I did myself
failed. Anyway, Coffee (the name of this FS) looks like a good long term
solution for NOR flash (incl. internal flash). Not sure about NAND flash.

Like Coffee, most file systems will not work well with serial flash,
because these devices require a full page erase with every byte
modification. On the other hand, the internal RAM buffers of Atmel's
Dataflash is an interesting feature.

Harald