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

[Henrik Maier]

Hi Harald,

Thanks for the update. At least I learned that it is technically possible
and should I start with an AT91SAM7 project I can work on the linker scripts
and contribute those findings back to Nut/OS.

The dataflash option is nice too, I actually thought it is already
supported.

Henrik

> -----Original Message-----
> From: en-nut-discussion-bounces at egnite.de [mailto:en-nut-discussion-
> bounces at egnite.de] On Behalf Of Harald Kipp
> Sent: Thursday, 25 February 2010 10:24 PM
> To: Ethernut User Chat (English)
> Subject: Re: [En-Nut-Discussion] UROM file system and RAM vs Flash
> allocation on AT91SAM
> 
> 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
> 
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