[ECOS] Creating eCos flash application image for AT91 EB40a Redboot

Andrew Lunn andrew.lunn@ascom.ch
Fri May 23 13:32:00 GMT 2003


On Fri, May 23, 2003 at 02:32:29PM +0200, Øyvind Harboe wrote:
> >However, there's a problem here in that if your 
> >executable is larger than the available RAM, which you 
> >say it is, then the usual mechanism of loading it into 
> >RAM and the writing it all to flash will not work. You 
> >may have to write a RAM-resident flash loader that 
> >downloads and writes chunks of data to flash.
> >
> >Once you have it in flash you can then execute it with 
> >the go command.
> 
> I see.
> 
> Is there a reason(other than that it isn't done yet) 
> why the Redboot load command does not support writing to flash?

Its not been needed. All the applications of eCos that i know of have
had sufficient RAM to put the whole image into RAM first before
writing to ROM.

There is a simple workaround. Split your image into blocks, which are
multiple of the FLASH block size. Then load to RAM and write to flash
each block separately.

One thing to think about. All this writing to flash every time you
want to run and debug your application is going to really slow you
down. Maybe:

1) Get a custom board for development work which has a lot more RAM.
2) Is your 2Mbyte image all code? Is a large part of it data? Can you
   separate out the data and allocate it dedicated blocks in the flash.
   You then just have to write the application to flash each time.
3) Get hold of a eeprom/flash emulator. You can then bypass all the flash 
   writing business. 
 
   Andrew

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