[ECOS] Re: Placing data at an absolute address

[Grant Edwards <grante@visi.com>]

On 2007-04-01, Gary Thomas <gary@mlbassoc.com> wrote:
> Laurie Gellatly wrote:

>> For our eCos application, I'd like to place the MAC address at
>> a particular address in flash and have it loaded as part of
>> storing Redboot into the flash. At production time, a script
>> would be run that finds that address section in redboot.elf
>> and updates it before it is stored into the next unit. Finding
>> the section in the elf is not the hard bit. I've tried adding
>> a new section on the gcc command line and adding a variable
>> into the C source which almost works except the section size
>> is of length 0. How can I make the section 6 bytes long or is
>> there a better way to do this whole thing?
>
> The best way would be to assign this data to a particular
> section of its own, using "attribute".  Then in the linker
> file, put that section at the desired physical address.

The question is then how to alter the contents of that section
during production in order to uniquely set the MAC address of
each unit.  AFAICT, you'd have to use objcopy to alter the .elf
file each time before you convert to hex/binary and download.

Personally, I think putting the MAC addres into the program
itself before download is way the wrong way to go.  It makes
updating firmware way too difficult.

Just reserve an "external" spot in flash memory that's not
written to when the program is downloaded.  Then download the
MAC address in a separate operation.

-- 
Grant Edwards                   grante             Yow!  PEGGY FLEMMING is
                                  at               stealing BASKET BALLS to
                               visi.com            feed the babies in VERMONT.


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