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Re: [avr-gcc-list] Patching EEPROM image for production

From: Andy Warner
Subject: Re: [avr-gcc-list] Patching EEPROM image for production
Date: Thu, 5 Oct 2006 09:35:49 -0500

On 10/5/06, dimax un <address@hidden> wrote:
Hi Folks,

I'm trying to find clean solution for the following system problem.
I have configuration structure in EEPROM:
struct VPD_t
   char sn[10];
   char id[20];

Is the location in eeprom fixed between releases of the
code (usually true for firmware upgrade purposes..) ?

If so, I split the problem into two pieces - programming the
invariant parts, and then programming the serialisation. I then
have two makefile targets, one for each. The serialisation target
can do lots of different things, like get the next serial number from
a mysql database, update manufacturing records etc etc. For a
simple case where I can write all of eeprom, I just use a perl script
along the lines of:

      # do whatever it takes to dream up $serial and $id
      $eeprom = pack("Z10 a20", $serial, $id);
      print STDOUT $eeprom;

then pipe that to "avrdude <other options> -U eeprom:w:-:r"

For more complex operations, for instance where you're not writing from 0 in
eeprom, or need to write 2 or more disjoint sections of eeprom, then
you can try all
all kinds of cuteness: creating temorary c files, compiling and
downloading them;
directly generating hex/srec files; or using tools such as avr-objcopy
or srecord
utilities before feeding them to avrdude.

I also have a habit of putting build/programming data (host, time, user etc)
in any unused eeprom locations. You never know when that info might help
you isolate the root cause of a bad batch of widgets.

Does this help at all ?
What you are trying to do is totally reasonable, and easily accomplished.

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