[En-Nut-Discussion] at91sam7x bloader

[Szemző András]

Hi guys,

You have answered my problem, this is thy reason I would like to use
dataflash. :) Dataflash is relative cheap, so with a 512Kb part I can easyly
store
a backup image in the dataflash, what can be restored if something goes
wrong. 

Yes, sorry, of course I thought at91sam7x_rom.ld,it was a typo. 

I'm currently using AES 128bit extensively, and I would upload encrypted
firmware, and decrypt it at flash time. With all code 
together, ( dataflash handling, AES decrypt, crc or md5 ), I don't want to
store all my code it the RAM always. So if I use a small separate
bootloader,
I save some RAM maybe, but I don't really know.

I've done a small test. Bootloader linked with NUT, ( ok, it's a first time
test, space consuming etc... ) I've written a small xmodem uploader, what
will
upload the NUT app from hyperterm to address 0x4000. The loader read rs232
and write flash successfully (seems) and jump to address 0x4000.
I used my own usart function, without IRQs, no Nut's libs.

I modified the .ld script, so Nut app is linked to 0x4000, but no success,
after the jump, it's not starting. 

My exact problem is, what other steps needed before the jump :)
I'll try to found the answers from myself, but if anybody has an idea, it
will speed up the things :)

Thanks and Best Regards,
Andras


Ps: Ole, do you received my patch about AHDLC on at91?


-----Original Message-----
From: en-nut-discussion-bounces at egnite.de
[mailto:en-nut-discussion-bounces at egnite.de] On Behalf Of Ole Reinhardt
Sent: Wednesday, February 06, 2008 11:02 PM
To: Ethernut User Chat (English)
Subject: Re: [En-Nut-Discussion] at91sam7x bloader

Hi,

> I would not do it that way too. The problem is security, if the 
> bootloader doesn't find an acceptable image or if some bit is not 
> reset, the next time it could revert to a previous image. If it is 
> done online, it can and up with an unuseable device...

Right. To prevent this an md5, or at minimum a crc32 check should be done
before flashing the code. As SAM7x does not have that much flash (to store
the new and a fallback image) the dataflash solution ist not the best one,
but the only I see at the moment.

Bye,

Ole

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