[ECOS] Redboot on load part2

Chris Balthrop chris@mitsi.com
Mon Jul 23 19:23:00 GMT 2007


Hello All,



The "Redboot on load" discussion has prompted me to ask an opinion from
our experts about a proposed solution to booting a new system that we
are now writing the software for.



I apologize for the long post and if this is not the correct forum for
this question.



Background:

We have been using eCos/Redboot for about 2+ years, and on the previous
3 systems that we have built.  These were all Xilinx PowerPC based
systems with Flash and SDram.  The boot sequence was controlled by a
CPLD that loaded the Xilinx FPGA with a bitfile from the flash memory
and then a small boot monitor program was run from within the FPGA block
ram memory.  This program loaded Redboot from the flash into SDram and
jumped to it.  This allowed us to use Redboot, with the serial ports, to
debug our application.  For the deliverable systems, we enabled a
Redboot FIS script in the FLASH that called back into our boot monitor
that then loaded one of the several application images from FLASH into
SDram and ran it.



New boot sequence:

In the new system there is no CPLD or FLASH.  The CPLD/FLASH has been
replaced by a small ARM processor and an SDCard.  The SDCard is
formatted FAT32 so that it can be read or written on a PC.  The ARM
processor reads the SDCard and loads the Xilinx bitfile. The boot
monitor then reads the SDCard and loads the Redboot image and an
application into SDram. The proposed solution for the deliverable units
was to use one of the older systems to initialize the Redboot FIS file
system with a boot script and copy this to a file image that could be
loaded by the boot monitor into the SDram. Then a Redboot would be built
that thought that there was flash at the location that the FIS image was
loaded.  If the Redboot found the Sdram "FIS" it would then run the
script from the Sdram to run our application otherwise it would stop in
Redboot for debugging.



Question:

Is this a viable solution, or is there a simpler one?  Can Redboot
create an FIS in the SDram that we could save to the SDCard and have the
boot monitor reload into Sdram so that Redboot could run it if it was
there?  We would like to keep the Redboot debug standalone and/or run
script functionality in the final system.



I thank you for your comments.



Good Huntin'
cb



Chris Balthrop
Sr. Engineer
Micro Technology Services Inc.
chris@mitsi.com




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