The 6 pin header is the serial debug. It’s what gets you into u-boot and gives you a serial prompt if you don’t stop the boot process. It has some useful info but unfortunately it doesn’t seem to allow any mods to the boot env. Variables. There is a patch that I found for u-boot that is supposed to allow writing to the eMMC but I have not messed with it yet to see if it works. When I get around to it and get it figured out I will post my thoughts and experiences.
I was thinking of moding boot cmds to see if I could get the board to boot from eMMC with uSD inserted or making it look for uENV.txt on sd and if not present boot from internal. But like I said haven’t gotten around to it yet(trying to spend more time with my kids instead of in front of a monitor).
-Wil
The 6 pin header is the serial debug. It's what gets you
into u-boot and gives you a serial prompt if you don't stop
the boot process. It has some useful info but unfortunately
it doesn't seem to allow any mods to the boot
env. Variables. There is a patch that I found for u-boot
that is supposed to allow writing to the eMMC but I have not
messed with it yet to see if it works. When I get around to
it and get it figured out I will post my thoughts and
experiences.
I was thinking of moding boot cmds to see if I could get
the board to boot from eMMC with uSD inserted or making it
look for uENV.txt on sd and if not present boot from
internal. But like I said haven't gotten around to it
yet(trying to spend more time with my kids instead of in
front of a monitor).
If you want to edit the uEnv.txt file on the eMMC, just login at the
serial console login prompt, mount the vfat filesystem, edit, unmount
like so:
mount /dev/mmcblk0p1 /mnt
vi /mnt/uEnv.txt
umount /mnt
Done.
Hey Russell,
Thanks for the info but what I am trying to do is change the bootcmd environment variable for uboot so that the board boots from eMMC if it does not find uEnv.txt on the uSD. uEnv.txt is loaded after the bootcmd is run, that is if I read the cmd right. I can change it with setenv but cannot commit with saveenv because I get " attempt to erase non block-aligned data" and if I run bootcmd after I use setenv it just resets to default. If you have any info on this I am all ears. Das uboot website is kind of vague on the info I am looking for.
-Wil
Hey Russell, Thanks for the info but what I am trying to
do is change the bootcmd environment variable for uboot so
that the board boots from eMMC if it does not find uEnv.txt
on the uSD. uEnv.txt is loaded after the bootcmd is run,
that is if I read the cmd right. I can change it with setenv
but cannot commit with saveenv because I get " attempt to
erase non block-aligned data" and if I run bootcmd after I
use setenv it just resets to default. If you have any info
on this I am all ears. Das uboot website is kind of vague on
the info I am looking for.
Probably you need to modify the u-boot source in the Angstrom build
system then (provide a patch to do what you want, reference it in the
u-boot bitbake recipe, etc).
http://www.angstrom-distribution.org/building-angstrom
Thanks Russell, I’ll check it out when I get home tonight.
-Wil