[U-Boot] reverse engineering a Philips photoframe

[Walter Heck]

Hi all,

I'm completely new to the world of U-boot, so please forgive me if I spout
nonsense. I'm looking for a bit of guidance.

I'm reverse engineering an old Philips 10FF2 Photoframe, hoping to one day
customize it, just for the fun of it. I've been researching quite a bit and
after downloading an updated firmware from the philips site and unpacking
it, I notice it contains (among a bunch of others) 3 files of interest:
1) UBLDM350.BIN, sized at about 23k. The binwalk utility tells me it
contains "ARM executable code, 32-bit, little endian, at least 984 valid
instructions". I'm guessing this is uboot, not sure how I can confirm?
2) A file called Philips.cmd, containing a very simple script which among a
lot of other stuff has a line that says: "//[UPDATE BOOTLOADER]"
3) A file called P350MAIN.BIN, which I have no real idea what it contains
yet. It's about 2.3MB large and using a tool called mediaextract I was able
to extract at least some JPEGs that contain artwork for the menu of the
picture frame.

Now, I have a bunch of questions:
1) How can I confirm this is indeed uboot? How would I know if it's stock
UBoot or a modified version?
2) Can I compile uboot myself and replace this one without bricking my
frame?
3) As far as I understand Uboot loads the actual OS. Would it be possible
the P350MAIN.BIN file is that OS?

Any input is welcome. To be clear here I'm not doing this out of commercial
interest, just trying to customise this frame for fun.

kind regards,


-- 
Walter Heck