PDA ramblings...

Ian Molton spyro at f2s.com
Sun Feb 2 09:45:47 PST 2003


On Sun, 2 Feb 2003 17:16:42 -0000
"Matthew Burgess" <ca9mbu at eos.sunderland.ac.uk> wrote:

> > Im reverse engineering the bootloader of my PDA. Im hoping to get
> > linux running on it ;-)
> 
> Ian,  how big a job is this going to be?

If I can get either serial or display to work, it should be relatively
easy.

I can upload my own code, and, apparently, it executes OK (well, if I
put an infinite loop before the code that otherwise makes it reset, it
/doesnt/, so I assume its busilly inifinitely looping...).

Now I am trying to work out why any attempt to access either IO space or
what appears to be the IO for the LCD (which is actually mapped into one
of the SDRAM banks, from what I can tell), causes a reset... I suspect
the MMU is already on, and that I am in 'supervisor' mode, so I should
be able to disable it / remap the memory to something useful.

> Does the compiler toolchain
> and linux kernel actually support the processor inside your PDA (what
> processor is it?)

Sort of. its a PXA250 (XScale, 400MHz). The armv4 GCC should cope with
generating useable, if not particularly optimal, code. right now, Im
just writing little hacks in assembler, though.

> or have you actually voluntarily condemned youself
> to a life of solitary confinement whilst you port that little lot
> across?:)

LOL! thats my other project ;-) (bring GCC up to date for ARM26).

no, once I can get a semi-sensible memory map, it should be as simple as
compile a kernel, copy it to CF, and boot. The PXA250 is already
supported by (2.5.x) armlinux kernels.

Of course, I am looking for a nice friendly surface mount capable shop
that would be willing to replace my PXA250 with a PXA255, which is a LOT
quicker, and has less bugs.
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