From: [IDC]Dragon <idc-dragon_at_gmx.de>
Date: Wed, 23 Jun 2004 16:24:16 +0200 (MEST)

Pretty much correct, see below.

> > Does the uart boot mod does allow to boot even with an erased flash?
> > How does it do that? is it a sh1 feature?
> > Is there lot of difference with the full duplex serial mod?
>
> As I understood it ([IDC]Dragon, please correct me if I'm wrong), it's a
> feature the archos engineers built in for debugging purpose. The sh1 cpu
> has
> some internal flash memory which is always executed at startup.

It's ROM memory. The SH has 64k of it, but only a small fraction is used.
What a pity, it's fast memory, they could have exploited that better.

> It is
> programmed to load the actual firmware from flash memory. But this
> bootloader can do more: if you pull the lcd lines low during booting, it
> gets you into this special uart boot mode, in which it accepts any code
> from
> the serial line. I guess the archos engineers used it the same way as we
> do
> now:as a fallback solution for the case that the content of the flash is
> somehow garbled.
>
> So you need three things: a bidirectional serial connection (as described
> in
> the serial mod section on the rockbox homepage), the uart boot mod (which
> is
> only pulling down some port pins) and [IDC]Dragon's nice serial boot tool
> which manages the communication between your computer and the jukebox.

It's pulling down port PB1-3. These lines have 10k pullups on the PCB, you
may either change that or "override" by pulling low. Don't pull to strong
(don't short them to ground), because those lines will become outputs later
on.
For player models, these lines are available at the diagnostic pads(?) where
you find the serial lines, too.
Please excercise caution, I broke a player while attempting this. Never
found out how and why, maybe electrostatics.

> I'd love to help more, but I'm afraid I don't know too much about the
> player/studio model and if the procedure is the same on those. I managed
> to program a completely empty flash chip in my recorder this way.

Maybe you have some links to postings at hand?

Jörg

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Received on 2004-06-23