[E3-hacking] PBL & running arbitrary code
Thu, 10 Mar 2005 15:04:01 +0000
On Thu, 2005-03-10 at 14:31 +0000, Matt Evans wrote:
> Last night I bodged an old USB mobile phone serial cable onto my EXP
> port - I'm pretty sure the E3 and the E2 differ with regard to the
> voltages on the EXP port. That is, that webpage suggests that E3 is at
> RS232 levels and doesn't need any line drivers. The E2 appears to be
> at TTL levels (0V and 5V) and as such won't work when connected
> straight to an RS232 port.
Ung. Less good.
The core itself is powered at 3.3V, so if you're getting 5V, then it
sounds like the device does have a line converter of its own... what
does the device run off? Could this be tweakable?
> Yes this sounds sensible - if there's an Easy Enough way to get
> bootstrap code in there via serial/EXP then we don't need any horrible
> JTAG stuff. Ideally something like loading our own loader through PBL
> - our loader takes over and then we can download a DRAM image, or get
> it to reflash the NAND in such a way that PBL will later load our own
Another, slightly scary, alternative is to replace the PBL with our own
bootloader --- does the PBL copy itself to RAM before executing? If so
this reprogramming could be done through the PBL itself. If not, it
would have to be a JTAG thing. However, I think I'll let someone else
try this first...
Does anyone have a dump of the PBL?
David Given <email@example.com>