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 code.
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?