[Openec] Few questions about KB3700/3926

[Frieder Ferlemann]

Hi,

Maxim Levitsky schrieb:
> But writing firmware for EC with partial data sheet, no information on 
> schematics, and having constant danger of damaging the system I say is 
> impossible.

there is one (out of 23) schematic sheets for an early XO available.
It shows the EC, the SPI flash, debug-connector, LEDs, and 3x3 keyboard matrix.
So it's only close to impossible:)

>> But likely not legal to use if I gained this information
>> by disassembling the first 64k of XOs firmware (IANAL).
> 
> Some day I might help with that, you say I can disassemble the firmware,
> and give you directions how to power up the CPU?

Most likely - that would be great!

> Btw, using some instruments and destroying a single OLPC you could 
> figure the schematics by unsoldering the parts?

While this might technically work (given sufficient resources/time)
it socially probably would not: you would get to know how it is
done (but not why, or how future version would look like, and
the chance to be involved early in the development phase would be lost).

> I guess that small devices like sensors and voltage regulators should 
> have datasheets.

yes.

> Or maybe you can order bare parts that werent soldered yet from OLPC ?
> 
> Btw you say that on newer models access via debug port to EC was blocked.
> Was it blocked completely, or there is a way to unlock it?

It's not the debug port that is blocked, instead a bit (don't have its
name at hand) is flipped by EC firmware that switches off main CPU access
(security/anti-theft rationale).

> If it was blocked completely, this  against the spirit of openness of 
> OLPC isn't it?

With a developer key the XO should be free. (But it would not be wise
to reprogram the EC area with OpenEC without a debug adapter)


Richard, Paul, are you following this thread?


Greetings,
Frieder