Re: Black box flight recorder for Linux

Andy Green
2006-04-10T12:01:48Z

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Krzysztof Halasa wrote:

> I think the most trivial and reliable way would be to solder some
> I^2 or similar EEPROM chip to, for example, parallel port connector.
>
> Most motherboards have an internal I^2C bus / SMBus (for reading RAM
> types and for other things) and I think it could be used to connect
> the EEPROM instead of external port.
>
> There are 512 Kbit (64 KB) and 1 Mbit (128 KB) EEPROMs available -
> there is plenty of space not only for crash dump but for whole dmesg.

Just an additional thought on this idea... both VGA and DVI connectors
on modern video cards appear to have DDC-2 connections, which is in fact
I2C. This would provide an (inherently bidirectional :-) ) 3-pin
digital interface out of a mostly dead box even on laptops and so on
with no serial, parallel or legacy keyboard/mouse, so long as they had
reasonably modern VGA or DVI out. You would need to get access to the
two I2C pins and Gnd somehow in that scenario. Since I2C has a concept
of addressing it should be possible to choose I2C addresses for this
communication that doesn't address whatever may be listening on the same
bus in the monitor.

I don't know if you bitbang these or there is some kind of
shifter/management logic in the video chip, in which case some minimal
case by case support is needed, but since simple IO is otherwise all but
gone on modern laptops so I thought it worth mentioning.

-Andy

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