[coreboot] USB debug cables and emulation

Peter Stuge peter at stuge.se
Thu Jun 26 16:55:41 CEST 2008

On Thu, Jun 26, 2008 at 03:57:39PM +0200, Carl-Daniel Hailfinger wrote:
> Are there any easily available USB debug cables?
> The NET20DC is very difficult to get in Europe.

My experience is different. I bought mine from semiconductorstore.com

They have it in stock, accept credit card payment and are quick to

> Can I emulate such a cable with the Geode USB target mode?

Possibly. Debug Class devices have some limitations that the Geode
target will not be optimized for, but it might work, assuming of
course the Geode USB is up an running already - ie. it's not a good
plan to use this for bringing up the same Geode board itself, but it
could be possible to use a Geode as debug device and send out
ethernet on the other end for example.

Only one port on the Geode can be the target port, I don't know if
the alix boards bring out that port. And a driver has to be written.

On Thu, Jun 26, 2008 at 10:28:09AM -0400, Joseph Smith wrote:
> Yeh I think the NET20DC is way to expensive anyways, unless your in
> a mass production environment.

I don't find US$ 83 so bad actually. Granted, there's import duties
too, but still not too bad considering the hours of development that
would go into creating my own device.

> I read somewhere you could make one, but I don't know how difficult
> that would be.

In theory sure! It is a USB device, but it is special in several
ways, narrowing the possible development kits and USB chips that
can be used a bit. (In particular, it must do high-speed

> I was always wondering if you could just use two USB -> Serial
> adapters with a null modem cable in the middle???

No, you can not. More info on:


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