[coreboot] USB debug cables and emulation

Peter Stuge peter at stuge.se
Thu Jul 3 19:18:49 CEST 2008

On Thu, Jul 03, 2008 at 08:45:15AM -0400, Joseph Smith wrote:
> I'm thinking a Serial->USB debugger is the way to go

Ok. Keep in mind that the serial port will probably not be able to
handle full speed data from the debugged target. I'm not sure what
the transfer overhead is, but I expect the debug device to be able
to shuffle quite a bit of data even though each transfer is only 8
bytes max.

> to keep the costs down

As Tom pointed out, this is not a good argument. Serial will only be
simpler to implement, not lower cost to any degree that matters.

> Any suggestions, questions, comments?

You might want to look into the speed thing. I believe the best way
to do so is to run tests on the NET20DC.

On Thu, Jul 03, 2008 at 12:28:47PM -0400, Joseph Smith wrote:
> $20 Dollars for a PCB??? I am going to use a generic PCB you can
> pick up at radio shack for 2 dollars.

That will not work. There are no standalone USB 2 high-speed
function controllers that are usable with those PCBs. You will
have to design a PCB, or buy a devkit.

> This is more for educational, learning, and teaching purposes.
> Everything is not about money you know (or not) :-(

Manufacturing electronics is VERY expensive, and I think the concern
is that you will either be spending ridiculous $$ or be forced to
shut down the project before finish, and that either would be a high
price for whatever knowledge has been gained.

USB Debug Devices aren't the best target for learning USB in general
because the devices need to do some tricks here and there, and thus
require high end function controllers that can perform.


More information about the coreboot mailing list