[coreboot] USB debug cables and emulation

[Joseph Smith]

On Fri, 27 Jun 2008 19:34:10 +0200, Peter Stuge <peter at stuge.se> wrote:
> On Fri, Jun 27, 2008 at 01:15:32PM -0400, Joseph Smith wrote:
>> > You will find two PLX Technology NET 2270 chips and a microcontroller
>> > (I'm not sure which micro it was, maybe Ubicom SX) responsible for
>> > configuration and data flow control in the NET 2270s.
>> >
>> > http://www.plxtech.com/products/net2000/
>>
>> Is the datasheet publicly available?
> 
> Yes, but you have to register on their web site.
> 
Ok, thanks.
> 
>> >> I'll bet anyone all the electrical components inside that little
>> >> box can be purchased for less than 20 dollars.
>> >
>> > In which quantity?
>>
>> Maybe when I figure it out, I will buy a big batch and sell them
>> cheaper to those interested:-)
> 
> Even if you have to buy 1000 pcs?
> 
Sure if I have enough people interested.
> 
>> > So, you will have to reverse engineer the microcontroller software,
>> > and re-engineering a software that does what the NET20DC does.
>>
>> So is there some kind of memory device with the "microcontroller
>> software"? Like a eprom or eeprom??
> 
> I expect it to be stored in internal memory in the microcontroller
> package. I'll open my device up if I can find it to check if I
> remember correctly about the Ubicom.
> 
Thanks that would help a lot. What would be really great, is if you could
open it up and send me some high res pics of both sides of the board. If
you did that I may not need to buy one.
> 
>> > You will be learning a lot about USB - which I think is a great idea!
>>
>> Good, than maybe this little side project will work out great for
>> everyone. Maybe I will learn so much about USB I will be able
>> contribute else where; like filo, GRUB2, and LegacyBIOS :-)
> 
> USB has strict distinction between hosts and devices. This is a
> fundamental design decision detailed pretty well in the spec.
> 
> In order to create your own Debug Class device you need to learn a
> lot about devices and almost nothing about hosts.
>
> 
> When writing a USB stack for the host one needs to learn everything
> about the Host Controller and almost nothing about devices.
> 
Thanks for the tip. I would like to write it in C, my assembly is not so
good. Possible??
> 
>> Also, another question about this topic. I read somewhere someone
>> was working on a Linux Kernel driver for the NET20DC for the host
>> PC. Did this ever implimented? Can you use the NET20DC in linux on
>> a host PC?
> 
> Yes.
> 
Cool
> 
>> If so, how does it work?
> 
> USB serial port. CONFIG_USB_SERIAL_DEBUG enables the driver.
> 
> 
So if this is enabled in in the kernel, what kind of device does it show up
as in the serial terminal emulator?

-- 
Thanks,
Joseph Smith
Set-Top-Linux
www.settoplinux.org