[rescue] USB port card for sBus?

[Jonathan C. Patschke]

On Sat, 23 Aug 2008, Sridhar Ayengar wrote:

>>> I dunno, but you bring up a good point - what about using a serial to
>>> USB adapter? In *theory* they should work either way,
>> 
>> Whose theory would that be?  USB doesn't work that way.
>
> Why not?  There's nothing in the USB spec that would cause making a bus
> enumerator that talks upstream to a computer with RS-232/423 serial, is
> there?  The device would need a whole load of smarts, granted, but what
> would make it impossible?

Here, let me quote the part of Lionel's post that I trimmed:

<blockquote>
   I dunno, but you bring up a good point - what about using a serial to
   USB adapter? In *theory* they should work either way, just trade the USB
   plug to the proper gender and maybe power it from a wall-wart...
</blockquote>

If you can find an off-the-shelf USB-to-EIA232 adapter that will magically
sense which role it's supposed to play, and will either provide a USB
device-node endpoint (providing a '232 port via the "communications
device" USB profile) or a USB initiator endpoint (providing via the "root
hub" USB profile), depending on what it determines, and will make that
determination and a complete USB device tree by merely swapping the gender
of the USB side and receiving power from elsewhere, I'll buy you a
fantastic dinner at the restaurant of your choice anywhere on this
continent.

The bus Does Not work that way.

But, yes, if you wanted to create a USB controller, presumably mastering
the bus at a nominal 11Mb/s or 480Mb/s, that talked back to the host
system over a SPARCstation's Z8530-powered serial ports at a blazing
230Kb/s, that would probably be an excellent investment of some engineer's
time--much better than an SBus or PCMCIA implementation.

-- 
Jonathan Patschke | "There is more to life than increasing its speed."
Elgin, TX         |                                   --Mahatma Gandhi
USA               |