On Fri, Jan 23, 2004 at 11:12:00AM +0200, Juhana Sadeharju wrote:
> >From: Carl William Spitzer IV <[EMAIL PROTECTED]>
> >
> >why not use a crossover cable between two nic cards?
>
> Hello. What are those?
"NIC card" refers to an Ethernet device. A crossover cable can connect
two Ethernet devices together into a network without needing a hub or
switch in the middle.
> Is USB designed so that the cable and the hardware has to be
> reversed if one reverses the connection direction?
Yes. USB has an explicit concept of something being either a "device"
or a "host". It's not a peer-to-peer system like Firewire/IEEE1394.
> That is, a computer should have both in and out USB ports, and
> the cable must be switched from port to port.
Have you looked closely at a USB cable? They don't usually have the
same connector on both ends. Hosts use one type of connector and
devices use another. You can't simply hook two computers together
because they'll both have host connectors and the cable physically
won't work.
> How sad. Why USB is limited that way?
Probably because it's easier (and cheaper?) to implement.
> Does that limit possible USB applications?
Sure, like the one you're trying to do, for example. Another one I'd
like is to be able to use a computer as a USB sniffer, but again that
means my computer would need a device-type connection as well as a
host-type connection. There are some embedded systems and development
boards that can do that, but a typical desktop or laptop will not.
> What USB chips are used inside USB disk devices? What USB chips are
> used inside computers? If they are different kind of chips,
Yes, I think the chipsets are different based on whether you're
implementing a device or host. There are Linux drivers for some
device-side chipsets. For example Linux-based PDAs will usually be
devices rather than hosts.
-Dave Dodge
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