On Saturday, Jan 10, 2004, at 08:47 US/Pacific, Herbert Graf wrote:

> Which is what USB was NOT meant for, I don't know why you STILL
> don't get that. For most users a webcam WILL be near to PC,

A forum like PICList is likely to rate the merits of a comm port
based somewhat on how easily the defined "protocol" can be "bent"
to other purposes.  Use the printer port for input?  Cool.  Put a
disk drive on it?  Excellent!  And still have the printer work?
Uh...  The bidirectionally-communicating printer?  ummm...
And the SERIAL port, well.  Hardware flow control.  115200bps.
Deeper and deeper FIFOs, but don't get incompatible with that
venerable 8250 - too much legacy SW!  Generating Vpp from the
rs232 voltages, and using the modem signals for IO.  Back to cool!

I don't know who said that the legacy ports "just worked" - that
certainly doesn't match MY memories of struggling with (especially)
serial port cables and adaptors.  Things have settled down a bit now,
thanks to ... extinctions of entire species, essentially, but I think
the most common serial comm problem is STILL a wrong cable somewhere.

And I don't want to talk about lovely external interfaces like HPIB
and SCSI, where the cables often out-weighed the peripherals, and had
their own problems with chaining and termination...

Now, USB was designed (as I see it) to:

1) address the requirements of the sorts of devices people were
    mis-using serial and parallel ports to connect.
2) cut down on the scope and magnitude of the user errors that
    could occur in connecting devices to the computer.
3) permit a greater number of devices to be connected without
    interfering with each other.

They did pretty good, IMO.

USB2.0, OTOH, is a rather embarassing afterthought.  A sort of "oops,
here are the things we forgot about (or specifically excluded), cause
after all we don't want firewire to own those pieces..."

There's no doubt in my mind that USB can be abused.  Longer cables
are clearly possible, especially if you're willing to give up things
like hot-swap out at the end of that cable.  (yeah.  termination.
looks to me like USB is designed to keep working even if one or more
ends of the max-specified cable suddenly become un-terminated.  What
a good idea!)  It would probably be good for the computing world in
general if intentional abuses of the USB spec do not become rampant
the way they did with serial and parallel.  It's bad enough that
"evil" extension cables are widely available.  No selling USB cameras
with 50 foot of cable on them, please...

BillW

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