[OT] USB KVM switches

From: Tony Duell <ard_at_p850ug1.demon.co.uk>
Date: Wed Feb 2 19:43:27 2005

> In the olden days (which were only a few years ago), I had a PDA,
> a modem, and a computer, all with EIA-232 serial ports. The PDA
> cable and modem were wired as DCE, and the computer was DTE. Most
> of the time, I would plug the modem or the PDA into the computer, and
> that worked fine. But when travelling, I would take the modem along
> and plug it into the PDA using a null modem cable. This all worked
> fine.
> Now I have a PDA, a modem, and a computer, all with USB ports. The
> computer is a USB host, and the PDA and modem are USB devices. I
> can still use the PDA or the modem with the computer. But when I
> travel, I cannot use the modem with the PDA, since they're both
> USB devices, and USB devices can't talk to each other. (Yes, there's
> a USB On-the-Go spec which is supposed to address this, but it doesn't
> seem to be going anywhere, and I'm not sure it would solve the PDA and
> modem problem.)

This is exaclty my complaint against the HP49G+ calculator. The USB port
may be great for linking it to a modern PC, but it can't talk directly to
a printer, or to a ADC box, or to just about any other peripeheral.

It appeas that HP have realised this because they actually recomend
getting a 48GII if you want to link it to custom hardware. Pity that
machine is inferior in other ways.

What HP should have done is put an async serial port (either TTL levels
or RS232) on the 49G+ and included a USB to that interface 'cable' in the
box with the necessary drivers. Normal users could just have plugged it
in with no problems and not realised there was anything odd, hackers
could have used the async interface to link to their custom hardware. Oh

> This is progress?

As a friend of mine says 'Oh no, not another improvement' :-)

> USB vs. EIA-232 is like a point-and-click GUI vs. a command line. A
> point-and-click GUI makes simple things easy, and more complicated things
> impossible. So does USB

Exactly :-( If you want to do something the designer hasn't thought of
you're going to have problems. And I always seem to want to do that.

Received on Wed Feb 02 2005 - 19:43:27 GMT

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