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Re: [PLUG] OT: Mouse Protocols
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On Saturday 05 October 2002 15H:36, gabriel rosenkoetter wrote:
> On Sat, Oct 05, 2002 at 01:32:15PM -0400, Paul wrote:
> > I advised a guy that, depending on the internals of the mouse, a ps/2
> > mouse might not work with a serial port adapter. Is that generally true?
>
> To the best of my knowledge, that's not true. The software's looking
> for a certain set of signals, those signals are conveyed in one way on
> a PS/2 cable, in another on a serial cable, but they're *there* in
> both, so a converter should just work.
I'd agree somewhat for signalling, but power is a definite issue here.
My understanding is that the power available can be quite different for each
of these three "mouse standards". The power available from a USB port
probably being the most well defined of these three. And most USB mice
probably fail to function if the minimum power specified is unavailable. The
main problem here is that the "standard" PC serial port is definitely not
designed to provide any significant amount of power.
Haven't looked at the USB spec recently, though. And, haven't really looked at
the USB 2.0 spec in any great detail. The PS/2 port is probably the most
"abused" source of power for mice as well as other assorted PC devices. I've
seen some pretty odd devices piggy-back the PS/2 port simply to get some
decent juice. Haven't seen a true spec on PS/2 power availability, though.
>
> > The guy bought a USB mouse which came with a ps/2 adapter. Then, he
> > wanted to buy a ps/2 to serial port adapter, which I thought was...not
> > what I would do. USB --> ps/2 --> serial I told him he would be better
> > off buying a USB card which would enable the mouse to work and give him
> > the option of adding other USB devices in the future. (I know buying an
> > actual serial port mouse would be the simplest solution.)
>
> That's a pretty ridiculous series of adaptors, though. Forget
> translation problems, what about signal loss?
>
> And, actually, you may end up with trouble getting power out to the
> mouse if it needs a lot of juice (like, say, those fancy optical
> mice).
Probably even just a little juice. As I mentioned above, the serial port is
really not designed for devices that intend to draw power. This would be the
most likely problem with attaching any mouse not intended to possibly be
plugged into a serial port (directly or via converter). This could be more of
a problem due to optical, lighted scrollwheel, wireless features, other
add-on features, or simply inefficient design. Probably most newer retail
mice fail this criteria in at least one way or another.
Mice that can plug into a plain-old RS-232 serial port is a pretty narrow and
continually vanishing market. Unless there's some odd mice for Palm Pilots or
something coming out somewhere (I don't have a Palm Pilot, so I wouldn't
know). Even those might not be compatible...
>
> > I also advised (sorry for this) that if he is running Win98 that using
> > USB wouldn't be a problem.
>
<snip>
Briefly: USB is problematic under Windows 95, and I believe the initial
release of Windows 98. Windows NT 3.5 and 4.0 do not have USB support from
Microsoft (but it was available from other sources). All newer versions of
Windows should support USB, at least for prior to USB 2.0 controllers and
devices.
> > Did I offer sound advice or am I getting rusty?
>
<snip>
I'd say advising any other option besides serial mice is probably pretty
sound, and USB is definitely a more forward-looking option than either PS/2
or serial.
>
> > Has anyone had a problem using USB cards either under Linux or Windows?
<snip>
I've never actually used a USB plugin adapter under either. Should come down
to chipset support and quality of the drivers. IMHO, I'd expect the Linux
crowd to come up with better support due to the more common use and reuse of
less expensive hardware.
Cheers,
Jason
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