Re: [driver] New life for Serial mice

Vojtech Pavlik
2001-06-08T16:28:56Z

On Fri, Jun 08, 2001 at 06:20:46PM +0200, Pavel Machek wrote:
> Hi!
>
> > > > If you still have your 3-button MouseSystems (or any other serial) mouse
> > > > somewhere in your driver, forgotten becase of the incredibly slow update
> > > > rate causing so much jumping of the pointer on the screen that it is
> > > > unusable, you may want to pull it out and give it a try.
> > > >
> > > > Or if you're still using it with some old 486 computer, this driver is
> > > > for you.
> > > >
> > > > What it does is that it enhances the update rate from 24 (with current
> > > > GPM and X drivers) to 96. This is almost what the best USB mice do.
> > >
> > > What's the "prediction" stuff? Does it mean you are guessing some values
> > > by interpolation?
> >
> > Extrapolation, yes.
>
> Can't it make mouse jump forward and back when user suddenly stops?

In theory - yes. It doesn't seem to be a problem in practice, though.
It'll happen when a user slows down the mouse pointer motion faster than
exponentially (base 2). I haven't been able to stop that fast.

> > > [If so, what kind of update rate would it do on USB?]
> >
> > It wouldn't make any difference - on USB you always get whole packets,
> > while over serial port the data is processed byte by byte and thus we
> > know a little of the information before the whole packet arrives.
>
> Ouch, nice trick!

Most importantly - it makes serial mice usable.

--
Vojtech Pavlik
SuSE Labs