Re: USB device just moves

Tim Roberts <timr@xxxxxxxxx> writes:
Eric <Scorpus@xxxxxxxxxxxxxx> wrote:
USB must be polled at regular intervals,...

Interrupt and isochronous pipes must be polled at regular intervals. Other
pipe types do not.

Your first statements means nothing more than 'USB must be polled at
regular intervals'. Assuming there are neither interrupt (unlikely)
nor isosychronous endpoints active on any device connected to some
USB, what is left would basically be bulk in- out out-pipes, which
only need to be 'polled at regular intervals' if one actually wants to
receive or transmit data over the USB. Therefore, the only USB not
being 'polled at regular intervals' is one without used devices
connected to ti.

[...]

There is nothing inherently wrong with a polled, dedicated master/slave bus
design.

There was nothing wrong with the various token-passing based LAN
technologies people considered to be a good idea (more than) twenty
years ago, either. But for some mysterious reason, they have basically
completely disappeared from the market.

It avoids all the problems of assigning a bus master or handling
collisions among multiple senders.

And there were lots and lots of wrongs inherent in CSMA/CD networks,
but again, for some mysterious reasons, they were cheap and worked
well in practice. But they were invented at a time when putting all of
the practically stupid 'intelligent design' into mass-produced and
therefore cheap ICs wasn't even possible. That's why it took some
twenty years of technical progress until the 'intelligent design'
finally became the chance to again rise from its well-deserved grave,
where it rather should have been rested until kingdom come.

The PS/2-mouse connected to my computer at work is a true real-time
capable device, ie it 'works' whenever I move it. The USB-mouse I have
at home cannot do that: If it has been inactive for some time, there
is a noticable delay between the time I try to use it again and the
time it actually reacts.

A design which needs lots of high-developed components which are
literally busy doing nothing almost all of the time is stupid.

That it can be produced cheaply, given that the right proponents are
pushing it and works 'good enough' doesn't make it any less stupid.

.