Re: EZ-USB

--- In CAD_CAM_EDM_DRO@y..., Jon Elson <jmelson@a...> wrote:

>
> >Ian Wright wrote:
> >
> >Just how reliable is USB supposed to be now? <snip>
>
> Yes, reliability is a PRIME concern! If a motion control system on

a machine

> tool hangs up once a year, some people would scream! There is also

the safety

> issue - if the machine suddenly took off at full speed while the

operator was

> measuring a part, with his head and hands in the work area, it

could be a MESS!

>
> Jon

The USB bus, like anything on a PC, is subject to have
some problems. The early compatibility and lockup problems
seem to be easing as the USB interface matures and more
OEM's get their act together. Many problems that have occurred
with device interfaces (i.e. serial, parallel, or network) are
often traced to the system software (Windoze especially) trying
to run them. The USB interface provides a very structured device
interface which should result in fewer system bugs in the long
run.

It would probably be a good idea to have any CNC device on
a USB bus by itself. This would reduce the possibility of
any problems related to hubs and multiple devices. Most
computers now have two or more USB busses so this should
be reasonable.

CNC control run away is an issue with any system. The USB board
that we are working on will have a "dead man" timer so that any
loss of USB control would cause a controlled shutdown. Also, USB
communications have built in CRC checking of the data content
being transferred so corrupt data is not likely to cause problems.

Steve Stallings