Re: [CAD_CAM_EDM_DRO] USB DRO

james owens wrote:

> I have been speaking to a programmer this afternoon and he is
> convinced USB is the way to go in all things computer. There is
> nothing that cannot be done with USB that can be done with other
> ports.
>
> 127 devices can be daisy-chained through one hub with a further 127
> hubs being daisy-chained. The possiblilty of having a whole workshop
> running from one computer which each axis controlled by the host
> computer via a USB hub. Which equates to 16129 axis control
> simultaneously from one computer. One hell of a CNC control
> program!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Well, that's a programmer for you. Not a computer scientist, or
engineer! DRO, sure, if you
use an encoder counter chip, then you don't have to worry about latency,
and the human
eye is so slow, the update rate is no problem. But, for CNC control,
you need absolute
certainty that messages will be processed within a certain time, and the
update rate is
hundreds of times higher. I think 8 axes plus digital control is
reasonable with respect
to bandwidth of the USB, but I have no idea about latency.

Jon