On Sun, Jul 26, 2015 at 01:45:42PM -0400, Gene Heskett wrote: > There is no buffering in a cnc setup. The computer expects to get > uptodate data from the machine which I have done at rates to 4,000 times > a second, but normal is 1,000/second. Ditto sending data back to the > machine, that data cannot lollygag around in a buffer someplace for 20 > milliseconds while USB is searching for a suitable sock to put it in. > Even 2 milliseconds will likely put the resultant part out of tolerance > bad enough its a mantle decorator. Are you saying there is motion feedback from the machine and the PC is supposed to 'close the loop' ? In that case indeed any delay due to buffering would needs to be taken into account, or could (depending on required closed loop BW) render things impossible. But *none* of the machines I've ever driven (that includes all sorts of milling machines, and tangential knife, laser and water jet cutters) required feedback to control the motion of the tool as function of time. They did only for things like changing tools and/or workpiece, or to signal general state. If there were feedback loops involved in controlling motion then these were local and certainly not implemented in the controlling PC (which in those times only had RS232 interfaces, orders of magnitude slower than anything USB). And anyway, what is the BW of any heavy piece of machinery ? Probably at most 10 Hz or so, and that you can control using a feedabck loop even with 5 or 10 ms of latency. -- FA A world of exhaustive, reliable metadata would be an utopia. It's also a pipe-dream, founded on self-delusion, nerd hubris and hysterically inflated market opportunities. (Cory Doctorow) _______________________________________________ Linux-audio-user mailing list Linux-audio-user@xxxxxxxxxxxxxxxxxxxx http://lists.linuxaudio.org/listinfo/linux-audio-user
