On Thu, Feb 24, 2011 at 12:29 PM, Jean-Paul Moniz <jpmo...@pmiautomation.com > wrote:
> Phil > > Safety should always be a hardware solution. Safety software applications > should be tested and certified to international standards. > I much prefer hardwired safety and no software :-) > In the case of emc. The pc is the controller and not hacked up at all. > My concern is the following: Note: Do Not upgrade Ubuntu from the installed version as it will prevent EMC from working. If EMC was running on pure stock Linux rather than Linux+Realtime extensions it would be able to tollerate upgrades through the regular process. If the responsibility for timing was shifted from the kernel to the controller it would not be necessary to run with the 'realtime' package installed in the kernel. > However if it was a windows os there would be lots of hacking going on to > get something that appears to be real time Windows is not built to support real time. Although rather ironically the original kernel was. It is pretty difficult to timeshare a machine between real time tasks and supporting a GUI with real-time response. One or the other is going to end up taking precedence. The problem with USB is that it is a contended bus. So even if your host is running in real time there is no guarantee that signals get out to the end points in real time. That is why there is still a demand for MIDI interfaces despite them being much slower than USB. I would really prefer to have separate CPUs dedicated to scheduling and GUI. That way I don't have to worry about keeping the timing clean over the data wires, the only timing sensitive wires are carrying the signal. If I could eliminate the parallel port requirement, I can eliminate the need for a separate controller box entirely and just bring down one of the laptops when necessary. It also makes it possible to use the mill and the lathe simultaneously from a single host. > -----Original Message----- > From: Phillip Hallam-Baker <hal...@gmail.com> > Date: Thu, 24 Feb 2011 12:03:05 > To: Enhanced Machine Controller (EMC)<emc-users@lists.sourceforge.net> > Reply-To: "Enhanced Machine Controller \(EMC\)" > <emc-users@lists.sourceforge.net> > Subject: Re: [Emc-users] Guidance on usb comp > > On Thu, Feb 24, 2011 at 6:44 AM, John Thornton <bjt...@gmail.com> wrote: > > > Frank Tkalcevic wrote: > > >> The PoKeys55 docs claim that the device implements a standard USB HID > > >> keyboard and joystick. Based on that, I'd expect it to just work with > > >> hal_input. Is that not the case? > > >> > > > You are correct. It doesn't use the HID Descriptor reports, so generic > > > software can't query the device for its capabilities or message > formats. > > > Their messaging is specified in their document, but needs to be code > > > specifically. > > > > > > The pokeys makers approached me to add support for it to hidcomp, but > > given > > > how little spare time I have, it was too much work. > > > > > What would be involved in getting it to work? > > > > When I tested it I only tested the analog inputs then lost track of it > > for a while. > > > It would be nice if there was a way to interface CNC equipment via USB such > that the timing of actions was being scheduled in the controller rather > than > by the host O/S. > > That way it would not be necessary to run a specific version of the O/S > hacked up to provide real time scheduling. All that would be necessary > would > be to have the host able to guarantee response within a few seconds. > > > Parallel ports are effectively obsolete these days and finding a > motherboard > with support is starting to confine selection. So this is effectively > meaning I have to use an obsolete machine that I am not sure I could > replace > in a hurry. > > Making such an implementation safe would require a little more. There > really > should be some form of safety switch in the loop and that really should be > capable of shutting the machine down dead, cutting power to the stepper > motors and the spindle. > > A safety stop should be hardwired and failsafe. > > > I am just making a box for my xylotec controller and I am seriously > thinking > about adding a safety stop and routing power to the machine being driven > through the box. > > But in the longer term, I am thinking of maybe programing an ardulino or > the > like to replace the parallel port i/f. > > -- > Website: http://hallambaker.com/ > > ------------------------------------------------------------------------------ > Free Software Download: Index, Search & Analyze Logs and other IT data in > Real-Time with Splunk. Collect, index and harness all the fast moving IT > data > generated by your applications, servers and devices whether physical, > virtual > or in the cloud. Deliver compliance at lower cost and gain new business > insights. http://p.sf.net/sfu/splunk-dev2dev > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > > > ------------------------------------------------------------------------------ > Free Software Download: Index, Search & Analyze Logs and other IT data in > Real-Time with Splunk. Collect, index and harness all the fast moving IT > data > generated by your applications, servers and devices whether physical, > virtual > or in the cloud. Deliver compliance at lower cost and gain new business > insights. http://p.sf.net/sfu/splunk-dev2dev > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > -- Website: http://hallambaker.com/ ------------------------------------------------------------------------------ Free Software Download: Index, Search & Analyze Logs and other IT data in Real-Time with Splunk. Collect, index and harness all the fast moving IT data generated by your applications, servers and devices whether physical, virtual or in the cloud. Deliver compliance at lower cost and gain new business insights. http://p.sf.net/sfu/splunk-dev2dev _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
