On Tue, 30 Oct 2007, Jon Elson wrote: > Date: Tue, 30 Oct 2007 00:36:41 -0600 > From: Jon Elson <[EMAIL PROTECTED]> > Reply-To: "Enhanced Machine Controller (EMC)" > <emc-users@lists.sourceforge.net> > To: "Enhanced Machine Controller (EMC)" <emc-users@lists.sourceforge.net> > Subject: Re: [Emc-users] Ethernet I/O > > Peter C. Wallace wrote: >> On Mon, 29 Oct 2007, Jon Elson wrote: >> >>> The idea is that 100 mbit/sec ethernet is fast. What other >>> RS485 device do you have that runs that fast? >> >> >> Of course a RS-485 link can have smaller packets, and may actually have much >> better real time performance. (a single 10 MBps RS-485 link will have much >> better performance than 100 BT Ethernet connected to a single encoder) >> >> Also 100BT with its MLT3 encoding is not as electrically robust as isolated >> RS-485 or 10BT. >> >> Ethernet is great for broadcast but I don't think so good for collecting data >> from a large number of separate real time devices (say encoders) >> > Yes, I think this would be a bad way to do things. Having a > single motion control board that interfaces by Ethernet, as I > have been envisioning, would have a lot of advantages. It keeps > the sampling of all the encoders synchronized, it compresses all > the information interchange into a couple packets, it saves on > hardware. Putting a separate ethernet interface into each > encoder is a great way to sell a lot of hardware.
Sounds good to me :-) We _are_ looking into building a controller/encoder interface on an encoder board however. As a controller, this would communicate with our amp via RS-422. (4 byte packet at 5 MBps = 10 usec delay). As an encoder only it would report absolute position, hall status, and temperature. Now if Avago would only make a reflective sensor with 3 tracks... For accurate Ethernet timing I notice Freescale, AMCC (PPC) and Luminary (ARM) offer micros with IEEE 1588 support. The Luminary chip is interesting because it contains both 100 BT MAC and PHY. >> I think Ethernet would be a really good way to connect a multi channel motion >> controller to a PC where the large packet size is not such nuisance. You >> would >> likely need a separate Ethernet card from the main network connection. > RTnet, for instance, gets around this to some extent. But, that > is one way to do it, have 2 ethernet ports on the computer, one > for RT, one for the local net. Otherwise some kind of router > needs to be used to keep outside traffic from flooding the RT > segment. > > Jon > > ------------------------------------------------------------------------- > This SF.net email is sponsored by: Splunk Inc. > Still grepping through log files to find problems? Stop. > Now Search log events and configuration files using AJAX and a browser. > Download your FREE copy of Splunk now >> http://get.splunk.com/ > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > Peter Wallace Mesa Electronics (\__/) (='.'=) This is Bunny. Copy and paste bunny into your (")_(") signature to help him gain world domination. ------------------------------------------------------------------------- This SF.net email is sponsored by: Splunk Inc. Still grepping through log files to find problems? Stop. Now Search log events and configuration files using AJAX and a browser. Download your FREE copy of Splunk now >> http://get.splunk.com/ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
