For me, the issue of RTnet is irrelevant. I would, instead, just want to use the Linux driver. If we can get that to generate and receive ethernet frames in real time, we are in business.
Then we could let the PC be a master and any peripherals be slaves. In the case of the UPC board, there might be only one slave. The master would poll each of the slaves as appropriate. Ken [EMAIL PROTECTED] Mark Kenny Products Company, LLC 55 Main Street Voice: (888)ISO-SEVO (888)476-7386 Newtown, CT 06470 Fax: (203)426-9138 http://www.MarkKenny.com -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of Jon Elson Sent: Sunday, October 28, 2007 4:43 PM To: Enhanced Machine Controller (EMC) Subject: Re: [Emc-users] Ethernet I/O Jon Elson wrote: > Stephen Wille Padnos wrote: You can't use any old >>topology with RTNet. RTNet is a TDMA scheme - each device gets a time >>slot in which it may transmit. This eliminates collisions, which are >>the main cause of timing jitter on ethernet. Well, after some more reading of the RTnet documents, I'm not sure that rtnet is really appropriate for this project. The biggest problem is that I have no rtnet driver for the "slave" device. Depending on the way the ethernet stack has been written for the ARM7 chips I'm looking at using, it could be anywhere from difficult to nearly impossible to implement RTnet on these microcontrollers. Now, maybe I am underestimating the sophistication of how these stacks are constructed, and it might be quite straightforward to port RTnet to the ARM7 with built-in ethernet MAC. I think this is way beyond my level of expertise. One thing I couldn't figure out from the RTnet docs what what the rate of the schedule frames is. I guess it matters what bit rate the media is running at, and packet size, number of nodes, etc. I was just trying to figure out what these rates might come out to. As long as a router would throttle any incoming traffic, this particular application doesn't actually require all the features of RTnet. If the problem of porting the RTnet driver to non-PC, non-Linux systems can be solved, then it certainly will work. 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 ------------------------------------------------------------------------- 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
