Jon Elson wrote: >Kenneth Lerman wrote: > > >>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. >> >> >Well, that's the problem, it is NOT real time code. I don't >know how far it is from being real time compatible, but I >suspect there's a lot of things in there that might cause >problems. > > >>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. >> >> >As long as you could throttle traffic on that ethernet segment, >so a network file transfer, for instance, couldn't bog down the >ethernet, then that would work. > No, it wouldn't (not necessarily). You'd also have to set the MTU pretty low. A single UDP packet of 12.5kBytes takes 1ms to transmit on the wire. (12.5k * 8 bits = 100 kbits = 1/1000 of 100 mbits/sec = 1msec) Even if you throttle large transfers, and you can somehow convince multiple hosts on the segment to all share the same "throttled pool" of bandwidth, a single large packet can throw a wrench in the works.
> But, I have no idea what would >be involved in making the ethernet port driver and network stack >RT compatible. Some time ago the RT stuff didn't do anything >well except regularly-schenduled tasks, I think that is no >longar a problem. But, the net driver would have to respond to >interrupts whenever a packet came in. > > I think the base for interrupt-response threads is there - the current HAL thread mechanism uses it to grab the timer interrupt. ADEOS can route multiple interrupts (and multiple interrupt domains), and I'm pretty sure RTAI also supports this. It's just not part of RTAPI or HAL. - Steve ------------------------------------------------------------------------- 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
