Am Samstag, 28. Juli 2007 15:02 schrieb Jan Kiszka: > Karl Reichert schrieb: > > Jan Kizka wrote: > >> Karl Reichert schrieb: > >>> Sorry, some mistakes, please see correct settings ... > >>> > >>>> Hi everybody, > >>>> > >>>> I have a question concerning TDMA: > >>>> > >>>> When I set up RTnet with TDMA and a cycle length of 5000 ms, I get an > >>>> average master jitter (difference between scheduled and real > >> > >> transmission time > >> > >>>> of synchronisation frames) of less then 100 us, max 160 us. > >>> > >>> My setup was cycle length = 5000 us = 5 ms > >>> > >>>> When I do the same with cycle length 1000000 ms (1 second), I get an > >>>> average jitter of 8500 us (more then 8 ms). > >>> > >>> My setup was 1000000 us = 1000 ms = 1 s > >>> > >>>> With cycle length 2 seconds, I get an average jitter of 4500 us. > >>> > >>> My setup was 10000000 us = 10000 ms = 10 s > >> > >> What jitter do you get with the "latency" test running at the same > >> periods? > > > > I assume we're talking about /usr/xenomai/bin/latency: > > With 1 ms cycle length and latency tool running, jitter is much lower, > > between 5-25 us. > > > > The other two cycle lengths & latency-tool I didn't gave a try, because > > this seems already strang to me. I'm very busy ATM but if testing with > > those other cycles would help you with the problem, I could give you the > > values at end of august (when I'm finished with diploma). > > > >> What are the distributions of the jitters? All only around 4.5 > >> or 8.5 ms, or are they spread over a far wider range than with 5 ms > >> cycles? > > > > I general they spread little bit, but not very much, so I don't get > > values higher then 5 ms / 9 ms. So this seems to be normal. > > > >> I can't look into this soon, but it has high priority for time I will > >> have test equipment in reach again! > > > > Thanks Jan! Keep informed the list then, please ;) > > Would really like to know why this happens, although it's not so critical > > to my project. > > So far I didn't find any systematic error with large cycle times. > Capturing the outgoing master traffic, I got typical deltas of a few ten > microseconds (unloaded system) according to Wireshark. That quick test > took place over Xenomai trunk, but I would rather expect RTnet to be the > problem here - if at all. > > One further important question to you: How did you measure / read out > the master timing? Are you sure you didn't confuse micro- and > nanoseconds here as well? Note that e.g. Wireshark reports all TDMA > frame timing fields in _nanoseconds_ (all TDMA fields are in nanoseconds > - to answer your older question). > > Jan I read it via wireshark (with respect to nanoseconds) and also on my own slave implementation on TriCore 1130 via debugger. The values are really like that. I will send you a wireshark capture file on monday, so you can see on your own eyes!
Karl ------------------------------------------------------------------------- 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/ _______________________________________________ RTnet-users mailing list RTnet-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/rtnet-users
