Roland Tollenaar wrote: > Hi, > > Some more interesting findings (no i-pipe trace yet though). > >> Hmm, this doesn't convince me yet. Such skews during startup may as well >> be triggered by unusual load during runtime (non-RT activity or new RT >> components). Did you put your system under adequate non-RT load as well >> while measuring the outputs? > Running latencytest with my application shows an average latency of > about 40 and a max of 200ns. This was rather shocking so I turned off > rtcan in my application. Now the max latecy is 60ns. Turn off EML and > turn on rtcan, max latecy is 230ns. How is that for strange? But since I > can see the scope output bobbing with 200ns during the latency test, I > can also see that if I run my application without the latency test the > huge max latency disappears entirely. Maybe it is time for the trace but > then again I am still using CAN over the parallel port so will see what > it does on a machine with a PCI CAN adaptor first. Because I think I > know what happens: Due to the external loading the CAN recv interrupt > triggers the Rx ISR briefly before the 1ms task period ends. Due to the > priority of the ISR (huge debate over this) and its atomicness (if I > remember correctly) the reading out of the slow hardware delays the > start of the new task period. > > Just thought it was interesting to mention. Btw when the latency appears > there are no overflow messages or anything like that which support the > theory I have about the cause. > > Btw2 the 200ns latency spikes do not cause the scope to loose lock on > the saw-tooth so whatever causes that problem is of a different nature > still.
s/ns/us/ ? Wolfgang. ------------------------------------------------------------------------- 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
