Am 03.09.2013 um 05:41 schrieb Gene Heskett <ghesk...@wdtv.com>: > On Monday 02 September 2013 23:18:36 Jon Elson did opine: > >> I'm not sure theis is the right method to bring this up, but... >> I have had some discussions with Michael Haberler about having >> the capability for making HAL threads triggerable via an >> external interrupt. Apparently, there was a partial capability >> in an early version of rtapi, but it was removed, possibly because >> it didn't work. >> >> Anyway, my line of interface boards have always had the capability >> of sending an interrupt pulse through the parallel port on a regular >> interval of 1, 2 5 or 10 KHz. These boards also sample the encoder >> position in hardware at that time, and exchange signals on the >> parallel port bus so all boards sample within 1 us. Since this >> was not supported in HAL/rtapi, we have not been using this >> feature, so the hal_ppmc.c driver does the sampling by a software >> command. This causes some jitter in the sampling time. On an >> X86 machine with decent latency performance, this has been OK, >> but not optimal. Since we are now contemplating moving to >> other platforms, such as the BeagleBone, with somewhat worse >> latency jitter, and having to rework rtapi to adapt to other RT >> packages such as Xenomai, this might be a good time to >> explore whether triggering a HAL thread via external interrupt >> is possible and/or desirable. I would certainly like that option, >> as it would reduce position sampling jitter to sub-ns levels for >> one board, and no more than 1 us ever on multiple boards. >> Michael has some other reasons for allowing external interrupts >> on some systems, but doesn't want to go all the way through to >> HAL threads with it. Does anyone else have thoughts on this, >> or want to be able to trigger HAL threads externally? I can >> imagine some other projects that might benefit from this. >> >> Thanks for any thoughts, >> >> Jon >> now > > While 10khz sounds a little slow for us stepper users, the fact that the
I think Jon is talking about timing the servo thread. -m > samples are frozen in a very accurate timebase would appear to be a > worthwhile endeavor to me. with say a 30 to 50 khz clock, the base thread > could be clocked entirely in hardware. That can't help but be an advantage > for stepper drivers I'd think. > > OTOH, I have no clue just how big a re-write that might be. I can't imagine > it would be trivial. A change that big should probably be staged to simmer > in the devel branch until 3.0. > > Interesting times Jon. > > Cheers, Gene > -- > "There are four boxes to be used in defense of liberty: > soap, ballot, jury, and ammo. Please use in that order." > -Ed Howdershelt (Author) > My web page: <http://coyoteden.dyndns-free.com:85/gene> is up! > My views > <http://www.armchairpatriot.com/What%20Has%20America%20Become.shtml> > Favorite Windows game: "Guess what this icon does?" > A pen in the hand of this president is far more > dangerous than 200 million guns in the hands of > law-abiding citizens. > > ------------------------------------------------------------------------------ > Learn the latest--Visual Studio 2012, SharePoint 2013, SQL 2012, more! > Discover the easy way to master current and previous Microsoft technologies > and advance your career. Get an incredible 1,500+ hours of step-by-step > tutorial videos with LearnDevNow. Subscribe today and save! > http://pubads.g.doubleclick.net/gampad/clk?id=58040911&iu=/4140/ostg.clktrk > _______________________________________________ > Emc-developers mailing list > Emc-developers@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-developers ------------------------------------------------------------------------------ Learn the latest--Visual Studio 2012, SharePoint 2013, SQL 2012, more! Discover the easy way to master current and previous Microsoft technologies and advance your career. Get an incredible 1,500+ hours of step-by-step tutorial videos with LearnDevNow. Subscribe today and save! http://pubads.g.doubleclick.net/gampad/clk?id=58040911&iu=/4140/ostg.clktrk _______________________________________________ Emc-developers mailing list Emc-developers@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-developers
