Peter's solution will work. I was going to add a dead-band to the PID control internal to the HAL component that talks to the PRU, but Peter's suggestion of pushing the PID outside the PRU driver and into HAL makes a lot more sense. The existing HAL PID component is vastly more sophisticated than the PID inside the PRU driver, and pushing it out into HAL not only makes the configuration more "unix and LinuxCNC like", but doesn't require any new code to implement.
I just don't have time to play with HAL right now (I'm getting ready for a 100K run this weekend), and my test machine is currently in various pieces so I couldn't check things out even if I had time to make the change. I can probably get to it next week sometime, but I'm hoping someone will beat me to it. On 2/20/2014 11:19 AM, Jeff wrote: > Hi, > > I looked at the DIR line on a bare beagle bone with no attachments. > The DIR line can end up toggling after a move has stopped. But it > does not *always* end up toggling after a move. Pressing the "power" > button in AXIS clears the situation until a future move. The STEP > line does remain inactive, so there is no unwanted movement. Mark is > using Geckos which are optically isolated, so the chance of > electrical noise contributing to the problem is unlikely. > > I've also noticed the problem with the Allegro A3977 drive chips. > I'm not sure why either the Geckos or the A3977 would care about a > toggling DIR line while STEP is inactive, but they do. Perhaps it is > some kind of "noise" issue within the drive itself (i.e. not > electrical in the wiring/grounding sense). In any case, the solution > (when found) will be to stop the line from toggling at all. > Hopefully Peter's suggestion of a different HAL configuration will > work. > > Jeff > > ---------------------------------------- >> Date: Thu, 20 Feb 2014 16:53:07 +0000 From: m...@rmtucker.f2s.com >> To: emc-users@lists.sourceforge.net Subject: Re: [Emc-users] >> Crackling motors using Beaglebone >> >> The drivers have been working on mach3 for the last 5years with no >> problem,and also work no problem with linuxcnc on a pc. I believe >> jeff pollard has scoped the output on the dir line and it is >> clearly visible. >> >> On 20/02/14 16:43, Josiah Morgan wrote: >>> Mark, when this happens, have you tried unplugging the step and >>> dir(everything but enable) from the beaglebone to verify that it >>> isn't just coming from microstepping on the driver itself? I know >>> I've experienced similar crackling sounds on some stepper >>> drivers that was completely isolated from input from step/dir >>> source. >>> >>> >>> On Thu, Feb 20, 2014 at 10:21 AM, Mark Tucker >>> <m...@rmtucker.f2s.com> wrote: >>> >>>> Ok i am not well enough conversed to explain this in detail,but >>>> i will try. Having recently been involved with the >>>> beaglebone/machinekit setup,i accidently came across a >>>> problem. I found that speradically the motors would make a >>>> noise like "frying an egg" after movement had finished. This >>>> after some investigation by Charles,Jeff pollard,and few >>>> others,was found to be the dir line hunting after a movement. >>>> This has turned out to be a known problem with the pru and the >>>> fact it is using position feedback and not velocity feedback. >>>> So the outcome after a few discussions was that the hal file >>>> needs changing to utilise the stepgen in velocity mode. Now i >>>> am at a complete loss how to do this,so is there anyone out >>>> there that can help? Charles is snowed under at the moment >>>> otherwise i am sure he would oblige. I will try attatching my >>>> hal file. I am sure there are others that will explain this >>>> better than me because of my limited knowledge. >>>> >>>> >>>> >>>> ------------------------------------------------------------------------------ >>>> >>>> Managing the Performance of Cloud-Based Applications >>>> Take advantage of what the Cloud has to offer - Avoid Common >>>> Pitfalls. Read the Whitepaper. >>>> >>>> http://pubads.g.doubleclick.net/gampad/clk?id=121054471&iu=/4140/ostg.clktrk >>>> >>>> _______________________________________________ >>>> Emc-users mailing list Emc-users@lists.sourceforge.net >>>> https://lists.sourceforge.net/lists/listinfo/emc-users >>>> >>>> >>> >> >> >> ------------------------------------------------------------------------------ >> >> Managing the Performance of Cloud-Based Applications >> Take advantage of what the Cloud has to offer - Avoid Common >> Pitfalls. Read the Whitepaper. >> http://pubads.g.doubleclick.net/gampad/clk?id=121054471&iu=/4140/ostg.clktrk >> >> _______________________________________________ >> Emc-users mailing list Emc-users@lists.sourceforge.net >> https://lists.sourceforge.net/lists/listinfo/emc-users > ------------------------------------------------------------------------------ > > Managing the Performance of Cloud-Based Applications > Take advantage of what the Cloud has to offer - Avoid Common > Pitfalls. Read the Whitepaper. > http://pubads.g.doubleclick.net/gampad/clk?id=121054471&iu=/4140/ostg.clktrk > > _______________________________________________ > Emc-users mailing list Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > -- Charles Steinkuehler char...@steinkuehler.net
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