On Wednesday, February 08, 2012 07:05:59 PM Ben Jackson did opine: > On Wed, Feb 08, 2012 at 06:38:48PM -0500, gene heskett wrote: > > > If you are using stepgen underneath you can capture the position at > > > the base period instead. It's tricky in 2.4 (to cancel out the > > > zero offsets) but I think someone brought out a simpler pin in 2.5. > > > I use that trick to get fine positioning information for laser > > > rastering. > > > > Since I am currently running the 2.6.0-master-rt, can you share the > > .hal changes to do that? > > I don't remember the name of the signal offhand but it brings out an > offset inside axis that reflects homing the axis. I'd have to look > at the source to find the name for it, but in 2.4 I got it by > subtracting axis.0.motor-pos-cmd from axis.0.joint-pos-cmd so I could > add it back to stepgen.0.position-fb (aka axis.0.motor-pos-fb) so that > I get the joint-pos at base period. > > You can see this in: > > https://github.com/bjj/2x_laser/blob/master/2x_Laser.hal > > look at xpos-fb, the calculation of motion-offset and raster-pos-fb. > > The motion-offset is actually calculated in the servo thread because it > changes very infrequently (when homing, when it basically becomes the > negative of the motor offset from zero when the machine was powered on).
I had to go back to the top of it where you renamed the BASE_THREAD to make sense out of it, but now I see how its done. Kewl, thanks & bookmarked, Ben. 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> Where's the man could ease a heart Like a satin gown? -- Dorothy Parker, "The Satin Dress" ------------------------------------------------------------------------------ Virtualization & Cloud Management Using Capacity Planning Cloud computing makes use of virtualization - but cloud computing also focuses on allowing computing to be delivered as a service. http://www.accelacomm.com/jaw/sfnl/114/51521223/ _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
