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).
--
Ben Jackson AD7GD
<[email protected]>
http://www.ben.com/
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