Various bugs in March 15 EMC release

[Fred Proctor <proctor-at-cme.nist.gov>]

EMC folks,

Clint Bach wrote:

>
This is a real live bug which was eradicated in the 2.0.36 version but
is still in the 2.2.13 version. The EMC adds an extra step in the
direction it was going before reversing direction.
<

Is this for freqmod.o or steppermod.o? Which EMC release were you
running on 2.0.36 that worked? This bug doesn't ring a bell with me, so
maybe it was fixed as a side effect of something else and then got
bugged again.

And Tim Goldstein wrote:

>
I just tried actually homing with the Mar 15 build on RedHat 5.2 and I
am having a problem. once I contact the home switch the axis is
continuing to travel about .1 " then it reverses direction and backs up
a few thousands then it starts back in the original direction of the
homing at a rate of a few steps per second and keeps going for 5 or so
seconds.

This is unlike homing has been working. Previously the direction would
reverse as soon as the homing switch was contacted and then it would
come at the switch again very slowly and stop the instant the contact
closed. No extra movement past the switch closing at all.
<

The way homing works is that motion proceeds at the [AXIS_#] HOMING_VEL
speed in the direction specified by [AXIS_#] HOMING_POLARITY until the
home switch trips. The polarity of the home switch is set by [AXIS_#]
HOME_SWITCH_POLARITY. Then, the axis position at the trip point is saved
and motion is aborted. Once the move stops, a move back to the saved
trip point plus any offset in [AXIS_#] HOME_OFFSET is done, and the axis
position is set to the value specified by [AXIS_#] HOME.

With HOME_OFFSET and HOME set to 0, the homing sequence would look like
this:

1. slow jog toward home switch.
2. switch trips.
3. jog decelerates and move terminates shortly after home switch.
4. jog back to switch trip position.
5. position set to 0, and digits turn green.

With HOME_OFFSET set to -0.1 (sign depends on value of HOMING_POLARITY),
and HOME set to 3.0, the homing sequence would look like this:

1. slow jog toward home switch.
2. switch trips.
3. jog decelerates and move terminates shortly after home switch.
4. jog back to point 0.1 units past switch trip position (to get off
switch if you need to)
5. position set to 3.0, and digits turn green (lets you specify 3.0 as
home for this axis).

This works on my servo system, but I haven't tried it on a stepper
system with switches. It sounds like it's not working, but it's hard for
me to tell.

Can stepper users try setting HOME_OFFSET to some non-zero value and see
if the behavior agrees with the writeup above? for both freqmod and
steppermod? Note that the motion control code for freqmod is
emc/src/emcmot/emcmot.c, and the code for steppermod is
emc/src/emcmot/emcstepmot.c, for the 15-Mar-2000 release. In prior
releases, the code for freqmod is emc/src/emcmot/emcfreqmot.c, and the
code for steppermod is emc/src/emcmot/emcmot.c. We did this to promote
the frequency stepping code to emcmot.c, hoping to give up on the
binning algorithm in steppermod eventually.

--Fred