A negative BDST was correctly applied to negative direction moves
if moves are absolute. When retries are enabled all moves become
relative and backlash was not applied correctly for negative direction
moves.
We can't compile motor against this commit of EPICS base:
commit 0f428ea3346d89719b03a6419319c85afb0fee13
Author: Michael Davidsaver <mdavidsaver@gmail.com>
Date: Thu Apr 1 10:57:19 2021 -0700
use DBCORE_API
Solution: Include <shareLib.h>
Partly revert the following commit:
commit 3090983c31
Author: Ron Sluiter <rsluiter@users.noreply.github.com>
Date: Wed Jul 29 15:50:23 2015 +0000
Bug fix for target position (VAL/DVAL/RVAL) initialization error
when the motor record is configured to do retries.
And from the release notes:
6) Kevin Peterson discovered an initialization bug when the motor record is
configured to do retries. When configured to do retries, the motor
record issues incremental rather than absolute moves. If the motor
behaves badly (e.g., a piezo stiction motor) the controller's absolute
step count can be far from its' absolute readback position. The motor
record initialization logic that determines how the target positions
are initialized at boot-up was not taking into consideration whether
or not the motor record is configured to do retries, and therefore,
whether or not absolute or incremental moves were issued by the motor
record. With this release, if the motor record is configured to do
retries, then the controller's absolute position is ignored (because
the controller's absolute position was "corrupted" by retries) and the
autosave/restore position is used to set the controllers position.
Switching between retries on and off (relative vs. absolute moves)
between reboots will cause unpredictable results and is not covered
by this bug fix.
Files modified: motor_init_record_com() in MotorSrc/motordevCom.cc
init_controller() in MotorSrc/devMotorAsyn.c
Commit 3090983c improves the situation for setups where autosave is
used, and makes things worse when autosave is not used.
When autosave is not used and the motor is configured to do retries,
the the DVAL field is loaded into the controller regardless.
And because DVAL is 0.0 at startup, the controller position is lost.
The first issue report is found here:
"Problem with R6-10 issue 6 fix - controller position can be lost on reboot"
https://github.com/epics-modules/motor/issues/85
And the we have another issue report here:
"IOC zeroes encoder on startup"
https://github.com/motorapp/Galil-3-0/issues/13
A possible way forward is discussed here:
"Add a field to the motor record to allow always restoring the
autosaved position"
https://github.com/epics-modules/motor/issues/151
This commit adds the "RSTM" field:
- 0 Disables restoring the autosaved position
- 1 Always restores the autosaved position
- 2 Uses the same logic as motorRecord 6.9 (or older)
- 3 Uses the same logic as motorRecord 6.10
This numbering maps 0 and 1 somewhat to false/true, uses 2/3 for
special handlings and leaves room for more choices.
E.g. "use the encoder value, if valid, fall back to autosave if not.
Or "use the URIP/RDBL" if possible.
I am getting off-topic,
those improvements should be done in later commits anyway.
When grepping for SUPPORT in the different files,
grep may fail, because "SUPPORT" is not present.
A failing grep will cause travis to fail.
Solution: Ignore the exit code of grep.
Kevin Peterson