fix(api): Fix liquid getting homed into pipette after certain protocols end #17285
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| if drop_tips_after_run: | ||
| await self._drop_tip() | ||
| await self._hardware_api.stop(home_after=home_after_stop) | ||
| else: | ||
| await self._hardware_api.stop(home_after=False) | ||
| if home_after_stop: | ||
| await self._home_everything_except_plungers() | ||
| await self._try_to_drop_tips() | ||
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| await self._hardware_api.stop(home_after=False) | ||
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| if home_after_stop: | ||
| await self._home_everything_except_plungers() |
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In the old code:
if drop_tips_after_run:
await self._drop_tip()
await self._hardware_api.stop(home_after=home_after_stop)If home_after_stop was True, the self._hardware_api.stop(...) call would home everything, including the plungers.
I think this used to be safe when this code was originally written. The line immediately preceding it, self._drop_tip(), would have ensured that there were no tips attached, and therefore no liquid for the home to accidentally aspirate.
But that assumption stopped holding for Flex protocols with PAPIv≥2.16; since then, self._drop_tip() has been a no-op (see the comments in _try_to_drop_tips().) So this self._hardware_api.stop(...) was accidentally homing with tips possibly still attached and liquid possibly still in them.
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With my fix here, nothing in this file should ever home the plungers anymore.
We could try to be a little fancier than that. We could home the plungers specifically in the cases where the robot did drop tips. I haven't done that here because it doesn't seem worth the complexity. The plungers will home when the next run begins, anyway.
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no, i agree with this fix. let's just not home the damn things, it's too hard to pick the right behavior
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| if drop_tips_after_run: | ||
| await self._drop_tip() | ||
| await self._hardware_api.stop(home_after=home_after_stop) | ||
| else: | ||
| await self._hardware_api.stop(home_after=False) | ||
| if home_after_stop: | ||
| await self._home_everything_except_plungers() | ||
| await self._try_to_drop_tips() | ||
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| await self._hardware_api.stop(home_after=False) | ||
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| if home_after_stop: | ||
| await self._home_everything_except_plungers() |
There was a problem hiding this comment.
no, i agree with this fix. let's just not home the damn things, it's too hard to pick the right behavior
That PR changed the stop behavior on OT-2 to fix some bugs but the tests didn't get changed. Fix the tests.
Overview
Closes RESC-345.
Test Plan and Hands on Testing
Run a PAPIv≥2.16 protocol on a Flex. Cancel it at a point when tips are attached and contain liquid. Without this PR, the pipette should accidentally aspirate when it homes, as shown in this video. With this PR, it should not do that; the liquid should remain in place. Ideally, use food dye to confirm this, because it can be difficult to notice.
Changelog
See comments.
Review requests
See comments.
Risk assessment
Medium.