Support OT-2 GEN2 eight-channel full-head operations - #1466
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hazlamshamin wants to merge 2 commits into
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hazlamshamin wants to merge 2 commits into
hazlamshamin wants to merge 2 commits into
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added 2 commits
October 3, 2026 05:19
Compare committed and pending tips before attaching either tip to its holder. Attachment changes resource placement and must not create a pending transaction from an unchanged committed state. Restore the committed tip's saved liquid state through its volume tracker. Reuse the same tip instance when committed and pending states match. Preserve distinct pending operations for commit or rollback. Keep physical tip custody in the resource tree and retain the saved state format.
Add an optional fixed_head_mount to select a P20 or P300 GEN2 pipette. Use the existing tip and liquid APIs with channels 0 through 7 together. Require aligned A-to-H columns at 9 mm pitch and shared nozzle settings. Validate the complete request before dispatch. Roll back queued tip transactions if a later channel fails validation. Keep per-nozzle liquid tracking while the backend operates the physical head as one unit. Use the same backend validation and dispatch in the chatterbox. Preserve the default mount-based channel mapping when fixed_head_mount is unset. OT-2 nozzles have fixed 9 mm spacing, unlike Hamilton STAR's independently positioned pipetting channels. Official Opentrons protocols support partial tip pickup, but this integration deliberately requires all eight nozzles. Partial layouts need separate client and backend support.
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Summary
Add opt-in, full-head operation for OT-2 P20 and P300 GEN2 eight-channel pipettes through the existing legacy liquid-handler APIs. Set
fixed_head_mountto"left"or"right"to select the pipette.fixed_head_mountis unset.The selected mount exposes all eight nozzles. It does not expose the other mount.
Scope and hardware limits
Opentrons supports partial tip pickup in its Python API from API level 2.20 and in Protocol Designer. An OT-2 eight-channel pipette can use a single nozzle at either end: A1 or H1. Partial columns use 2–7 consecutive nozzles from H1 toward A1. These layouts do not support gaps or partial columns starting at A1.
This integration deliberately supports all eight nozzles only. Partial layouts require a separate client/backend contract for layout configuration, anchor selection, and tip tracking. The selected
ot_apiclient has no dedicated nozzle-layout helper. Its generic command API can submit additional command types, so a transport change is not necessarily required.The OT-2 head has fixed 9 mm nozzle spacing. Partial tip pickup does not change that spacing. In contrast, PLR supports independent Y positioning of Hamilton STAR pipetting channels, as shown in its channel movement example. This OT-2 integration does not support adjustable spacing.
Verification
Checks used the candidate source tree:
python -m pytest -q pylabrobot/legacy/liquid_handling pylabrobot/resources pylabrobot/legacy/tip_tracker_tests.py— 883 passed, 8 skipped, and 300 subtests passed. The skipped tests were unchanged.python -m ruff checkandpython -m ruff check --select I— passed for the eight changed Python files.python -m ruff format --check— passed for the eight changed Python files.python -m mypy --follow-imports=silent --ignore-missing-imports— passed for the five changed source files. This was a scoped check, not the full repository type check.A direct PLR hardware run completed on a left-mounted P300 GEN2 with standard Opentrons 300 µL tips and a NEST 96-well, 200 µL flat-bottom plate. The run exercised full-column tip pickup, mixing, water transfers of 20 and 150 µL per nozzle, and tip disposal. The operator confirmed physical completion. This was a functional check, not a measurement of pipetting accuracy.
P20 GEN2 and right-mount operation have software coverage only. The full repository test suite and CI matrix did not run locally.