Carry three genuine Pololu item 2128 A4988 Black Edition modules on one Smoothieboard Y socket. Each channel has STEP and DIR; all three share one active-low ENABLE signal. The design is a KiCad-only CERN OHL hardware project.
The historical proposal links discontinued item 1182. This prototype freezes the current, mechanically compatible item 2128 because its current and thermal claims are supported by a current product page and dimension drawing. Generic “Pololu-format” clones are outside the supported configuration.
Baseline documentation snapshot: 2026-10-11, before the requested connector/protection/usability revision program. New revision features require their own reviewed source and qualification evidence.
This page documents an unqualified engineering study, not a released or tested product. Saved CAD, renders and automated checks do not establish a safe assembly, compatible cable, firmware support or a usable current rating.
The retained design record states:
V21–v26 retain bounded readability/routing/assembly/drawing improvements. V25 moves the D1 GND via outside its actual land with an original-width extension; v26 corrects the schematic translation to40.64mm, preserving the1.27mm connection grid. Fresh parent v26 confirms ERC0/DRC12/opens9/parity0,149 pin assignments,79 matching package hashes and zero actual via drill/ring/mask-to-SMD overlaps. All six own views, schematic and both actual copper/outline/drill CAM faces were inspected.
Board-specific qualification limits: v26 is rejected for 12 strict mechanical findings and 9 opens; full checklist, current/thermal, host, component lots and physical qualification remain unsigned.
The exact connector orientation, pin mapping and supply ownership must be taken from the selected revision’s schematic and connection specification. Do not infer wiring from the connector shape.
Power off before connecting or changing jumpers. Verify pin 1, signal direction, supply voltage and ground at both ends of every cable. A mechanically fitting connector is not proof of electrical compatibility. If a host pin mapping or current allocation remains unresolved in the design record, do not connect the board until it is resolved.
The following are specification requirements or study assumptions; they are not measured operating ratings. A newer selected-revision note takes precedence over historical draft options.
See current review. Retain exact Pololu A4988 carriers; guide ICs and stocked Trinamic chips require new driver hardware and are not carrier substitutions. Prefer only electrically qualified V1 0603 passive families; no new version. Current selected v26; retained native/stock/physical qualification limits remain explicit.
Use the configuration and firmware contract for the exact selected revision. Do not copy another module’s socket assignments or assume that an unused pin is available. First-article work must verify source selection, reset/unplug behavior, cable orientation and the actual load or sensor interface before normal operation.
The following are requirements for the next design iterations; this page does not claim they are already fitted:
Documentation route: smoothieware.org/extensions/pololu-driver-breakout-board.
The 2026-10-11 upgrade program has saved additional candidates v27, v28, v29. These studies preserve the historical design described above. Their connector, LED, mechanical and protection changes are revision-specific and remain unqualified.
See the per-board changes, failures and remaining work and mandatory family specification. Use the source hash and native check for the exact candidate being reviewed; do not infer hardware ratings from a rendered population.
The three additional revisions are v27, v28, v29. They are engineering studies; saved CAD and renders do not release the hardware. The latest candidate is described below. Older baseline notes above remain historical.
919d9e3299bf2bb846607bee8f1ae4cdd186ac40a3512b68c4aba31ddd520b71.Applicable protection, current-path, thermal, pinout, cable access and physical tests remain open wherever the linked board record has not verified them. A zero native-error count does not close those gates.
The latest third additive candidate replaces the input fuse with an LTC4368 automatic-retry electronic breaker and an external reverse/backfeed FET pair. It adds soft-start gate shaping, separate fault/overvoltage LEDs, a floating timer for blinking reverse indication, and individual solder links to disable status LEDs. Existing motor, host/isolation and mounting-pin contracts remain requirements.
This is an unreleased implementation study. Native opens/errors, shunt sourcing and Kelvin routing, FET linear SOA, continuous current/thermal limits, regeneration, input transients and enclosure compaction remain qualification gates. The controller does not support hot-plugging an externally powered output above 24 V; boards with a higher output domain still need a different qualified topology for that mode. Do not treat the candidate as approved for fabrication or motor operation. Exact source hashes and native checks are in the readback section and per-revision NATIVE-CHECKS.md.
The saved v34 engineering candidate reduces the nominal rectangular outline from120×139mm to115×139mm:695mm² less board area, or4.17%. It preserves the existing mounting-hole centres, all footprints/pads/routes/vias and zone settings; only the right outline and three ground-zone boundaries change. Ground fill decreases by944.9975mm² across both layers. This is a measured CAD-area reduction, not a fabrication quote or verified current/thermal rating.
Fresh enabled native design/schematic checks have zero findings, compared with three baseline text-thickness warnings. The current revision title, board name and Black Edition restriction are complete and readable after correcting a native polygon serialization defect; the initial failed artwork remains recorded as historical. Independent review verified all14 filled title contours, six current populated/bare views,65 model entries,74 artifact hashes and1601 unchanged historical files. Both board documentation URLs remain readable.
The right mounting-hole centre is5mm from the trimmed edge, with3.4mm from drill edge to board edge. Actual washers, screw/tool access, connector/cable/body fit and the current/thermal effect of reduced ground copper remain unqualified. Fault, host and manufacturing qualification remain open. Fabrication release is false and price savings remain unverified.
e51a4f5945a3ea59ad4a124f615735adeb44b2305b4c8eeb2894fce1dfc772a2.Earlier revision contracts/readbacks remain historical; do not infer hardware approval from their renders.
The last historically verified clean 115 × 80 mm study had 0 native errors, 3 open connections and 0 schematic-parity differences. Subsequent local transition searches failed and were not promoted. The earlier scratch PCB/result folders were removed by the configured scratch reaper; those historical diagnostics are not a claim that the corresponding scratch CAD remains retained. No v35 PCB was promoted. Recovery must use retained numbered sources and portable helpers, followed by the required remote zero-violation gate, exports and all final views.
New PCB computation uses the pinned remote whole-job runner only. The portable native warning-repair helper is prepared as source; execution and its same-font title repair remain unverified. The remote runner itself must pass its isolated synthetic routing/publication qualification before production repairs continue. Acceptance and fabrication release remain false.
Remote recovery receipt 2da94b83adb24e59b8aee08b9bb96d5f reconstructed the 115 × 80 mm placement from preserved v34 source and v28 zones with explicit libraries/font closure. Fresh native placement counts are 0 errors, 108 opens, 0 parity differences and 75 warnings; this is a reconstruction before control routing, not the historical three-open study. The native-only power/fanout attempt eeef6e3267ba4a7680913432a96077f6 stopped when the 2 mm fused-supply path occupied a controller sensing escape. The follow-up establishes controller escapes before routing the wide fused path around them. Java routing remains unavailable; no partial CAD or v35 revision is published. Acceptance and fabrication release remain false.
The second remote power/fanout repair (receipt b0d4bc83248d4560b8763d2620468886, exit 1) reconstructed the 0 rule-error, 108-open, 0-parity, 75-warning placement, then stopped at the MOTOR_EF_GATE controller escape at (40, 32) mm before a final power-stage check. It published no partial board. The next bounded repair reserves the remaining controller escape endpoints against earlier routed branches and vias, and records each completed transition. The power widths and 0.30 mm clearance remain unchanged. Native completion, warning removal, exports and renders remain open; no v35 is accepted.
The obstacle diagnostic (receipt 83d03b9a48e34303952a689f4572b3f6, exit 1) verified 0 rule errors, 105 opens, 0 parity differences and 80 warnings before fanout. The required power joins reduced opens by three; temporary unjoined escapes add dangling warnings. It identified the adjacent SENSE conductor at y = 32.5 mm as the search-only blocker of the GATE exit at y = 32 mm. Their 0.2 mm widths leave exactly the specified 0.30 mm gap; the next fanout uses that clearance without an additional 0.025 mm search margin. All native rules and publication gates remain unchanged.
The exact-clearance fanout run (receipt 98054f22de054b7bb93530b7c8f816fc, exit 1) routed all nine controller transitions and connected 57 signal branches. It reached 0 rule errors, 47 opens, 0 parity differences and 46 warnings, improving from 108 opens and 75 warnings. Remaining warnings are 1 silkscreen overlap, 1 silkscreen-over-copper finding, 41 dangling vias and 3 dangling tracks. The next immutable remote repair uses connected-island anchors and explicitly joins the controller RAW/FUSED/SENSE taps at the existing 0.2 mm fine-signal width; it retains the separate 2–4 mm load-current conductors. The strict publication gate continues to withhold partial CAD, exports and renders.
The controller-tap/island attempt (job f880a39f26f44623a03f97d5b8e26d6b, dispatcher exit 75) produced no native result: the worker reported an invalid identity or missing remote job directory, and one read-only check confirmed that exact directory was absent. Local immutable recovery inputs remained intact. This is a remote execution/custody failure, not evidence about the board; no receipt or CAD result is inferred. A fresh isolated retry retains the controller taps and adds native-gated alternate bridge faces. The last verified board state remains 0 rule errors, 47 opens, 0 parity differences and 46 warnings.
The isolated controller-tap retry (job 743da6abf8b1432d9f42d53365e1700f) produced no native receipt: the worker reported an invalid identity or missing remote directory, and a read-only check confirmed that exact job directory is absent. No board outcome is inferred. The last verified state remains 0 rule errors, 47 opens, 0 parity differences and 46 warnings. A new immutable remote trial retains the required power widths and controller taps, uses native effective pad polygons, and preserves the strict publication gate. No v35 PCB, corrected population render or fabrication release is accepted.