Position feedback board

Acquire one specified magnetic or quadrature encoder and report position to Smoothieboard for following-error detection.

Development status

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:

The retained native prototype supersedes the architecture choices in the historical draft below: LS7366R-S SPI counter, AM26LV32EDR differential ABZ receiver, TPS2553DBVR encoder-supply switch and 16 MHz oscillator, in the original50×47 mm envelope. It is a bounded differential quadrature design, not a universal or magnetic encoder interface. See component review, version evolution and parent reconciliation. Common V1 0603 bypass/bias families are conditional substitutions; exact stocked IC, manufacturer/lot and quantity equivalence is not established.

Board-specific qualification limits: v26 ERC/strict geometry/parity0 with fiveopens and unresolved netlist annotation warning; host/encoder current, ESD, timing and physical gates unsigned.

Interfaces and wiring

The retained BASE-DIFF prototype receives differential quadrature A/B/Z through AM26LV32EDR, counts with LS7366R-S and reports over SPI. A TPS2553DBVR switches the encoder supply and a 16 MHz oscillator clocks the counter. Magnetic-encoder and arbitrary encoder protocols are outside this selected implementation.

Power off before changing connections. Use the selected schematic and a continuity check to verify connector orientation and pin numbering before first power.

Electrical design requirements

Qualify encoder levels/current, differential cable/termination, counting rate, host SPI mapping, power-off behavior and source allocation. Five ground-pour opens and a netlist annotation warning remain; no reliable motion-feedback claim follows from the saved CAD.

Selected component architecture

See current review. Retain existing LS7366R-S/AM26LV32 differential ABZ SPI counter and TPS2553; no extra controller justified. Conditional V1 0603 bypass/pull families only; no successor. Current selected v26; retained native/stock/physical qualification limits remain explicit.

Configuration and commissioning

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.

Requested connector and usability upgrades

The following are requirements for the next design iterations; this page does not claim they are already fitted:

• On electrically suitable three/four-pin low-voltage ports, provide compact alternative 2.54 mm header/Molex-style and keyed STEMMA-family footprints. Populate one connector option per shared position and document its pin order. Use STEMMA QT only for compatible four-wire I²C; connector appearance does not make another signal protocol I²C-compatible.
• Render each supported connector population separately. Document clearances, cable access and the exact fitted option.
• Use uppercase titles in a consistent Montserrat-style face, labels on both sides, visible domain boundaries, a revision-specific wiring guide and this page’s URL on the silk where readable.
• Keep mounting-hole centers on a documented 10 mm lattice; add cable-tie holes where space and electrical clearances permit. Place status LEDs near accessible edges and give every indicator its own disable solder jumper. Provide labeled test pads and a ground observation point.
• Review applicable DC power entries for reverse-polarity cutoff with a blinking warning, overvoltage cutoff/indication, controlled startup and electronic overcurrent protection. Indicator and protection circuits must work in the fault state without defeating isolation or safe output defaults. Thermal protection belongs only where the power/thermal analysis justifies it.
• Electronic protection does not automatically replace a required mains/branch safety fuse. Backfeed blocking and inductive-load flyback clamps are separate design functions. Do not add identity EEPROMs, fault memory, calibration storage or paid self-test hardware under this upgrade program.

Design sources

• Board specification
• Architecture and component decisions
• Selected-revision review and qualification record
• All extension boards

Documentation route: smoothieware.org/extensions/position-feedback-board.

Additive design studies

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.

Upgrade candidate readback

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.

position-feedback

• Latest PCB source, SHA-256 55eeccd89ca54e538071bfa308fc75a5a800779f5b15ad67abd969260358a282.
• Last native check: 72 errors, including 5 open connections. This is a CAD result, not electrical, assembly or firmware qualification.
• No alternative connector population is recorded for this physical role. Any applicable connector conversion remains an explicit design-review item.
• normal population/render record: 6 images; source current; image hashes match; 0 unresolved models.
• Changes, failed trials and remaining work.

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.

Second-round annotation readback v33 — 2026-10-13

Protected source v32; current PCB SHA-256 e9ff7319c7506563b9b18d593dc6c7b26699494477569ac95608a7c91fa6a810. Fresh checks: zero enabled PCB errors/opens/parity and ERC errors; 25 PCB warnings. Electrical geometry, project rules and 60 historical files unchanged. Verified 30 model entries, 17 exports and 6 current population views, all inspected. Full documentation URL readable. Inherited jumper text overlaps remain; shared authored dependencies verified unchanged Inherited native warnings and enabled-rule exclusions remain explicit Physical/thermal/current/connector-fit qualification open No priced or area savings established by annotation candidate.

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