Dks1837 shield

EXT1 Tap PCB

A 4-layer "hat" that implements the Wiring Guide V1.0 circuit on a single board. J1 (underside) plugs straight onto the Olimex ESP32-P4-PC's EXT1 header and the DKS 20-way ribbon plugs into J2.

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Specifications

Bill of materials

All parts are through-hole and hand-solderable. See dks1837_shield_BOM.csv.

The LCSC numbers listed for the capacitors are unverified suggestions — check stock and ratings before ordering. The optional VEML7700 light sensor is not on this board; wire it to the Olimex UEXT connector (Wiring Guide §7).

Ordering

Zip the contents of gerbers/ (copper ×4, solder mask ×2, silkscreen ×2, board outline, drill file) and upload to any PCB fab. Select 4 layers, 1.6 mm, and the dimensions will be detected as 39 × 82 mm. The reference boards were made by JLCPCB (5 pcs, ENIG, standard build).

⚠️ J2 pinout — check before powering up

J2 is wired for the reference unit's ribbon socket, whose polarizing key sits on the even-pin side. With that socket seated, each conductor lands on the pad shown below, so the J2 net assignment is mirrored across the header's long axis relative to a textbook straight-through connection (every column pair 1↔2, 3↔4, … is swapped):

Before first power-up, confirm by continuity that the J2 pad marked GND connects to DKS ground. If your ribbon socket is keyed the standard way (pin 1 on the key side), revert the column-pair swap described in the NOTE block of netlist.py and regenerate the board.

Source of truth and regeneration

netlist.py defines every component and net and is the single source of truth — there is no separate KiCad schematic. dks1837-shield-netlist-review-v12.html is a readable net-by-net listing generated from it.

The committed dks1837_shield.kicad_pcb is the verified, DRC-clean board. To regenerate it you need KiCad 10 (its bundled Python provides pcbnew), Java 17+, and the Freerouting v2.4.1 jar. Tool locations default to a macOS install and can be overridden with KICAD_FOOTPRINT_DIR, JAVA, FREEROUTING_JAR and KICAD_CLI.

KPY=/Applications/KiCad/KiCad.app/Contents/Frameworks/Python.framework/Versions/3.9/bin/python3.9

$KPY generate_pcb.py            # place -> autoroute (Freerouting) -> 4-layer promotion -> DRC summary
$KPY generate_fab.py            # BOM + CPL
python3 generate_review.py      # netlist review page
kicad-cli pcb export gerbers --no-protel-ext -o gerbers/ dks1837_shield.kicad_pcb
kicad-cli pcb export drill -o gerbers/ dks1837_shield.kicad_pcb
kicad-cli pcb drc --severity-error dks1837_shield.kicad_pcb

generate_pcb.py place stops after placement if you want to route by hand. Freerouting is not deterministic, so a regenerated board will route differently from the committed one — always re-check DRC.