Isolator

Kelly UART isolator PCB

A galvanic isolator dongle between the Kelly KLS7218M SM-4P port (floating, traction-pack referenced) and the OBD-powered RejsaCAN. Electrical design rationale, part choices, and behavior notes live in ../ISOLATOR.md; this directory only adds the board.

Files

• generate_board.py — writes isolator.kicad_pcb from scratch. The script is the source of truth; edit it and re-run rather than editing the board in KiCad (or fork the .kicad_pcb if you prefer the GUI from here on). Output is deterministic — tstamp UUIDs are derived from the element each one belongs to, so re-running with no changes produces a byte-identical file and a real edit shows up in the diff as itself, not as 187 churned UUIDs.
• isolator.kicad_pcb — generated KiCad board (opens in KiCad 7+).
• gerbers/ — fab outputs (RS-274X + Excellon), exported with KiCad 10 kicad-cli. Zip the directory (command below) and upload to JLCPCB/PCBWay/ OSH Park. 2-layer, 50 x 32 mm, 1.6 mm, any finish; no special options.
• render_top.png / render_bottom.png — 3D renders for a quick look.

Regenerate everything:

python3 generate_board.py
KICLI=/Applications/KiCad/KiCad.app/Contents/MacOS/kicad-cli
$KICLI pcb drc --severity-error isolator.kicad_pcb
$KICLI pcb export gerbers --layers F.Cu,B.Cu,F.Mask,B.Mask,F.SilkS,B.SilkS,Edge.Cuts -o gerbers/ isolator.kicad_pcb
$KICLI pcb export drill --format excellon --excellon-units mm --generate-map --map-format gerberx2 -o gerbers/ isolator.kicad_pcb
(cd gerbers && zip -q ../isolator-gerbers.zip isolator-*.gb* isolator-*.gt* isolator.drl)
$KICLI pcb render --side top    --zoom 1.0 --width 1400 --height 950 --quality high -o render_top.png    isolator.kicad_pcb
$KICLI pcb render --side bottom --zoom 1.0 --width 1400 --height 950 --quality high -o render_bottom.png isolator.kicad_pcb

Generate-time checks

generate_board.py asserts these on every run, against the emitted board rather than its own variables:

• U1 pads match the ADuM1201 pinout (ADUM1201, transcribed from datasheet Rev. L Fig. 5).
• Package shape: supplies on pins 1/8, grounds on 4/5, signals on 2/3/6/7. This is a different statement than "Fig. 5 says X", so it still fires if the transcription itself is wrong — which is the hole rev A fell through. Rev A's pinout fails it.
• Isolation barrier: no copper of a Kelly-domain net may reach the chassis-domain side or vice versa. Measures the gap and requires ≥ 3.5 mm; currently 3.80 mm.
• Nothing dangling: every net lands on at least two pads.

What none of them catch: a wrong fact that is wrong everywhere. If the datasheet transcription and the package-shape rule were both wrong in the same direction, the board would still be wrong. The defence against that is a meter on a physical board: the GND1-to-GND2 open check in ../ISOLATOR.md "Power-up check".