Spirulo

What it is

Spirulo is a small, round NFC spiral-antenna PCB designed to mate with Golioth's "phial" board (the phial project was formerly named "pilulith" — see commit d9261b1: "add two cutouts to match phial (nee pilulith)"). The board's central feature is a copper spiral coil drawn directly in the PCB copper (the 20mm_NFC_Spiral footprint), i.e. an NFC antenna, plus a coin-cell battery holder and two small pin connectors. STEP exports of this board are used as 3D models in the companion phial-hw repo.

The exact system-level function of the board is [UNKNOWN] — this repo contained no documentation until this README was added (October 2026), and the design files alone do not state how the coil, battery, and connectors are used together.

Hardware summary

Everything below is taken from the schematic and PCB files (Rev B state):

• Copper spiral coil / NFC antenna: footprint 20mm_NFC_Spiral, net COIL
• BT101: Keystone Electronics 112TR SMD coin-cell battery holder (SnapEDA PN "112", a low-profile holder for a ~12 mm coin cell; the exact cell part number is not recorded in the design files [UNKNOWN])
• J101: 1x02 pin connector (Connector:Conn_01x02_Pin)
• J102: 1x03 pin connector (Connector:Conn_01x03_Pin)
• Cabling footprint placed on the board (purpose [UNKNOWN])
• Decorative "snail" artwork: snail-10mm placed on board, snail-5mm in the library
• Silkscreen text: "Spirulo", "Rev B", "V+"
• Board outline: round; sized up to ~22 mm in Rev B with two cutouts added to match the phial board (per commit d9261b1)
• The PCB embeds a 3D-model reference to the phial board's STEP export (see Known gaps — the reference is an absolute local path)

Repo contents

• spirulo-hw.kicad_pro / spirulo-hw.kicad_sch / spirulo-hw.kicad_pcb — KiCad 9.0 project (file format version 20241229)
• Input/ — project-local libraries:
  • Input/sch/112TR.kicad_sym — battery holder symbol
  • Input/Footprints.pretty/ — 20mm_NFC_Spiral, BAT_112TR, Cabling, snail-5mm, snail-10mm
  • Input/3d/112TR.step — battery holder 3D model
• output/gerber/ — committed gerber + drill files, generated 2025-03-06 with KiCad 9.0.0-rc3 (these are Rev A outputs, see Status)
• output/spirulo-a-202503052314.zip, output/spirulo-a-202503060837.zip — Rev A fabrication zips
• spirulo-202601201646.step — ~7 MB STEP export of the board (2026-01-20, Rev B era)
• .gitignore, fp-lib-table, sym-lib-table — project config
• spirulo-hw.kicad_prl, fp-info-cache, .DS_Store — local/cache files that should not be tracked (see Known gaps)

Status

• 6 commits total; initial commit 2025-03-06 ("Initial commit, RevA sent to JLC"), last activity 2026-01-20 ("move pads to match phial board")
• Rev A was sent to JLCPCB for fabrication in March 2025 (per the initial commit message); the committed gerbers and zips under output/ are those Rev A outputs
• The current design is marked Rev B (silkscreen + commit d9261b1, 2026-01-20): resized up to ~22 mm, two cutouts added, and pads moved to match the phial board
• Rev B gerbers have NOT been committed — the PCB's gerber output directory is configured as output/gerber/revb, which does not exist in this repo
• Whether Rev B was ever fabricated or tested: [UNKNOWN]
• KiCad version: 9.0 (project files version 20241229; committed gerbers generated by 9.0.0-rc3)

Known gaps

• No LICENSE file — this repo cannot be open-sourced until a license is chosen (other Golioth hardware repos such as reliquary-hw and lute-relay-hw use CERN OHL-P v2)
• No CODE_OF_CONDUCT.md (present in the other Golioth hardware repos)
• No schematic title block: no title/rev/date/company fields exist in spirulo-hw.kicad_sch or the PCB title block; revision is only identifiable from silkscreen text and commit messages
• Tracked junk: .DS_Store, fp-info-cache, and spirulo-hw.kicad_prl (user-local KiCad settings) are all committed
• Committed fab outputs contradict .gitignore: output/* and *.zip are listed in .gitignore, yet output/gerber/* and output/spirulo-a-*.zip remain tracked (they predate the .gitignore, added 2025-03-06)
• The committed gerbers/zips are Rev A and stale relative to the current Rev B layout
• Local path leak: spirulo-hw.kicad_pcb embeds the absolute macOS path /Users/chrisg/golioth/pilulith-hw/output/mech/phial-b-boardonly_202601201541.step as a 3D model reference (also reveals the old "pilulith" repo name)
• ~7 MB STEP file committed at the repo root
• No BOM committed (the board has only ~4 placed parts: battery holder, two connectors, and the coil)
• Secrets sweep (2026-10-02): no passwords, private keys, API keys, tokens, or email addresses found; the only personal/local data is the /Users/chrisg/... path noted above