KiCad Donut Pad Designer

Generate annular-ring (donut) copper pads for KiCad footprints. These appear on components like MEMS microphones where a GND pad surrounds a central acoustic port hole (NPTH).

What it does

• Interactive Hydrogen webview app with live SVG preview
• Adjustable parameters: outer/inner radius, drill diameter, segments, paste aperture config, mask margin
• Presets for common MEMS microphones: IM72D128, IM69D130, SPH0645
• Exports valid .kicad_mod files directly to your project directory
• Python CLI generator (donut_pad.py) for scripted/batch use

How the donut pad works

KiCad has no native ring pad shape. The workaround uses a custom SMD pad with a gr_poly primitive whose outline traces the outer circle CCW, then bridges to the inner circle and traces it CW. This creates a filled polygon with a hole.

Outer copper (R_outer) ──┐
                         │  copper annulus
Inner clearance (R_inner)┘
         NPTH drill ─── acoustic port / vent hole

The generator also produces:

• NPTH hole at the center
• Segmented paste apertures (quarter-arc stencil openings with gaps)
• Solder mask opening circle
• Courtyard rectangle

Installation

The skill is installed via gallia. It lives at ~/.claude/skills/kicad-donut-pad/.

To launch the interactive designer:

# Start the server (if not already running)
cd ~/.claude/skills/kicad-donut-pad && python3 server.py &

# Open in Hydrogen webview
adom-cli hydrogen webview open-or-refresh --name "Donut Pad Designer" \
  --url "$(echo $VSCODE_PROXY_URI | sed 's/{{port}}/8847/')"

Or use the Python CLI directly:

python3 ~/.claude/skills/kicad-donut-pad/donut_pad.py \
  --outer 1.04 --inner 0.58 --drill 0.8 \
  --center-x 0 --center-y 0.68 \
  --pad-number 5 --segments 36

Common use cases

Source

• Gallia repo: skills/kicad-donut-pad/ in adom-inc/gallia
• Files: SKILL.md, index.html (webview app), server.py (HTTP + save API), donut_pad.py (CLI generator)