Hackpad

Hackpad

A 12-key macropad with a rotary encoder and an OLED display, built on a Seeed XIAO RP2040 and running KMK firmware. Submitted to Hack Club's Hackpad You Ship, We Ship program.

v2 — the most loaded build that fits the Hackpad rules at once: 12 MX keys, 1 EC11 rotary encoder, 1 OLED display, and every usable GPIO on the XIAO consumed (11 / 11). 13 inputs, well under the 16-input cap; 95 × 95 mm board, well inside the 100 × 100 mm size cap.

Features

• 12 MX mechanical switches in a 4 × 3 diode matrix (COL2ROW, 1N4148)
• 1 EC11 rotary encoder — defaults to volume +/− (re-mapped per layer)
• 0.91" 128 × 32 SSD1306 OLED showing the active layer name
• 3 firmware layers (default / media / numpad), momentary switching via the bottom-right key (and bottom-right-2 for L2)
• Two-part 3D-printed case (red top plate + black bottom tray), M3 heatset insert bosses, USB-C side cutout
• Individual STL part files for every printable AND hardware item (top, bottom, M3 screws, heatset inserts)

CAD model

Full assembled view in cad/assembled-model.step — GitHub renders the STEP inline. STL version in cad/assembled-model.stl.

Printable + hardware parts (all generated by build_scripts/build_case.py):

Case fits within 99 × 99 × 15 mm — well inside Hackpad's 200 × 200 × 100 mm limit. Screwed together with 4 × M3 × 16 mm SHCS bolts into M3 × 5 × 4 mm brass heatset inserts.

PCB

Built in KiCad 9 from pcb/hackpad.kicad_pro. The whole board is generated programmatically by build_scripts/build_pcb.py from the netlist

• placement CSVs — re-running it reproduces the .kicad_pcb byte-for-byte.

Schematic:

PCB layout (top and bottom copper):

• Dimensions: 95 × 95 mm (within the Hackpad 100 × 100 mm rule)
• Layers: 2 (F.Cu signal trunks + B.Cu GND pour and ROW trunks)
• OLED header pin order: GND – VCC – SCL – SDA (kit spec)
• Footprints: Cherry MX 1.00u PCB, 1N4148 DO-35 horizontal, EC11E vertical, XIAO on 2 × PinHeader_1x07_P2.54mm_Vertical, OLED on PinHeader_1x04_P2.54mm_Vertical, MountingHole_3.2mm_M3
• Routing: matrix is fully routed in copper (4 COL trunks F.Cu, 3 ROW trunks B.Cu with cathode tabs, 12 switch→anode bridges, GND pour). 11 short XIAO ↔ peripheral signal pulls (4 COL + 3 ROW + SDA
  • SCL + 5V + ENC_A + ENC_B) are left as ratlines for ~5 min of interactive routing — see pcb/HOW_TO_FINISH.md for the exact start/end coordinates of each pull.
• Silkscreen: HACKPAD v2.0 on the front, github.com/rishith-c/hackpad on the back.
• DRC: passes at error level (kicad-cli pcb drc --severity-error → 0 violations)

Gerbers exported and ready for JLCPCB: production/gerbers.zip. Order at 2 layers · 1.6 mm · HASL · green.

Firmware

KMK (CircuitPython). See firmware/README.md for flashing instructions. Sources in firmware/KMK/:

Pin map

The XIAO RP2040 exposes 11 usable GPIO. All 11 are used.

No spare GPIOs. See pcb/DESIGN_NOTES.md for alternate firmware tweaks (drop OLED for encoder push + RGB; shrink matrix to 3×3 for a second encoder; etc.) — each one reuses this same PCB without changes.

Bill of Materials

See production/BOM.csv. Everything except the PLA filament is in the Hackpad kit.

• 1 × Seeed XIAO RP2040 (through-hole, mounts on 2 × 1×7 pin sockets)
• 12 × Cherry MX mechanical switch
• 12 × DSA blank keycap
• 12 × 1N4148 diode (DO-35)
• 1 × EC11 rotary encoder (A/B wired, push left unwired)
• 1 × 0.91" SSD1306 128 × 32 OLED (I²C, addr 0x3C, pin order GND-VCC-SCL-SDA)
• 4 × M3 × 16 mm SHCS bolt
• 4 × M3 × 5 × 4 mm brass heatset insert
• 1 × 3D-printed top plate (production/Top.stl)
• 1 × 3D-printed bottom tray (production/Bottom.stl)

Repository layout

├── README.md
├── LICENSE
├── cad/
│   ├── assembled-model.step              # full assembly (Hackpad spec)
│   └── assembled-model.stl               # same, STL (GitHub interactive viewer)
├── pcb/
│   ├── hackpad.kicad_pro                 # KiCad project
│   ├── hackpad.kicad_sch                 # schematic stub (canonical viz in assets/schematic.png)
│   ├── hackpad.kicad_pcb                 # placed + matrix-routed board
│   ├── netlist.csv                       # canonical net list
│   ├── placement.csv                     # per-part X/Y/rotation
│   ├── DESIGN_NOTES.md                   # build variants / pin budget reasoning
│   └── HOW_TO_FINISH.md                  # 5-min interactive routing checklist
├── firmware/
│   ├── README.md
│   └── KMK/
│       ├── main.py                       # KMK firmware (matrix + encoder + OLED, 3 layers)
│       ├── code.py                       # CircuitPython entry point
│       └── boot.py                       # boot-time config
├── production/
│   ├── gerbers.zip                       # for JLCPCB (2 layers, 1.6 mm)
│   ├── Top.step / Top.stl                # top plate
│   ├── Bottom.step / Bottom.stl          # bottom tray
│   ├── M3x16_Screw.step / .stl           # individual screw model (used x4)

Submitting to Hackpad

This repo matches the Hackpad submission requirements:

• PCB ≤ 100 × 100 mm ✅ (this board is 95 × 95 mm)
• < 16 inputs ✅ (13: 12 keys + 1 encoder)
• 2-layer PCB ✅
• Through-hole XIAO RP2040 ✅
• All-3D-printed case ✅
• Folder layout: cad/, pcb/, firmware/, production/, README.md ✅ (matches the Orpheuspad reference)

Submission steps:

1. Post a ship in #hackpad-ships on the Hack Club Slack (link to this repo + photos from assets/).
2. Fill out the submission form: https://forms.hackclub.com/hackpad-submission.
3. Reviewed by @alexren. On approval you receive the kit + a $15 grant for JLCPCB PCB fab + a free 3D-printed case from another Hack Clubber, plus optionally $18 for a soldering iron.

Regenerating from source

# PCB (uses KiCad 9 bundled Python — pcbnew API)
/Applications/KiCad.app/Contents/Frameworks/Python.framework/Versions/Current/bin/python3 build_scripts/build_pcb.py

# Case + screws + assembled model (pip install cadquery)
python3 build_scripts/build_case.py

# Schematic (pip install schemdraw cairosvg; cairo from Homebrew)
DYLD_FALLBACK_LIBRARY_PATH=/opt/homebrew/lib python3 build_scripts/build_schematic.py

# Mockup PNG (pip install cadquery trimesh matplotlib)
python3 build_scripts/build_mockup.py

# Gerbers + drill files, bundled to production/gerbers.zip
mkdir -p /tmp/gerbers && \
  /Applications/KiCad.app/Contents/MacOS/kicad-cli pcb export gerbers \
    --output /tmp/gerbers/ \
    --layers "F.Cu,B.Cu,F.Silkscreen,B.Silkscreen,F.Mask,B.Mask,Edge.Cuts" \
    pcb/hackpad.kicad_pcb && \
  /Applications/KiCad.app/Contents/MacOS/kicad-cli pcb export drill \
    --output /tmp/gerbers/ --excellon-separate-th pcb/hackpad.kicad_pcb && \
  ( cd /tmp/gerbers && zip /path/to/production/gerbers.zip *.gtl *.gbl *.gto *.gbo *.gts *.gbs *.gm1 *.drl )

License

MIT.