Building one
Right now there's only one way to get an OTP gadget: build it yourself. Built units aren't being sold — we don't yet have the tests and EEA certifications needed to ship hardware to people. The project is fully open source for exactly this reason. Firmware, parts list, slicer settings, wiring diagram, and the printable case .3mf files all live in the public repo.
What you'll do
- Order parts. Roughly USD 60–70 per device. You want two devices (a single gadget on its own does nothing useful), so plan for about USD 120–140 plus a few dollars of filament.
- Print the case. Two shells per device, FDM.
- Solder a few wires. Two small soldering jobs total — battery to its connector, and the guest SD breakout to the main board. The QR scanner comes pre-wired with a connector you just plug in. All through-hole, no surface-mount.
- Flash the firmware. Two pieces over USB-C — MicroPython runtime first (one-time per board), then the OTP firmware itself. See Firmware.
- First-time card swap. Meet your partner in person and swap a MicroSD card. That's the entire key exchange — see Using the gadget.
A full assembly walkthrough is on the Assembly page, including a video showing the build end to end.
Skill level
If you've soldered through-hole before, it's a relaxed evening per device. If you haven't, watch a 10-minute soldering tutorial first — the work itself is hobby-level. You don't need a custom PCB, a hot-air station, or a reflow oven.
If you'd rather design your own case than use the supplied .3mf files, the hardware page documents the internal layout.
Next: Bill of Materials — parts list and where to order each one.