Dev log·

Smart Notebook: moving the sensor from the notebook to the pen

A redesign on 24 September, a decoder bake-off that picked ArUco tiles over De Bruijn dots, and a Reminders list that still describes the old design.

Smart Notebook records handwriting from ordinary paper. The current design is a clip-on sleeve near the pen’s nib with a small camera that reads a printed dot or fiducial pattern and decodes an absolute position and page identity on every frame — in the style of the Anoto and Livescribe pens — then streams it over BLE to a laptop. There is no sensor board in the notebook, no clipboard backing and no dock.

The pivot

On 24 September the repository archived its earlier design — a fixed sensor panel with disc binding, and a clipboard dock — and started the pen-camera build. The old plan is kept whole under old-plan/, with a survey of what carried forward, rather than deleted. One practical gain is that page identity comes free from the position decode itself.

Phase 1: choosing a pattern by measuring

The decoders are pure Python with no hardware, and all of Phase 1 was committed on 24 September. The commits tell it in order:

  1. Shared geometry and two pattern generators.
  2. A De Bruijn dot-grid decoder: 100 percent on clean crops, after two real bugs.
  3. An ArUco tile decoder: 100 percent on clean crops, with no rotation ambiguity.
  4. A camera-degradation simulator, then the bake-off. ArUco won, and the commit says De Bruijn’s failure is structural, not a tuning problem.
  5. ArUco’s tilt-tolerance gap closed by majority vote instead of unanimity.

Phase 2, the hardware-independent firmware pieces, is scaffolded. The firmware itself, the laptop app and the enclosure are marked not started in the README.

A mismatch worth knowing about

The Reminders list for this project was written for the earlier design: it talks about a disc-binding chassis, sheet-removal detection and a deferred dock. The repository has moved past that. The most recent commit, on 10 October, adds an IMU backup plan, a print test sheet and a project plan. Until the list is rewritten, treat its hardware tasks as stale — the project page says the same.

Written on 16 Oct 2026 from the repository’s README and commit history. Open items below come from Reminders and predate the pivot.