Danzeff Lab — Flipper Zero proof-of-concept text editor

An experimental native Flipper Zero application to evaluate whether the PSP-era Danzeff 3×3 keyboard is intuitive and fast with the Flipper's five text-entry buttons (D-pad + OK). The hardware Back button is reserved for canceling or leaving the editor, never for deleting text. The keyboard is not a firmware-wide text-input replacement.

Status

• Implemented: single-line, append/backspace ASCII text editor (255 characters)
• Implemented: authentic Danzeff character table, including cases, digits and symbols
• Implemented: two-stage navigation/choice UI with fixed-size minimized cells and edge-anchored 44-48x20 hover expansion
• Implemented: three fixed, timed typing trials and CSV result capture
• Implemented: persistent free-edit draft on the SD card
• Verified: portable keyboard engine passes local C11 unit tests
• Verified by initial tester: v0.1 compiles with uFBT and runs on Flipper Zero.
• Verified by tester: v0.2 renders on-device; inconsistent row reflow motivates v0.3.
• Verified in CI: v0.4 builds using the official release SDK and passes portable tests.
• v0.5 anchors compact cells to the LCD edges.
• v0.6 shortens the drawn whitespace mark from 6×5 to 5×3 pixels without changing the cell layout.
• v0.7 restricts text editing to five buttons and removes hardware Back-to-delete.
• v0.8 uses a compact custom 9×7 pixel ⌫ backspace symbol instead of < while preserving the on-screen delete action.
• v0.9 adds 1px of left/right padding around ⌫ and ⎵ in compact and expanded cells, without changing the visible glyphs or cell dimensions. Physical-device visual verification remains pending.

Controls

Context	Input	Action
Main menu	Up / Down	Select a menu item
Main menu	OK	Open the selection
Main menu	Back	Exit app
Editor: grid	Short D-pad	Move between 3×3 cells
Editor: grid	Hold Left / Right	Previous / next character set (wraps)
Editor: grid	Focused cell	Enlarges to show the 4 directional characters
Editor: grid	OK short	Select the cell (double-thick border)
Editor: choosing	Up / Left / Down / Right	Enter the displayed character, reset focus to center
Editor: choosing	Back short	Cancel choice (no text modification)
Editor: grid	Back short	Return to menu; save free-edit draft (do not delete)
Editor	OK long	Cycle lowercase → uppercase → digits → symbols → extra symbols
Editor	Back long	Return to menu; saves free-edit draft
Results	OK short	Retry the same phrase
Results	Back short	Return to menu

Deletion is only available through the on-screen keyboard: move to the center cell and press OK → Up to erase one character. A short hardware Back press cannot erase text: it cancels an active selection or leaves the editor. An unfinished typing trial is abandoned when returning to the menu.

The character positions mirror the original PSP implementation: Triangle = Up, Square = Left, Cross = Down, Circle = Right. The central lowercase cell is [backspace, m, space, n] in that order. In the cell grid, ⌫ means backspace (drawn as a 9×7-pixel icon); ⎵ indicates space (rendered as a compact 5×3-pixel open-top bracket matching the v0.6 mockup; text storage remains ASCII space). Blank entries in the numbers layer have no function; they leave the four-way chooser open. A usable 0 has been added to the numbers layer at center-cell Left. An extra symbol page (EX+) regroups common ASCII punctuation and digits for quicker access. The original four Danzeff pages otherwise retain their mappings.

Example: type a

From the default center cell, press Up, Left, OK, Left. That enters a and returns to the grid with the middle cell highlighted. A hovered cell previews its four characters in a small directional cross. All unselected cells remain 40×12 px. Left-column cells start at pixel x=0, right-column cells end at x=127, and every bottom-row cell ends at y=63. The grid starts at y=20, preserving the two text-preview lines. The focused cell expands into the available gutters without resizing any other cell: 44×20 px on the left or right, or 48×20 px in the middle (to fill both horizontal gaps). Row positions adjust only as needed to accommodate the 20-pixel focus. All direction glyphs remain centered. Press OK to activate the double-thick border; press a direction to type. Non-hovered cells always keep their four characters inline, so the full layout remains visible. Canceling selection with Back retains the hovered cell. Choosing an empty position in the number layer keeps the selection open.

Layout experiment history

• v0.3: focused row/column widened all cells, which distorted the grid.
• v0.4: all minimized cells became fixed at 40x12, but were still packed together rather than anchored to the outer display edges.
• v0.5 onward: outer columns and bottom row are edge-aligned; the focused cell consumes the empty spaces between compact cells, which keep their original 40x12 size.

Character-set switching

In grid mode, hold Left for the previous set and Right for the next set: abc ↔ ABC ↔ 123 ↔ SYM ↔ EX+ (wraps at either end). Hold OK still advances one set. The current set is displayed next to the entered-text preview, even during a timed trial. While choosing a character, normal short arrow presses still type the expected character; hold Left/Right only switches sets in grid mode. Horizontal navigation intentionally does not auto-repeat because a hold switches the page.

Build and install

This directory is a complete standalone uFBT application project; it does not need to be placed inside a full firmware checkout.

Install the official uFBT tool (on Windows, use PowerShell):

py -m pip install --upgrade ufbt

From inside the extracted project directory:

ufbt
ufbt launch

ufbt creates a .fap under dist/. ufbt launch deploys it to a connected Flipper Zero via USB. The first run downloads the toolchain and official SDK. For reliability, match the SDK channel with the firmware installed on your Flipper. If compiling with uFBT locally is inconvenient, the included GitHub workflow publishes a downloadable .fap build artifact after each push.

To test the portable C core independently on macOS/Linux:

./tests/run.sh

Real-world feasibility testing

Use the built-in trial modes and the reproducible protocol in docs/TEST_PROTOCOL.md. The app records the following:

• duration_ms: from first physical button press to exact correct completion
• wpm_x10: gross five-character-standard words per minute, multiplied by 10
• button_presses: physical presses, including presses that initiate long actions
• backspaces: effective deletions
• wrong_entries: inserted characters that mismatched the target at insertion time
• insertions: total accepted character insertions, including later-corrected errors

Trial results are appended to results.csv; the free-edit draft is stored in draft.txt. Both live in the Flipper app data directory, normally /ext/apps_data/danzeff_lab/ on the microSD card. The editor stores up to 255 ASCII bytes and supports append/backspace only, not cursor insertion or multiline editing. The app is purpose-built to benchmark keyboard ergonomics, not to serve as a full-featured notepad.

Future experiments

• Two-button-chord or long-press shortcuts to skip the cell-open step
• A/B testing of v0.1 retained-selection navigation vs v0.2+ home-reset navigation
• Alternative layouts designed specifically for the Flipper D-pad
• In-device comparison against the Flipper's stock text entry mechanism
• Adaptive visual hints and practice indicators
• Cursor editing and richer text buffer, only after input method feasibility

Attribution and license

Danzeff Lab acknowledges the authors and maintainers of Danzeff-G: danzel, Jeff Chen, and geecko (Clément G). Our foundational four character layouts have been reviewed against the latest master source (2012-07-04, daf3c4cd04b264504781d758c38411419d48bca1), not copied as a PSP library. The BSD 3-Clause copyright and disclaimer are preserved in full at docs/licenses/DANZEFF-G-LICENSE.txt, with provenance and port-specific differences in docs/THIRD_PARTY.md. Our own Flipper-only implementation is BSD 2-Clause. Attribution is not endorsement by the original authors.