@thermal-label/letratag

TypeScript-first DYMO LetraTag LT-200B driver — browser Web Bluetooth.

Driver for the DYMO LetraTag LT-200B, a 12 mm Bluetooth LE handheld label printer with a custom chunked-GATT print protocol. This repo ships two workspace packages:

• @thermal-label/letratag-core — pure TypeScript protocol encoder, status parser, and media registry. Browser- and Node-safe; no transport coupling.
• @thermal-label/letratag-web — Web Bluetooth driver built on @thermal-label/transport/web.

Verification runs on the shared thermal-label harness; a remote tester points their LT-200B-paired Chrome at it, runs the test pattern matrix, and exports the captured trace for triage.

Layout

packages/
  core/     — encoder, registry, status parser
  web/      — Web Bluetooth printer adapter
scripts/
  compile-data.mjs — emits data/*.json + src/*.generated.ts
.github/workflows/
  ci.yml      — typecheck / lint / format / test:coverage / build

Workflow

pnpm install
pnpm --filter @thermal-label/letratag-core compile-data
pnpm typecheck && pnpm lint && pnpm test && pnpm build

Phase status

Phase 1 is web-only; Node BLE support is deferred. The encoder matches the byte stream observed on the wire from a paired LT-200B — see docs/protocol/letratag-bt.md for the authoritative spec and INTEROPERABILITY.md for the project's sources and legal posture. Current hardware status for the LT-200B is in the Supported hardware table below (generated from the device registry) and on the hardware docs page — see also DECISIONS.md. Node BLE support, a replay CLI, and hardware issue templates are deferred to a later phase.

For the remote tester

Verification runs on the shared thermal-label harness in Chrome or Edge on a desktop or Android device:

1. Connect via Web Bluetooth and pick your LT-200B from the picker.
2. Run T1 (single-pixel test) → expect a single dot at the leading edge of the tape, in the row closest to the cassette opening. Export the diagnostics JSON and paste into a new GitHub issue along with a close-up photo.
3. Run T2 (asymmetric rectangle) → expect a rectangle wider across the head than along the feed.
4. Run CUSTOM with any short text → expect normal printing.

The diagnostics JSON contains everything needed to debug remotely: the captured TX/RX trace, the bitmap that was sent, and the encoder settings used.

Supported hardware

1 devices — 1 verified · 0 partial · 0 broken · 0 untested

Model	Key	USB PID	Transports	Status
LetraTag LT-200B	LT_200B	—	BT LE	✅ verified

Click any model to open its detail page on the docs site, where engines, supported media, and verification reports live. The same data backs the interactive cross-driver table.