Getting Started

The LT-200B is BLE-only — no USB, no serial, no TCP. The driver runs in the browser via Web Bluetooth. There is no Node.js package today.

Install

bash

pnpm add @thermal-label/letratag-web

@thermal-label/letratag-web re-exports the registry, types, status parsers, and encoder from @thermal-label/letratag-core, so you usually only need the one package.

Browser support

Browser	Support
Chrome 56+	✅ desktop + Android
Edge 79+	✅
Firefox	❌ no Web Bluetooth
Safari	❌ no Web Bluetooth

Web Bluetooth requires a secure context (https:// or localhost) and a user gesture for the initial requestDevice call.

Quick start

import {
  requestPrinter,
  LT_PAPER_WHITE,
  renderText,
} from '@thermal-label/letratag-web';

// Must be called from a user gesture (button click, etc.)
const { printer } = await requestPrinter();
try {
  // Render a 1bpp label bitmap from a string. The encoder will
  // centre it within the printer's 32-row protocol frame.
  const bitmap = renderText('hello LT-200B', { fontSizePt: 18 });
  await printer.print(bitmap, LT_PAPER_WHITE);
} finally {
  await printer.close();
}

requestPrinter() opens the browser's BLE picker filtered to LetraTag-family advertisements (Letratag <MAC> + the canonical be3dd650-… service UUID), connects, and resolves the GATT characteristics by service-UUID-tail derivation. The returned PairResult also exposes the observed UUIDs and link MTU for diagnostics — see the Web guide for the full surface.

Cassette / battery status without printing

Cassette presence, tape width, and battery level ride in the LT-200B's BLE advertising-data manufacturer payload — readable on a passive scan, no connection required. The status parser is re-exported from the web package:

import { parseAdvertisingStatus } from '@thermal-label/letratag-web';

// In a `BluetoothAdvertisingEvent` handler:
const bytes = new Uint8Array(event.manufacturerData.values().next().value.buffer);
const status = parseAdvertisingStatus(bytes);
// status.cassetteId, status.batteryLevel, status.tapeJam, …

Note: the advertising-event API is experimental and currently flag-gated in Chrome (chrome://flags/#enable-experimental-web-platform-features). The protocol reference documents the byte layout.

Next steps

Web guide — pairing, status, multi-copy jobs, React example.
Core API — registries, encoder, offline preview.
Protocol reference — every byte on the wire.
Hardware harness — the hosted browser app for pairing, diagnostic prints, and verification reports.

Getting Started ​

Install ​

Browser support ​

Quick start ​

Cassette / battery status without printing ​