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CLAUDE.md

This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.

Project Overview

This is a JavaScript library for interfacing with the OWON B41T+ digital multimeter via Web Bluetooth. The project enables browser-based communication with the multimeter to read measurements in real-time.

Development Commands

Build Commands

  • npm run dev - Build unminified development version to ./dist/bt-owon-bt.js
  • npm run dist - Build minified production version to ./dist/bt-owon-bt.min.js

Testing

  • npm test - Run Jest tests

Package Management

  • npm ci - Install dependencies (preferred for CI/clean installs)

Core Architecture

Main Entry Point

  • owon.js - Main API module that exports Start(), Stop(), SetLogLevel() functions and exposes btState object

Core Modules

  • webbluetooth.js - Contains the main Bluetooth state machine and protocol implementation

    • Implements Bluetooth Low Energy communication using Web Bluetooth API
    • Handles device pairing, service discovery, and notification subscriptions
    • Contains protocol parser for OWON B35/B41T+ data format
    • State machine with states: NOT_CONNECTED, CONNECTING, DEVICE_PAIRED, SUBSCRIBING, IDLE, BUSY, ERROR, STOPPING, STOPPED, METER_INIT, METER_INITIALIZING

  • utils.js - Utility functions for async operations and data conversion

    • sleep(), waitFor(), waitForTimeout() - async helpers
    • buf2hex(), hex2buf() - ArrayBuffer conversion utilities

Protocol Implementation

The project implements the OWON B35 protocol (compatible with B41T+):

  • Bluetooth service UUID: 0000fff0-0000-1000-8000-00805f9b34fb
  • Notifications UUID: 0000fff4-0000-1000-8000-00805f9b34fb
  • Each notification contains 3 int16 values: measurement type/decimals/units, measure type flags, and display digits with sign bit

Frontend Integration

  • multimeter.html - Demo web interface using Bootstrap and Chart.js
  • Built files in dist/ are standalone and can be included via script tags
  • Library exports OwonBT global when used in browser

Build System

  • Uses Browserify to create standalone browser bundles
  • UglifyJS for minification with source maps
  • Jest for unit testing with jsdom environment

Key Implementation Details

State Management

The core state is managed in webbluetooth.js through the btState object which contains:

  • Connection state and state machine status
  • Bluetooth device/service/characteristic references
  • Raw and parsed measurement data
  • Statistics and debugging information

Error Handling

  • Auto-reconnection logic on GATT disconnections
  • Timeout handling for various operations (30s default, 1s in simulation)
  • Error states trigger cleanup and potential reconnection attempts

Data Flow

  1. User calls OwonBT.Start() to initiate connection
  2. State machine handles Bluetooth pairing and service discovery
  3. Notifications from multimeter are parsed and stored in btState.parsedResponse
  4. Frontend can read live data from btState object
  5. OwonBT.Stop() cleanly disconnects and stops state machine

Testing Strategy

  • Unit tests focus on API existence and state object structure
  • Uses Jest with jsdom environment for browser API mocking
  • Tests are in tests/OwonBT.test.js