# Technology Stack

**Analysis Date:** 2026-04-16

## Languages

**Primary:**
- **Dart** >=3.4.3 - Flutter plugin Dart-side code (`lib/`, `test/`)
- **Java** 8 - Android native plugin implementation (`android/src/main/java/`)

**Secondary:**
- **Kotlin** 1.7.10 - Declared in example app Gradle plugins (`example/android/settings.gradle`) but not actively used in plugin code

## Runtime

**Environment:**
- **Flutter** >=3.3.0
- **Android SDK** - compileSdk 34, minSdk 21

**Package Manager:**
- **pub** (Dart) - Lockfile: `pubspec.lock` present
- **Gradle** 7.3.0 - Android build system

## Frameworks

**Core:**
- **Flutter** >=3.3.0 - Cross-platform plugin framework
- **Flutter Plugin API** - `FlutterPlugin`, `MethodCallHandler`, `MethodChannel`, `EventChannel`

**Testing:**
- **flutter_test** (Flutter SDK) - Unit testing framework
- **JUnit** 4.13.2 - Android native unit testing
- **Mockito** 5.0.0 - Java mocking for Android tests
- **integration_test** (Flutter SDK) - Integration testing

**Build/Dev:**
- **flutter_lints** ^3.0.0 - Lint rules
- **Gradle** 7.3.0 - Android build automation

## Key Dependencies

**Critical:**
- **plugin_platform_interface** ^2.0.2 - Federated plugin platform interface pattern (`Ch34Platform` extends `PlatformInterface`)
- **CH34XUARTDriver** (local JAR, 140KB) - WCH official UART library, located at `android/libs/CH34XUARTDriver.jar`. Provides `WCHUARTManager`, `ChipType2`, `IDataCallback`, `IModemStatus`, `GPIO_Status` etc.

**Infrastructure:**
- **cupertino_icons** ^1.0.6 - Example app only, Material/Cupertino icon support

**Android Native Dependencies (WCH SDK):**
- `cn.wch.uartlib.WCHUARTManager` - Core manager singleton
- `cn.wch.uartlib.chipImpl.type.ChipType2` - Chip type identification
- `cn.wch.uartlib.callback.IDataCallback` - Serial data callback interface
- `cn.wch.uartlib.callback.IModemStatus` - Modem status callback interface
- `cn.wch.uartlib.callback.IUsbStateChange` - USB state change callback
- `cn.wch.uartlib.exception.*` - Exception classes (ChipException, NoPermissionException, UartLibException)

## Configuration

**Environment:**
- `analysis_options.yaml` - Includes `package:flutter_lints/flutter.yaml`
- No `.env` or environment variable configuration required
- Secrets stored in example `local.properties` (flutter.sdk path)

**Build:**
- `pubspec.yaml` - Main plugin manifest, package: `ch34`, version `1.0.0`
- `pubspec.lock` - Dependency lockfile
- `android/build.gradle` - Android library build config (namespace: `com.example.ch34`)
- `android/settings.gradle` - Project name: `ch34`
- `example/android/build.gradle` - Example app root build
- `example/android/app/build.gradle` - Example app module (namespace: `com.example.ch34_example`)
- `example/android/settings.gradle` - Gradle plugins including dev.flutter.flutter-plugin-loader

## Platform Requirements

**Development:**
- Flutter SDK >=3.3.0
- Dart SDK >=3.4.3
- Android SDK compileSdk 34
- Java 8+ (sourceCompatibility/targetCompatibility = JavaVersion.VERSION_1_8)

**Production:**
- Android device with USB Host support (`android.hardware.usb.host` feature declared in `android/src/main/AndroidManifest.xml`)
- Android minSdk 21 (Android 5.0 Lollipop)
- Physical CH34X series USB-to-serial hardware connected via USB OTG

## Supported Chip Models

CH340, CH341, CH342, CH343, CH344, CH347, CH9101, CH9102, CH9103, CH9104, CH9143

## Build System

**Flutter Plugin:** Standard Flutter plugin structure with Android platform implementation.

**Communication Pattern:**
- `MethodChannel('ch34')` - 33 method calls for device control
- `EventChannel('ch34/data')` - Serial data streaming
- `EventChannel('ch34/modem')` - Modem status streaming  
- `EventChannel('ch34/usb_state')` - USB plug/unplug events

**Architecture Pattern:** Federated plugin with platform interface (`Ch34Platform`), method channel implementation (`MethodChannelCh34`), and manager facade (`Ch34Manager`).

---

*Stack analysis: 2026-04-16*