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.planning/codebase/STACK.md

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+# 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*