initial commit

Signed-off-by: ale <ale@manalejandro.com>

app/src/androidTest/java/com/manalejandro/odb2bluetooth/ExampleInstrumentedTest.kt

@@ -0,0 +1,24 @@
+package com.manalejandro.odb2bluetooth
+
+import androidx.test.platform.app.InstrumentationRegistry
+import androidx.test.ext.junit.runners.AndroidJUnit4
+
+import org.junit.Test
+import org.junit.runner.RunWith
+
+import org.junit.Assert.*
+
+/**
+ * Instrumented test, which will execute on an Android device.
+ *
+ * See [testing documentation](http://d.android.com/tools/testing).
+ */
+@RunWith(AndroidJUnit4::class)
+class ExampleInstrumentedTest {
+    @Test
+    fun useAppContext() {
+        // Context of the app under test.
+        val appContext = InstrumentationRegistry.getInstrumentation().targetContext
+        assertEquals("com.manalejandro.odb2bluetooth", appContext.packageName)
+    }
+}

app/src/main/AndroidManifest.xml

@@ -0,0 +1,37 @@
+<?xml version="1.0" encoding="utf-8"?>
+<manifest xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:tools="http://schemas.android.com/tools">
+
+    <!-- Bluetooth permissions for Android 11 and below -->
+    <uses-permission android:name="android.permission.BLUETOOTH" android:maxSdkVersion="30" />
+    <uses-permission android:name="android.permission.BLUETOOTH_ADMIN" android:maxSdkVersion="30" />
+
+    <!-- Bluetooth permissions for Android 12+ -->
+    <uses-permission android:name="android.permission.BLUETOOTH_CONNECT" />
+    <uses-permission android:name="android.permission.BLUETOOTH_SCAN" />
+
+    <uses-feature android:name="android.hardware.bluetooth" android:required="true" />
+
+    <application
+        android:allowBackup="true"
+        android:dataExtractionRules="@xml/data_extraction_rules"
+        android:fullBackupContent="@xml/backup_rules"
+        android:icon="@mipmap/ic_launcher"
+        android:label="@string/app_name"
+        android:roundIcon="@mipmap/ic_launcher_round"
+        android:supportsRtl="true"
+        android:theme="@style/Theme.ODB2Bluetooth">
+        <activity
+            android:name=".MainActivity"
+            android:exported="true"
+            android:label="@string/app_name"
+            android:theme="@style/Theme.ODB2Bluetooth">
+            <intent-filter>
+                <action android:name="android.intent.action.MAIN" />
+
+                <category android:name="android.intent.category.LAUNCHER" />
+            </intent-filter>
+        </activity>
+    </application>
+
+</manifest>

app/src/main/java/com/manalejandro/odb2bluetooth/MainActivity.kt

@@ -0,0 +1,97 @@
+package com.manalejandro.odb2bluetooth
+
+import android.os.Bundle
+import androidx.activity.ComponentActivity
+import androidx.activity.compose.setContent
+import androidx.activity.enableEdgeToEdge
+import androidx.compose.foundation.layout.fillMaxSize
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.Surface
+import androidx.compose.runtime.Composable
+import androidx.compose.ui.Modifier
+import androidx.lifecycle.viewmodel.compose.viewModel
+import androidx.navigation.compose.NavHost
+import androidx.navigation.compose.composable
+import androidx.navigation.compose.rememberNavController
+import com.manalejandro.odb2bluetooth.ui.navigation.Screen
+import com.manalejandro.odb2bluetooth.ui.screens.*
+import com.manalejandro.odb2bluetooth.ui.theme.ODB2BluetoothTheme
+import com.manalejandro.odb2bluetooth.ui.viewmodel.MainViewModel
+
+/**
+ * Main Activity - Entry point of the OBD2 Bluetooth application
+ */
+class MainActivity : ComponentActivity() {
+    override fun onCreate(savedInstanceState: Bundle?) {
+        super.onCreate(savedInstanceState)
+        enableEdgeToEdge()
+        setContent {
+            ODB2BluetoothTheme {
+                Surface(
+                    modifier = Modifier.fillMaxSize(),
+                    color = MaterialTheme.colorScheme.background
+                ) {
+                    OBD2App()
+                }
+            }
+        }
+    }
+}
+
+@Composable
+fun OBD2App() {
+    val navController = rememberNavController()
+    val mainViewModel: MainViewModel = viewModel()
+
+    NavHost(
+        navController = navController,
+        startDestination = Screen.Home.route
+    ) {
+        composable(Screen.Home.route) {
+            HomeScreen(
+                viewModel = mainViewModel,
+                onNavigateToBluetooth = {
+                    navController.navigate(Screen.Bluetooth.route)
+                },
+                onNavigateToVehicleSelection = {
+                    navController.navigate(Screen.VehicleSelection.route)
+                },
+                onNavigateToDiagnostic = {
+                    navController.navigate(Screen.Diagnostic.route)
+                },
+                onNavigateToCustomCommand = {
+                    navController.navigate(Screen.CustomCommand.route)
+                }
+            )
+        }
+
+        composable(Screen.Bluetooth.route) {
+            BluetoothScreen(
+                viewModel = mainViewModel,
+                onNavigateBack = { navController.popBackStack() }
+            )
+        }
+
+        composable(Screen.VehicleSelection.route) {
+            VehicleSelectionScreen(
+                mainViewModel = mainViewModel,
+                onNavigateBack = { navController.popBackStack() }
+            )
+        }
+
+        composable(Screen.Diagnostic.route) {
+            DiagnosticScreen(
+                viewModel = mainViewModel,
+                onNavigateBack = { navController.popBackStack() }
+            )
+        }
+
+        composable(Screen.CustomCommand.route) {
+            CustomCommandScreen(
+                viewModel = mainViewModel,
+                onNavigateBack = { navController.popBackStack() }
+            )
+        }
+    }
+}
+

app/src/main/java/com/manalejandro/odb2bluetooth/data/bluetooth/BluetoothService.kt

@@ -0,0 +1,202 @@
+package com.manalejandro.odb2bluetooth.data.bluetooth
+
+import android.annotation.SuppressLint
+import android.bluetooth.BluetoothAdapter
+import android.bluetooth.BluetoothDevice
+import android.bluetooth.BluetoothSocket
+import android.util.Log
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.flow.StateFlow
+import kotlinx.coroutines.withContext
+import java.io.IOException
+import java.io.InputStream
+import java.io.OutputStream
+import java.util.UUID
+
+/**
+ * Service to manage Bluetooth connection with ELM327 OBD2 adapter
+ */
+class BluetoothService {
+
+    private var bluetoothSocket: BluetoothSocket? = null
+    private var inputStream: InputStream? = null
+    private var outputStream: OutputStream? = null
+
+    private val _connectionState = MutableStateFlow(ConnectionState.DISCONNECTED)
+    val connectionState: StateFlow<ConnectionState> = _connectionState
+
+    private val _lastResponse = MutableStateFlow("")
+    val lastResponse: StateFlow<String> = _lastResponse
+
+    companion object {
+        private const val TAG = "BluetoothService"
+        // Standard SPP UUID for Bluetooth Serial
+        private val SPP_UUID: UUID = UUID.fromString("00001101-0000-1000-8000-00805F9B34FB")
+    }
+
+    enum class ConnectionState {
+        DISCONNECTED,
+        CONNECTING,
+        CONNECTED,
+        ERROR
+    }
+
+    /**
+     * Get list of paired Bluetooth devices
+     */
+    @SuppressLint("MissingPermission")
+    fun getPairedDevices(): List<BluetoothDevice> {
+        val bluetoothAdapter = BluetoothAdapter.getDefaultAdapter()
+        return bluetoothAdapter?.bondedDevices?.toList() ?: emptyList()
+    }
+
+    /**
+     * Connect to a Bluetooth device
+     */
+    @SuppressLint("MissingPermission")
+    suspend fun connect(device: BluetoothDevice): Result<Unit> = withContext(Dispatchers.IO) {
+        try {
+            _connectionState.value = ConnectionState.CONNECTING
+
+            // Close any existing connection
+            disconnect()
+
+            // Create socket and connect
+            bluetoothSocket = device.createRfcommSocketToServiceRecord(SPP_UUID)
+            bluetoothSocket?.connect()
+
+            inputStream = bluetoothSocket?.inputStream
+            outputStream = bluetoothSocket?.outputStream
+
+            // Initialize ELM327
+            initializeElm327()
+
+            _connectionState.value = ConnectionState.CONNECTED
+            Log.d(TAG, "Connected to ${device.name}")
+            Result.success(Unit)
+        } catch (e: Exception) {
+            Log.e(TAG, "Connection error", e)
+            _connectionState.value = ConnectionState.ERROR
+            disconnect()
+            Result.failure(e)
+        }
+    }
+
+    /**
+     * Initialize ELM327 with default commands
+     */
+    private suspend fun initializeElm327() {
+        // Reset device
+        sendCommand("ATZ")
+        kotlinx.coroutines.delay(1000)
+
+        // Turn off echo
+        sendCommand("ATE0")
+        kotlinx.coroutines.delay(100)
+
+        // Set line feed off
+        sendCommand("ATL0")
+        kotlinx.coroutines.delay(100)
+
+        // Set spaces off
+        sendCommand("ATS0")
+        kotlinx.coroutines.delay(100)
+
+        // Set protocol to automatic
+        sendCommand("ATSP0")
+        kotlinx.coroutines.delay(100)
+    }
+
+    /**
+     * Send a command to the ELM327 device
+     */
+    suspend fun sendCommand(command: String): Result<String> = withContext(Dispatchers.IO) {
+        if (_connectionState.value != ConnectionState.CONNECTED) {
+            return@withContext Result.failure(IOException("Not connected"))
+        }
+
+        try {
+            val commandWithCR = "$command\r"
+            outputStream?.write(commandWithCR.toByteArray())
+            outputStream?.flush()
+
+            Log.d(TAG, "Sent: $command")
+
+            // Read response
+            val response = readResponse()
+            _lastResponse.value = response
+
+            Log.d(TAG, "Received: $response")
+            Result.success(response)
+        } catch (e: Exception) {
+            Log.e(TAG, "Send command error", e)
+            Result.failure(e)
+        }
+    }
+
+    /**
+     * Read response from ELM327
+     */
+    private fun readResponse(): String {
+        val buffer = ByteArray(1024)
+        val response = StringBuilder()
+        var bytesRead: Int
+
+        try {
+            val startTime = System.currentTimeMillis()
+            val timeout = 5000 // 5 seconds timeout
+
+            while (System.currentTimeMillis() - startTime < timeout) {
+                if (inputStream?.available() ?: 0 > 0) {
+                    bytesRead = inputStream?.read(buffer) ?: 0
+                    if (bytesRead > 0) {
+                        val chunk = String(buffer, 0, bytesRead)
+                        response.append(chunk)
+
+                        // Check for prompt character '>'
+                        if (chunk.contains('>')) {
+                            break
+                        }
+                    }
+                }
+                Thread.sleep(10)
+            }
+        } catch (e: Exception) {
+            Log.e(TAG, "Read response error", e)
+        }
+
+        return response.toString()
+            .replace(">", "")
+            .replace("\r", "")
+            .replace("\n", "")
+            .trim()
+    }
+
+    /**
+     * Disconnect from the Bluetooth device
+     */
+    fun disconnect() {
+        try {
+            inputStream?.close()
+            outputStream?.close()
+            bluetoothSocket?.close()
+        } catch (e: Exception) {
+            Log.e(TAG, "Disconnect error", e)
+        } finally {
+            inputStream = null
+            outputStream = null
+            bluetoothSocket = null
+            _connectionState.value = ConnectionState.DISCONNECTED
+        }
+    }
+
+    /**
+     * Check if Bluetooth is available and enabled
+     */
+    fun isBluetoothAvailable(): Boolean {
+        val bluetoothAdapter = BluetoothAdapter.getDefaultAdapter()
+        return bluetoothAdapter != null && bluetoothAdapter.isEnabled
+    }
+}
+

app/src/main/java/com/manalejandro/odb2bluetooth/data/database/ObdDatabase.kt

@@ -0,0 +1,56 @@
+package com.manalejandro.odb2bluetooth.data.database
+
+import android.content.Context
+import androidx.room.Database
+import androidx.room.Room
+import androidx.room.RoomDatabase
+import com.manalejandro.odb2bluetooth.data.database.dao.DtcCodeDao
+import com.manalejandro.odb2bluetooth.data.database.dao.ObdSignalDao
+import com.manalejandro.odb2bluetooth.data.database.dao.VehicleDao
+import com.manalejandro.odb2bluetooth.data.database.entities.Brand
+import com.manalejandro.odb2bluetooth.data.database.entities.DtcCode
+import com.manalejandro.odb2bluetooth.data.database.entities.Generation
+import com.manalejandro.odb2bluetooth.data.database.entities.Model
+import com.manalejandro.odb2bluetooth.data.database.entities.ObdSignal
+
+/**
+ * Main Room database for the OBD2 application
+ */
+@Database(
+    entities = [
+        Brand::class,
+        Model::class,
+        Generation::class,
+        ObdSignal::class,
+        DtcCode::class
+    ],
+    version = 1,
+    exportSchema = false
+)
+abstract class ObdDatabase : RoomDatabase() {
+
+    abstract fun vehicleDao(): VehicleDao
+    abstract fun obdSignalDao(): ObdSignalDao
+    abstract fun dtcCodeDao(): DtcCodeDao
+
+    companion object {
+        @Volatile
+        private var INSTANCE: ObdDatabase? = null
+
+        fun getDatabase(context: Context): ObdDatabase {
+            return INSTANCE ?: synchronized(this) {
+                val instance = Room.databaseBuilder(
+                    context.applicationContext,
+                    ObdDatabase::class.java,
+                    "obd_database"
+                )
+                    .createFromAsset("obd_database.db")
+                    .fallbackToDestructiveMigration()
+                    .build()
+                INSTANCE = instance
+                instance
+            }
+        }
+    }
+}
+

app/src/main/java/com/manalejandro/odb2bluetooth/data/database/dao/DtcCodeDao.kt

@@ -0,0 +1,28 @@
+package com.manalejandro.odb2bluetooth.data.database.dao
+
+import androidx.room.Dao
+import androidx.room.Query
+import com.manalejandro.odb2bluetooth.data.database.entities.DtcCode
+import kotlinx.coroutines.flow.Flow
+
+/**
+ * Data Access Object for DTC (Diagnostic Trouble Codes) queries
+ */
+@Dao
+interface DtcCodeDao {
+
+    @Query("SELECT * FROM dtc_codes ORDER BY code")
+    fun getAllDtcCodes(): Flow<List<DtcCode>>
+
+    @Query("SELECT * FROM dtc_codes WHERE code = :code")
+    suspend fun getDtcCodeByCode(code: String): DtcCode?
+
+    @Query("""
+        SELECT * FROM dtc_codes 
+        WHERE code LIKE '%' || :query || '%' 
+           OR description LIKE '%' || :query || '%'
+        ORDER BY code
+    """)
+    fun searchDtcCodes(query: String): Flow<List<DtcCode>>
+}
+

app/src/main/java/com/manalejandro/odb2bluetooth/data/database/dao/ObdSignalDao.kt

@@ -0,0 +1,50 @@
+package com.manalejandro.odb2bluetooth.data.database.dao
+
+import androidx.room.Dao
+import androidx.room.Query
+import com.manalejandro.odb2bluetooth.data.database.dto.SignalDto
+import com.manalejandro.odb2bluetooth.data.database.entities.ObdSignal
+import kotlinx.coroutines.flow.Flow
+
+/**
+ * Data Access Object for OBD signals queries
+ */
+@Dao
+interface ObdSignalDao {
+
+    @Query("SELECT * FROM obd_signals WHERE model_id = :modelId ORDER BY signal_id")
+    fun getSignalsByModel(modelId: Int): Flow<List<ObdSignal>>
+
+    @Query("""
+        SELECT 
+            s.id,
+            b.name as brand,
+            m.name as model,
+            s.signal_id as signalId,
+            s.name as signalName,
+            s.path,
+            s.unit,
+            s.header,
+            s.command,
+            s.frequency,
+            s.description
+        FROM obd_signals s
+        JOIN models m ON s.model_id = m.id
+        JOIN brands b ON m.brand_id = b.id
+        WHERE s.model_id = :modelId
+        ORDER BY s.signal_id
+    """)
+    fun getSignalsDtoByModel(modelId: Int): Flow<List<SignalDto>>
+
+    @Query("SELECT * FROM obd_signals WHERE id = :signalId")
+    suspend fun getSignalById(signalId: Int): ObdSignal?
+
+    @Query("""
+        SELECT * FROM obd_signals 
+        WHERE model_id = :modelId 
+        AND (name LIKE '%' || :query || '%' OR signal_id LIKE '%' || :query || '%')
+        ORDER BY signal_id
+    """)
+    fun searchSignals(modelId: Int, query: String): Flow<List<ObdSignal>>
+}
+

app/src/main/java/com/manalejandro/odb2bluetooth/data/database/dao/VehicleDao.kt

@@ -0,0 +1,59 @@
+package com.manalejandro.odb2bluetooth.data.database.dao
+
+import androidx.room.Dao
+import androidx.room.Query
+import com.manalejandro.odb2bluetooth.data.database.dto.VehicleDto
+import com.manalejandro.odb2bluetooth.data.database.entities.Brand
+import com.manalejandro.odb2bluetooth.data.database.entities.Model
+import kotlinx.coroutines.flow.Flow
+
+/**
+ * Data Access Object for vehicle-related queries (brands and models)
+ */
+@Dao
+interface VehicleDao {
+
+    @Query("SELECT * FROM brands ORDER BY name")
+    fun getAllBrands(): Flow<List<Brand>>
+
+    @Query("SELECT * FROM models WHERE brand_id = :brandId ORDER BY name")
+    fun getModelsByBrand(brandId: Int): Flow<List<Model>>
+
+    @Query("""
+        SELECT 
+            m.id as modelId,
+            b.name as brand,
+            m.name as model,
+            m.full_name as fullName,
+            COUNT(DISTINCT g.id) as generationCount,
+            COUNT(DISTINCT s.id) as signalCount
+        FROM models m
+        JOIN brands b ON m.brand_id = b.id
+        LEFT JOIN generations g ON m.id = g.model_id
+        LEFT JOIN obd_signals s ON m.id = s.model_id
+        GROUP BY m.id, b.name, m.name, m.full_name
+        ORDER BY b.name, m.name
+    """)
+    fun getAllVehicles(): Flow<List<VehicleDto>>
+
+    @Query("""
+        SELECT 
+            m.id as modelId,
+            b.name as brand,
+            m.name as model,
+            m.full_name as fullName,
+            COUNT(DISTINCT g.id) as generationCount,
+            COUNT(DISTINCT s.id) as signalCount
+        FROM models m
+        JOIN brands b ON m.brand_id = b.id
+        LEFT JOIN generations g ON m.id = g.model_id
+        LEFT JOIN obd_signals s ON m.id = s.model_id
+        WHERE b.name LIKE '%' || :query || '%' 
+           OR m.name LIKE '%' || :query || '%'
+           OR m.full_name LIKE '%' || :query || '%'
+        GROUP BY m.id, b.name, m.name, m.full_name
+        ORDER BY b.name, m.name
+    """)
+    fun searchVehicles(query: String): Flow<List<VehicleDto>>
+}
+

app/src/main/java/com/manalejandro/odb2bluetooth/data/database/dto/SignalDto.kt

@@ -0,0 +1,19 @@
+package com.manalejandro.odb2bluetooth.data.database.dto
+
+/**
+ * Data Transfer Object for signal information including vehicle details
+ */
+data class SignalDto(
+    val id: Int,
+    val brand: String,
+    val model: String,
+    val signalId: String,
+    val signalName: String,
+    val path: String?,
+    val unit: String?,
+    val header: String?,
+    val command: String?,
+    val frequency: Double?,
+    val description: String?
+)
+

app/src/main/java/com/manalejandro/odb2bluetooth/data/database/dto/VehicleDto.kt

@@ -0,0 +1,14 @@
+package com.manalejandro.odb2bluetooth.data.database.dto
+
+/**
+ * Data Transfer Object for vehicle information combining brand and model data
+ */
+data class VehicleDto(
+    val modelId: Int,
+    val brand: String,
+    val model: String,
+    val fullName: String,
+    val generationCount: Int,
+    val signalCount: Int
+)
+

app/src/main/java/com/manalejandro/odb2bluetooth/data/database/entities/Brand.kt

@@ -0,0 +1,15 @@
+package com.manalejandro.odb2bluetooth.data.database.entities
+
+import androidx.room.Entity
+import androidx.room.PrimaryKey
+
+/**
+ * Entity representing a vehicle brand in the database
+ */
+@Entity(tableName = "brands")
+data class Brand(
+    @PrimaryKey(autoGenerate = true)
+    val id: Int = 0,
+    val name: String
+)
+

app/src/main/java/com/manalejandro/odb2bluetooth/data/database/entities/DtcCode.kt

@@ -0,0 +1,15 @@
+package com.manalejandro.odb2bluetooth.data.database.entities
+
+import androidx.room.Entity
+import androidx.room.PrimaryKey
+
+/**
+ * Entity representing a diagnostic trouble code (DTC) in the database
+ */
+@Entity(tableName = "dtc_codes")
+data class DtcCode(
+    @PrimaryKey
+    val code: String,
+    val description: String
+)
+

app/src/main/java/com/manalejandro/odb2bluetooth/data/database/entities/Generation.kt

@@ -0,0 +1,37 @@
+package com.manalejandro.odb2bluetooth.data.database.entities
+
+import androidx.room.ColumnInfo
+import androidx.room.Entity
+import androidx.room.ForeignKey
+import androidx.room.Index
+import androidx.room.PrimaryKey
+
+/**
+ * Entity representing a vehicle generation in the database
+ */
+@Entity(
+    tableName = "generations",
+    foreignKeys = [
+        ForeignKey(
+            entity = Model::class,
+            parentColumns = ["id"],
+            childColumns = ["model_id"],
+            onDelete = ForeignKey.CASCADE
+        )
+    ],
+    indices = [Index("model_id")]
+)
+data class Generation(
+    @PrimaryKey(autoGenerate = true)
+    val id: Int = 0,
+    @ColumnInfo(name = "model_id")
+    val modelId: Int,
+    val name: String,
+    val code: String?,
+    @ColumnInfo(name = "start_year")
+    val startYear: Int?,
+    @ColumnInfo(name = "end_year")
+    val endYear: Int?,
+    val description: String?
+)
+

app/src/main/java/com/manalejandro/odb2bluetooth/data/database/entities/Model.kt

@@ -0,0 +1,33 @@
+package com.manalejandro.odb2bluetooth.data.database.entities
+
+import androidx.room.ColumnInfo
+import androidx.room.Entity
+import androidx.room.ForeignKey
+import androidx.room.Index
+import androidx.room.PrimaryKey
+
+/**
+ * Entity representing a vehicle model in the database
+ */
+@Entity(
+    tableName = "models",
+    foreignKeys = [
+        ForeignKey(
+            entity = Brand::class,
+            parentColumns = ["id"],
+            childColumns = ["brand_id"],
+            onDelete = ForeignKey.CASCADE
+        )
+    ],
+    indices = [Index("brand_id")]
+)
+data class Model(
+    @PrimaryKey(autoGenerate = true)
+    val id: Int = 0,
+    @ColumnInfo(name = "brand_id")
+    val brandId: Int,
+    val name: String,
+    @ColumnInfo(name = "full_name")
+    val fullName: String
+)
+

app/src/main/java/com/manalejandro/odb2bluetooth/data/database/entities/ObdSignal.kt

@@ -0,0 +1,43 @@
+package com.manalejandro.odb2bluetooth.data.database.entities
+
+import androidx.room.ColumnInfo
+import androidx.room.Entity
+import androidx.room.ForeignKey
+import androidx.room.Index
+import androidx.room.PrimaryKey
+
+/**
+ * Entity representing an OBD signal (PID command) in the database
+ */
+@Entity(
+    tableName = "obd_signals",
+    foreignKeys = [
+        ForeignKey(
+            entity = Model::class,
+            parentColumns = ["id"],
+            childColumns = ["model_id"],
+            onDelete = ForeignKey.CASCADE
+        )
+    ],
+    indices = [Index("model_id")]
+)
+data class ObdSignal(
+    @PrimaryKey(autoGenerate = true)
+    val id: Int = 0,
+    @ColumnInfo(name = "model_id")
+    val modelId: Int,
+    @ColumnInfo(name = "signal_id")
+    val signalId: String,
+    val name: String,
+    val path: String?,
+    val unit: String?,
+    val description: String?,
+    val header: String?,
+    val command: String?,
+    val frequency: Double?,
+    @ColumnInfo(name = "min_value")
+    val minValue: Double?,
+    @ColumnInfo(name = "max_value")
+    val maxValue: Double?
+)
+

app/src/main/java/com/manalejandro/odb2bluetooth/data/obd/ObdCommands.kt

@@ -0,0 +1,160 @@
+package com.manalejandro.odb2bluetooth.data.obd
+
+/**
+ * Generic OBD2 commands for diagnostics
+ */
+object ObdCommands {
+
+    /**
+     * Generic safe diagnostic commands
+     */
+    val SAFE_DIAGNOSTIC_COMMANDS = listOf(
+        ObdCommand(
+            name = "Vehicle Speed",
+            command = "010D",
+            description = "Current vehicle speed in km/h",
+            unit = "km/h",
+            isSafe = true
+        ),
+        ObdCommand(
+            name = "Engine RPM",
+            command = "010C",
+            description = "Engine revolutions per minute",
+            unit = "RPM",
+            isSafe = true
+        ),
+        ObdCommand(
+            name = "Coolant Temperature",
+            command = "0105",
+            description = "Engine coolant temperature",
+            unit = "°C",
+            isSafe = true
+        ),
+        ObdCommand(
+            name = "Throttle Position",
+            command = "0111",
+            description = "Throttle position percentage",
+            unit = "%",
+            isSafe = true
+        ),
+        ObdCommand(
+            name = "Fuel Level",
+            command = "012F",
+            description = "Fuel tank level input",
+            unit = "%",
+            isSafe = true
+        ),
+        ObdCommand(
+            name = "Intake Air Temperature",
+            command = "010F",
+            description = "Intake air temperature",
+            unit = "°C",
+            isSafe = true
+        ),
+        ObdCommand(
+            name = "MAF Air Flow Rate",
+            command = "0110",
+            description = "Mass air flow sensor air flow rate",
+            unit = "g/s",
+            isSafe = true
+        ),
+        ObdCommand(
+            name = "Engine Load",
+            command = "0104",
+            description = "Calculated engine load value",
+            unit = "%",
+            isSafe = true
+        )
+    )
+
+    /**
+     * DTC (Diagnostic Trouble Codes) commands
+     */
+    val DTC_COMMANDS = listOf(
+        ObdCommand(
+            name = "Read DTCs",
+            command = "03",
+            description = "Request diagnostic trouble codes",
+            unit = "",
+            isSafe = true
+        ),
+        ObdCommand(
+            name = "Clear DTCs",
+            command = "04",
+            description = "Clear diagnostic trouble codes and stored values",
+            unit = "",
+            isSafe = false
+        ),
+        ObdCommand(
+            name = "Pending DTCs",
+            command = "07",
+            description = "Request pending diagnostic trouble codes",
+            unit = "",
+            isSafe = true
+        )
+    )
+
+    /**
+     * Parse OBD2 response for common PIDs
+     */
+    fun parseResponse(command: String, response: String): String? {
+        if (response.contains("NO DATA") || response.contains("ERROR")) {
+            return null
+        }
+
+        // Remove spaces and common prefixes
+        val cleanResponse = response.replace(" ", "").replace("41", "").replace("43", "")
+
+        return when (command) {
+            "010C" -> { // RPM
+                try {
+                    val value = cleanResponse.substring(2, 6).toInt(16)
+                    "${value / 4} RPM"
+                } catch (e: Exception) { null }
+            }
+            "010D" -> { // Speed
+                try {
+                    val value = cleanResponse.substring(2, 4).toInt(16)
+                    "$value km/h"
+                } catch (e: Exception) { null }
+            }
+            "0105" -> { // Coolant temp
+                try {
+                    val value = cleanResponse.substring(2, 4).toInt(16) - 40
+                    "$value °C"
+                } catch (e: Exception) { null }
+            }
+            "010F" -> { // Intake air temp
+                try {
+                    val value = cleanResponse.substring(2, 4).toInt(16) - 40
+                    "$value °C"
+                } catch (e: Exception) { null }
+            }
+            "0111", "0104", "012F" -> { // Percentage values
+                try {
+                    val value = (cleanResponse.substring(2, 4).toInt(16) * 100) / 255
+                    "$value %"
+                } catch (e: Exception) { null }
+            }
+            "0110" -> { // MAF
+                try {
+                    val value = cleanResponse.substring(2, 6).toInt(16) / 100.0
+                    String.format("%.2f g/s", value)
+                } catch (e: Exception) { null }
+            }
+            else -> cleanResponse
+        }
+    }
+}
+
+/**
+ * Data class representing an OBD command
+ */
+data class ObdCommand(
+    val name: String,
+    val command: String,
+    val description: String,
+    val unit: String,
+    val isSafe: Boolean
+)
+

app/src/main/java/com/manalejandro/odb2bluetooth/data/repository/ObdRepository.kt

@@ -0,0 +1,48 @@
+package com.manalejandro.odb2bluetooth.data.repository
+
+import com.manalejandro.odb2bluetooth.data.database.dao.DtcCodeDao
+import com.manalejandro.odb2bluetooth.data.database.dao.ObdSignalDao
+import com.manalejandro.odb2bluetooth.data.database.dao.VehicleDao
+import com.manalejandro.odb2bluetooth.data.database.dto.SignalDto
+import com.manalejandro.odb2bluetooth.data.database.dto.VehicleDto
+import com.manalejandro.odb2bluetooth.data.database.entities.Brand
+import com.manalejandro.odb2bluetooth.data.database.entities.DtcCode
+import com.manalejandro.odb2bluetooth.data.database.entities.ObdSignal
+import kotlinx.coroutines.flow.Flow
+
+/**
+ * Repository for OBD database operations
+ */
+class ObdRepository(
+    private val vehicleDao: VehicleDao,
+    private val obdSignalDao: ObdSignalDao,
+    private val dtcCodeDao: DtcCodeDao
+) {
+
+    // Vehicle operations
+    fun getAllVehicles(): Flow<List<VehicleDto>> = vehicleDao.getAllVehicles()
+
+    fun searchVehicles(query: String): Flow<List<VehicleDto>> = vehicleDao.searchVehicles(query)
+
+    fun getAllBrands(): Flow<List<Brand>> = vehicleDao.getAllBrands()
+
+    // Signal operations
+    fun getSignalsByModel(modelId: Int): Flow<List<SignalDto>> =
+        obdSignalDao.getSignalsDtoByModel(modelId)
+
+    suspend fun getSignalById(signalId: Int): ObdSignal? =
+        obdSignalDao.getSignalById(signalId)
+
+    fun searchSignals(modelId: Int, query: String): Flow<List<ObdSignal>> =
+        obdSignalDao.searchSignals(modelId, query)
+
+    // DTC operations
+    fun getAllDtcCodes(): Flow<List<DtcCode>> = dtcCodeDao.getAllDtcCodes()
+
+    suspend fun getDtcCodeByCode(code: String): DtcCode? =
+        dtcCodeDao.getDtcCodeByCode(code)
+
+    fun searchDtcCodes(query: String): Flow<List<DtcCode>> =
+        dtcCodeDao.searchDtcCodes(query)
+}
+

app/src/main/java/com/manalejandro/odb2bluetooth/ui/components/CommonComponents.kt

@@ -0,0 +1,148 @@
+package com.manalejandro.odb2bluetooth.ui.components
+
+import androidx.compose.foundation.layout.*
+import androidx.compose.material.icons.Icons
+import androidx.compose.material.icons.filled.Warning
+import androidx.compose.material3.*
+import androidx.compose.runtime.*
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.text.font.FontWeight
+import androidx.compose.ui.text.style.TextAlign
+import androidx.compose.ui.unit.dp
+
+/**
+ * Warning dialog to inform users about potential risks when sending OBD commands
+ */
+@Composable
+fun WarningDialog(
+    onDismiss: () -> Unit,
+    onAccept: () -> Unit,
+    title: String = "Warning",
+    message: String
+) {
+    AlertDialog(
+        onDismissRequest = onDismiss,
+        icon = {
+            Icon(
+                imageVector = Icons.Default.Warning,
+                contentDescription = "Warning",
+                tint = MaterialTheme.colorScheme.error,
+                modifier = Modifier.size(48.dp)
+            )
+        },
+        title = {
+            Text(
+                text = title,
+                style = MaterialTheme.typography.headlineSmall,
+                fontWeight = FontWeight.Bold
+            )
+        },
+        text = {
+            Text(
+                text = message,
+                style = MaterialTheme.typography.bodyMedium,
+                textAlign = TextAlign.Justify
+            )
+        },
+        confirmButton = {
+            Button(
+                onClick = onAccept,
+                colors = ButtonDefaults.buttonColors(
+                    containerColor = MaterialTheme.colorScheme.error
+                )
+            ) {
+                Text("I Understand - Continue")
+            }
+        },
+        dismissButton = {
+            TextButton(onClick = onDismiss) {
+                Text("Cancel")
+            }
+        }
+    )
+}
+
+/**
+ * Connection status indicator
+ */
+@Composable
+fun ConnectionStatusIndicator(
+    isConnected: Boolean,
+    deviceName: String?,
+    modifier: Modifier = Modifier
+) {
+    Surface(
+        modifier = modifier,
+        color = if (isConnected) 
+            MaterialTheme.colorScheme.primaryContainer 
+        else 
+            MaterialTheme.colorScheme.errorContainer,
+        shape = MaterialTheme.shapes.small
+    ) {
+        Row(
+            modifier = Modifier.padding(horizontal = 16.dp, vertical = 8.dp),
+            verticalAlignment = Alignment.CenterVertically,
+            horizontalArrangement = Arrangement.spacedBy(8.dp)
+        ) {
+            // Status dot
+            Surface(
+                modifier = Modifier.size(12.dp),
+                shape = MaterialTheme.shapes.extraLarge,
+                color = if (isConnected)
+                    MaterialTheme.colorScheme.primary
+                else
+                    MaterialTheme.colorScheme.error
+            ) {}
+            
+            Text(
+                text = if (isConnected) {
+                    "Connected${deviceName?.let { " to $it" } ?: ""}"
+                } else {
+                    "Disconnected"
+                },
+                style = MaterialTheme.typography.labelLarge,
+                color = if (isConnected)
+                    MaterialTheme.colorScheme.onPrimaryContainer
+                else
+                    MaterialTheme.colorScheme.onErrorContainer
+            )
+        }
+    }
+}
+
+/**
+ * Loading overlay
+ */
+@Composable
+fun LoadingOverlay(
+    isLoading: Boolean,
+    message: String = "Loading..."
+) {
+    if (isLoading) {
+        Box(
+            modifier = Modifier.fillMaxSize(),
+            contentAlignment = Alignment.Center
+        ) {
+            Surface(
+                shape = MaterialTheme.shapes.medium,
+                color = MaterialTheme.colorScheme.surface,
+                tonalElevation = 8.dp,
+                shadowElevation = 8.dp
+            ) {
+                Column(
+                    modifier = Modifier.padding(32.dp),
+                    horizontalAlignment = Alignment.CenterHorizontally,
+                    verticalArrangement = Arrangement.spacedBy(16.dp)
+                ) {
+                    CircularProgressIndicator()
+                    Text(
+                        text = message,
+                        style = MaterialTheme.typography.bodyMedium
+                    )
+                }
+            }
+        }
+    }
+}
+

app/src/main/java/com/manalejandro/odb2bluetooth/ui/navigation/Screen.kt

@@ -0,0 +1,14 @@
+package com.manalejandro.odb2bluetooth.ui.navigation
+
+/**
+ * Navigation routes for the app
+ */
+sealed class Screen(val route: String) {
+    object Home : Screen("home")
+    object Bluetooth : Screen("bluetooth")
+    object VehicleSelection : Screen("vehicle_selection")
+    object Diagnostic : Screen("diagnostic")
+    object CustomCommand : Screen("custom_command")
+    object About : Screen("about")
+}
+

app/src/main/java/com/manalejandro/odb2bluetooth/ui/screens/BluetoothScreen.kt

@@ -0,0 +1,314 @@
+package com.manalejandro.odb2bluetooth.ui.screens
+
+import android.Manifest
+import android.bluetooth.BluetoothDevice
+import android.os.Build
+import androidx.compose.foundation.layout.*
+import androidx.compose.foundation.lazy.LazyColumn
+import androidx.compose.foundation.lazy.items
+import androidx.compose.material.icons.Icons
+import androidx.compose.material.icons.filled.*
+import androidx.compose.material3.*
+import androidx.compose.runtime.*
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.text.font.FontWeight
+import androidx.compose.ui.unit.dp
+import com.google.accompanist.permissions.ExperimentalPermissionsApi
+import com.google.accompanist.permissions.rememberMultiplePermissionsState
+import com.manalejandro.odb2bluetooth.data.bluetooth.BluetoothService
+import com.manalejandro.odb2bluetooth.ui.components.ConnectionStatusIndicator
+import com.manalejandro.odb2bluetooth.ui.viewmodel.MainViewModel
+
+/**
+ * Bluetooth screen - Device pairing and connection
+ */
+@OptIn(ExperimentalMaterial3Api::class, ExperimentalPermissionsApi::class)
+@Composable
+fun BluetoothScreen(
+    viewModel: MainViewModel,
+    onNavigateBack: () -> Unit
+) {
+    val connectionState by viewModel.bluetoothService.connectionState.collectAsState()
+    val pairedDevices by viewModel.pairedDevices.collectAsState()
+    val selectedDevice by viewModel.selectedDevice.collectAsState()
+    val isLoading by viewModel.isLoading.collectAsState()
+    val errorMessage by viewModel.errorMessage.collectAsState()
+
+    val isConnected = connectionState == BluetoothService.ConnectionState.CONNECTED
+
+    // Handle Bluetooth permissions
+    val bluetoothPermissions = if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.S) {
+        listOf(
+            Manifest.permission.BLUETOOTH_CONNECT,
+            Manifest.permission.BLUETOOTH_SCAN
+        )
+    } else {
+        listOf(
+            Manifest.permission.BLUETOOTH,
+            Manifest.permission.BLUETOOTH_ADMIN
+        )
+    }
+
+    val permissionsState = rememberMultiplePermissionsState(bluetoothPermissions)
+
+    LaunchedEffect(Unit) {
+        if (!permissionsState.allPermissionsGranted) {
+            permissionsState.launchMultiplePermissionRequest()
+        } else {
+            viewModel.loadPairedDevices()
+        }
+    }
+
+    Scaffold(
+        topBar = {
+            TopAppBar(
+                title = { Text("Bluetooth Connection") },
+                navigationIcon = {
+                    IconButton(onClick = onNavigateBack) {
+                        Icon(Icons.Default.ArrowBack, contentDescription = "Back")
+                    }
+                },
+                colors = TopAppBarDefaults.topAppBarColors(
+                    containerColor = MaterialTheme.colorScheme.primaryContainer,
+                    titleContentColor = MaterialTheme.colorScheme.onPrimaryContainer
+                )
+            )
+        }
+    ) { paddingValues ->
+        Box(
+            modifier = Modifier
+                .fillMaxSize()
+                .padding(paddingValues)
+        ) {
+            if (!permissionsState.allPermissionsGranted) {
+                // Permission request UI
+                Column(
+                    modifier = Modifier
+                        .fillMaxSize()
+                        .padding(16.dp),
+                    verticalArrangement = Arrangement.Center,
+                    horizontalAlignment = Alignment.CenterHorizontally
+                ) {
+                    Icon(
+                        imageVector = Icons.Default.Phone,
+                        contentDescription = null,
+                        modifier = Modifier.size(64.dp),
+                        tint = MaterialTheme.colorScheme.primary
+                    )
+                    Spacer(modifier = Modifier.height(16.dp))
+                    Text(
+                        text = "Bluetooth Permission Required",
+                        style = MaterialTheme.typography.headlineSmall,
+                        fontWeight = FontWeight.Bold
+                    )
+                    Spacer(modifier = Modifier.height(8.dp))
+                    Text(
+                        text = "This app needs Bluetooth permission to connect to OBD2 devices.",
+                        style = MaterialTheme.typography.bodyMedium
+                    )
+                    Spacer(modifier = Modifier.height(24.dp))
+                    Button(onClick = { permissionsState.launchMultiplePermissionRequest() }) {
+                        Text("Grant Permission")
+                    }
+                }
+            } else {
+                Column(
+                    modifier = Modifier
+                        .fillMaxSize()
+                        .padding(16.dp),
+                    verticalArrangement = Arrangement.spacedBy(16.dp)
+                ) {
+                    // Connection status
+                    ConnectionStatusIndicator(
+                        isConnected = isConnected,
+                        deviceName = selectedDevice?.name,
+                        modifier = Modifier.fillMaxWidth()
+                    )
+
+                    // Connection controls
+                    if (isConnected) {
+                        ElevatedCard(
+                            modifier = Modifier.fillMaxWidth()
+                        ) {
+                            Column(
+                                modifier = Modifier.padding(16.dp),
+                                verticalArrangement = Arrangement.spacedBy(8.dp)
+                            ) {
+                                Text(
+                                    text = "Connected Device",
+                                    style = MaterialTheme.typography.titleMedium,
+                                    fontWeight = FontWeight.Bold
+                                )
+                                Text(
+                                    text = selectedDevice?.name ?: "Unknown",
+                                    style = MaterialTheme.typography.bodyLarge
+                                )
+                                Text(
+                                    text = selectedDevice?.address ?: "",
+                                    style = MaterialTheme.typography.bodySmall,
+                                    color = MaterialTheme.colorScheme.onSurfaceVariant
+                                )
+                                Spacer(modifier = Modifier.height(8.dp))
+                                Button(
+                                    onClick = { viewModel.disconnect() },
+                                    colors = ButtonDefaults.buttonColors(
+                                        containerColor = MaterialTheme.colorScheme.error
+                                    ),
+                                    modifier = Modifier.fillMaxWidth()
+                                ) {
+                                    Icon(Icons.Default.Close, contentDescription = null)
+                                    Spacer(modifier = Modifier.width(8.dp))
+                                    Text("Disconnect")
+                                }
+                            }
+                        }
+                    }
+
+                    // Error message
+                    errorMessage?.let { error ->
+                        Card(
+                            colors = CardDefaults.cardColors(
+                                containerColor = MaterialTheme.colorScheme.errorContainer
+                            ),
+                            modifier = Modifier.fillMaxWidth()
+                        ) {
+                            Row(
+                                modifier = Modifier.padding(16.dp),
+                                horizontalArrangement = Arrangement.spacedBy(8.dp)
+                            ) {
+                                Icon(
+                                    imageVector = Icons.Default.Warning,
+                                    contentDescription = null,
+                                    tint = MaterialTheme.colorScheme.error
+                                )
+                                Text(
+                                    text = error,
+                                    color = MaterialTheme.colorScheme.onErrorContainer
+                                )
+                            }
+                        }
+                    }
+
+                    // Paired devices list
+                    Row(
+                        modifier = Modifier.fillMaxWidth(),
+                        horizontalArrangement = Arrangement.SpaceBetween,
+                        verticalAlignment = Alignment.CenterVertically
+                    ) {
+                        Text(
+                            text = "Paired Devices",
+                            style = MaterialTheme.typography.titleLarge,
+                            fontWeight = FontWeight.Bold
+                        )
+                        IconButton(onClick = { viewModel.loadPairedDevices() }) {
+                            Icon(Icons.Default.Refresh, contentDescription = "Refresh")
+                        }
+                    }
+
+                    if (pairedDevices.isEmpty()) {
+                        Card(
+                            modifier = Modifier.fillMaxWidth()
+                        ) {
+                            Column(
+                                modifier = Modifier
+                                    .fillMaxWidth()
+                                    .padding(32.dp),
+                                horizontalAlignment = Alignment.CenterHorizontally
+                            ) {
+                                Icon(
+                                    imageVector = Icons.Default.Search,
+                                    contentDescription = null,
+                                    modifier = Modifier.size(48.dp),
+                                    tint = MaterialTheme.colorScheme.onSurfaceVariant
+                                )
+                                Spacer(modifier = Modifier.height(16.dp))
+                                Text(
+                                    text = "No paired devices found",
+                                    style = MaterialTheme.typography.bodyLarge,
+                                    color = MaterialTheme.colorScheme.onSurfaceVariant
+                                )
+                                Text(
+                                    text = "Pair your ELM327 device in system settings",
+                                    style = MaterialTheme.typography.bodySmall,
+                                    color = MaterialTheme.colorScheme.onSurfaceVariant
+                                )
+                            }
+                        }
+                    } else {
+                        LazyColumn(
+                            verticalArrangement = Arrangement.spacedBy(8.dp)
+                        ) {
+                            items(pairedDevices) { device ->
+                                DeviceCard(
+                                    device = device,
+                                    isConnected = device.address == selectedDevice?.address && isConnected,
+                                    isLoading = isLoading && device.address == selectedDevice?.address,
+                                    onConnect = { viewModel.connectToDevice(device) }
+                                )
+                            }
+                        }
+                    }
+                }
+            }
+        }
+    }
+}
+
+@Composable
+private fun DeviceCard(
+    device: BluetoothDevice,
+    isConnected: Boolean,
+    isLoading: Boolean,
+    onConnect: () -> Unit
+) {
+    ElevatedCard(
+        modifier = Modifier.fillMaxWidth()
+    ) {
+        Row(
+            modifier = Modifier
+                .fillMaxWidth()
+                .padding(16.dp),
+            horizontalArrangement = Arrangement.SpaceBetween,
+            verticalAlignment = Alignment.CenterVertically
+        ) {
+            Column(
+                modifier = Modifier.weight(1f)
+            ) {
+                Text(
+                    text = device.name ?: "Unknown Device",
+                    style = MaterialTheme.typography.titleMedium,
+                    fontWeight = FontWeight.SemiBold
+                )
+                Text(
+                    text = device.address,
+                    style = MaterialTheme.typography.bodySmall,
+                    color = MaterialTheme.colorScheme.onSurfaceVariant
+                )
+            }
+
+            if (isLoading) {
+                CircularProgressIndicator(
+                    modifier = Modifier.size(32.dp)
+                )
+            } else if (isConnected) {
+                Surface(
+                    shape = MaterialTheme.shapes.small,
+                    color = MaterialTheme.colorScheme.primaryContainer
+                ) {
+                    Text(
+                        text = "Connected",
+                        modifier = Modifier.padding(horizontal = 12.dp, vertical = 6.dp),
+                        style = MaterialTheme.typography.labelMedium,
+                        color = MaterialTheme.colorScheme.onPrimaryContainer
+                    )
+                }
+            } else {
+                Button(onClick = onConnect) {
+                    Text("Connect")
+                }
+            }
+        }
+    }
+}
+

app/src/main/java/com/manalejandro/odb2bluetooth/ui/screens/CustomCommandScreen.kt

@@ -0,0 +1,358 @@
+package com.manalejandro.odb2bluetooth.ui.screens
+
+import androidx.compose.foundation.layout.*
+import androidx.compose.foundation.lazy.LazyColumn
+import androidx.compose.foundation.lazy.items
+import androidx.compose.foundation.text.KeyboardActions
+import androidx.compose.foundation.text.KeyboardOptions
+import androidx.compose.material.icons.Icons
+import androidx.compose.material.icons.filled.*
+import androidx.compose.material3.*
+import androidx.compose.runtime.*
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.text.font.FontWeight
+import androidx.compose.ui.text.input.ImeAction
+import androidx.compose.ui.text.input.KeyboardCapitalization
+import androidx.compose.ui.unit.dp
+import com.manalejandro.odb2bluetooth.ui.components.WarningDialog
+import com.manalejandro.odb2bluetooth.ui.viewmodel.CommandResult
+import com.manalejandro.odb2bluetooth.ui.viewmodel.MainViewModel
+import java.text.SimpleDateFormat
+import java.util.*
+
+/**
+ * Custom command screen - Send custom OBD2 commands
+ */
+@OptIn(ExperimentalMaterial3Api::class)
+@Composable
+fun CustomCommandScreen(
+    viewModel: MainViewModel,
+    onNavigateBack: () -> Unit
+) {
+    var commandText by remember { mutableStateOf("") }
+    var editedCommand by remember { mutableStateOf("") }
+    var showWarning by remember { mutableStateOf(false) }
+    val commandHistory by viewModel.commandHistory.collectAsState()
+    val isLoading by viewModel.isLoading.collectAsState()
+
+    if (showWarning) {
+        WarningDialog(
+            onDismiss = {
+                showWarning = false
+                editedCommand = ""
+            },
+            onAccept = {
+                showWarning = false
+                viewModel.sendCommand(editedCommand)
+                commandText = ""
+                editedCommand = ""
+            },
+            title = "⚠️ DANGER - Read Carefully",
+            message = "YOU ARE ABOUT TO SEND A CUSTOM COMMAND TO YOUR VEHICLE.\n\n" +
+                    "Command: $editedCommand\n\n" +
+                    "⚠️ WARNING:\n" +
+                    "• Sending incorrect commands can DAMAGE your vehicle\n" +
+                    "• You are FULLY RESPONSIBLE for any consequences\n" +
+                    "• This action may VOID your warranty\n" +
+                    "• Only proceed if you KNOW what this command does\n\n" +
+                    "Do you accept ALL RISKS and want to proceed?"
+        )
+    }
+
+    Scaffold(
+        topBar = {
+            TopAppBar(
+                title = { Text("Custom Commands") },
+                navigationIcon = {
+                    IconButton(onClick = onNavigateBack) {
+                        Icon(Icons.Default.ArrowBack, contentDescription = "Back")
+                    }
+                },
+                actions = {
+                    IconButton(onClick = { viewModel.clearHistory() }) {
+                        Icon(Icons.Default.Delete, contentDescription = "Clear history")
+                    }
+                },
+                colors = TopAppBarDefaults.topAppBarColors(
+                    containerColor = MaterialTheme.colorScheme.primaryContainer,
+                    titleContentColor = MaterialTheme.colorScheme.onPrimaryContainer
+                )
+            )
+        }
+    ) { paddingValues ->
+        Column(
+            modifier = Modifier
+                .fillMaxSize()
+                .padding(paddingValues)
+        ) {
+            // Warning card
+            Card(
+                modifier = Modifier
+                    .fillMaxWidth()
+                    .padding(16.dp),
+                colors = CardDefaults.cardColors(
+                    containerColor = MaterialTheme.colorScheme.errorContainer
+                )
+            ) {
+                Row(
+                    modifier = Modifier.padding(16.dp),
+                    horizontalArrangement = Arrangement.spacedBy(12.dp)
+                ) {
+                    Icon(
+                        imageVector = Icons.Default.Warning,
+                        contentDescription = null,
+                        tint = MaterialTheme.colorScheme.error
+                    )
+                    Column {
+                        Text(
+                            text = "⚠️ DANGER ZONE",
+                            style = MaterialTheme.typography.titleSmall,
+                            fontWeight = FontWeight.Bold,
+                            color = MaterialTheme.colorScheme.onErrorContainer
+                        )
+                        Text(
+                            text = "Custom commands can damage your vehicle. Use ONLY if you know what you're doing. YOU are responsible for any consequences.",
+                            style = MaterialTheme.typography.bodySmall,
+                            color = MaterialTheme.colorScheme.onErrorContainer
+                        )
+                    }
+                }
+            }
+
+            // Command input
+            Column(
+                modifier = Modifier.padding(horizontal = 16.dp),
+                verticalArrangement = Arrangement.spacedBy(8.dp)
+            ) {
+                OutlinedTextField(
+                    value = commandText,
+                    onValueChange = { commandText = it.uppercase() },
+                    label = { Text("OBD2 Command") },
+                    placeholder = { Text("e.g., 010C, ATZ, 0105") },
+                    leadingIcon = {
+                        Icon(Icons.Default.Settings, contentDescription = null)
+                    },
+                    trailingIcon = {
+                        if (commandText.isNotEmpty()) {
+                            IconButton(onClick = { commandText = "" }) {
+                                Icon(Icons.Default.Clear, contentDescription = "Clear")
+                            }
+                        }
+                    },
+                    keyboardOptions = KeyboardOptions(
+                        capitalization = KeyboardCapitalization.Characters,
+                        imeAction = ImeAction.Send
+                    ),
+                    keyboardActions = KeyboardActions(
+                        onSend = {
+                            if (commandText.isNotBlank()) {
+                                editedCommand = commandText
+                                showWarning = true
+                            }
+                        }
+                    ),
+                    singleLine = true,
+                    modifier = Modifier.fillMaxWidth()
+                )
+
+                Button(
+                    onClick = {
+                        if (commandText.isNotBlank()) {
+                            editedCommand = commandText
+                            showWarning = true
+                        }
+                    },
+                    modifier = Modifier.fillMaxWidth(),
+                    enabled = commandText.isNotBlank() && !isLoading,
+                    colors = ButtonDefaults.buttonColors(
+                        containerColor = MaterialTheme.colorScheme.error
+                    )
+                ) {
+                    Icon(Icons.Default.Send, contentDescription = null)
+                    Spacer(modifier = Modifier.width(8.dp))
+                    Text("Send Command")
+                }
+            }
+
+            Spacer(modifier = Modifier.height(16.dp))
+
+            // Loading indicator
+            if (isLoading) {
+                LinearProgressIndicator(
+                    modifier = Modifier.fillMaxWidth()
+                )
+            }
+
+            // Common commands
+            Text(
+                text = "Common Commands",
+                style = MaterialTheme.typography.titleMedium,
+                fontWeight = FontWeight.Bold,
+                modifier = Modifier.padding(horizontal = 16.dp)
+            )
+
+            Row(
+                modifier = Modifier
+                    .fillMaxWidth()
+                    .padding(horizontal = 16.dp, vertical = 8.dp),
+                horizontalArrangement = Arrangement.spacedBy(8.dp)
+            ) {
+                listOf("010C", "010D", "0105", "ATZ").forEach { cmd ->
+                    FilterChip(
+                        selected = false,
+                        onClick = { commandText = cmd },
+                        label = { Text(cmd) }
+                    )
+                }
+            }
+
+            Divider(modifier = Modifier.padding(vertical = 8.dp))
+
+            // Command history
+            Text(
+                text = "Response History",
+                style = MaterialTheme.typography.titleMedium,
+                fontWeight = FontWeight.Bold,
+                modifier = Modifier.padding(horizontal = 16.dp)
+            )
+
+            if (commandHistory.isEmpty()) {
+                Box(
+                    modifier = Modifier
+                        .fillMaxSize()
+                        .padding(32.dp),
+                    contentAlignment = Alignment.Center
+                ) {
+                    Column(
+                        horizontalAlignment = Alignment.CenterHorizontally,
+                        verticalArrangement = Arrangement.spacedBy(16.dp)
+                    ) {
+                        Icon(
+                            imageVector = Icons.Default.Info,
+                            contentDescription = null,
+                            modifier = Modifier.size(64.dp),
+                            tint = MaterialTheme.colorScheme.onSurfaceVariant
+                        )
+                        Text(
+                            text = "No commands sent yet",
+                            style = MaterialTheme.typography.bodyLarge,
+                            color = MaterialTheme.colorScheme.onSurfaceVariant
+                        )
+                    }
+                }
+            } else {
+                LazyColumn(
+                    contentPadding = PaddingValues(16.dp),
+                    verticalArrangement = Arrangement.spacedBy(8.dp)
+                ) {
+                    items(commandHistory) { result ->
+                        CommandResultCard(
+                            result = result,
+                            onResend = {
+                                commandText = result.command
+                            }
+                        )
+                    }
+                }
+            }
+        }
+    }
+}
+
+@Composable
+private fun CommandResultCard(
+    result: CommandResult,
+    onResend: () -> Unit
+) {
+    val dateFormat = remember { SimpleDateFormat("HH:mm:ss", Locale.getDefault()) }
+    val isError = result.parsedResponse.contains("Error", ignoreCase = true) ||
+                  result.rawResponse.contains("NO DATA", ignoreCase = true) ||
+                  result.rawResponse.contains("ERROR", ignoreCase = true)
+
+    ElevatedCard(
+        modifier = Modifier.fillMaxWidth()
+    ) {
+        Column(
+            modifier = Modifier
+                .fillMaxWidth()
+                .padding(16.dp),
+            verticalArrangement = Arrangement.spacedBy(8.dp)
+        ) {
+            Row(
+                modifier = Modifier.fillMaxWidth(),
+                horizontalArrangement = Arrangement.SpaceBetween,
+                verticalAlignment = Alignment.CenterVertically
+            ) {
+                Row(
+                    horizontalArrangement = Arrangement.spacedBy(8.dp),
+                    verticalAlignment = Alignment.CenterVertically
+                ) {
+                    if (isError) {
+                        Icon(
+                            imageVector = Icons.Default.Warning,
+                            contentDescription = null,
+                            tint = MaterialTheme.colorScheme.error,
+                            modifier = Modifier.size(20.dp)
+                        )
+                    }
+                    Text(
+                        text = result.command,
+                        style = MaterialTheme.typography.titleMedium,
+                        fontWeight = FontWeight.Bold,
+                        fontFamily = androidx.compose.ui.text.font.FontFamily.Monospace
+                    )
+                }
+                IconButton(
+                    onClick = onResend,
+                    modifier = Modifier.size(32.dp)
+                ) {
+                    Icon(
+                        imageVector = Icons.Default.Refresh,
+                        contentDescription = "Resend",
+                        modifier = Modifier.size(20.dp)
+                    )
+                }
+            }
+
+            Divider()
+
+            Text(
+                text = "Response:",
+                style = MaterialTheme.typography.labelSmall,
+                color = MaterialTheme.colorScheme.onSurfaceVariant
+            )
+
+            Surface(
+                shape = MaterialTheme.shapes.small,
+                color = MaterialTheme.colorScheme.surfaceVariant
+            ) {
+                Text(
+                    text = result.rawResponse.ifBlank { "No response" },
+                    style = MaterialTheme.typography.bodyMedium,
+                    fontFamily = androidx.compose.ui.text.font.FontFamily.Monospace,
+                    modifier = Modifier.padding(8.dp)
+                )
+            }
+
+            if (result.parsedResponse != result.rawResponse && result.parsedResponse.isNotBlank()) {
+                Text(
+                    text = "Parsed: ${result.parsedResponse}",
+                    style = MaterialTheme.typography.bodyMedium,
+                    fontWeight = FontWeight.Medium,
+                    color = if (isError)
+                        MaterialTheme.colorScheme.error
+                    else
+                        MaterialTheme.colorScheme.primary
+                )
+            }
+
+            Text(
+                text = dateFormat.format(Date(result.timestamp)),
+                style = MaterialTheme.typography.labelSmall,
+                color = MaterialTheme.colorScheme.onSurfaceVariant
+            )
+        }
+    }
+}
+

app/src/main/java/com/manalejandro/odb2bluetooth/ui/screens/DiagnosticScreen.kt

@@ -0,0 +1,266 @@
+package com.manalejandro.odb2bluetooth.ui.screens
+
+import androidx.compose.foundation.layout.*
+import androidx.compose.foundation.lazy.LazyColumn
+import androidx.compose.foundation.lazy.items
+import androidx.compose.material.icons.Icons
+import androidx.compose.material.icons.filled.*
+import androidx.compose.material3.*
+import androidx.compose.runtime.*
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.text.font.FontWeight
+import androidx.compose.ui.unit.dp
+import com.manalejandro.odb2bluetooth.data.obd.ObdCommands
+import com.manalejandro.odb2bluetooth.ui.components.WarningDialog
+import com.manalejandro.odb2bluetooth.ui.viewmodel.CommandResult
+import com.manalejandro.odb2bluetooth.ui.viewmodel.MainViewModel
+import java.text.SimpleDateFormat
+import java.util.*
+
+/**
+ * Diagnostic screen - Run safe diagnostic tests
+ */
+@OptIn(ExperimentalMaterial3Api::class)
+@Composable
+fun DiagnosticScreen(
+    viewModel: MainViewModel,
+    onNavigateBack: () -> Unit
+) {
+    val commandHistory by viewModel.commandHistory.collectAsState()
+    val isLoading by viewModel.isLoading.collectAsState()
+    var showWarning by remember { mutableStateOf(false) }
+
+    if (showWarning) {
+        WarningDialog(
+            onDismiss = { showWarning = false },
+            onAccept = {
+                showWarning = false
+                viewModel.runDiagnosticTest()
+            },
+            title = "Diagnostic Test",
+            message = "This will run a series of safe, read-only diagnostic commands to gather information from your vehicle. No modifications will be made to your vehicle's systems.\n\nThe test will read:\n• Engine RPM\n• Vehicle Speed\n• Coolant Temperature\n• Throttle Position\n• Fuel Level\n• And more...\n\nDo you want to continue?"
+        )
+    }
+
+    Scaffold(
+        topBar = {
+            TopAppBar(
+                title = { Text("Quick Diagnostic") },
+                navigationIcon = {
+                    IconButton(onClick = onNavigateBack) {
+                        Icon(Icons.Default.ArrowBack, contentDescription = "Back")
+                    }
+                },
+                actions = {
+                    IconButton(onClick = { viewModel.clearHistory() }) {
+                        Icon(Icons.Default.Delete, contentDescription = "Clear history")
+                    }
+                },
+                colors = TopAppBarDefaults.topAppBarColors(
+                    containerColor = MaterialTheme.colorScheme.primaryContainer,
+                    titleContentColor = MaterialTheme.colorScheme.onPrimaryContainer
+                )
+            )
+        },
+        floatingActionButton = {
+            if (!isLoading) {
+                ExtendedFloatingActionButton(
+                    onClick = { showWarning = true },
+                    icon = { Icon(Icons.Default.PlayArrow, contentDescription = null) },
+                    text = { Text("Run Test") }
+                )
+            }
+        }
+    ) { paddingValues ->
+        Column(
+            modifier = Modifier
+                .fillMaxSize()
+                .padding(paddingValues)
+        ) {
+            // Info card
+            Card(
+                modifier = Modifier
+                    .fillMaxWidth()
+                    .padding(16.dp),
+                colors = CardDefaults.cardColors(
+                    containerColor = MaterialTheme.colorScheme.primaryContainer
+                )
+            ) {
+                Row(
+                    modifier = Modifier.padding(16.dp),
+                    horizontalArrangement = Arrangement.spacedBy(12.dp)
+                ) {
+                    Icon(
+                        imageVector = Icons.Default.Info,
+                        contentDescription = null,
+                        tint = MaterialTheme.colorScheme.primary
+                    )
+                    Column {
+                        Text(
+                            text = "Safe Diagnostic Test",
+                            style = MaterialTheme.typography.titleSmall,
+                            fontWeight = FontWeight.Bold,
+                            color = MaterialTheme.colorScheme.onPrimaryContainer
+                        )
+                        Text(
+                            text = "This test only reads data from your vehicle and will not make any modifications.",
+                            style = MaterialTheme.typography.bodySmall,
+                            color = MaterialTheme.colorScheme.onPrimaryContainer
+                        )
+                    }
+                }
+            }
+
+            // Loading indicator
+            if (isLoading) {
+                LinearProgressIndicator(
+                    modifier = Modifier.fillMaxWidth()
+                )
+            }
+
+            // Command history
+            if (commandHistory.isEmpty()) {
+                Box(
+                    modifier = Modifier
+                        .fillMaxSize()
+                        .padding(32.dp),
+                    contentAlignment = Alignment.Center
+                ) {
+                    Column(
+                        horizontalAlignment = Alignment.CenterHorizontally,
+                        verticalArrangement = Arrangement.spacedBy(16.dp)
+                    ) {
+                        Icon(
+                            imageVector = Icons.Default.Star,
+                            contentDescription = null,
+                            modifier = Modifier.size(64.dp),
+                            tint = MaterialTheme.colorScheme.onSurfaceVariant
+                        )
+                        Text(
+                            text = "No diagnostic data yet",
+                            style = MaterialTheme.typography.bodyLarge,
+                            color = MaterialTheme.colorScheme.onSurfaceVariant
+                        )
+                        Text(
+                            text = "Tap 'Run Test' to start",
+                            style = MaterialTheme.typography.bodySmall,
+                            color = MaterialTheme.colorScheme.onSurfaceVariant
+                        )
+                    }
+                }
+            } else {
+                LazyColumn(
+                    contentPadding = PaddingValues(16.dp),
+                    verticalArrangement = Arrangement.spacedBy(8.dp)
+                ) {
+                    items(commandHistory) { result ->
+                        DiagnosticResultCard(result)
+                    }
+                }
+            }
+        }
+    }
+}
+
+@Composable
+private fun DiagnosticResultCard(result: CommandResult) {
+    val dateFormat = remember { SimpleDateFormat("HH:mm:ss", Locale.getDefault()) }
+    val commandName = ObdCommands.SAFE_DIAGNOSTIC_COMMANDS
+        .find { it.command == result.command }?.name ?: result.command
+
+    val isError = result.parsedResponse.contains("Error", ignoreCase = true) ||
+                  result.parsedResponse.contains("NO DATA", ignoreCase = true)
+
+    ElevatedCard(
+        modifier = Modifier.fillMaxWidth()
+    ) {
+        Column(
+            modifier = Modifier
+                .fillMaxWidth()
+                .padding(16.dp),
+            verticalArrangement = Arrangement.spacedBy(8.dp)
+        ) {
+            Row(
+                modifier = Modifier.fillMaxWidth(),
+                horizontalArrangement = Arrangement.SpaceBetween,
+                verticalAlignment = Alignment.CenterVertically
+            ) {
+                Text(
+                    text = commandName,
+                    style = MaterialTheme.typography.titleMedium,
+                    fontWeight = FontWeight.SemiBold
+                )
+                if (isError) {
+                    Icon(
+                        imageVector = Icons.Default.Warning,
+                        contentDescription = null,
+                        tint = MaterialTheme.colorScheme.error,
+                        modifier = Modifier.size(20.dp)
+                    )
+                } else {
+                    Icon(
+                        imageVector = Icons.Default.Check,
+                        contentDescription = null,
+                        tint = MaterialTheme.colorScheme.primary,
+                        modifier = Modifier.size(20.dp)
+                    )
+                }
+            }
+
+            Divider()
+
+            Row(
+                modifier = Modifier.fillMaxWidth(),
+                horizontalArrangement = Arrangement.SpaceBetween
+            ) {
+                Text(
+                    text = "Command:",
+                    style = MaterialTheme.typography.bodySmall,
+                    color = MaterialTheme.colorScheme.onSurfaceVariant
+                )
+                Text(
+                    text = result.command,
+                    style = MaterialTheme.typography.bodySmall,
+                    fontWeight = FontWeight.Medium
+                )
+            }
+
+            Row(
+                modifier = Modifier.fillMaxWidth(),
+                horizontalArrangement = Arrangement.SpaceBetween
+            ) {
+                Text(
+                    text = "Response:",
+                    style = MaterialTheme.typography.bodySmall,
+                    color = MaterialTheme.colorScheme.onSurfaceVariant
+                )
+                Text(
+                    text = result.parsedResponse,
+                    style = MaterialTheme.typography.bodyMedium,
+                    fontWeight = FontWeight.Bold,
+                    color = if (isError)
+                        MaterialTheme.colorScheme.error
+                    else
+                        MaterialTheme.colorScheme.primary
+                )
+            }
+
+            if (result.rawResponse.isNotBlank()) {
+                Text(
+                    text = "Raw: ${result.rawResponse}",
+                    style = MaterialTheme.typography.bodySmall,
+                    color = MaterialTheme.colorScheme.onSurfaceVariant,
+                    fontFamily = androidx.compose.ui.text.font.FontFamily.Monospace
+                )
+            }
+
+            Text(
+                text = dateFormat.format(Date(result.timestamp)),
+                style = MaterialTheme.typography.labelSmall,
+                color = MaterialTheme.colorScheme.onSurfaceVariant
+            )
+        }
+    }
+}
+

app/src/main/java/com/manalejandro/odb2bluetooth/ui/screens/HomeScreen.kt

@@ -0,0 +1,231 @@
+package com.manalejandro.odb2bluetooth.ui.screens
+
+import androidx.compose.foundation.layout.*
+import androidx.compose.foundation.rememberScrollState
+import androidx.compose.foundation.verticalScroll
+import androidx.compose.material.icons.Icons
+import androidx.compose.material.icons.filled.*
+import androidx.compose.material3.*
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.collectAsState
+import androidx.compose.runtime.getValue
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.text.font.FontWeight
+import androidx.compose.ui.unit.dp
+import com.manalejandro.odb2bluetooth.data.bluetooth.BluetoothService
+import com.manalejandro.odb2bluetooth.ui.components.ConnectionStatusIndicator
+import com.manalejandro.odb2bluetooth.ui.viewmodel.MainViewModel
+
+/**
+ * Home screen - Main dashboard
+ */
+@OptIn(ExperimentalMaterial3Api::class)
+@Composable
+fun HomeScreen(
+    viewModel: MainViewModel,
+    onNavigateToBluetooth: () -> Unit,
+    onNavigateToVehicleSelection: () -> Unit,
+    onNavigateToDiagnostic: () -> Unit,
+    onNavigateToCustomCommand: () -> Unit
+) {
+    val connectionState by viewModel.bluetoothService.connectionState.collectAsState()
+    val selectedDevice by viewModel.selectedDevice.collectAsState()
+
+    val isConnected = connectionState == BluetoothService.ConnectionState.CONNECTED
+
+    Scaffold(
+        topBar = {
+            TopAppBar(
+                title = { Text("OBD2 Bluetooth") },
+                colors = TopAppBarDefaults.topAppBarColors(
+                    containerColor = MaterialTheme.colorScheme.primaryContainer,
+                    titleContentColor = MaterialTheme.colorScheme.onPrimaryContainer
+                )
+            )
+        }
+    ) { paddingValues ->
+        Column(
+            modifier = Modifier
+                .fillMaxSize()
+                .padding(paddingValues)
+                .verticalScroll(rememberScrollState())
+                .padding(16.dp),
+            verticalArrangement = Arrangement.spacedBy(16.dp)
+        ) {
+            // Connection status
+            ConnectionStatusIndicator(
+                isConnected = isConnected,
+                deviceName = selectedDevice?.name,
+                modifier = Modifier.fillMaxWidth()
+            )
+
+            // Welcome card
+            ElevatedCard(
+                modifier = Modifier.fillMaxWidth()
+            ) {
+                Column(
+                    modifier = Modifier.padding(16.dp),
+                    verticalArrangement = Arrangement.spacedBy(8.dp)
+                ) {
+                    Text(
+                        text = "Welcome to OBD2 Bluetooth",
+                        style = MaterialTheme.typography.headlineSmall,
+                        fontWeight = FontWeight.Bold
+                    )
+                    Text(
+                        text = "Connect to your vehicle's ELM327 adapter to read and send OBD2 commands.",
+                        style = MaterialTheme.typography.bodyMedium,
+                        color = MaterialTheme.colorScheme.onSurfaceVariant
+                    )
+                }
+            }
+
+            Text(
+                text = "Quick Actions",
+                style = MaterialTheme.typography.titleLarge,
+                fontWeight = FontWeight.Bold,
+                modifier = Modifier.padding(top = 8.dp)
+            )
+
+            // Bluetooth connection button
+            MenuCard(
+                title = "Bluetooth Connection",
+                description = if (isConnected)
+                    "Manage connection"
+                else
+                    "Connect to OBD2 device",
+                icon = Icons.Default.Phone,
+                onClick = onNavigateToBluetooth
+            )
+
+            // Vehicle selection button
+            MenuCard(
+                title = "Vehicle Database",
+                description = "Browse OBD signals by vehicle model",
+                icon = Icons.Default.Build,
+                onClick = onNavigateToVehicleSelection,
+                enabled = isConnected
+            )
+
+            // Diagnostic test button
+            MenuCard(
+                title = "Quick Diagnostic",
+                description = "Run safe diagnostic test",
+                icon = Icons.Default.Star,
+                onClick = onNavigateToDiagnostic,
+                enabled = isConnected
+            )
+
+            // Custom command button
+            MenuCard(
+                title = "Custom Commands",
+                description = "Send custom OBD2 commands",
+                icon = Icons.Default.Settings,
+                onClick = onNavigateToCustomCommand,
+                enabled = isConnected
+            )
+
+            // Safety notice
+            Card(
+                modifier = Modifier.fillMaxWidth(),
+                colors = CardDefaults.cardColors(
+                    containerColor = MaterialTheme.colorScheme.errorContainer
+                )
+            ) {
+                Row(
+                    modifier = Modifier.padding(16.dp),
+                    horizontalArrangement = Arrangement.spacedBy(12.dp)
+                ) {
+                    Icon(
+                        imageVector = Icons.Default.Warning,
+                        contentDescription = null,
+                        tint = MaterialTheme.colorScheme.error
+                    )
+                    Column {
+                        Text(
+                            text = "Safety Notice",
+                            style = MaterialTheme.typography.titleSmall,
+                            fontWeight = FontWeight.Bold,
+                            color = MaterialTheme.colorScheme.onErrorContainer
+                        )
+                        Text(
+                            text = "Sending incorrect commands can damage your vehicle. Use at your own risk.",
+                            style = MaterialTheme.typography.bodySmall,
+                            color = MaterialTheme.colorScheme.onErrorContainer
+                        )
+                    }
+                }
+            }
+        }
+    }
+}
+
+@Composable
+private fun MenuCard(
+    title: String,
+    description: String,
+    icon: androidx.compose.ui.graphics.vector.ImageVector,
+    onClick: () -> Unit,
+    enabled: Boolean = true
+) {
+    ElevatedCard(
+        onClick = onClick,
+        modifier = Modifier.fillMaxWidth(),
+        enabled = enabled
+    ) {
+        Row(
+            modifier = Modifier
+                .fillMaxWidth()
+                .padding(16.dp),
+            horizontalArrangement = Arrangement.spacedBy(16.dp),
+            verticalAlignment = Alignment.CenterVertically
+        ) {
+            Surface(
+                shape = MaterialTheme.shapes.medium,
+                color = if (enabled)
+                    MaterialTheme.colorScheme.primaryContainer
+                else
+                    MaterialTheme.colorScheme.surfaceVariant,
+                modifier = Modifier.size(56.dp)
+            ) {
+                Box(
+                    contentAlignment = Alignment.Center,
+                    modifier = Modifier.fillMaxSize()
+                ) {
+                    Icon(
+                        imageVector = icon,
+                        contentDescription = null,
+                        modifier = Modifier.size(32.dp),
+                        tint = if (enabled)
+                            MaterialTheme.colorScheme.onPrimaryContainer
+                        else
+                            MaterialTheme.colorScheme.onSurfaceVariant
+                    )
+                }
+            }
+
+            Column(
+                modifier = Modifier.weight(1f)
+            ) {
+                Text(
+                    text = title,
+                    style = MaterialTheme.typography.titleMedium,
+                    fontWeight = FontWeight.SemiBold
+                )
+                Text(
+                    text = description,
+                    style = MaterialTheme.typography.bodySmall,
+                    color = MaterialTheme.colorScheme.onSurfaceVariant
+                )
+            }
+
+            Icon(
+                imageVector = Icons.Default.KeyboardArrowRight,
+                contentDescription = null,
+                tint = MaterialTheme.colorScheme.onSurfaceVariant
+            )
+        }
+    }
+}
+

app/src/main/java/com/manalejandro/odb2bluetooth/ui/screens/VehicleSelectionScreen.kt

@@ -0,0 +1,414 @@
+package com.manalejandro.odb2bluetooth.ui.screens
+
+import androidx.compose.foundation.layout.*
+import androidx.compose.foundation.lazy.LazyColumn
+import androidx.compose.foundation.lazy.items
+import androidx.compose.material.icons.Icons
+import androidx.compose.material.icons.filled.*
+import androidx.compose.material3.*
+import androidx.compose.runtime.*
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.text.font.FontWeight
+import androidx.compose.ui.unit.dp
+import androidx.lifecycle.viewmodel.compose.viewModel
+import com.manalejandro.odb2bluetooth.data.database.dto.SignalDto
+import com.manalejandro.odb2bluetooth.data.database.dto.VehicleDto
+import com.manalejandro.odb2bluetooth.ui.components.WarningDialog
+import com.manalejandro.odb2bluetooth.ui.viewmodel.MainViewModel
+import com.manalejandro.odb2bluetooth.ui.viewmodel.VehicleViewModel
+
+/**
+ * Vehicle selection screen - Browse vehicles and their OBD signals
+ */
+@OptIn(ExperimentalMaterial3Api::class)
+@Composable
+fun VehicleSelectionScreen(
+    mainViewModel: MainViewModel,
+    onNavigateBack: () -> Unit
+) {
+    val vehicleViewModel: VehicleViewModel = viewModel()
+
+    val vehicles by vehicleViewModel.vehicles.collectAsState()
+    val selectedVehicle by vehicleViewModel.selectedVehicle.collectAsState()
+    val signals by vehicleViewModel.signals.collectAsState()
+    val searchQuery by vehicleViewModel.searchQuery.collectAsState()
+    val isLoading by vehicleViewModel.isLoading.collectAsState()
+
+    var searchText by remember { mutableStateOf("") }
+    var showWarning by remember { mutableStateOf(false) }
+    var selectedSignal by remember { mutableStateOf<SignalDto?>(null) }
+
+    if (showWarning && selectedSignal != null) {
+        WarningDialog(
+            onDismiss = {
+                showWarning = false
+                selectedSignal = null
+            },
+            onAccept = {
+                showWarning = false
+                selectedSignal?.command?.let { command ->
+                    mainViewModel.sendCommand(command)
+                }
+                selectedSignal = null
+            },
+            title = "Send OBD Command",
+            message = "You are about to send this command:\n\n" +
+                    "Signal: ${selectedSignal?.signalName}\n" +
+                    "Command: ${selectedSignal?.command}\n" +
+                    "Description: ${selectedSignal?.description ?: "N/A"}\n\n" +
+                    "⚠️ Warning: Sending commands can potentially affect your vehicle. " +
+                    "Make sure you understand what this command does.\n\n" +
+                    "Do you want to proceed?"
+        )
+    }
+
+    Scaffold(
+        topBar = {
+            TopAppBar(
+                title = { Text("Vehicle Database") },
+                navigationIcon = {
+                    IconButton(onClick = {
+                        if (selectedVehicle != null) {
+                            vehicleViewModel.clearSelection()
+                        } else {
+                            onNavigateBack()
+                        }
+                    }) {
+                        Icon(Icons.Default.ArrowBack, contentDescription = "Back")
+                    }
+                },
+                colors = TopAppBarDefaults.topAppBarColors(
+                    containerColor = MaterialTheme.colorScheme.primaryContainer,
+                    titleContentColor = MaterialTheme.colorScheme.onPrimaryContainer
+                )
+            )
+        }
+    ) { paddingValues ->
+        Column(
+            modifier = Modifier
+                .fillMaxSize()
+                .padding(paddingValues)
+        ) {
+            if (selectedVehicle == null) {
+                // Vehicle list view
+                Column(
+                    modifier = Modifier.fillMaxSize()
+                ) {
+                    // Search bar
+                    OutlinedTextField(
+                        value = searchText,
+                        onValueChange = {
+                            searchText = it
+                            vehicleViewModel.searchVehicles(it)
+                        },
+                        label = { Text("Search vehicles") },
+                        placeholder = { Text("Brand, model...") },
+                        leadingIcon = {
+                            Icon(Icons.Default.Search, contentDescription = null)
+                        },
+                        trailingIcon = {
+                            if (searchText.isNotEmpty()) {
+                                IconButton(onClick = {
+                                    searchText = ""
+                                    vehicleViewModel.searchVehicles("")
+                                }) {
+                                    Icon(Icons.Default.Clear, contentDescription = "Clear")
+                                }
+                            }
+                        },
+                        singleLine = true,
+                        modifier = Modifier
+                            .fillMaxWidth()
+                            .padding(16.dp)
+                    )
+
+                    if (isLoading) {
+                        LinearProgressIndicator(
+                            modifier = Modifier.fillMaxWidth()
+                        )
+                    }
+
+                    if (vehicles.isEmpty()) {
+                        Box(
+                            modifier = Modifier
+                                .fillMaxSize()
+                                .padding(32.dp),
+                            contentAlignment = Alignment.Center
+                        ) {
+                            Column(
+                                horizontalAlignment = Alignment.CenterHorizontally,
+                                verticalArrangement = Arrangement.spacedBy(16.dp)
+                            ) {
+                                Icon(
+                                    imageVector = Icons.Default.Build,
+                                    contentDescription = null,
+                                    modifier = Modifier.size(64.dp),
+                                    tint = MaterialTheme.colorScheme.onSurfaceVariant
+                                )
+                                Text(
+                                    text = "No vehicles found",
+                                    style = MaterialTheme.typography.bodyLarge,
+                                    color = MaterialTheme.colorScheme.onSurfaceVariant
+                                )
+                            }
+                        }
+                    } else {
+                        LazyColumn(
+                            contentPadding = PaddingValues(16.dp),
+                            verticalArrangement = Arrangement.spacedBy(8.dp)
+                        ) {
+                            items(vehicles) { vehicle ->
+                                VehicleCard(
+                                    vehicle = vehicle,
+                                    onClick = { vehicleViewModel.selectVehicle(vehicle) }
+                                )
+                            }
+                        }
+                    }
+                }
+            } else {
+                // Signal list view
+                Column(
+                    modifier = Modifier.fillMaxSize()
+                ) {
+                    // Vehicle info
+                    ElevatedCard(
+                        modifier = Modifier
+                            .fillMaxWidth()
+                            .padding(16.dp)
+                    ) {
+                        Column(
+                            modifier = Modifier.padding(16.dp),
+                            verticalArrangement = Arrangement.spacedBy(4.dp)
+                        ) {
+                            Text(
+                                text = selectedVehicle!!.brand,
+                                style = MaterialTheme.typography.labelLarge,
+                                color = MaterialTheme.colorScheme.primary
+                            )
+                            Text(
+                                text = selectedVehicle!!.fullName,
+                                style = MaterialTheme.typography.titleLarge,
+                                fontWeight = FontWeight.Bold
+                            )
+                            Text(
+                                text = "${selectedVehicle!!.signalCount} OBD signals available",
+                                style = MaterialTheme.typography.bodySmall,
+                                color = MaterialTheme.colorScheme.onSurfaceVariant
+                            )
+                        }
+                    }
+
+                    if (isLoading) {
+                        LinearProgressIndicator(
+                            modifier = Modifier.fillMaxWidth()
+                        )
+                    }
+
+                    if (signals.isEmpty()) {
+                        Box(
+                            modifier = Modifier
+                                .fillMaxSize()
+                                .padding(32.dp),
+                            contentAlignment = Alignment.Center
+                        ) {
+                            Column(
+                                horizontalAlignment = Alignment.CenterHorizontally,
+                                verticalArrangement = Arrangement.spacedBy(16.dp)
+                            ) {
+                                Icon(
+                                    imageVector = Icons.Default.Settings,
+                                    contentDescription = null,
+                                    modifier = Modifier.size(64.dp),
+                                    tint = MaterialTheme.colorScheme.onSurfaceVariant
+                                )
+                                Text(
+                                    text = "No signals available",
+                                    style = MaterialTheme.typography.bodyLarge,
+                                    color = MaterialTheme.colorScheme.onSurfaceVariant
+                                )
+                            }
+                        }
+                    } else {
+                        LazyColumn(
+                            contentPadding = PaddingValues(16.dp),
+                            verticalArrangement = Arrangement.spacedBy(8.dp)
+                        ) {
+                            items(signals) { signal ->
+                                SignalCard(
+                                    signal = signal,
+                                    onSend = {
+                                        selectedSignal = signal
+                                        showWarning = true
+                                    }
+                                )
+                            }
+                        }
+                    }
+                }
+            }
+        }
+    }
+}
+
+@Composable
+private fun VehicleCard(
+    vehicle: VehicleDto,
+    onClick: () -> Unit
+) {
+    ElevatedCard(
+        onClick = onClick,
+        modifier = Modifier.fillMaxWidth()
+    ) {
+        Row(
+            modifier = Modifier
+                .fillMaxWidth()
+                .padding(16.dp),
+            horizontalArrangement = Arrangement.spacedBy(12.dp),
+            verticalAlignment = Alignment.CenterVertically
+        ) {
+            Surface(
+                shape = MaterialTheme.shapes.medium,
+                color = MaterialTheme.colorScheme.primaryContainer,
+                modifier = Modifier.size(56.dp)
+            ) {
+                Box(
+                    contentAlignment = Alignment.Center,
+                    modifier = Modifier.fillMaxSize()
+                ) {
+                    Icon(
+                        imageVector = Icons.Default.Build,
+                        contentDescription = null,
+                        modifier = Modifier.size(32.dp),
+                        tint = MaterialTheme.colorScheme.onPrimaryContainer
+                    )
+                }
+            }
+
+            Column(
+                modifier = Modifier.weight(1f)
+            ) {
+                Text(
+                    text = vehicle.brand,
+                    style = MaterialTheme.typography.labelMedium,
+                    color = MaterialTheme.colorScheme.primary
+                )
+                Text(
+                    text = vehicle.model,
+                    style = MaterialTheme.typography.titleMedium,
+                    fontWeight = FontWeight.SemiBold
+                )
+                Text(
+                    text = "${vehicle.signalCount} signals • ${vehicle.generationCount} generations",
+                    style = MaterialTheme.typography.bodySmall,
+                    color = MaterialTheme.colorScheme.onSurfaceVariant
+                )
+            }
+
+            Icon(
+                imageVector = Icons.Default.KeyboardArrowRight,
+                contentDescription = null,
+                tint = MaterialTheme.colorScheme.onSurfaceVariant
+            )
+        }
+    }
+}
+
+@Composable
+private fun SignalCard(
+    signal: SignalDto,
+    onSend: () -> Unit
+) {
+    ElevatedCard(
+        modifier = Modifier.fillMaxWidth()
+    ) {
+        Column(
+            modifier = Modifier
+                .fillMaxWidth()
+                .padding(16.dp),
+            verticalArrangement = Arrangement.spacedBy(8.dp)
+        ) {
+            Row(
+                modifier = Modifier.fillMaxWidth(),
+                horizontalArrangement = Arrangement.SpaceBetween,
+                verticalAlignment = Alignment.CenterVertically
+            ) {
+                Column(modifier = Modifier.weight(1f)) {
+                    Text(
+                        text = signal.signalName,
+                        style = MaterialTheme.typography.titleMedium,
+                        fontWeight = FontWeight.SemiBold
+                    )
+                    Text(
+                        text = signal.signalId,
+                        style = MaterialTheme.typography.bodySmall,
+                        color = MaterialTheme.colorScheme.primary,
+                        fontFamily = androidx.compose.ui.text.font.FontFamily.Monospace
+                    )
+                }
+                Button(
+                    onClick = onSend,
+                    enabled = signal.command != null
+                ) {
+                    Icon(
+                        imageVector = Icons.Default.Send,
+                        contentDescription = null,
+                        modifier = Modifier.size(18.dp)
+                    )
+                }
+            }
+
+            if (signal.description != null) {
+                Text(
+                    text = signal.description,
+                    style = MaterialTheme.typography.bodySmall,
+                    color = MaterialTheme.colorScheme.onSurfaceVariant
+                )
+            }
+
+            Divider()
+
+            Row(
+                modifier = Modifier.fillMaxWidth(),
+                horizontalArrangement = Arrangement.spacedBy(16.dp)
+            ) {
+                signal.command?.let {
+                    InfoChip("Command", it)
+                }
+                signal.unit?.let {
+                    InfoChip("Unit", it)
+                }
+                signal.frequency?.let {
+                    InfoChip("Freq", "${it}Hz")
+                }
+            }
+        }
+    }
+}
+
+@Composable
+private fun InfoChip(label: String, value: String) {
+    Surface(
+        shape = MaterialTheme.shapes.small,
+        color = MaterialTheme.colorScheme.secondaryContainer
+    ) {
+        Row(
+            modifier = Modifier.padding(horizontal = 8.dp, vertical = 4.dp),
+            horizontalArrangement = Arrangement.spacedBy(4.dp)
+        ) {
+            Text(
+                text = "$label:",
+                style = MaterialTheme.typography.labelSmall,
+                color = MaterialTheme.colorScheme.onSecondaryContainer
+            )
+            Text(
+                text = value,
+                style = MaterialTheme.typography.labelSmall,
+                fontWeight = FontWeight.Bold,
+                color = MaterialTheme.colorScheme.onSecondaryContainer
+            )
+        }
+    }
+}
+

app/src/main/java/com/manalejandro/odb2bluetooth/ui/theme/Color.kt

@@ -0,0 +1,19 @@
+package com.manalejandro.odb2bluetooth.ui.theme
+
+import androidx.compose.ui.graphics.Color
+
+// Light theme colors - Modern tech/automotive inspired
+val Blue80 = Color(0xFF80C7FF)
+val BlueGrey80 = Color(0xFFB0C7D6)
+val Teal80 = Color(0xFF76D9D9)
+
+val Blue40 = Color(0xFF0066CC)
+val BlueGrey40 = Color(0xFF546E7A)
+val Teal40 = Color(0xFF00897B)
+
+// Additional custom colors
+val Success = Color(0xFF4CAF50)
+val Warning = Color(0xFFFF9800)
+val Error = Color(0xFFF44336)
+val Info = Color(0xFF2196F3)
+

app/src/main/java/com/manalejandro/odb2bluetooth/ui/theme/Theme.kt

@@ -0,0 +1,60 @@
+package com.manalejandro.odb2bluetooth.ui.theme
+
+import android.app.Activity
+import android.os.Build
+import androidx.compose.foundation.isSystemInDarkTheme
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.darkColorScheme
+import androidx.compose.material3.dynamicDarkColorScheme
+import androidx.compose.material3.dynamicLightColorScheme
+import androidx.compose.material3.lightColorScheme
+import androidx.compose.runtime.Composable
+import androidx.compose.ui.platform.LocalContext
+
+private val DarkColorScheme = darkColorScheme(
+    primary = Blue80,
+    secondary = BlueGrey80,
+    tertiary = Teal80,
+    error = Error
+)
+
+private val LightColorScheme = lightColorScheme(
+    primary = Blue40,
+    secondary = BlueGrey40,
+    tertiary = Teal40,
+    error = Error
+
+    /* Other default colors to override
+    background = Color(0xFFFFFBFE),
+    surface = Color(0xFFFFFBFE),
+    onPrimary = Color.White,
+    onSecondary = Color.White,
+    onTertiary = Color.White,
+    onBackground = Color(0xFF1C1B1F),
+    onSurface = Color(0xFF1C1B1F),
+    */
+)
+
+@Composable
+fun ODB2BluetoothTheme(
+    darkTheme: Boolean = isSystemInDarkTheme(),
+    // Dynamic color is available on Android 12+
+    dynamicColor: Boolean = true,
+    content: @Composable () -> Unit
+) {
+    val colorScheme = when {
+        dynamicColor && Build.VERSION.SDK_INT >= Build.VERSION_CODES.S -> {
+            val context = LocalContext.current
+            if (darkTheme) dynamicDarkColorScheme(context) else dynamicLightColorScheme(context)
+        }
+
+        darkTheme -> DarkColorScheme
+        else -> LightColorScheme
+    }
+
+    MaterialTheme(
+        colorScheme = colorScheme,
+        typography = Typography,
+        content = content
+    )
+}

app/src/main/java/com/manalejandro/odb2bluetooth/ui/theme/Type.kt

@@ -0,0 +1,34 @@
+package com.manalejandro.odb2bluetooth.ui.theme
+
+import androidx.compose.material3.Typography
+import androidx.compose.ui.text.TextStyle
+import androidx.compose.ui.text.font.FontFamily
+import androidx.compose.ui.text.font.FontWeight
+import androidx.compose.ui.unit.sp
+
+// Set of Material typography styles to start with
+val Typography = Typography(
+    bodyLarge = TextStyle(
+        fontFamily = FontFamily.Default,
+        fontWeight = FontWeight.Normal,
+        fontSize = 16.sp,
+        lineHeight = 24.sp,
+        letterSpacing = 0.5.sp
+    )
+    /* Other default text styles to override
+    titleLarge = TextStyle(
+        fontFamily = FontFamily.Default,
+        fontWeight = FontWeight.Normal,
+        fontSize = 22.sp,
+        lineHeight = 28.sp,
+        letterSpacing = 0.sp
+    ),
+    labelSmall = TextStyle(
+        fontFamily = FontFamily.Default,
+        fontWeight = FontWeight.Medium,
+        fontSize = 11.sp,
+        lineHeight = 16.sp,
+        letterSpacing = 0.5.sp
+    )
+    */
+)

app/src/main/java/com/manalejandro/odb2bluetooth/ui/viewmodel/MainViewModel.kt

@@ -0,0 +1,168 @@
+package com.manalejandro.odb2bluetooth.ui.viewmodel
+
+import android.app.Application
+import android.bluetooth.BluetoothDevice
+import androidx.lifecycle.AndroidViewModel
+import androidx.lifecycle.viewModelScope
+import com.manalejandro.odb2bluetooth.data.bluetooth.BluetoothService
+import com.manalejandro.odb2bluetooth.data.database.ObdDatabase
+import com.manalejandro.odb2bluetooth.data.obd.ObdCommand
+import com.manalejandro.odb2bluetooth.data.obd.ObdCommands
+import com.manalejandro.odb2bluetooth.data.repository.ObdRepository
+import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.flow.StateFlow
+import kotlinx.coroutines.launch
+
+/**
+ * Main ViewModel for Bluetooth connection and OBD communication
+ */
+class MainViewModel(application: Application) : AndroidViewModel(application) {
+
+    private val database = ObdDatabase.getDatabase(application)
+    val repository = ObdRepository(
+        database.vehicleDao(),
+        database.obdSignalDao(),
+        database.dtcCodeDao()
+    )
+
+    val bluetoothService = BluetoothService()
+
+    private val _pairedDevices = MutableStateFlow<List<BluetoothDevice>>(emptyList())
+    val pairedDevices: StateFlow<List<BluetoothDevice>> = _pairedDevices
+
+    private val _selectedDevice = MutableStateFlow<BluetoothDevice?>(null)
+    val selectedDevice: StateFlow<BluetoothDevice?> = _selectedDevice
+
+    private val _commandHistory = MutableStateFlow<List<CommandResult>>(emptyList())
+    val commandHistory: StateFlow<List<CommandResult>> = _commandHistory
+
+    private val _isLoading = MutableStateFlow(false)
+    val isLoading: StateFlow<Boolean> = _isLoading
+
+    private val _errorMessage = MutableStateFlow<String?>(null)
+    val errorMessage: StateFlow<String?> = _errorMessage
+
+    /**
+     * Load paired Bluetooth devices
+     */
+    fun loadPairedDevices() {
+        try {
+            _pairedDevices.value = bluetoothService.getPairedDevices()
+        } catch (e: SecurityException) {
+            _errorMessage.value = "Bluetooth permission denied"
+        }
+    }
+
+    /**
+     * Connect to a Bluetooth device
+     */
+    fun connectToDevice(device: BluetoothDevice) {
+        viewModelScope.launch {
+            _isLoading.value = true
+            _selectedDevice.value = device
+
+            bluetoothService.connect(device).fold(
+                onSuccess = {
+                    _errorMessage.value = null
+                },
+                onFailure = { error ->
+                    _errorMessage.value = "Connection failed: ${error.message}"
+                    _selectedDevice.value = null
+                }
+            )
+
+            _isLoading.value = false
+        }
+    }
+
+    /**
+     * Disconnect from current device
+     */
+    fun disconnect() {
+        bluetoothService.disconnect()
+        _selectedDevice.value = null
+        _commandHistory.value = emptyList()
+    }
+
+    /**
+     * Send a command to the OBD device
+     */
+    fun sendCommand(command: String) {
+        viewModelScope.launch {
+            _isLoading.value = true
+
+            bluetoothService.sendCommand(command).fold(
+                onSuccess = { response ->
+                    val parsed = ObdCommands.parseResponse(command, response) ?: response
+                    addCommandToHistory(command, response, parsed)
+                    _errorMessage.value = null
+                },
+                onFailure = { error ->
+                    _errorMessage.value = "Command failed: ${error.message}"
+                    addCommandToHistory(command, "", "Error: ${error.message}")
+                }
+            )
+
+            _isLoading.value = false
+        }
+    }
+
+    /**
+     * Run generic safe diagnostic test
+     */
+    fun runDiagnosticTest() {
+        viewModelScope.launch {
+            _commandHistory.value = emptyList()
+
+            for (cmd in ObdCommands.SAFE_DIAGNOSTIC_COMMANDS) {
+                sendCommand(cmd.command)
+                kotlinx.coroutines.delay(500) // Wait between commands
+            }
+        }
+    }
+
+    /**
+     * Clear command history
+     */
+    fun clearHistory() {
+        _commandHistory.value = emptyList()
+    }
+
+    /**
+     * Clear error message
+     */
+    fun clearError() {
+        _errorMessage.value = null
+    }
+
+    private fun addCommandToHistory(command: String, rawResponse: String, parsedResponse: String) {
+        val history = _commandHistory.value.toMutableList()
+        history.add(
+            0, // Add to beginning
+            CommandResult(
+                command = command,
+                rawResponse = rawResponse,
+                parsedResponse = parsedResponse,
+                timestamp = System.currentTimeMillis()
+            )
+        )
+        // Keep only last 50 commands
+        _commandHistory.value = history.take(50)
+    }
+
+    override fun onCleared() {
+        super.onCleared()
+        bluetoothService.disconnect()
+    }
+}
+
+/**
+ * Data class representing a command result
+ */
+data class CommandResult(
+    val command: String,
+    val rawResponse: String,
+    val parsedResponse: String,
+    val timestamp: Long
+)
+

app/src/main/java/com/manalejandro/odb2bluetooth/ui/viewmodel/VehicleViewModel.kt

@@ -0,0 +1,109 @@
+package com.manalejandro.odb2bluetooth.ui.viewmodel
+
+import android.app.Application
+import androidx.lifecycle.AndroidViewModel
+import androidx.lifecycle.viewModelScope
+import com.manalejandro.odb2bluetooth.data.database.ObdDatabase
+import com.manalejandro.odb2bluetooth.data.database.dto.SignalDto
+import com.manalejandro.odb2bluetooth.data.database.dto.VehicleDto
+import com.manalejandro.odb2bluetooth.data.repository.ObdRepository
+import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.flow.StateFlow
+import kotlinx.coroutines.flow.collectLatest
+import kotlinx.coroutines.launch
+
+/**
+ * ViewModel for vehicle selection and signal browsing
+ */
+class VehicleViewModel(application: Application) : AndroidViewModel(application) {
+
+    private val database = ObdDatabase.getDatabase(application)
+    private val repository = ObdRepository(
+        database.vehicleDao(),
+        database.obdSignalDao(),
+        database.dtcCodeDao()
+    )
+
+    private val _vehicles = MutableStateFlow<List<VehicleDto>>(emptyList())
+    val vehicles: StateFlow<List<VehicleDto>> = _vehicles
+
+    private val _selectedVehicle = MutableStateFlow<VehicleDto?>(null)
+    val selectedVehicle: StateFlow<VehicleDto?> = _selectedVehicle
+
+    private val _signals = MutableStateFlow<List<SignalDto>>(emptyList())
+    val signals: StateFlow<List<SignalDto>> = _signals
+
+    private val _searchQuery = MutableStateFlow("")
+    val searchQuery: StateFlow<String> = _searchQuery
+
+    private val _isLoading = MutableStateFlow(false)
+    val isLoading: StateFlow<Boolean> = _isLoading
+
+    init {
+        loadVehicles()
+    }
+
+    /**
+     * Load all vehicles from database
+     */
+    private fun loadVehicles() {
+        viewModelScope.launch {
+            _isLoading.value = true
+            repository.getAllVehicles().collectLatest { vehicleList ->
+                _vehicles.value = vehicleList
+                _isLoading.value = false
+            }
+        }
+    }
+
+    /**
+     * Search vehicles by query
+     */
+    fun searchVehicles(query: String) {
+        _searchQuery.value = query
+        viewModelScope.launch {
+            _isLoading.value = true
+            if (query.isBlank()) {
+                repository.getAllVehicles().collectLatest { vehicleList ->
+                    _vehicles.value = vehicleList
+                    _isLoading.value = false
+                }
+            } else {
+                repository.searchVehicles(query).collectLatest { vehicleList ->
+                    _vehicles.value = vehicleList
+                    _isLoading.value = false
+                }
+            }
+        }
+    }
+
+    /**
+     * Select a vehicle and load its signals
+     */
+    fun selectVehicle(vehicle: VehicleDto) {
+        _selectedVehicle.value = vehicle
+        loadSignalsForVehicle(vehicle.modelId)
+    }
+
+    /**
+     * Clear vehicle selection
+     */
+    fun clearSelection() {
+        _selectedVehicle.value = null
+        _signals.value = emptyList()
+    }
+
+    /**
+     * Load signals for a specific vehicle
+     */
+    private fun loadSignalsForVehicle(modelId: Int) {
+        viewModelScope.launch {
+            _isLoading.value = true
+            repository.getSignalsByModel(modelId).collectLatest { signalList ->
+                _signals.value = signalList
+                _isLoading.value = false
+            }
+        }
+    }
+}
+

app/src/main/res/drawable/ic_launcher_background.xml

@@ -0,0 +1,170 @@
+<?xml version="1.0" encoding="utf-8"?>
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="108dp"
+    android:height="108dp"
+    android:viewportWidth="108"
+    android:viewportHeight="108">
+    <path
+        android:fillColor="#3DDC84"
+        android:pathData="M0,0h108v108h-108z" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M9,0L9,108"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M19,0L19,108"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M29,0L29,108"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M39,0L39,108"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M49,0L49,108"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M59,0L59,108"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M69,0L69,108"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M79,0L79,108"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M89,0L89,108"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M99,0L99,108"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M0,9L108,9"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M0,19L108,19"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M0,29L108,29"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M0,39L108,39"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M0,49L108,49"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M0,59L108,59"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M0,69L108,69"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M0,79L108,79"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M0,89L108,89"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M0,99L108,99"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M19,29L89,29"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M19,39L89,39"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M19,49L89,49"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M19,59L89,59"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M19,69L89,69"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M19,79L89,79"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M29,19L29,89"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M39,19L39,89"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M49,19L49,89"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M59,19L59,89"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M69,19L69,89"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M79,19L79,89"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+</vector>

app/src/main/res/drawable/ic_launcher_foreground.xml

@@ -0,0 +1,30 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:aapt="http://schemas.android.com/aapt"
+    android:width="108dp"
+    android:height="108dp"
+    android:viewportWidth="108"
+    android:viewportHeight="108">
+    <path android:pathData="M31,63.928c0,0 6.4,-11 12.1,-13.1c7.2,-2.6 26,-1.4 26,-1.4l38.1,38.1L107,108.928l-32,-1L31,63.928z">
+        <aapt:attr name="android:fillColor">
+            <gradient
+                android:endX="85.84757"
+                android:endY="92.4963"
+                android:startX="42.9492"
+                android:startY="49.59793"
+                android:type="linear">
+                <item
+                    android:color="#44000000"
+                    android:offset="0.0" />
+                <item
+                    android:color="#00000000"
+                    android:offset="1.0" />
+            </gradient>
+        </aapt:attr>
+    </path>
+    <path
+        android:fillColor="#FFFFFF"
+        android:fillType="nonZero"
+        android:pathData="M65.3,45.828l3.8,-6.6c0.2,-0.4 0.1,-0.9 -0.3,-1.1c-0.4,-0.2 -0.9,-0.1 -1.1,0.3l-3.9,6.7c-6.3,-2.8 -13.4,-2.8 -19.7,0l-3.9,-6.7c-0.2,-0.4 -0.7,-0.5 -1.1,-0.3C38.8,38.328 38.7,38.828 38.9,39.228l3.8,6.6C36.2,49.428 31.7,56.028 31,63.928h46C76.3,56.028 71.8,49.428 65.3,45.828zM43.4,57.328c-0.8,0 -1.5,-0.5 -1.8,-1.2c-0.3,-0.7 -0.1,-1.5 0.4,-2.1c0.5,-0.5 1.4,-0.7 2.1,-0.4c0.7,0.3 1.2,1 1.2,1.8C45.3,56.528 44.5,57.328 43.4,57.328L43.4,57.328zM64.6,57.328c-0.8,0 -1.5,-0.5 -1.8,-1.2s-0.1,-1.5 0.4,-2.1c0.5,-0.5 1.4,-0.7 2.1,-0.4c0.7,0.3 1.2,1 1.2,1.8C66.5,56.528 65.6,57.328 64.6,57.328L64.6,57.328z"
+        android:strokeWidth="1"
+        android:strokeColor="#00000000" />
+</vector>

app/src/main/res/mipmap-anydpi-v26/ic_launcher.xml

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="utf-8"?>
+<adaptive-icon xmlns:android="http://schemas.android.com/apk/res/android">
+    <background android:drawable="@drawable/ic_launcher_background" />
+    <foreground android:drawable="@drawable/ic_launcher_foreground" />
+    <monochrome android:drawable="@drawable/ic_launcher_foreground" />
+</adaptive-icon>

app/src/main/res/mipmap-anydpi-v26/ic_launcher_round.xml

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="utf-8"?>
+<adaptive-icon xmlns:android="http://schemas.android.com/apk/res/android">
+    <background android:drawable="@drawable/ic_launcher_background" />
+    <foreground android:drawable="@drawable/ic_launcher_foreground" />
+    <monochrome android:drawable="@drawable/ic_launcher_foreground" />
+</adaptive-icon>

app/src/main/res/values/colors.xml

@@ -0,0 +1,10 @@
+<?xml version="1.0" encoding="utf-8"?>
+<resources>
+    <color name="purple_200">#FFBB86FC</color>
+    <color name="purple_500">#FF6200EE</color>
+    <color name="purple_700">#FF3700B3</color>
+    <color name="teal_200">#FF03DAC5</color>
+    <color name="teal_700">#FF018786</color>
+    <color name="black">#FF000000</color>
+    <color name="white">#FFFFFFFF</color>
+</resources>

app/src/main/res/values/strings.xml

@@ -0,0 +1,4 @@
+<resources>
+    <string name="app_name">OBD2 Bluetooth</string>
+</resources>
+

app/src/main/res/values/themes.xml

@@ -0,0 +1,5 @@
+<?xml version="1.0" encoding="utf-8"?>
+<resources>
+
+    <style name="Theme.ODB2Bluetooth" parent="android:Theme.Material.Light.NoActionBar" />
+</resources>

app/src/main/res/xml/backup_rules.xml

@@ -0,0 +1,13 @@
+<?xml version="1.0" encoding="utf-8"?><!--
+   Sample backup rules file; uncomment and customize as necessary.
+   See https://developer.android.com/guide/topics/data/autobackup
+   for details.
+   Note: This file is ignored for devices older than API 31
+   See https://developer.android.com/about/versions/12/backup-restore
+-->
+<full-backup-content>
+    <!--
+   <include domain="sharedpref" path="."/>
+   <exclude domain="sharedpref" path="device.xml"/>
+-->
+</full-backup-content>

app/src/main/res/xml/data_extraction_rules.xml

@@ -0,0 +1,19 @@
+<?xml version="1.0" encoding="utf-8"?><!--
+   Sample data extraction rules file; uncomment and customize as necessary.
+   See https://developer.android.com/about/versions/12/backup-restore#xml-changes
+   for details.
+-->
+<data-extraction-rules>
+    <cloud-backup>
+        <!-- TODO: Use <include> and <exclude> to control what is backed up.
+        <include .../>
+        <exclude .../>
+        -->
+    </cloud-backup>
+    <!--
+    <device-transfer>
+        <include .../>
+        <exclude .../>
+    </device-transfer>
+    -->
+</data-extraction-rules>

app/src/test/java/com/manalejandro/odb2bluetooth/ExampleUnitTest.kt

@@ -0,0 +1,17 @@
+package com.manalejandro.odb2bluetooth
+
+import org.junit.Test
+
+import org.junit.Assert.*
+
+/**
+ * Example local unit test, which will execute on the development machine (host).
+ *
+ * See [testing documentation](http://d.android.com/tools/testing).
+ */
+class ExampleUnitTest {
+    @Test
+    fun addition_isCorrect() {
+        assertEquals(4, 2 + 2)
+    }
+}