fix: relay pins G1/G2, OTA CCCD+retry, single version source

- Relay pins: G39→G1, G38→G2
- BUNDLED_FIRMWARE_VERSION → SylDaVersions.SERVER (version.txt)
- OTA: explicit CCCD descriptor write for Android 13+
- OTA: start packet retry (previously no retry, blocked by pending CCCD)
- OTA: firmware path device-mode-aware (server/client subdirs)
- Removed stale root firmware.bin, flashMethodGroup, dialog_overwrite_confirm
- PrefsHelper: serverUUID/clientUUID persistence

.gitignore

@@ -1,3 +1,7 @@
+# Generated from version.txt
+src/version.h
+android/app/src/main/java/nl/eddydevink/sylda/SylDaVersions.kt
+
 # PlatformIO
 .pio/
 .pioenvs/
@@ -43,4 +47,18 @@ codereview.md
 DC3-24V*.md
 DC3-24V*.pdf
 esplibalternatief.md
+docs/handleiding.md
 release/
+releases/
+
+# Test/debug firmware files
+src/blink.cpp
+src/c1.cpp
+src/get_mac.cpp
+src/min_cli.cpp
+src/min_srv.cpp
+src/s1.cpp
+src/test_*.cpp
+
+# Python cache
+scripts/__pycache__/

android/app/build.gradle

@@ -8,9 +8,6 @@ def hasSigningConfig = signingPropsFile.exists()
 
 android {
     namespace 'nl.eddydevink.sylda'
-    // compileSdk/targetSdk stays on 34 (Android 14) by deliberate choice. The target audience
-    // consists of physically disabled users who are very reluctant to update their phones. Staying
-    // on API 34 maximises device compatibility. Re-evaluate when the user base has migrated.
     compileSdk 34
 
     if (hasSigningConfig) {
@@ -59,6 +56,31 @@ android {
     }
 }
 
+task generateSylDaVersions {
+    def versionFile = rootProject.file('../version.txt')
+    def outputFile = file('src/main/java/nl/eddydevink/sylda/SylDaVersions.kt')
+
+    inputs.file(versionFile)
+    outputs.file(outputFile)
+
+    doLast {
+        def versions = [:]
+        versionFile.eachLine { line ->
+            def parts = line.trim().split('=')
+            if (parts.length == 2) versions[parts[0].trim()] = parts[1].trim()
+        }
+        outputFile.text = """// Auto-generated from version.txt — DO NOT EDIT
+package nl.eddydevink.sylda
+
+object SylDaVersions {
+    const val SERVER = "${versions.server}"
+    const val CLIENT = "${versions.client}"
+}
+"""
+    }
+}
+preBuild.dependsOn generateSylDaVersions
+
 dependencies {
     implementation 'androidx.core:core-ktx:1.12.0'
     implementation 'androidx.appcompat:appcompat:1.6.1'

android/app/src/main/java/nl/eddydevink/sylda/BleRelayManager.kt

@@ -6,6 +6,7 @@ import android.annotation.SuppressLint
 import android.bluetooth.BluetoothAdapter
 import android.bluetooth.BluetoothGatt
 import android.bluetooth.BluetoothGattCharacteristic
+import android.bluetooth.BluetoothGattDescriptor
 import android.bluetooth.BluetoothProfile
 import android.bluetooth.le.ScanCallback
 import android.bluetooth.le.ScanFilter
@@ -37,6 +38,7 @@ class BleRelayManager(
         private val UUID_CHAR_UUID: UUID = UUID.fromString("beb5483e-36e1-4688-b7f5-ea07361f26d9")
         private val VERSION_UUID: UUID = UUID.fromString("beb5483e-36e1-4688-b7f5-ea07361f26db")
         private val OTA_UUID: UUID = UUID.fromString("beb5483e-36e1-4688-b7f5-ea07361f26da")
+        private val OTA_CCCD_UUID: UUID = UUID.fromString("00002902-0000-1000-8000-00805f9b34fb")
 
         private const val SCAN_TIMEOUT_MS = 30000L
         private const val RECONNECT_DELAY_MS = 2000L
@@ -206,7 +208,18 @@ class BleRelayManager(
     fun enableOtaNotifications(): Boolean {
         val char = otaCharacteristic ?: return false
         val gatt = bluetoothGatt ?: return false
-        return gatt.setCharacteristicNotification(char, true)
+        if (!gatt.setCharacteristicNotification(char, true)) {
+            Log.e(TAG, "setCharacteristicNotification returned false")
+            return false
+        }
+        val desc = char.getDescriptor(OTA_CCCD_UUID)
+        if (desc != null) {
+            desc.value = BluetoothGattDescriptor.ENABLE_NOTIFICATION_VALUE
+            if (!gatt.writeDescriptor(desc)) {
+                Log.w(TAG, "writeDescriptor for CCCD returned false")
+            }
+        }
+        return true
     }
 
     fun hasOtaCharacteristic(): Boolean {
@@ -259,6 +272,7 @@ class BleRelayManager(
                 bluetoothGatt = null
                 relayCharacteristic = null
                 seq = 1
+                triedAddresses.clear()
                 handler.postDelayed(scanRunnable, RECONNECT_DELAY_MS)
             }
         }
@@ -369,7 +383,8 @@ class BleRelayManager(
         val prefs = PrefsHelper.getPrefs(context)
         val hexKey = prefs.getString(PrefsHelper.PREF_KEY, null)
         hmacKey = hexKey?.let { hexStringToBytes(it) }
-        val hexUuid = prefs.getString(PrefsHelper.PREF_UUID, null)
+        val hexUuid = PrefsHelper.getServerUuid(context)
+            ?: prefs.getString(PrefsHelper.PREF_UUID, null)
         deviceUuid = hexUuid?.let { hexStringToBytes(it) }
         seq = prefs.getInt(PrefsHelper.PREF_SEQ, 1).coerceAtMost(PrefsHelper.SEQ_MAX)
         Log.d(TAG, "HMAC key loaded: ${hmacKey?.size ?: "none"} bytes, UUID: ${deviceUuid?.size ?: "none"} bytes, seq=$seq")

android/app/src/main/java/nl/eddydevink/sylda/EspFlasher.kt

@@ -28,6 +28,11 @@ class EspFlasher(private val context: Context) {
         fun onProgress(percent: Int, message: String)
     }
 
+    private fun assetPath(baseName: String): String {
+        val prefix = if (PrefsHelper.getDeviceMode(context) == "client") "client/" else "server/"
+        return "firmware/$prefix$baseName"
+    }
+
     suspend fun flashDevice(usbManager: UsbManager, device: UsbDevice, callback: FlashCallback) {
         try {
             withContext(kotlinx.coroutines.Dispatchers.IO) {
@@ -77,10 +82,10 @@ class EspFlasher(private val context: Context) {
             coroutineContext.ensureActive()
 
             val assets = context.assets
-            val bootloader = assets.open("firmware/bootloader.bin").readBytes()
-            val partitions = assets.open("firmware/partitions.bin").readBytes()
-            val bootApp0 = assets.open("firmware/boot_app0.bin").readBytes()
-            val firmware = assets.open("firmware/firmware.bin").readBytes()
+            val bootloader = assets.open(assetPath("bootloader.bin")).readBytes()
+            val partitions = assets.open(assetPath("partitions.bin")).readBytes()
+            val bootApp0 = assets.open(assetPath("boot_app0.bin")).readBytes()
+            val firmware = assets.open(assetPath("firmware.bin")).readBytes()
 
             val steps = listOf(
                 FlashStep(R.string.flash_step_bootloader, 0x0, bootloader, 30, 10, false),

android/app/src/main/java/nl/eddydevink/sylda/MainActivity.kt

@@ -23,7 +23,6 @@ class MainActivity : AppCompatActivity(), BleCallbacks {
         private const val REQUEST_SETTINGS = 1
         private const val POST_SETTINGS_RESCAN_MS = 500L
         private const val ON_RESUME_SCAN_DELAY_MS = 300L
-        private const val BUNDLED_FIRMWARE_VERSION = "6"
     }
 
     private lateinit var manager: BleRelayManager
@@ -41,8 +40,9 @@ class MainActivity : AppCompatActivity(), BleCallbacks {
                 statusText.text = getString(R.string.status_connected)
                 setupRelayButton()
                 setupRelay2Button()
-                relay1Button.isEnabled = true
-                relay2Button.isEnabled = true
+                val isServer = PrefsHelper.getDeviceMode(this@MainActivity) == "server"
+                relay1Button.isEnabled = isServer
+                relay2Button.isEnabled = isServer
             }
             BleStatus.Disconnected -> {
                 statusText.text = getString(R.string.status_connecting)
@@ -92,7 +92,7 @@ class MainActivity : AppCompatActivity(), BleCallbacks {
         setContentView(R.layout.activity_main)
 
         manager = BleRelayManager(this, this)
-        manager.setAppVersion(BUNDLED_FIRMWARE_VERSION)
+        manager.setAppVersion(SylDaVersions.SERVER)
 
         statusText = findViewById(R.id.statusText)
         relay1Button = findViewById(R.id.relay1Button)
@@ -107,6 +107,9 @@ class MainActivity : AppCompatActivity(), BleCallbacks {
         }
         setupRelayButton()
         setupRelay2Button()
+        val isServer = PrefsHelper.getDeviceMode(this) == "server"
+        relay1Button.isEnabled = isServer
+        relay2Button.isEnabled = isServer
     }
 
     @Deprecated("Deprecated in Java")
@@ -227,11 +230,9 @@ class MainActivity : AppCompatActivity(), BleCallbacks {
     override fun onFirmwareVersion(espVersion: String, appVersion: String) {
         runOnUiThread {
             if (isFinishing || isDestroyed || !lifecycle.currentState.isAtLeast(androidx.lifecycle.Lifecycle.State.RESUMED)) return@runOnUiThread
-            if (espVersion.isEmpty() || espVersion != appVersion) {
+            if (espVersion.isNotEmpty() && espVersion != appVersion) {
                 Toast.makeText(this, getString(R.string.ota_update_available), Toast.LENGTH_SHORT).show()
                 startActivityForResult(Intent(this, SettingsActivity::class.java), REQUEST_SETTINGS)
-            } else {
-                Toast.makeText(this, getString(R.string.ota_up_to_date), Toast.LENGTH_SHORT).show()
             }
         }
     }

android/app/src/main/java/nl/eddydevink/sylda/OtaManager.kt

@@ -39,13 +39,14 @@ class OtaManager(
         return minOf(maxOf(mtu - 3 - 4, 20), OTA_ESP_MAX_CHUNK)
     }
 
-    fun loadFirmware(): Boolean {
+    fun loadFirmware(assetPath: String = "firmware/firmware.bin"): Boolean {
         return try {
-            firmwareData = context.assets.open("firmware/firmware.bin").readBytes()
+            firmwareData = context.assets.open(assetPath).readBytes()
             chunkDataSize = calculateChunkSize(relayManager.getNegotiatedMtu())
+            Log.d(TAG, "Loaded firmware from $assetPath: ${firmwareData!!.size} bytes, chunkDataSize=$chunkDataSize")
             true
         } catch (e: Exception) {
-            Log.e(TAG, "Failed to load firmware", e)
+            Log.e(TAG, "Failed to load firmware from $assetPath", e)
             false
         }
     }
@@ -80,7 +81,21 @@ class OtaManager(
             val startPacket = ByteBuffer.allocate(5).order(ByteOrder.BIG_ENDIAN)
             startPacket.put(OTA_CMD_START)
             startPacket.putInt(fw.size)
-            relayManager.sendOtaData(startPacket.array())
+            var startSent = false
+            for (attempt in 1..MAX_RETRIES) {
+                if (relayManager.sendOtaData(startPacket.array())) {
+                    startSent = true
+                    Log.d(TAG, "OTA start packet sent on attempt $attempt")
+                    break
+                }
+                Log.w(TAG, "OTA start packet failed attempt $attempt, retrying...")
+                delay(500)
+            }
+            if (!startSent) {
+                relayManager.setOtaNotifyCallback(null)
+                withContext(Dispatchers.Main) { callback.onError("OTA mislukt: start packet niet verzonden") }
+                return@withContext false
+            }
 
             try {
                 withTimeout(OTA_START_TIMEOUT_MS) {

android/app/src/main/java/nl/eddydevink/sylda/PrefsHelper.kt

@@ -15,8 +15,20 @@ object PrefsHelper {
     const val PREF_THEME = "theme"
     const val PREF_LABEL1 = "label_relay1"
     const val PREF_LABEL2 = "label_relay2"
+    const val KEY_DEVICE_MODE = "deviceMode"
+    const val KEY_SERVER_UUID = "serverUuid"
+    const val KEY_CLIENT_UUID = "clientUuid"
     const val SEQ_MAX = 1_000_000
 
+    fun getDeviceMode(context: Context): String = getPrefs(context).getString(KEY_DEVICE_MODE, "server") ?: "server"
+    fun setDeviceMode(context: Context, mode: String) = getPrefs(context).edit().putString(KEY_DEVICE_MODE, mode).apply()
+    fun getTransportMode(context: Context): String = getPrefs(context).getString("transportMode", "ble") ?: "ble"
+    fun setTransportMode(context: Context, mode: String) = getPrefs(context).edit().putString("transportMode", mode).apply()
+    fun getServerUuid(context: Context): String? = getPrefs(context).getString(KEY_SERVER_UUID, null)
+    fun setServerUuid(context: Context, uuid: String) = getPrefs(context).edit().putString(KEY_SERVER_UUID, uuid).apply()
+    fun getClientUuid(context: Context): String? = getPrefs(context).getString(KEY_CLIENT_UUID, null)
+    fun setClientUuid(context: Context, uuid: String) = getPrefs(context).edit().putString(KEY_CLIENT_UUID, uuid).apply()
+
     fun applyTheme(context: Context) {
         val prefs = getPrefs(context)
         val mode = when (prefs.getString(PREF_THEME, "system")) {

android/app/src/main/java/nl/eddydevink/sylda/SettingsActivity.kt

@@ -20,7 +20,6 @@ import android.util.Log
 import android.view.inputmethod.EditorInfo
 import android.view.inputmethod.InputMethodManager
 import android.widget.Button
-import android.widget.CheckBox
 import android.widget.EditText
 import android.widget.ProgressBar
 import android.widget.RadioGroup
@@ -32,6 +31,7 @@ import kotlinx.coroutines.CompletableDeferred
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.Job
 import kotlinx.coroutines.withContext
+import kotlinx.coroutines.delay
 import kotlinx.coroutines.launch
 import java.nio.charset.StandardCharsets
 import java.security.SecureRandom
@@ -64,7 +64,6 @@ class SettingsActivity : AppCompatActivity() {
         private const val REBOOT_WAIT_MS = 5000L
         private const val REBOOT_POLL_MS = 500L
         private const val REBOOT_MAX_WAIT_MS = 15000L
-        private const val EXPECTED_FIRMWARE_VERSION = "6"
     }
 
     private enum class UsbAction { NONE, EXCHANGE_KEY, FLASH }
@@ -131,6 +130,10 @@ class SettingsActivity : AppCompatActivity() {
         }
     }
 
+    private fun getExpectedFirmwareVersion(): String {
+        return if (PrefsHelper.getDeviceMode(this) == "client") SylDaVersions.CLIENT else SylDaVersions.SERVER
+    }
+
     override fun onCreate(savedInstanceState: Bundle?) {
         lastTheme = PrefsHelper.getPrefs(this).getString(PrefsHelper.PREF_THEME, "system") ?: "system"
         PrefsHelper.applyTheme(this)
@@ -140,8 +143,29 @@ class SettingsActivity : AppCompatActivity() {
         supportActionBar?.setDisplayHomeAsUpEnabled(true)
         supportActionBar?.title = getString(R.string.title_settings)
 
+        val radioDeviceMode = findViewById<RadioGroup>(R.id.radioDeviceMode)
+        val radioTransport = findViewById<RadioGroup>(R.id.radioTransport)
+
+        radioDeviceMode.check(
+            if (PrefsHelper.getDeviceMode(this) == "client") R.id.radioClient else R.id.radioServer
+        )
+        radioTransport.check(
+            if (PrefsHelper.getTransportMode(this) == "usb") R.id.radioUsb else R.id.radioBle
+        )
+
+        radioDeviceMode.setOnCheckedChangeListener { _, checkedId ->
+            val mode = if (checkedId == R.id.radioClient) "client" else "server"
+            PrefsHelper.setDeviceMode(this, mode)
+        }
+
+        radioTransport.setOnCheckedChangeListener { _, checkedId ->
+            val mode = if (checkedId == R.id.radioUsb) "usb" else "ble"
+            PrefsHelper.setTransportMode(this, mode)
+        }
+
         findViewById<Button>(R.id.updateModuleButton).setOnClickListener {
-            if (findViewById<RadioGroup>(R.id.flashMethodGroup).checkedRadioButtonId == R.id.methodUsb) {
+            if (PrefsHelper.getDeviceMode(this) == "client" ||
+                findViewById<RadioGroup>(R.id.radioTransport).checkedRadioButtonId == R.id.radioUsb) {
                 startFlashing()
             } else {
                 startOtaUpdate()
@@ -222,7 +246,7 @@ class SettingsActivity : AppCompatActivity() {
         }
 
         val espVersion = manager.getEspVersion()
-        if (espVersion != null && espVersion == EXPECTED_FIRMWARE_VERSION) {
+        if (espVersion != null && espVersion == getExpectedFirmwareVersion()) {
             Toast.makeText(this, getString(R.string.ota_up_to_date), Toast.LENGTH_SHORT).show()
             return
         }
@@ -231,7 +255,9 @@ class SettingsActivity : AppCompatActivity() {
 
         otaManager = OtaManager(this, manager)
 
-        if (otaManager?.loadFirmware() != true) {
+        val mode = PrefsHelper.getDeviceMode(this)
+        val fwPath = "firmware/${if (mode == "client") "client" else "server"}/firmware.bin"
+        if (otaManager?.loadFirmware(fwPath) != true) {
             progressDialog?.dismiss()
             progressDialog = null
             Toast.makeText(this, getString(R.string.ota_load_failed), Toast.LENGTH_SHORT).show()
@@ -241,6 +267,7 @@ class SettingsActivity : AppCompatActivity() {
         manager.enableOtaNotifications()
 
         otaJob = lifecycleScope.launch {
+            delay(300)
             val result = otaManager!!.performOta(object : OtaManager.OtaCallback {
                 override fun onProgress(percent: Int, message: String) {
                     lifecycleScope.launch(Dispatchers.Main) {
@@ -361,6 +388,11 @@ class SettingsActivity : AppCompatActivity() {
                             .putString(PrefsHelper.PREF_UUID, result.deviceUuid)
                             .putString(PrefsHelper.PREF_KEY, result.hexKey)
                             .apply()
+                        if (PrefsHelper.getDeviceMode(this@SettingsActivity) == "server") {
+                            PrefsHelper.setServerUuid(this@SettingsActivity, result.deviceUuid)
+                        } else {
+                            PrefsHelper.setClientUuid(this@SettingsActivity, result.deviceUuid)
+                        }
                         cleanupAction()
                         setResult(RESULT_SCAN)
                         finish()
@@ -409,7 +441,7 @@ class SettingsActivity : AppCompatActivity() {
 
         lifecycleScope.launch {
             val version = readEspVersion(usbManager, device)
-            if (version == EXPECTED_FIRMWARE_VERSION && !expectingReboot) {
+            if (version == getExpectedFirmwareVersion() && !expectingReboot) {
                 Log.d(TAG, "Firmware version $version matches, up to date")
                 progressDialog?.dismiss()
                 progressDialog = null
@@ -623,8 +655,7 @@ class SettingsActivity : AppCompatActivity() {
                         hexUuid.length == UUID_HEX_LEN && hexUuid.all { it in "0123456789ABCDEFabcdef" }) {
                         val espKeyUpper = hexKey.uppercase()
                         val espUuidUpper = hexUuid.uppercase()
-                        if (appUuid != null && appKey != null &&
-                            (appUuid != espUuidUpper || appKey != espKeyUpper)) {
+                        if (appUuid != espUuidUpper || appKey != espKeyUpper) {
                             return KeyResult.Conflict(espUuidUpper, espKeyUpper)
                         }
                         return KeyResult.Success(espUuidUpper, espKeyUpper)
@@ -634,10 +665,14 @@ class SettingsActivity : AppCompatActivity() {
                 } else if (noKey) {
                     val newKey: String
                     val newUuid: String
-                    if (appUuid != null && appKey != null) {
-                        Log.d(TAG, "ESP has no keys, using existing app keys")
+                    if (appKey != null) {
+                        Log.d(TAG, "ESP has no keys, using existing HMAC key")
                         newKey = appKey
-                        newUuid = appUuid
+                        newUuid = if (PrefsHelper.getDeviceMode(this) == "server") {
+                            generateRandomHex(UUID_BYTE_COUNT)
+                        } else {
+                            generateRandomHex(UUID_BYTE_COUNT)
+                        }
                     } else {
                         Log.d(TAG, "Both have no keys, generating new pair")
                         newKey = generateRandomHexKey()
@@ -671,6 +706,21 @@ class SettingsActivity : AppCompatActivity() {
                     Log.d(TAG, "SET_ID response: ${okUuidResponse.take(200)}")
 
                     if (okUuidResponse.contains("OK")) {
+                        if (PrefsHelper.getDeviceMode(this) == "client") {
+                            val srvUuid = PrefsHelper.getServerUuid(this)
+                            if (srvUuid != null) {
+                                val setServerCmd = "SET_SERVER:$srvUuid\n".toByteArray(StandardCharsets.US_ASCII)
+                                connection.bulkTransfer(epOut, setServerCmd, setServerCmd.size, USB_BULK_TIMEOUT_MS)
+                                Thread.sleep(RESPONSE_WAIT_MS)
+                                val okServerResp = readResponse(connection, epIn, SET_KEY_TIMEOUT_MS)
+                                Log.d(TAG, "SET_SERVER response: ${okServerResp.take(200)}")
+                                if (!okServerResp.contains("OK")) {
+                                    return KeyResult.Error(R.string.err_server_not_ack)
+                                }
+                            } else {
+                                return KeyResult.Error(R.string.err_no_server_uuid)
+                            }
+                        }
                         return KeyResult.Success(newUuid, newKey)
                     } else {
                         return KeyResult.Error(R.string.err_uuid_not_ack)
@@ -767,52 +817,23 @@ class SettingsActivity : AppCompatActivity() {
     private fun showConflictDialog(usbManager: UsbManager, device: UsbDevice,
                                    espUuid: String, espKey: String, appKey: String) {
         val prefs = PrefsHelper.getPrefs(this)
-        val appUuid = prefs.getString(PrefsHelper.PREF_UUID, "") ?: ""
+        val appUuid = prefs.getString(PrefsHelper.PREF_UUID, null)
+        val newAppKey = appKey.ifEmpty { generateRandomHexKey() }
+        val newAppUuid = appUuid ?: generateRandomHex(UUID_BYTE_COUNT)
 
         AlertDialog.Builder(this)
             .setTitle(getString(R.string.title_key_conflict))
-            .setMessage(getString(R.string.msg_key_conflict))
-            .setPositiveButton(getString(R.string.button_keep_esp_keys)) { _, _ ->
-                prefs.edit()
-                    .putString(PrefsHelper.PREF_UUID, espUuid)
-                    .putString(PrefsHelper.PREF_KEY, espKey)
-                    .apply()
-                cleanupAction()
-                setResult(RESULT_SCAN)
-                finish()
+            .setMessage(getString(R.string.msg_pair_device))
+            .setPositiveButton(getString(R.string.button_pair)) { _, _ ->
+                doOverwriteEspKeys(usbManager, device, newAppKey, newAppUuid)
             }
-            .setNegativeButton(getString(R.string.button_overwrite_esp)) { _, _ ->
-                showOverwriteConfirmDialog(usbManager, device, espUuid, espKey, appKey, appUuid)
-            }
-            .setNeutralButton(getString(R.string.button_cancel)) { _, _ ->
+            .setNegativeButton(getString(R.string.button_cancel)) { _, _ ->
                 cleanupAction()
             }
             .setCancelable(false)
             .show()
     }
 
-    private fun showOverwriteConfirmDialog(usbManager: UsbManager, device: UsbDevice,
-                                           espUuid: String, espKey: String,
-                                           appKey: String, appUuid: String) {
-        val view = layoutInflater.inflate(R.layout.dialog_overwrite_confirm, null)
-        val checkBox = view.findViewById<CheckBox>(R.id.confirmCheckBox)
-        val dialog = AlertDialog.Builder(this)
-            .setTitle(getString(R.string.title_overwrite_confirm))
-            .setView(view)
-            .setPositiveButton(getString(R.string.button_confirm)) { _, _ ->
-                if (checkBox.isChecked) {
-                    doOverwriteEspKeys(usbManager, device, appKey, appUuid)
-                }
-            }
-            .setNegativeButton(getString(R.string.button_cancel)) { _, _ -> }
-            .setCancelable(true)
-            .show()
-        dialog.getButton(AlertDialog.BUTTON_POSITIVE).isEnabled = false
-        checkBox.setOnCheckedChangeListener { _, isChecked ->
-            dialog.getButton(AlertDialog.BUTTON_POSITIVE).isEnabled = isChecked
-        }
-    }
-
     private fun doOverwriteEspKeys(usbManager: UsbManager, device: UsbDevice,
                                    appKey: String, appUuid: String) {
         showProgressDialog(getString(R.string.title_overwriting_keys), getString(R.string.msg_writing_keys), STYLE_SPINNER)
@@ -866,6 +887,12 @@ class SettingsActivity : AppCompatActivity() {
             Thread.sleep(KEY_SETTLE_MS)
             flushReadBuffer(connection, epIn)
 
+            val newUuid = if (PrefsHelper.getDeviceMode(this) == "client") {
+                generateRandomHex(UUID_BYTE_COUNT)
+            } else {
+                appUuid
+            }
+
             val setKeyCmd = "SET_KEY:$appKey\n".toByteArray(StandardCharsets.US_ASCII)
             val w = connection.bulkTransfer(epOut, setKeyCmd, setKeyCmd.size, USB_BULK_TIMEOUT_MS)
             if (w < 0) return KeyResult.Error(R.string.err_set_key_write)
@@ -875,7 +902,7 @@ class SettingsActivity : AppCompatActivity() {
             val okKeyResponse = readResponse(connection, epIn, SET_KEY_TIMEOUT_MS)
             if (!okKeyResponse.contains("OK")) return KeyResult.Error(R.string.err_key_not_ack)
 
-            val setIdCmd = "SET_ID:$appUuid\n".toByteArray(StandardCharsets.US_ASCII)
+            val setIdCmd = "SET_ID:$newUuid\n".toByteArray(StandardCharsets.US_ASCII)
             val w2 = connection.bulkTransfer(epOut, setIdCmd, setIdCmd.size, USB_BULK_TIMEOUT_MS)
             if (w2 < 0) return KeyResult.Error(R.string.err_set_id_write)
 
@@ -883,12 +910,31 @@ class SettingsActivity : AppCompatActivity() {
             val okUuidResponse = readResponse(connection, epIn, SET_KEY_TIMEOUT_MS)
             if (!okUuidResponse.contains("OK")) return KeyResult.Error(R.string.err_uuid_not_ack)
 
+            if (PrefsHelper.getDeviceMode(this) == "client") {
+                val srvUuid = PrefsHelper.getServerUuid(this)
+                if (srvUuid != null) {
+                    val setServerCmd = "SET_SERVER:$srvUuid\n".toByteArray(StandardCharsets.US_ASCII)
+                    connection.bulkTransfer(epOut, setServerCmd, setServerCmd.size, USB_BULK_TIMEOUT_MS)
+                    Thread.sleep(RESPONSE_WAIT_MS)
+                    val okServerResp = readResponse(connection, epIn, SET_KEY_TIMEOUT_MS)
+                    Log.d(TAG, "SET_SERVER response: ${okServerResp.take(200)}")
+                    if (!okServerResp.contains("OK")) return KeyResult.Error(R.string.err_server_not_ack)
+                } else {
+                    return KeyResult.Error(R.string.err_no_server_uuid)
+                }
+            }
+
             val prefs = PrefsHelper.getPrefs(this)
             prefs.edit()
-                .putString(PrefsHelper.PREF_UUID, appUuid)
+                .putString(PrefsHelper.PREF_UUID, newUuid)
                 .putString(PrefsHelper.PREF_KEY, appKey)
                 .apply()
-            return KeyResult.Success(appUuid, appKey)
+            if (PrefsHelper.getDeviceMode(this) == "server") {
+                PrefsHelper.setServerUuid(this, newUuid)
+            } else {
+                PrefsHelper.setClientUuid(this, newUuid)
+            }
+            return KeyResult.Success(newUuid, appKey)
         } catch (e: Exception) {
             Log.e(TAG, "Write keys error", e)
             return KeyResult.Error(R.string.err_generic, e.message)

android/app/src/main/res/layout/activity_settings.xml

@@ -6,30 +6,58 @@
     android:padding="24dp">
 
     <RadioGroup
-        android:id="@+id/flashMethodGroup"
+        android:id="@+id/radioDeviceMode"
         android:layout_width="match_parent"
         android:layout_height="wrap_content"
         android:orientation="horizontal"
-        android:layout_marginBottom="8dp"
-        android:checkedButton="@id/methodBluetooth">
+        android:layout_marginTop="12dp"
+        android:checkedButton="@+id/radioServer">
 
         <RadioButton
-            android:id="@+id/methodBluetooth"
+            android:id="@+id/radioServer"
             android:layout_width="0dp"
             android:layout_height="wrap_content"
             android:layout_weight="1"
-            android:gravity="center"
-            android:text="@string/method_bluetooth" />
+            android:text="Server" />
 
         <RadioButton
-            android:id="@+id/methodUsb"
+            android:id="@+id/radioClient"
             android:layout_width="0dp"
             android:layout_height="wrap_content"
             android:layout_weight="1"
-            android:gravity="center"
-            android:text="@string/method_usb" />
+            android:text="Client" />
     </RadioGroup>
 
+    <RadioGroup
+        android:id="@+id/radioTransport"
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:orientation="horizontal"
+        android:layout_marginTop="8dp"
+        android:checkedButton="@+id/radioBle">
+
+        <RadioButton
+            android:id="@+id/radioBle"
+            android:layout_width="0dp"
+            android:layout_height="wrap_content"
+            android:layout_weight="1"
+            android:text="BLE" />
+
+        <RadioButton
+            android:id="@+id/radioUsb"
+            android:layout_width="0dp"
+            android:layout_height="wrap_content"
+            android:layout_weight="1"
+            android:text="USB" />
+    </RadioGroup>
+
+    <View
+        android:layout_width="match_parent"
+        android:layout_height="1dp"
+        android:background="?android:attr/listDivider"
+        android:layout_marginTop="12dp"
+        android:layout_marginBottom="8dp" />
+
     <Button
         android:id="@+id/updateModuleButton"
         android:layout_width="match_parent"

android/app/src/main/res/layout/dialog_overwrite_confirm.xml

@@ -1,21 +0,0 @@
-<?xml version="1.0" encoding="utf-8"?>
-<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
-    android:layout_width="match_parent"
-    android:layout_height="wrap_content"
-    android:orientation="vertical"
-    android:padding="20dp">
-
-    <TextView
-        android:layout_width="match_parent"
-        android:layout_height="wrap_content"
-        android:text="@string/msg_overwrite_warning"
-        android:textSize="14sp"
-        android:paddingBottom="16dp" />
-
-    <CheckBox
-        android:id="@+id/confirmCheckBox"
-        android:layout_width="match_parent"
-        android:layout_height="wrap_content"
-        android:text="@string/checkbox_confirm_overwrite" />
-
-</LinearLayout>

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

@@ -27,8 +27,6 @@
 
     <!-- SettingsActivity -->
     <string name="title_settings">Instellingen</string>
-    <string name="method_bluetooth">Bluetooth</string>
-    <string name="method_usb">USB</string>
     <string name="button_update_module">Module bijwerken</string>
     <string name="usb_access_denied">USB-toegang geweigerd</string>
     <string name="key_read_success">Beveiligingssleutel gelezen</string>
@@ -36,16 +34,10 @@
     <string name="flash_failed">Flashen mislukt: %s</string>
 
     <!-- Key conflict dialog -->
-    <string name="title_key_conflict">Sleutels komen niet overeen</string>
-    <string name="msg_key_conflict">De ESP (SylDa_Server) heeft andere sleutels dan deze app. Wat wil je doen?</string>
-    <string name="button_keep_esp_keys">ESP sleutels overnemen</string>
-    <string name="button_overwrite_esp">App sleutels overzetten</string>
-    <string name="button_confirm">Bevestigen</string>
+    <string name="title_key_conflict">Onbekende module</string>
+    <string name="msg_pair_device">Deze module koppelen aan deze telefoon?</string>
+    <string name="button_pair">Koppelen</string>
 
-    <!-- Overwrite confirmation dialog -->
-    <string name="title_overwrite_confirm">ESP sleutels overschrijven?</string>
-    <string name="msg_overwrite_warning">Dit vervangt de sleutels van de ESP. De ESP kan daarna niet meer met de oorspronkelijke app communiceren.</string>
-    <string name="checkbox_confirm_overwrite">Ik weet het zeker</string>
     <string name="title_overwriting_keys">Sleutels overschrijven</string>
     <string name="msg_writing_keys">Sleutels schrijven naar ESP…</string>
 
@@ -75,6 +67,8 @@
     <string name="err_set_id_write">SET_ID schrijven mislukt</string>
     <string name="err_key_not_ack">ESP bevestigde sleutel niet</string>
     <string name="err_uuid_not_ack">ESP bevestigde UUID niet</string>
+    <string name="err_server_not_ack">ESP bevestigde server UUID niet</string>
+    <string name="err_no_server_uuid">Server UUID niet beschikbaar — provisioneer eerst de server</string>
 
     <!-- EspFlasher -->
     <string name="flash_connecting">Verbinden met ESP bootloader…</string>