diff --git a/android/app/src/main/java/nl/eddydevink/sylda/BleRelayManager.kt b/android/app/src/main/java/nl/eddydevink/sylda/BleRelayManager.kt
index 1cc0195..9ec1740 100644
--- a/android/app/src/main/java/nl/eddydevink/sylda/BleRelayManager.kt
+++ b/android/app/src/main/java/nl/eddydevink/sylda/BleRelayManager.kt
@@ -23,23 +23,27 @@ import java.nio.ByteOrder
 import java.util.UUID
 import javax.crypto.Mac
 import javax.crypto.spec.SecretKeySpec
+import kotlin.text.Charsets
 
 class BleRelayManager(
     private val context: Context,
     private val callbacks: BleCallbacks
 ) {
     companion object {
+        var instance: BleRelayManager? = null
         private const val TAG = "BleRelayManager"
         private val SERVICE_UUID: UUID = UUID.fromString("4fafc201-1fb5-459e-8fcc-c5c9c331914b")
         private val CHARACTERISTIC_UUID: UUID = UUID.fromString("beb5483e-36e1-4688-b7f5-ea07361f26d8")
         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 const val SCAN_TIMEOUT_MS = 30000L
         private const val RECONNECT_DELAY_MS = 2000L
         private const val MAX_SCAN_RETRIES = 3
         private const val HMAC_PKT_SIZE = 37
         private const val HMAC_LEN = 32
-        private const val BLE_MTU = 256
+        private const val BLE_MTU = 512
     }
 
     private var bluetoothGatt: BluetoothGatt? = null
@@ -52,6 +56,13 @@ class BleRelayManager(
     private var hmacKey: ByteArray? = null
     private var deviceUuid: ByteArray? = null
     private var triedAddresses = mutableSetOf<String>()
+    private var otaCharacteristic: BluetoothGattCharacteristic? = null
+    private var espVersion: String? = null
+    private var appVersion: String = ""
+
+    init {
+        instance = this
+    }
     private val scanRunnable = Runnable { startScan() }
     private var scanTimeoutRunnable: Runnable? = null
 
@@ -170,6 +181,22 @@ class BleRelayManager(
         stopScan()
         bluetoothGatt?.disconnect()
     }
+
+    @SuppressLint("MissingPermission")
+    fun sendOtaData(data: ByteArray) {
+        val char = otaCharacteristic ?: return
+        val gatt = bluetoothGatt ?: return
+        char.value = data
+        char.writeType = BluetoothGattCharacteristic.WRITE_TYPE_NO_RESPONSE
+        gatt.writeCharacteristic(char)
+    }
+
+    @SuppressLint("MissingPermission")
+    fun enableOtaNotifications(): Boolean {
+        val char = otaCharacteristic ?: return false
+        val gatt = bluetoothGatt ?: return false
+        return gatt.setCharacteristicNotification(char, true)
+    }
     fun updateKeys() {
         loadState()
     }
@@ -182,6 +209,10 @@ class BleRelayManager(
         return bluetoothGatt != null
     }
 
+    fun setAppVersion(version: String) {
+        appVersion = version
+    }
+
     @SuppressLint("MissingPermission")
     private fun connectToDevice(device: android.bluetooth.BluetoothDevice) {
         handler.post { callbacks.onStatusChanged(BleStatus.Connecting) }
@@ -230,7 +261,9 @@ class BleRelayManager(
             val service = gatt.getService(SERVICE_UUID)
             if (service != null) {
                 relayCharacteristic = service.getCharacteristic(CHARACTERISTIC_UUID)
+                otaCharacteristic = service.getCharacteristic(OTA_UUID)
                 val uuidChar = service.getCharacteristic(UUID_CHAR_UUID)
+                val versionChar = service.getCharacteristic(VERSION_UUID)
                 if (relayCharacteristic != null && uuidChar != null) {
                     Log.d(TAG, "Reading device UUID characteristic...")
                     gatt.readCharacteristic(uuidChar)
@@ -249,14 +282,26 @@ class BleRelayManager(
             if (characteristic.uuid == UUID_CHAR_UUID && status == BluetoothGatt.GATT_SUCCESS) {
                 val storedUuid = deviceUuid
                 if (storedUuid != null && value.contentEquals(storedUuid)) {
-                    Log.d(TAG, "UUID verified, setting up relay")
-                    handler.post { callbacks.onStatusChanged(BleStatus.Connected) }
+                    Log.d(TAG, "UUID verified, reading version...")
+                    val service = gatt.getService(SERVICE_UUID)
+                    val versionChar = service?.getCharacteristic(VERSION_UUID)
+                    if (versionChar != null) {
+                        gatt.readCharacteristic(versionChar)
+                    } else {
+                        handler.post { callbacks.onStatusChanged(BleStatus.Connected) }
+                    }
                 } else {
                     Log.w(TAG, "UUID mismatch -- disconnecting")
                     triedAddresses.add(gatt.device.address)
                     handler.post { callbacks.onStatusChanged(BleStatus.WrongDevice) }
                     gatt.disconnect()
                 }
+            } else if (characteristic.uuid == VERSION_UUID && status == BluetoothGatt.GATT_SUCCESS) {
+                val version = String(value, Charsets.UTF_8).trim()
+                espVersion = version
+                Log.d(TAG, "ESP firmware version: $version, app bundled: $appVersion")
+                handler.post { callbacks.onFirmwareVersion(version, appVersion) }
+                handler.post { callbacks.onStatusChanged(BleStatus.Connected) }
             }
         }