feat: Desktop USB serial transport (#4836)

Signed-off-by: James Rich <2199651+jamesarich@users.noreply.github.com>

desktop/README.md

@@ -49,7 +49,7 @@ The module depends on the JVM variants of KMP modules:
 | `navigation/DesktopSettingsNavigation.kt` | Real settings feature composables wired into nav graph (~35 screens) |
 | `navigation/DesktopNodeNavigation.kt` | Real adaptive node list-detail + real metrics screens (logs + charts); map routes remain placeholders |
 | `navigation/DesktopMessagingNavigation.kt` | Real adaptive contacts list-detail + real Messages/Share/QuickChat route screens |
-| `radio/DesktopRadioInterfaceService.kt` | TCP socket transport with auto-reconnect, heartbeat, and backoff retry |
+| `radio/DesktopRadioInterfaceService.kt` | TCP, Serial/USB, and BLE transports with auto-reconnect, heartbeat, and backoff retry |
 | `radio/DesktopMeshServiceController.kt` | Mesh service lifecycle — orchestrates `want_config` handshake chain |
 | `radio/DesktopMessageQueue.kt` | Message queue for outbound mesh packets |
 | `ui/firmware/DesktopFirmwareScreen.kt` | Placeholder firmware screen (native DFU is Android-only) |
@@ -91,6 +91,7 @@ The module depends on the JVM variants of KMP modules:
 - [x] Add desktop language picker backed by shared `UiPreferencesDataSource.locale` with live translation updates
 - [ ] Wire remaining `feature:*` composables (map) into the nav graph
 - [ ] Move remaining node detail and message composables from `androidMain` to `commonMain`
-- [ ] Add serial/USB transport for direct radio connection on Desktop
+- [x] Add serial/USB transport for direct radio connection on Desktop
+- [x] Add BLE transport (via Kable) for direct radio connection on Desktop
 - [ ] Add MQTT transport for cloud-connected operation
 - [x] Package as native distributions (DMG, MSI, DEB) via CI release pipeline

desktop/src/main/kotlin/org/meshtastic/desktop/radio/DesktopRadioInterfaceService.kt

@@ -56,7 +56,11 @@ class DesktopRadioInterfaceService(
 ) : RadioInterfaceService {
 
     override val supportedDeviceTypes: List<org.meshtastic.core.model.DeviceType> =
-        listOf(org.meshtastic.core.model.DeviceType.TCP, org.meshtastic.core.model.DeviceType.BLE)
+        listOf(
+            org.meshtastic.core.model.DeviceType.TCP,
+            org.meshtastic.core.model.DeviceType.BLE,
+            org.meshtastic.core.model.DeviceType.USB,
+        )
 
     private val _connectionState = MutableStateFlow<ConnectionState>(ConnectionState.Disconnected)
     override val connectionState: StateFlow<ConnectionState> = _connectionState.asStateFlow()
@@ -76,6 +80,7 @@ class DesktopRadioInterfaceService(
 
     private var transport: TcpTransport? = null
     private var bleTransport: DesktopBleInterface? = null
+    private var serialTransport: org.meshtastic.core.network.SerialTransport? = null
 
     init {
         // Observe radioPrefs to handle asynchronous loads from DataStore
@@ -136,6 +141,7 @@ class DesktopRadioInterfaceService(
         serviceScope.handledLaunch {
             transport?.sendPacket(bytes)
             bleTransport?.handleSendToRadio(bytes)
+            serialTransport?.handleSendToRadio(bytes)
         }
     }
 
@@ -170,6 +176,8 @@ class DesktopRadioInterfaceService(
     private fun startConnection(address: String) {
         if (address.startsWith("t")) {
             startTcpConnection(address.removePrefix("t"))
+        } else if (address.startsWith("s")) {
+            startSerialConnection(address.removePrefix("s"))
         } else if (address.startsWith("x")) {
             startBleConnection(address.removePrefix("x"))
         } else {
@@ -179,6 +187,18 @@ class DesktopRadioInterfaceService(
         }
     }
 
+    private fun startSerialConnection(portName: String) {
+        transport?.stop()
+        bleTransport?.close()
+        serialTransport?.close()
+
+        val serial = org.meshtastic.core.network.SerialTransport(portName = portName, service = this)
+        serialTransport = serial
+        if (!serial.startConnection()) {
+            onDisconnect(isPermanent = true, errorMessage = "Failed to connect to $portName")
+        }
+    }
+
     private fun startBleConnection(address: String) {
         transport?.stop()
         bleTransport?.close()
@@ -228,6 +248,9 @@ class DesktopRadioInterfaceService(
         bleTransport?.close()
         bleTransport = null
 
+        serialTransport?.close()
+        serialTransport = null
+
         // Recreate the service scope
         serviceScope.cancel("stopping interface")
         serviceScope = CoroutineScope(dispatchers.io + SupervisorJob())