feat: dual BLE+USB serial — single firmware replaces separate BLE/USB builds

- DualSerialInterface: enable()/disable() control BLE only, USB always on;
  USB state machine not read while BLE connected to avoid partial-frame
  corruption; reset USB on BLE disconnect for clean reconnect
- Fix -UBLE_DEBUG_LOGGING (no space) to avoid PlatformIO SCons parse error
- build.sh: drop separate USB/BLE builds, dual_settings only
- wio-tracker-l1-eink: enable DUAL_SERIAL in companion_radio_ble build

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

build.sh

@@ -231,8 +231,6 @@ build_companion_firmwares() {
 }
 
 build_wio_tracker_l1_firmwares() {
-  build_firmware "WioTrackerL1_companion_radio_usb_settings"
-  build_firmware "WioTrackerL1_companion_radio_ble_settings"
   build_firmware "WioTrackerL1_companion_radio_dual_settings"
 }
 

src/helpers/nrf52/DualSerialInterface.h

@@ -5,22 +5,29 @@
 #include "SerialBLEInterface.h"
 
 // Wraps BLE + USB serial interfaces: BLE takes priority when connected,
-// USB is always ready as a fallback. Both state machines run continuously.
+// USB is always ready as a fallback.
+// enable()/disable() control BLE only — USB is always on.
+// BLE state machine is only pumped when BLE is enabled; USB is not read while BLE is connected.
 class DualSerialInterface : public BaseSerialInterface {
   SerialBLEInterface _ble;
   ArduinoSerialInterface _usb;
   uint8_t _ble_buf[MAX_FRAME_SIZE];
   uint8_t _usb_buf[MAX_FRAME_SIZE];
+  bool _ble_enabled;
+  bool _ble_was_connected;
 
 public:
+  DualSerialInterface() : _ble_enabled(false), _ble_was_connected(false) {}
+
   void begin(const char* ble_prefix, char* node_name, uint32_t pin_code, Stream& usb_stream) {
     _ble.begin(ble_prefix, node_name, pin_code);
     _usb.begin(usb_stream);
+    _usb.enable();  // USB is always on
   }
 
-  void enable() override  { _ble.enable();  _usb.enable(); }
-  void disable() override { _ble.disable(); _usb.disable(); }
-  bool isEnabled() const override { return _ble.isEnabled() || _usb.isEnabled(); }
+  void enable() override  { _ble.enable(); _ble_enabled = true; }
+  void disable() override { _ble.disable(); _ble_enabled = false; }
+  bool isEnabled() const override { return _ble_enabled; }
 
   // Always true — USB is always available as fallback, so the mesh can send.
   bool isConnected() const override { return true; }
@@ -36,16 +43,26 @@ public:
   }
 
   size_t checkRecvFrame(uint8_t dest[]) override {
-    // Always pump both state machines: BLE needs this for TX queue drain and
-    // advertising watchdog; USB needs it to drain its input buffer.
+    if (_ble_enabled) {
       size_t ble_len = _ble.checkRecvFrame(_ble_buf);
-    size_t usb_len = _usb.checkRecvFrame(_usb_buf);
+      bool ble_now = _ble.isConnected();
 
-    if (_ble.isConnected()) {
+      if (ble_now) {
+        _ble_was_connected = true;
         if (ble_len > 0) { memcpy(dest, _ble_buf, ble_len); return ble_len; }
-    } else {
-      if (usb_len > 0) { memcpy(dest, _usb_buf, usb_len); return usb_len; }
+        return 0;  // BLE active — don't read USB to keep its state machine clean
       }
+
+      if (_ble_was_connected) {
+        // BLE just disconnected — reset USB state machine so stale partial frames don't block it
+        _ble_was_connected = false;
+        _usb.enable();
+        return 0;
+      }
+    }
+
+    size_t usb_len = _usb.checkRecvFrame(_usb_buf);
+    if (usb_len > 0) { memcpy(dest, _usb_buf, usb_len); return usb_len; }
     return 0;
   }
 };

variants/wio-tracker-l1-eink/platformio.ini

@@ -57,6 +57,7 @@ build_flags = ${WioTrackerL1Eink.build_flags}
   ; -D MESH_DEBUG=1
   -D UI_RECENT_LIST_SIZE=6
   -D UI_SENSORS_PAGE=1
+  -D DUAL_SERIAL
 build_src_filter = ${WioTrackerL1Eink.build_src_filter}
   +<helpers/nrf52/SerialBLEInterface.cpp>
   +<helpers/ui/MomentaryButton.cpp>