Implement scanning for ESP devices with UART service

companion/bluetooth.py

 from time import sleep
 
-from able import BluetoothDispatcher
+from able import BluetoothDispatcher, GATT_SUCCESS
+from able.filters import ServiceUUIDFilter
 from kivy.logger import Logger
 
+_UART_SERVICE_UUID = "6e400001-b5a3-f393-e0a9-e50e24dcca9e"
+
+
 class MynitBluetooth(BluetoothDispatcher):
 
     def __init__(self, app, *args, **kwargs):
@@ -10,9 +14,10 @@ class MynitBluetooth(BluetoothDispatcher):
 
         self._app = app
         self._available_devices = set()
+        self._current_device = None
 
         Logger.info("Starting BLE scanning")
-        self.start_scan()
+        self.start_scan(filters=[ServiceUUIDFilter(_UART_SERVICE_UUID)])
 
     def on_device(self, device, rssi, advertisement):
         Logger.debug("BLE device discovered: %s" % device.getAddress())
@@ -22,3 +27,18 @@ class MynitBluetooth(BluetoothDispatcher):
             self._available_devices.add(device)
 
             self._app.update_device_list(self._available_devices)
+
+    def on_connection_state_change(self, status, state):
+        Logger.debug("Connection state changed")
+
+        if status == GATT_SUCCESS and state:
+            Logger.info("Connection successful, discovering services")
+            self._current_device = device
+            self.discover_services()
+        else:
+            Logger.warning("Connection failed, disconnecting and resetting")
+            self.close_gatt()
+            self._current_device = None
+
+    def on_services(self, status, services):
+        pass