Merge pull request #13 from google/gbg/standard-profiles

support for type adapters and framework for standard GATT profiles

19 files changed, 937 insertions, 274 deletions

diff --git a/.gitignore b/.gitignore
index 4f24f01..5cb29bb 100644
--- a/.gitignore
+++ b/.gitignore
@@ -8,3 +8,4 @@ docs/mkdocs/site
 tests/__pycache__
 test-results.xml
 bumble/transport/__pycache__
+bumble/profiles/__pycache__
diff --git a/apps/gatt_dump.py b/apps/gatt_dump.py
index c055626..02c3641 100644
--- a/apps/gatt_dump.py
+++ b/apps/gatt_dump.py
@@ -32,10 +32,10 @@ async def dump_gatt_db(peer, done):
     # Discover all services
     print(color('### Discovering Services and Characteristics', 'magenta'))
     await peer.discover_services()
-    await peer.discover_characteristics()
     for service in peer.services:
+        await service.discover_characteristics()
         for characteristic in service.characteristics:
-            await peer.discover_descriptors(characteristic)
+            await characteristic.discover_descriptors()
 
     print(color('=== Services ===', 'yellow'))
     show_services(peer.services)
@@ -47,7 +47,7 @@ async def dump_gatt_db(peer, done):
     for attribute in attributes:
         print(attribute)
         try:
-            value = await peer.read_value(attribute)
+            value = await attribute.read_value()
             print(color(f'{value.hex()}', 'green'))
         except ProtocolError as error:
             print(color(error, 'red'))
diff --git a/apps/gg_bridge.py b/apps/gg_bridge.py
index ac4ae5a..d524913 100644
--- a/apps/gg_bridge.py
+++ b/apps/gg_bridge.py
@@ -73,7 +73,7 @@ class GattlinkHubBridge(Device.Listener):
         gattlink_service = services[0]
 
         # Discover all the characteristics for the service
-        characteristics = await self.peer.discover_characteristics(service = gattlink_service)
+        characteristics = await gattlink_service.discover_characteristics()
         print(color('=== Characteristics discovered', 'yellow'))
         for characteristic in characteristics:
             if characteristic.uuid == GG_GATTLINK_RX_CHARACTERISTIC_UUID:
diff --git a/bumble/att.py b/bumble/att.py
index 9f82424..22b683e 100644
--- a/bumble/att.py
+++ b/bumble/att.py
@@ -682,11 +682,14 @@ class Attribute(EventEmitter):
 
     def __init__(self, attribute_type, permissions, value = b''):
         EventEmitter.__init__(self)
-        self.handle      = 0
-        self.permissions = permissions
-
-        # Convert the type to a UUID
-        if type(attribute_type) is bytes:
+        self.handle           = 0
+        self.end_group_handle = 0
+        self.permissions      = permissions
+
+        # Convert the type to a UUID object if it isn't already
+        if type(attribute_type) is str:
+            self.type = UUID(attribute_type)
+        elif type(attribute_type) is bytes:
             self.type = UUID.from_bytes(attribute_type)
         else:
             self.type = attribute_type
@@ -698,16 +701,13 @@ class Attribute(EventEmitter):
             self.value = value
 
     def read_value(self, connection):
-        if type(self.value) is bytes:
-            return self.value
+        if read := getattr(self.value, 'read', None):
+            try:
+                return read(connection)
+            except ATT_Error as error:
+                raise ATT_Error(error_code=error.error_code, att_handle=self.handle)
         else:
-            if read := getattr(self.value, 'read', None):
-                try:
-                    return read(connection)
-                except ATT_Error as error:
-                    raise ATT_Error(error_code=error.error_code, att_handle=self.handle)
-            else:
-                return bytes(self.value)
+            return self.value
 
     def write_value(self, connection, value):
         if write := getattr(self.value, 'write', None):
diff --git a/bumble/device.py b/bumble/device.py
index f834f9e..97ead5e 100644
--- a/bumble/device.py
+++ b/bumble/device.py
@@ -137,6 +137,17 @@ class Peer:
     def get_characteristics_by_uuid(self, uuid, service = None):
         return self.gatt_client.get_characteristics_by_uuid(uuid, service)
 
+    def create_service_proxy(self, proxy_class):
+        return proxy_class.from_client(self.gatt_client)
+
+    async def discover_service_and_create_proxy(self, proxy_class):
+        # Discover the first matching service and its characteristics
+        services = await self.discover_service(proxy_class.SERVICE_CLASS.UUID)
+        if services:
+            service = services[0]
+            await service.discover_characteristics()
+            return self.create_service_proxy(proxy_class)
+
     # [Classic only]
     async def request_name(self):
         return await self.connection.request_remote_name()
diff --git a/bumble/gatt.py b/bumble/gatt.py
index 31f5625..df760c3 100644
--- a/bumble/gatt.py
+++ b/bumble/gatt.py
@@ -22,6 +22,8 @@
 # -----------------------------------------------------------------------------
 # Imports
 # -----------------------------------------------------------------------------
+import asyncio
+import types
 import logging
 from colors import color
 
@@ -53,13 +55,13 @@ GATT_NEXT_DST_CHANGE_SERVICE                = UUID.from_16_bits(0x1807, 'Next DS
 GATT_GLUCOSE_SERVICE                        = UUID.from_16_bits(0x1808, 'Glucose')
 GATT_HEALTH_THERMOMETER_SERVICE             = UUID.from_16_bits(0x1809, 'Health Thermometer')
 GATT_DEVICE_INFORMATION_SERVICE             = UUID.from_16_bits(0x180A, 'Device Information')
-GATT_DEVICE_HEART_RATE_SERVICE              = UUID.from_16_bits(0x180D, 'Heart Rate')
-GATT_PHONE_ALTERT_STATUS_SERVICE            = UUID.from_16_bits(0x180E, 'Phone Alert Status')
-GATT_DEVICE_BATTERY_SERVICE                 = UUID.from_16_bits(0x180F, 'Battery')
+GATT_HEART_RATE_SERVICE                     = UUID.from_16_bits(0x180D, 'Heart Rate')
+GATT_PHONE_ALERT_STATUS_SERVICE             = UUID.from_16_bits(0x180E, 'Phone Alert Status')
+GATT_BATTERY_SERVICE                        = UUID.from_16_bits(0x180F, 'Battery')
 GATT_BLOOD_PRESSURE_SERVICE                 = UUID.from_16_bits(0x1810, 'Blood Pressure')
-GATT_ALTERT_NOTIFICATION_SERVICE            = UUID.from_16_bits(0x1811, 'Alert Notification')
-GATT_DEVICE_HUMAN_INTERFACE_DEVICE_SERVICE  = UUID.from_16_bits(0x1812, 'Human Interface Device')
-GATT_DEVICE_SCAN_PARAMETERS_SERVICE         = UUID.from_16_bits(0x1813, 'Scan Parameters')
+GATT_ALERT_NOTIFICATION_SERVICE             = UUID.from_16_bits(0x1811, 'Alert Notification')
+GATT_HUMAN_INTERFACE_DEVICE_SERVICE         = UUID.from_16_bits(0x1812, 'Human Interface Device')
+GATT_SCAN_PARAMETERS_SERVICE                = UUID.from_16_bits(0x1813, 'Scan Parameters')
 GATT_RUNNING_SPEED_AND_CADENCE_SERVICE      = UUID.from_16_bits(0x1814, 'Running Speed and Cadence')
 GATT_AUTOMATION_IO_SERVICE                  = UUID.from_16_bits(0x1815, 'Automation IO')
 GATT_CYCLING_SPEED_AND_CADENCE_SERVICE      = UUID.from_16_bits(0x1816, 'Cycling Speed and Cadence')
@@ -119,7 +121,7 @@ GATT_ENVIRONMENTAL_SENSING_CONFIGURATION_DESCRIPTOR  = UUID.from_16_bits(0x290B,
 GATT_ENVIRONMENTAL_SENSING_MEASUREMENT_DESCRIPTOR    = UUID.from_16_bits(0x290C, 'Environmental Sensing Measurement')
 GATT_ENVIRONMENTAL_SENSING_TRIGGER_DESCRIPTOR        = UUID.from_16_bits(0x290D, 'Environmental Sensing Trigger Setting')
 GATT_TIME_TRIGGER_DESCRIPTOR                         = UUID.from_16_bits(0x290E, 'Time Trigger Setting')
-GATT_COMPLETE_BE_EDR_TRANSPORT_BLOCK_DATA_DESCRIPTOR = UUID.from_16_bits(0x290F, 'Complete BR-EDR Transport Block Data')
+GATT_COMPLETE_BR_EDR_TRANSPORT_BLOCK_DATA_DESCRIPTOR = UUID.from_16_bits(0x290F, 'Complete BR-EDR Transport Block Data')
 
 # Device Information Service
 GATT_SYSTEM_ID_CHARACTERISTIC                          = UUID.from_16_bits(0x2A23, 'System ID')
@@ -140,19 +142,19 @@ GATT_REPORT_CHARACTERISTIC            = UUID.from_16_bits(0x2A4D, 'Report')
 GATT_PROTOCOL_MODE_CHARACTERISTIC     = UUID.from_16_bits(0x2A4E, 'Protocol Mode')
 
 # Misc
-GATT_DEVICE_NAME_CHARACTERISTIC                                  = UUID.from_16_bits(0x2A00, 'Device Name')
-GATT_APPEARANCE_CHARACTERISTIC                                   = UUID.from_16_bits(0x2A01, 'Appearance')
-GATT_PERIPHERAL_PRIVACY_FLAG_CHARACTERISTIC                      = UUID.from_16_bits(0x2A02, 'Peripheral Privacy Flag')
-GATT_RECONNECTION_ADDRESS_CHARACTERISTIC                         = UUID.from_16_bits(0x2A03, 'Reconnection Address')
-GATT_PERIPHERAL_PREFERRREED_CONNECTION_PARAMETERS_CHARACTERISTIC = UUID.from_16_bits(0x2A04, 'Peripheral Preferred Connection Parameters')
-GATT_SERVICE_CHANGED_CHARACTERISTIC                              = UUID.from_16_bits(0x2A05, 'Service Changed')
-GATT_ALERT_LEVEL_CHARACTERISTIC                                  = UUID.from_16_bits(0x2A06, 'Alert Level')
-GATT_TX_POWER_LEVEL_CHARACTERISTIC                               = UUID.from_16_bits(0x2A07, 'Tx Power Level')
-GATT_BATTERY_LEVEL_CHARACTERISTIC                                = UUID.from_16_bits(0x2A19, 'Battery Level')
-GATT_BOOT_KEYBOARD_INPUT_REPORT_CHARACTERISTIC                   = UUID.from_16_bits(0x2A22, 'Boot Keyboard Input Report')
-GATT_CURRENT_TIME_CHARACTERISTIC                                 = UUID.from_16_bits(0x2A2B, 'Current Time')
-GATT_BOOT_KEYBOARD_OUTPUT_REPORT_CHARACTERISTIC                  = UUID.from_16_bits(0x2A32, 'Boot Keyboard Output Report')
-GATT_CENTRAL_ADDRESS_RESOLUTION__CHARACTERISTIC                  = UUID.from_16_bits(0x2AA6, 'Central Address Resolution')
+GATT_DEVICE_NAME_CHARACTERISTIC                                = UUID.from_16_bits(0x2A00, 'Device Name')
+GATT_APPEARANCE_CHARACTERISTIC                                 = UUID.from_16_bits(0x2A01, 'Appearance')
+GATT_PERIPHERAL_PRIVACY_FLAG_CHARACTERISTIC                    = UUID.from_16_bits(0x2A02, 'Peripheral Privacy Flag')
+GATT_RECONNECTION_ADDRESS_CHARACTERISTIC                       = UUID.from_16_bits(0x2A03, 'Reconnection Address')
+GATT_PERIPHERAL_PREFERRED_CONNECTION_PARAMETERS_CHARACTERISTIC = UUID.from_16_bits(0x2A04, 'Peripheral Preferred Connection Parameters')
+GATT_SERVICE_CHANGED_CHARACTERISTIC                            = UUID.from_16_bits(0x2A05, 'Service Changed')
+GATT_ALERT_LEVEL_CHARACTERISTIC                                = UUID.from_16_bits(0x2A06, 'Alert Level')
+GATT_TX_POWER_LEVEL_CHARACTERISTIC                             = UUID.from_16_bits(0x2A07, 'Tx Power Level')
+GATT_BATTERY_LEVEL_CHARACTERISTIC                              = UUID.from_16_bits(0x2A19, 'Battery Level')
+GATT_BOOT_KEYBOARD_INPUT_REPORT_CHARACTERISTIC                 = UUID.from_16_bits(0x2A22, 'Boot Keyboard Input Report')
+GATT_CURRENT_TIME_CHARACTERISTIC                               = UUID.from_16_bits(0x2A2B, 'Current Time')
+GATT_BOOT_KEYBOARD_OUTPUT_REPORT_CHARACTERISTIC                = UUID.from_16_bits(0x2A32, 'Boot Keyboard Output Report')
+GATT_CENTRAL_ADDRESS_RESOLUTION__CHARACTERISTIC                = UUID.from_16_bits(0x2AA6, 'Central Address Resolution')
 
 
 # -----------------------------------------------------------------------------
@@ -189,7 +191,6 @@ class Service(Attribute):
         self.uuid              = uuid
         self.included_services = []
         self.characteristics   = characteristics[:]
-        self.end_group_handle  = 0
         self.primary           = primary
 
     def __str__(self):
@@ -197,6 +198,18 @@ class Service(Attribute):
 
 
 # -----------------------------------------------------------------------------
+class TemplateService(Service):
+    '''
+    Convenience abstract class that can be used by profile-specific subclasses that want
+    to expose their UUID as a class property
+    '''
+    UUID = None
+
+    def __init__(self, characteristics, primary=True):
+        super().__init__(self.UUID, characteristics, primary)
+
+
+# -----------------------------------------------------------------------------
 class Characteristic(Attribute):
     '''
     See Vol 3, Part G - 3.3 CHARACTERISTIC DEFINITION
@@ -227,56 +240,34 @@ class Characteristic(Attribute):
     def property_name(property):
         return Characteristic.PROPERTY_NAMES.get(property, '')
 
-    def __init__(self, uuid, properties, permissions, value = b'', descriptors = []):
-        # Convert the uuid to a UUID object if it isn't already
-        if type(uuid) is str:
-            uuid = UUID(uuid)
+    @staticmethod
+    def properties_as_string(properties):
+        return ','.join([
+            Characteristic.property_name(p) for p in Characteristic.PROPERTY_NAMES.keys()
+            if properties & p
+        ])
 
+    def __init__(self, uuid, properties, permissions, value = b'', descriptors = []):
         super().__init__(uuid, permissions, value)
-        self.uuid                    = uuid
-        self.properties              = properties
-        self._descriptors            = descriptors
-        self._descriptors_discovered = False
-        self.end_group_handle        = 0
-        self.attach_descriptors()
-
-    def attach_descriptors(self):
-        """ Let all the descriptors know they are attached to this characteristic """
-        for descriptor in self._descriptors:
-            descriptor.characteristic = self
-
-    def add_descriptor(self, descriptor):
-        descriptor.characteristic = self
-        self.descriptors.append(descriptor)
+        self.uuid        = self.type
+        self.properties  = properties
+        self.descriptors = descriptors
 
     def get_descriptor(self, descriptor_type):
         for descriptor in self.descriptors:
             if descriptor.uuid == descriptor_type:
                 return descriptor
 
-    @property
-    def descriptors(self):
-        return self._descriptors
-
-    @descriptors.setter
-    def descriptors(self, value):
-        self._descriptors = value
-        self._descriptors_discovered = True
-        self.attach_descriptors()
-
-    @property
-    def descriptors_discovered(self):
-        return self._descriptors_discovered
-
-    def get_properties_as_string(self):
-        return ','.join([self.property_name(p) for p in self.PROPERTY_NAMES.keys() if self.properties & p])
-
     def __str__(self):
-        return f'Characteristic(handle=0x{self.handle:04X}, end=0x{self.end_group_handle:04X}, uuid={self.uuid}, properties={self.get_properties_as_string()})'
+        return f'Characteristic(handle=0x{self.handle:04X}, end=0x{self.end_group_handle:04X}, uuid={self.uuid}, properties={Characteristic.properties_as_string(self.properties)})'
 
 
 # -----------------------------------------------------------------------------
 class CharacteristicValue:
+    '''
+    Characteristic value where reading and/or writing is delegated to functions
+    passed as arguments to the constructor.
+    '''
     def __init__(self, read=None, write=None):
         self._read = read
         self._write = write
@@ -290,19 +281,144 @@ class CharacteristicValue:
 
 
 # -----------------------------------------------------------------------------
+class CharacteristicAdapter:
+    '''
+    An adapter that can adapt any object with `read_value` and `write_value`
+    methods (like Characteristic and CharacteristicProxy objects) by wrapping
+    those methods with ones that return/accept encoded/decoded values.
+    Objects with async methods are considered proxies, so the adaptation is one
+    where the return value of `read_value` is decoded and the value passed to
+    `write_value` is encoded. Other objects are considered local characteristics
+    so the adaptation is one where the return value of `read_value` is encoded
+    and the value passed to `write_value` is decoded.
+    If the characteristic has a `subscribe` method, it is wrapped with one where
+    the values are decoded before being passed to the subscriber.
+    '''
+    def __init__(self, characteristic):
+        self.wrapped_characteristic = characteristic
+
+        if (
+            asyncio.iscoroutinefunction(characteristic.read_value) and
+            asyncio.iscoroutinefunction(characteristic.write_value)
+        ):
+            self.read_value  = self.read_decoded_value
+            self.write_value = self.write_decoded_value
+        else:
+            self.read_value  = self.read_encoded_value
+            self.write_value = self.write_encoded_value
+
+        if hasattr(self.wrapped_characteristic, 'subscribe'):
+            self.subscribe = self.wrapped_subscribe
+
+    def __getattr__(self, name):
+        return getattr(self.wrapped_characteristic, name)
+
+    def read_encoded_value(self, connection):
+        return self.encode_value(self.wrapped_characteristic.read_value(connection))
+
+    def write_encoded_value(self, connection, value):
+        return self.wrapped_characteristic.write_value(connection, self.decode_value(value))
+
+    async def read_decoded_value(self):
+        return self.decode_value(await self.wrapped_characteristic.read_value())
+
+    async def write_decoded_value(self, value):
+        return await self.wrapped_characteristic.write_value(self.encode_value(value))
+
+    def encode_value(self, value):
+        return value
+
+    def decode_value(self, value):
+        return value
+
+    def wrapped_subscribe(self, subscriber=None):
+        return self.wrapped_characteristic.subscribe(
+            None if subscriber is None else lambda value: subscriber(self.decode_value(value))
+        )
+
+
+# -----------------------------------------------------------------------------
+class DelegatedCharacteristicAdapter(CharacteristicAdapter):
+    def __init__(self, characteristic, encode, decode):
+        super().__init__(characteristic)
+        self.encode = encode
+        self.decode = decode
+
+    def encode_value(self, value):
+        return self.encode(value)
+
+    def decode_value(self, value):
+        return self.decode(value)
+
+
+# -----------------------------------------------------------------------------
+class PackedCharacteristicAdapter(CharacteristicAdapter):
+    '''
+    Adapter that packs/unpacks characteristic values according to a standard
+    Python `struct` format.
+    For formats with a single value, the adapted `read_value` and `write_value`
+    methods return/accept single values. For formats with multiple values,
+    they return/accept a tuple with the same number of elements as is required for
+    the format.
+    '''
+    def __init__(self, characteristic, format):
+        super().__init__(characteristic)
+        self.struct = struct.Struct(format)
+
+    def pack(self, *values):
+        return self.struct.pack(*values)
+
+    def unpack(self, buffer):
+        return self.struct.unpack(buffer)
+
+    def encode_value(self, value):
+        return self.pack(*value if type(value) is tuple else (value,))
+
+    def decode_value(self, value):
+        unpacked = self.unpack(value)
+        return unpacked[0] if len(unpacked) == 1 else unpacked
+
+
+# -----------------------------------------------------------------------------
+class MappedCharacteristicAdapter(PackedCharacteristicAdapter):
+    '''
+    Adapter that packs/unpacks characteristic values according to a standard
+    Python `struct` format.
+    The adapted `read_value` and `write_value` methods return/accept aa dictionary which
+    is packed/unpacked according to format, with the arguments extracted from the dictionary
+    by key, in the same order as they occur in the `keys` parameter.
+    '''
+    def __init__(self, characteristic, format, keys):
+        super().__init__(characteristic, format)
+        self.keys = keys
+
+    def pack(self, values):
+        return super().pack(*(values[key] for key in self.keys))
+
+    def unpack(self, buffer):
+        return dict(zip(self.keys, super().unpack(buffer)))
+
+
+# -----------------------------------------------------------------------------
+class UTF8CharacteristicAdapter(CharacteristicAdapter):
+    '''
+    Adapter that converts strings to/from bytes using UTF-8 encoding
+    '''
+    def encode_value(self, value):
+        return value.encode('utf-8')
+
+    def decode_value(self, value):
+        return value.decode('utf-8')
+
+
+# -----------------------------------------------------------------------------
 class Descriptor(Attribute):
     '''
     See Vol 3, Part G - 3.3.3 Characteristic Descriptor Declarations
     '''
 
-    def __init__(self, uuid, permissions, value = b''):
-        # Convert the uuid to a UUID object if it isn't already
-        if type(uuid) is str:
-            uuid = UUID(uuid)
-
-        super().__init__(uuid, permissions, value)
-        self.uuid = uuid
-        self.characteristic = None
+    def __init__(self, descriptor_type, permissions, value = b''):
+        super().__init__(descriptor_type, permissions, value)
 
     def __str__(self):
-        return f'Descriptor(handle=0x{self.handle:04X}, uuid={self.uuid}, value={self.read_value(None).hex()})'
+        return f'Descriptor(handle=0x{self.handle:04X}, type={self.type}, value={self.read_value(None).hex()})'
diff --git a/bumble/gatt_client.py b/bumble/gatt_client.py
index 729f74e..e817e2e 100644
--- a/bumble/gatt_client.py
+++ b/bumble/gatt_client.py
@@ -35,10 +35,9 @@ from .gatt import (
     GATT_CLIENT_CHARACTERISTIC_CONFIGURATION_DESCRIPTOR,
     GATT_REQUEST_TIMEOUT,
     GATT_PRIMARY_SERVICE_ATTRIBUTE_TYPE,
+    GATT_SECONDARY_SERVICE_ATTRIBUTE_TYPE,
     GATT_CHARACTERISTIC_ATTRIBUTE_TYPE,
-    Service,
-    Characteristic,
-    Descriptor
+    Characteristic
 )
 
 # -----------------------------------------------------------------------------
@@ -48,6 +47,91 @@ logger = logging.getLogger(__name__)
 
 
 # -----------------------------------------------------------------------------
+# Proxies
+# -----------------------------------------------------------------------------
+class AttributeProxy(EventEmitter):
+    def __init__(self, client, handle, end_group_handle, attribute_type):
+        EventEmitter.__init__(self)
+        self.client           = client
+        self.handle           = handle
+        self.end_group_handle = end_group_handle
+        self.type             = attribute_type
+
+    async def read_value(self, no_long_read=False):
+        return await self.client.read_value(self.handle, no_long_read)
+
+    async def write_value(self, value, with_response=False):
+        return await self.client.write_value(self.handle, value, with_response)
+
+    def __str__(self):
+        return f'Attribute(handle=0x{self.handle:04X}, type={self.uuid})'
+
+
+class ServiceProxy(AttributeProxy):
+    @staticmethod
+    def from_client(cls, client, service_uuid):
+        # The service and its characteristics are considered to have already been discovered
+        services = client.get_services_by_uuid(service_uuid)
+        service = services[0] if services else None
+        return cls(service) if service else None
+
+    def __init__(self, client, handle, end_group_handle, uuid, primary=True):
+        attribute_type = GATT_PRIMARY_SERVICE_ATTRIBUTE_TYPE if primary else GATT_SECONDARY_SERVICE_ATTRIBUTE_TYPE
+        super().__init__(client, handle, end_group_handle, attribute_type)
+        self.uuid            = uuid
+        self.characteristics = []
+
+    async def discover_characteristics(self, uuids=[]):
+        return await self.client.discover_characteristics(uuids, self)
+
+    def get_characteristics_by_uuid(self, uuid):
+        return self.client.get_characteristics_by_uuid(uuid, self)
+
+    def __str__(self):
+        return f'Service(handle=0x{self.handle:04X}, uuid={self.uuid})'
+
+
+class CharacteristicProxy(AttributeProxy):
+    def __init__(self, client, handle, end_group_handle, uuid, properties):
+        super().__init__(client, handle, end_group_handle, uuid)
+        self.uuid                   = uuid
+        self.properties             = properties
+        self.descriptors            = []
+        self.descriptors_discovered = False
+
+    def get_descriptor(self, descriptor_type):
+        for descriptor in self.descriptors:
+            if descriptor.type == descriptor_type:
+                return descriptor
+
+    async def discover_descriptors(self):
+        return await self.client.discover_descriptors(self)
+
+    async def subscribe(self, subscriber=None):
+        return await self.client.subscribe(self, subscriber)
+
+    def __str__(self):
+        return f'Characteristic(handle=0x{self.handle:04X}, uuid={self.uuid}, properties={Characteristic.properties_as_string(self.properties)})'
+
+
+class DescriptorProxy(AttributeProxy):
+    def __init__(self, client, handle, descriptor_type):
+        super().__init__(client, handle, 0, descriptor_type)
+
+    def __str__(self):
+        return f'Descriptor(handle=0x{self.handle:04X}, type={self.type})'
+
+
+class ProfileServiceProxy:
+    '''
+    Base class for profile-specific service proxies
+    '''
+    @classmethod
+    def from_client(cls, client):
+        return ServiceProxy.from_client(cls, client, cls.SERVICE_CLASS.UUID)
+
+
+# -----------------------------------------------------------------------------
 # GATT Client
 # -----------------------------------------------------------------------------
 class Client:
@@ -173,10 +257,14 @@ class Client:
                     logger.warning(f'bogus handle values: {attribute_handle} {end_group_handle}')
                     return
 
-                # Create a primary service object
-                service = Service(UUID.from_bytes(attribute_value), [], True)
-                service.handle = attribute_handle
-                service.end_group_handle = end_group_handle
+                # Create a service proxy for this service
+                service = ServiceProxy(
+                    self,
+                    attribute_handle,
+                    end_group_handle,
+                    UUID.from_bytes(attribute_value),
+                    True
+                )
 
                 # Filter out returned services based on the given uuids list
                 if (not uuids) or (service.uuid in uuids):
@@ -233,10 +321,8 @@ class Client:
                     logger.warning(f'bogus handle values: {attribute_handle} {end_group_handle}')
                     return
 
-                # Create a primary service object
-                service = Service(uuid, [], True)
-                service.handle = attribute_handle
-                service.end_group_handle = end_group_handle
+                # Create a service proxy for this service
+                service = ServiceProxy(self, attribute_handle, end_group_handle, uuid, True)
 
                 # Add the service to the peer's service list
                 services.append(service)
@@ -314,8 +400,7 @@ class Client:
 
                     properties, handle = struct.unpack_from('<BH', attribute_value)
                     characteristic_uuid = UUID.from_bytes(attribute_value[3:])
-                    characteristic = Characteristic(characteristic_uuid, properties, 0)
-                    characteristic.handle = handle
+                    characteristic = CharacteristicProxy(self, handle, 0, characteristic_uuid, properties)
 
                     # Set the previous characteristic's end handle
                     if characteristics:
@@ -382,8 +467,7 @@ class Client:
                     logger.warning(f'bogus handle value: {attribute_handle}')
                     return []
 
-                descriptor = Descriptor(UUID.from_bytes(attribute_uuid), 0)
-                descriptor.handle = attribute_handle
+                descriptor = DescriptorProxy(self, attribute_handle, UUID.from_bytes(attribute_uuid))
                 descriptors.append(descriptor)
                 # TODO: read descriptor value
 
@@ -427,8 +511,7 @@ class Client:
                     logger.warning(f'bogus handle value: {attribute_handle}')
                     return []
 
-                attribute = Attribute(attribute_uuid, 0)
-                attribute.handle = attribute_handle
+                attribute = AttributeProxy(self, attribute_handle, 0, UUID.from_bytes(attribute_uuid))
                 attributes.append(attribute)
 
             # Move on to the next attributes
diff --git a/bumble/profiles/__init__.py b/bumble/profiles/__init__.py
new file mode 100644
index 0000000..4b7e706
--- /dev/null
+++ b/bumble/profiles/__init__.py
@@ -0,0 +1,13 @@
+# Copyright 2021-2022 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
diff --git a/bumble/profiles/battery_service.py b/bumble/profiles/battery_service.py
new file mode 100644
index 0000000..a978c05
--- /dev/null
+++ b/bumble/profiles/battery_service.py
@@ -0,0 +1,61 @@
+# Copyright 2021-2022 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+
+# -----------------------------------------------------------------------------
+# Imports
+# -----------------------------------------------------------------------------
+from ..gatt_client import ProfileServiceProxy
+from ..gatt import (
+    GATT_BATTERY_SERVICE,
+    GATT_BATTERY_LEVEL_CHARACTERISTIC,
+    TemplateService,
+    Characteristic,
+    CharacteristicValue,
+    PackedCharacteristicAdapter
+)
+
+
+# -----------------------------------------------------------------------------
+class BatteryService(TemplateService):
+    UUID = GATT_BATTERY_SERVICE
+    BATTERY_LEVEL_FORMAT = 'B'
+
+    def __init__(self, read_battery_level):
+        self.battery_level_characteristic = PackedCharacteristicAdapter(
+            Characteristic(
+                GATT_BATTERY_LEVEL_CHARACTERISTIC,
+                Characteristic.READ | Characteristic.NOTIFY,
+                Characteristic.READABLE,
+                CharacteristicValue(read=read_battery_level)
+            ),
+            format=BatteryService.BATTERY_LEVEL_FORMAT
+        )
+        super().__init__([self.battery_level_characteristic])
+
+
+# -----------------------------------------------------------------------------
+class BatteryServiceProxy(ProfileServiceProxy):
+    SERVICE_CLASS = BatteryService
+
+    def __init__(self, service_proxy):
+        self.service_proxy = service_proxy
+
+        if characteristics := service_proxy.get_characteristics_by_uuid(GATT_BATTERY_LEVEL_CHARACTERISTIC):
+            self.battery_level = PackedCharacteristicAdapter(
+                characteristics[0],
+                format=BatteryService.BATTERY_LEVEL_FORMAT
+            )
+        else:
+            self.battery_level = None
diff --git a/bumble/profiles/device_information_service.py b/bumble/profiles/device_information_service.py
new file mode 100644
index 0000000..99765b4
--- /dev/null
+++ b/bumble/profiles/device_information_service.py
@@ -0,0 +1,135 @@
+# Copyright 2021-2022 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+
+# -----------------------------------------------------------------------------
+# Imports
+# -----------------------------------------------------------------------------
+import struct
+from typing import Tuple
+
+from ..gatt_client import ProfileServiceProxy
+from ..gatt import (
+    GATT_DEVICE_INFORMATION_SERVICE,
+    GATT_FIRMWARE_REVISION_STRING_CHARACTERISTIC,
+    GATT_HARDWARE_REVISION_STRING_CHARACTERISTIC,
+    GATT_MANUFACTURER_NAME_STRING_CHARACTERISTIC,
+    GATT_MODEL_NUMBER_STRING_CHARACTERISTIC,
+    GATT_SERIAL_NUMBER_STRING_CHARACTERISTIC,
+    GATT_SOFTWARE_REVISION_STRING_CHARACTERISTIC,
+    GATT_SYSTEM_ID_CHARACTERISTIC,
+    GATT_REGULATORY_CERTIFICATION_DATA_LIST_CHARACTERISTIC,
+    TemplateService,
+    Characteristic,
+    DelegatedCharacteristicAdapter,
+    UTF8CharacteristicAdapter
+)
+
+
+# -----------------------------------------------------------------------------
+class DeviceInformationService(TemplateService):
+    UUID = GATT_DEVICE_INFORMATION_SERVICE
+
+    @staticmethod
+    def pack_system_id(oui, manufacturer_id):
+        return struct.pack('<Q', oui << 40 | manufacturer_id)
+
+    @staticmethod
+    def unpack_system_id(buffer):
+        system_id = struct.unpack('<Q', buffer)[0]
+        return (system_id >> 40, system_id & 0xFFFFFFFFFF)
+
+    def __init__(
+        self,
+        manufacturer_name: str = None,
+        model_number: str = None,
+        serial_number: str = None,
+        hardware_revision: str = None,
+        firmware_revision: str = None,
+        software_revision: str = None,
+        system_id: Tuple[int, int] = None,  # (OUI, Manufacturer ID)
+        ieee_regulatory_certification_data_list: bytes = None
+        # TODO: pnp_id
+    ):
+        characteristics = [
+            Characteristic(
+                uuid,
+                Characteristic.READ,
+                Characteristic.READABLE,
+                field
+            )
+            for (field, uuid) in (
+                (manufacturer_name, GATT_MANUFACTURER_NAME_STRING_CHARACTERISTIC),
+                (model_number,      GATT_MODEL_NUMBER_STRING_CHARACTERISTIC),
+                (serial_number,     GATT_SERIAL_NUMBER_STRING_CHARACTERISTIC),
+                (hardware_revision, GATT_HARDWARE_REVISION_STRING_CHARACTERISTIC),
+                (firmware_revision, GATT_FIRMWARE_REVISION_STRING_CHARACTERISTIC),
+                (software_revision, GATT_SOFTWARE_REVISION_STRING_CHARACTERISTIC)
+            )
+            if field is not None
+        ]
+
+        if system_id is not None:
+            characteristics.append(Characteristic(
+                GATT_SYSTEM_ID_CHARACTERISTIC,
+                Characteristic.READ,
+                Characteristic.READABLE,
+                self.pack_system_id(*system_id)
+            ))
+
+        if ieee_regulatory_certification_data_list is not None:
+            characteristics.append(Characteristic(
+                GATT_REGULATORY_CERTIFICATION_DATA_LIST_CHARACTERISTIC,
+                Characteristic.READ,
+                Characteristic.READABLE,
+                ieee_regulatory_certification_data_list
+            ))
+
+        super().__init__(characteristics)
+
+
+# -----------------------------------------------------------------------------
+class DeviceInformationServiceProxy(ProfileServiceProxy):
+    SERVICE_CLASS = DeviceInformationService
+
+    def __init__(self, service_proxy):
+        self.service_proxy = service_proxy
+
+        for (field, uuid) in (
+            ('manufacturer_name', GATT_MANUFACTURER_NAME_STRING_CHARACTERISTIC),
+            ('model_number',      GATT_MODEL_NUMBER_STRING_CHARACTERISTIC),
+            ('serial_number',     GATT_SERIAL_NUMBER_STRING_CHARACTERISTIC),
+            ('hardware_revision', GATT_HARDWARE_REVISION_STRING_CHARACTERISTIC),
+            ('firmware_revision', GATT_FIRMWARE_REVISION_STRING_CHARACTERISTIC),
+            ('software_revision', GATT_SOFTWARE_REVISION_STRING_CHARACTERISTIC)
+        ):
+            if characteristics := service_proxy.get_characteristics_by_uuid(uuid):
+                characteristic = UTF8CharacteristicAdapter(characteristics[0])
+            else:
+                characteristic = None
+            self.__setattr__(field, characteristic)
+
+        if characteristics := service_proxy.get_characteristics_by_uuid(GATT_SYSTEM_ID_CHARACTERISTIC):
+            self.system_id = DelegatedCharacteristicAdapter(
+                characteristics[0],
+                encode=lambda v: DeviceInformationService.pack_system_id(*v),
+                decode=DeviceInformationService.unpack_system_id
+            )
+        else:
+            self.system_id = None
+
+        if characteristics := service_proxy.get_characteristics_by_uuid(GATT_REGULATORY_CERTIFICATION_DATA_LIST_CHARACTERISTIC):
+            self.ieee_regulatory_certification_data_list = characteristics[0]
+        else:
+            self.ieee_regulatory_certification_data_list = None
diff --git a/examples/battery_client.py b/examples/battery_client.py
new file mode 100644
index 0000000..888b23e
--- /dev/null
+++ b/examples/battery_client.py
@@ -0,0 +1,72 @@
+# Copyright 2021-2022 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# -----------------------------------------------------------------------------
+# Imports
+# -----------------------------------------------------------------------------
+import asyncio
+import sys
+import os
+import logging
+from colors import color
+from bumble.device import Device, Peer
+from bumble.transport import open_transport
+from bumble.profiles.battery_service import BatteryServiceProxy
+
+
+# -----------------------------------------------------------------------------
+async def main():
+    if len(sys.argv) != 3:
+        print('Usage: battery_client.py <transport-spec> <bluetooth-address>')
+        print('example: battery_client.py usb:0 E1:CA:72:48:C4:E8')
+        return
+
+    print('<<< connecting to HCI...')
+    async with await open_transport(sys.argv[1]) as (hci_source, hci_sink):
+        print('<<< connected')
+
+        # Create and start a device
+        device = Device.with_hci('Bumble', 'F0:F1:F2:F3:F4:F5', hci_source, hci_sink)
+        await device.power_on()
+
+        # Connect to the peer
+        target_address = sys.argv[2]
+        print(f'=== Connecting to {target_address}...')
+        connection = await device.connect(target_address)
+        print(f'=== Connected to {connection}')
+
+        # Discover the Battery Service
+        peer = Peer(connection)
+        print('=== Discovering Battery Service')
+        battery_service = await peer.discover_and_create_service_proxy(BatteryServiceProxy)
+
+        # Check that the service was found
+        if not battery_service:
+            print('!!! Service not found')
+            return
+
+        # Subscribe to and read the battery level
+        if battery_service.battery_level:
+            await battery_service.battery_level.subscribe(
+                lambda value: print(f'{color("Battery Level Update:", "green")} {value}')
+            )
+            value = await battery_service.battery_level.read_value()
+            print(f'{color("Initial Battery Level:", "green")} {value}')
+
+        await hci_source.wait_for_termination()
+
+
+# -----------------------------------------------------------------------------
+logging.basicConfig(level = os.environ.get('BUMBLE_LOGLEVEL', 'DEBUG').upper())
+asyncio.run(main())
diff --git a/examples/battery_service.py b/examples/battery_server.py
index b205687..3fabf0d 100644
--- a/examples/battery_service.py
+++ b/examples/battery_server.py
@@ -25,59 +25,41 @@ import struct
 from bumble.core import AdvertisingData
 from bumble.device import Device
 from bumble.transport import open_transport_or_link
-from bumble.gatt import (
-    Service,
-    Characteristic,
-    CharacteristicValue,
-    GATT_DEVICE_BATTERY_SERVICE,
-    GATT_BATTERY_LEVEL_CHARACTERISTIC
-)
-
-
-# -----------------------------------------------------------------------------
-def read_battery_level(connection):
-    return bytes([random.randint(0, 100)])
+from bumble.profiles.battery_service import BatteryService
 
 
 # -----------------------------------------------------------------------------
 async def main():
     if len(sys.argv) != 3:
-        print('Usage: python battery_service.py <device-config> <transport-spec>')
-        print('example: python battery_service.py device1.json usb:0')
+        print('Usage: python battery_server.py <device-config> <transport-spec>')
+        print('example: python battery_server.py device1.json usb:0')
         return
 
     async with await open_transport_or_link(sys.argv[2]) as (hci_source, hci_sink):
-        # Create a device to manage the host
         device = Device.from_config_file_with_hci(sys.argv[1], hci_source, hci_sink)
 
-        # Add a Battery Service to the GATT sever
-        device.add_services([
-            Service(
-                GATT_DEVICE_BATTERY_SERVICE,
-                [
-                    Characteristic(
-                        GATT_BATTERY_LEVEL_CHARACTERISTIC,
-                        Characteristic.READ,
-                        Characteristic.READABLE,
-                        CharacteristicValue(read=read_battery_level)
-                    )
-                ]
-            )
-        ])
+        # Add a Device Information Service and Battery Service to the GATT sever
+        battery_service = BatteryService(lambda _: random.randint(0, 100))
+        device.add_service(battery_service)
 
         # Set the advertising data
         device.advertising_data = bytes(
             AdvertisingData([
                 (AdvertisingData.COMPLETE_LOCAL_NAME, bytes('Bumble Battery', 'utf-8')),
-                (AdvertisingData.INCOMPLETE_LIST_OF_16_BIT_SERVICE_CLASS_UUIDS, struct.pack('<H', 0x180F)),
+                (AdvertisingData.INCOMPLETE_LIST_OF_16_BIT_SERVICE_CLASS_UUIDS, bytes(battery_service.uuid)),
                 (AdvertisingData.APPEARANCE, struct.pack('<H', 0x0340))
             ])
         )
 
         # Go!
         await device.power_on()
-        await device.start_advertising()
-        await hci_source.wait_for_termination()
+        await device.start_advertising(auto_restart=True)
+
+        # Notify every 3 seconds
+        while True:
+            await asyncio.sleep(3.0)
+            await device.notify_subscribers(battery_service.battery_level_characteristic)
+
 
 # -----------------------------------------------------------------------------
 logging.basicConfig(level = os.environ.get('BUMBLE_LOGLEVEL', 'DEBUG').upper())
diff --git a/examples/device_information_client.py b/examples/device_information_client.py
new file mode 100644
index 0000000..ed5892b
--- /dev/null
+++ b/examples/device_information_client.py
@@ -0,0 +1,80 @@
+# Copyright 2021-2022 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# -----------------------------------------------------------------------------
+# Imports
+# -----------------------------------------------------------------------------
+import asyncio
+import sys
+import os
+import logging
+from colors import color
+from bumble.device import Device, Peer
+from bumble.profiles.device_information_service import DeviceInformationServiceProxy
+from bumble.transport import open_transport
+
+
+# -----------------------------------------------------------------------------
+async def main():
+    if len(sys.argv) != 3:
+        print('Usage: device_information_client.py <transport-spec> <bluetooth-address>')
+        print('example: device_information_client.py usb:0 E1:CA:72:48:C4:E8')
+        return
+
+    print('<<< connecting to HCI...')
+    async with await open_transport(sys.argv[1]) as (hci_source, hci_sink):
+        print('<<< connected')
+
+        # Create and start a device
+        device = Device.with_hci('Bumble', 'F0:F1:F2:F3:F4:F5', hci_source, hci_sink)
+        await device.power_on()
+
+        # Connect to the peer
+        target_address = sys.argv[2]
+        print(f'=== Connecting to {target_address}...')
+        connection = await device.connect(target_address)
+        print(f'=== Connected to {connection}')
+
+        # Discover the Device Information service
+        peer = Peer(connection)
+        print('=== Discovering Device Information Service')
+        device_information_service = await peer.discover_service_and_create_proxy(DeviceInformationServiceProxy)
+
+        # Check that the service was found
+        if device_information_service is None:
+            print('!!! Service not found')
+            return
+
+        # Read and print the fields
+        if device_information_service.manufacturer_name is not None:
+            print(color('Manufacturer Name:       ', 'green'), await device_information_service.manufacturer_name.read_value())
+        if device_information_service.model_number is not None:
+            print(color('Model Number:            ', 'green'), await device_information_service.model_number.read_value())
+        if device_information_service.serial_number is not None:
+            print(color('Serial Number:           ', 'green'), await device_information_service.serial_number.read_value())
+        if device_information_service.hardware_revision is not None:
+            print(color('Hardware Revision:       ', 'green'), await device_information_service.hardware_revision.read_value())
+        if device_information_service.firmware_revision is not None:
+            print(color('Firmware Revision:       ', 'green'), await device_information_service.firmware_revision.read_value())
+        if device_information_service.software_revision is not None:
+            print(color('Software Revision:       ', 'green'), await device_information_service.software_revision.read_value())
+        if device_information_service.system_id is not None:
+            print(color('System ID:               ', 'green'), await device_information_service.system_id.read_value())
+        if device_information_service.ieee_regulatory_certification_data_list is not None:
+            print(color('Regulatory Certification:', 'green'), (await device_information_service.ieee_regulatory_certification_data_list.read_value()).hex())
+
+
+# -----------------------------------------------------------------------------
+logging.basicConfig(level = os.environ.get('BUMBLE_LOGLEVEL', 'DEBUG').upper())
+asyncio.run(main())
diff --git a/examples/device_information_server.py b/examples/device_information_server.py
new file mode 100644
index 0000000..9c3b6b1
--- /dev/null
+++ b/examples/device_information_server.py
@@ -0,0 +1,66 @@
+# Copyright 2021-2022 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# -----------------------------------------------------------------------------
+# Imports
+# -----------------------------------------------------------------------------
+import asyncio
+import sys
+import os
+import logging
+import struct
+
+from bumble.core import AdvertisingData
+from bumble.device import Device
+from bumble.transport import open_transport_or_link
+from bumble.profiles.device_information_service import DeviceInformationService
+
+
+# -----------------------------------------------------------------------------
+async def main():
+    if len(sys.argv) != 3:
+        print('Usage: python device_info_server.py <device-config> <transport-spec>')
+        print('example: python device_info_server.py device1.json usb:0')
+        return
+
+    async with await open_transport_or_link(sys.argv[2]) as (hci_source, hci_sink):
+        device = Device.from_config_file_with_hci(sys.argv[1], hci_source, hci_sink)
+
+        # Add a Device Information Service to the GATT sever
+        device_information_service = DeviceInformationService(
+            manufacturer_name = 'ACME',
+            model_number      = 'AB-102',
+            serial_number     = '7654321',
+            hardware_revision = '1.1.3',
+            software_revision = '2.5.6',
+            system_id         = (0x123456, 0x8877665544)
+        )
+        device.add_service(device_information_service)
+
+        # Set the advertising data
+        device.advertising_data = bytes(
+            AdvertisingData([
+                (AdvertisingData.COMPLETE_LOCAL_NAME, bytes('Bumble Device', 'utf-8')),
+                (AdvertisingData.APPEARANCE, struct.pack('<H', 0x0340))
+            ])
+        )
+
+        # Go!
+        await device.power_on()
+        await device.start_advertising(auto_restart=True)
+        await hci_source.wait_for_termination()
+
+# -----------------------------------------------------------------------------
+logging.basicConfig(level = os.environ.get('BUMBLE_LOGLEVEL', 'DEBUG').upper())
+asyncio.run(main())
diff --git a/examples/get_peer_device_info.py b/examples/get_peer_device_info.py
deleted file mode 100644
index e4babfc..0000000
--- a/examples/get_peer_device_info.py
+++ /dev/null
@@ -1,96 +0,0 @@
-# Copyright 2021-2022 Google LLC
-#
-# Licensed under the Apache License, Version 2.0 (the "License");
-# you may not use this file except in compliance with the License.
-# You may obtain a copy of the License at
-#
-#      https://www.apache.org/licenses/LICENSE-2.0
-#
-# Unless required by applicable law or agreed to in writing, software
-# distributed under the License is distributed on an "AS IS" BASIS,
-# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-# See the License for the specific language governing permissions and
-# limitations under the License.
-
-# -----------------------------------------------------------------------------
-# Imports
-# -----------------------------------------------------------------------------
-import asyncio
-import sys
-import os
-import logging
-from colors import color
-from bumble.device import Device, Peer
-from bumble.host import Host
-from bumble.transport import open_transport
-from bumble.utils import AsyncRunner
-from bumble import gatt
-
-
-# -----------------------------------------------------------------------------
-class Listener(Device.Listener):
-    def __init__(self, device):
-        self.device = device
-        self.done = asyncio.get_running_loop().create_future()
-
-    @AsyncRunner.run_in_task()
-    async def on_connection(self, connection):
-        print(f'=== Connected to {connection}')
-
-        # Discover the Device Info service
-        peer = Peer(connection)
-        print('=== Discovering Device Info')
-        await peer.discover_services([gatt.GATT_DEVICE_INFORMATION_SERVICE])
-
-        # Check that the service was found
-        device_info_services = peer.get_services_by_uuid(gatt.GATT_DEVICE_INFORMATION_SERVICE)
-        if not device_info_services:
-            print('!!! Service not found')
-            return
-
-        # Get the characteristics we want from the (first) device info service
-        service = device_info_services[0]
-        await peer.discover_characteristics([
-            gatt.GATT_MANUFACTURER_NAME_STRING_CHARACTERISTIC
-        ], service)
-
-        # Read the manufacturer name
-        manufacturer_name = peer.get_characteristics_by_uuid(gatt.GATT_MANUFACTURER_NAME_STRING_CHARACTERISTIC, service)
-        if manufacturer_name:
-            value = await peer.read_value(manufacturer_name[0])
-            print(color('Manufacturer Name:', 'green'), value.decode('utf-8'))
-        else:
-            print('>>> No manufacturer name')
-
-        self.done.set_result(None)
-
-
-# -----------------------------------------------------------------------------
-async def main():
-    if len(sys.argv) != 3:
-        print('Usage: get_peer_device_info.py <transport-spec> <bluetooth-address>')
-        print('example: get_peer_device_info.py usb:0 E1:CA:72:48:C4:E8')
-        return
-
-    print('<<< connecting to HCI...')
-    packet_source, packet_sink = await open_transport(sys.argv[1])
-    print('<<< connected')
-
-    # Create a host using the packet source and sink as controller
-    host = Host(controller_source=packet_source, controller_sink=packet_sink)
-
-    # Create a device to manage the host, with a custom listener
-    device = Device('Bumble', address = 'F0:F1:F2:F3:F4:F5', host = host)
-    device.listener = Listener(device)
-    await device.power_on()
-
-    # Connect to a peer
-    target_address = sys.argv[2]
-    print(f'=== Connecting to {target_address}...')
-    await device.connect(target_address)
-    await device.listener.done
-
-
-# -----------------------------------------------------------------------------
-logging.basicConfig(level = os.environ.get('BUMBLE_LOGLEVEL', 'DEBUG').upper())
-asyncio.run(main())
diff --git a/examples/run_controller.py b/examples/run_controller.py
index 1a8cd0e..d8295d4 100644
--- a/examples/run_controller.py
+++ b/examples/run_controller.py
@@ -45,8 +45,7 @@ async def main():
 
         # Create a first controller using the packet source/sink as its host interface
         controller1 = Controller('C1', host_source = hci_source, host_sink = hci_sink, link = link)
-        print("====", sys.argv)
-        controller1.address = sys.argv[1]
+        controller1.random_address = sys.argv[1]
 
         # Create a second controller using the same link
         controller2 = Controller('C2', link = link)
diff --git a/examples/run_gatt_client.py b/examples/run_gatt_client.py
index 99781fb..5af86fb 100644
--- a/examples/run_gatt_client.py
+++ b/examples/run_gatt_client.py
@@ -41,10 +41,10 @@ class Listener(Device.Listener):
         print('=== Discovering services')
         peer = Peer(connection)
         await peer.discover_services()
-        await peer.discover_characteristics()
         for service in peer.services:
+            await service.discover_characteristics()
             for characteristic in service.characteristics:
-                await peer.discover_descriptors(characteristic)
+                await characteristic.discover_descriptors()
 
         print('=== Services discovered')
         show_services(peer.services)
diff --git a/examples/run_gatt_client_and_server.py b/examples/run_gatt_client_and_server.py
index 211eb5c..940b1a8 100644
--- a/examples/run_gatt_client_and_server.py
+++ b/examples/run_gatt_client_and_server.py
@@ -25,7 +25,6 @@ from bumble.controller import Controller
 from bumble.device import Device, Peer
 from bumble.host import Host
 from bumble.link import LocalLink
-from bumble.utils import AsyncRunner
 from bumble.gatt import (
     Service,
     Characteristic,
@@ -38,43 +37,6 @@ from bumble.gatt import (
 
 
 # -----------------------------------------------------------------------------
-class ClientListener(Device.Listener):
-    def __init__(self, device):
-        self.device = device
-
-    @AsyncRunner.run_in_task()
-    async def on_connection(self, connection):
-        print(f'=== Client: connected to {connection}')
-
-        # Discover all services
-        print('=== Discovering services')
-        peer = Peer(connection)
-        await peer.discover_services()
-        await peer.discover_characteristics()
-        for service in peer.services:
-            for characteristic in service.characteristics:
-                await peer.discover_descriptors(characteristic)
-
-        print('=== Services discovered')
-        show_services(peer.services)
-
-        # Discover all attributes
-        print('=== Discovering attributes')
-        attributes = await peer.discover_attributes()
-        for attribute in attributes:
-            print(attribute)
-        print('=== Attributes discovered')
-
-        # Read all attributes
-        for attribute in attributes:
-            try:
-                value = await peer.read_value(attribute)
-                print(color(f'0x{attribute.handle:04X} = {value.hex()}', 'green'))
-            except ProtocolError as error:
-                print(color(f'cannot read {attribute.handle:04X}:', 'red'), error)
-
-
-# -----------------------------------------------------------------------------
 class ServerListener(Device.Listener):
     def on_connection(self, connection):
         print(f'### Server:  connected to {connection}')
@@ -90,7 +52,6 @@ async def main():
     client_host = Host()
     client_host.controller = client_controller
     client_device = Device("client", address = 'F0:F1:F2:F3:F4:F5', host = client_host)
-    client_device.listener = ClientListener(client_device)
     await client_device.power_on()
 
     # Setup a stack for the server
@@ -116,7 +77,36 @@ async def main():
     server_device.add_service(device_info_service)
 
     # Connect the client to the server
-    await client_device.connect(server_device.address)
+    connection = await client_device.connect(server_device.random_address)
+    print(f'=== Client: connected to {connection}')
+
+    # Discover all services
+    print('=== Discovering services')
+    peer = Peer(connection)
+    await peer.discover_services()
+    for service in peer.services:
+        await service.discover_characteristics()
+        for characteristic in service.characteristics:
+            await characteristic.discover_descriptors()
+
+    print('=== Services discovered')
+    show_services(peer.services)
+
+    # Discover all attributes
+    print('=== Discovering attributes')
+    attributes = await peer.discover_attributes()
+    for attribute in attributes:
+        print(attribute)
+    print('=== Attributes discovered')
+
+    # Read all attributes
+    for attribute in attributes:
+        try:
+            value = await attribute.read_value()
+            print(color(f'0x{attribute.handle:04X} = {value.hex()}', 'green'))
+        except ProtocolError as error:
+            print(color(f'cannot read {attribute.handle:04X}:', 'red'), error)
+
     await asyncio.get_running_loop().create_future()
 
 # -----------------------------------------------------------------------------
diff --git a/tests/gatt_test.py b/tests/gatt_test.py
index 867156c..5df6e08 100644
--- a/tests/gatt_test.py
+++ b/tests/gatt_test.py
@@ -18,6 +18,7 @@
 import asyncio
 import logging
 import os
+import struct
 import pytest
 
 from bumble.controller import Controller
@@ -25,6 +26,12 @@ from bumble.link import LocalLink
 from bumble.device import Device, Peer
 from bumble.host import Host
 from bumble.gatt import (
+    GATT_BATTERY_LEVEL_CHARACTERISTIC,
+    CharacteristicAdapter,
+    DelegatedCharacteristicAdapter,
+    PackedCharacteristicAdapter,
+    MappedCharacteristicAdapter,
+    UTF8CharacteristicAdapter,
     Service,
     Characteristic,
     CharacteristicValue
@@ -92,6 +99,96 @@ def test_ATT_Read_By_Group_Type_Request():
 
 
 # -----------------------------------------------------------------------------
+def test_CharacteristicAdapter():
+    # Check that the CharacteristicAdapter base class is transparent
+    v = bytes([1, 2, 3])
+    c = Characteristic(GATT_BATTERY_LEVEL_CHARACTERISTIC, Characteristic.READ, Characteristic.READABLE, v)
+    a = CharacteristicAdapter(c)
+
+    value = a.read_value(None)
+    assert(value == v)
+
+    v = bytes([3, 4, 5])
+    a.write_value(None, v)
+    assert(c.value == v)
+
+    # Simple delegated adapter
+    a = DelegatedCharacteristicAdapter(c, lambda x: bytes(reversed(x)), lambda x: bytes(reversed(x)))
+
+    value = a.read_value(None)
+    assert(value == bytes(reversed(v)))
+
+    v = bytes([3, 4, 5])
+    a.write_value(None, v)
+    assert(a.value == bytes(reversed(v)))
+
+    # Packed adapter with single element format
+    v = 1234
+    pv = struct.pack('>H', v)
+    c.value = v
+    a = PackedCharacteristicAdapter(c, '>H')
+
+    value = a.read_value(None)
+    assert(value == pv)
+    c.value = None
+    a.write_value(None, pv)
+    assert(a.value == v)
+
+    # Packed adapter with multi-element format
+    v1 = 1234
+    v2 = 5678
+    pv = struct.pack('>HH', v1, v2)
+    c.value = (v1, v2)
+    a = PackedCharacteristicAdapter(c, '>HH')
+
+    value = a.read_value(None)
+    assert(value == pv)
+    c.value = None
+    a.write_value(None, pv)
+    assert(a.value == (v1, v2))
+
+    # Mapped adapter
+    v1 = 1234
+    v2 = 5678
+    pv = struct.pack('>HH', v1, v2)
+    mapped = {'v1': v1, 'v2': v2}
+    c.value = mapped
+    a = MappedCharacteristicAdapter(c, '>HH', ('v1', 'v2'))
+
+    value = a.read_value(None)
+    assert(value == pv)
+    c.value = None
+    a.write_value(None, pv)
+    assert(a.value == mapped)
+
+    # UTF-8 adapter
+    v = 'Hello π'
+    ev = v.encode('utf-8')
+    c.value = v
+    a = UTF8CharacteristicAdapter(c)
+
+    value = a.read_value(None)
+    assert(value == ev)
+    c.value = None
+    a.write_value(None, ev)
+    assert(a.value == v)
+
+
+# -----------------------------------------------------------------------------
+def test_CharacteristicValue():
+    b = bytes([1, 2, 3])
+    c = CharacteristicValue(read=lambda _: b)
+    x = c.read(None)
+    assert(x == b)
+
+    result = []
+    c = CharacteristicValue(write=lambda connection, value: result.append((connection, value)))
+    z = object()
+    c.write(z, b)
+    assert(result == [(z, b)])
+
+
+# -----------------------------------------------------------------------------
 class TwoDevices:
     def __init__(self):
         self.connections = [None, None]
@@ -201,6 +298,56 @@ async def test_read_write():
 
 # -----------------------------------------------------------------------------
 @pytest.mark.asyncio
+async def test_read_write2():
+    [client, server] = TwoDevices().devices
+
+    v = bytes([0x11, 0x22, 0x33, 0x44])
+    characteristic1 = Characteristic(
+        'FDB159DB-036C-49E3-B3DB-6325AC750806',
+        Characteristic.READ | Characteristic.WRITE,
+        Characteristic.READABLE | Characteristic.WRITEABLE,
+        value=v
+    )
+
+    service1 = Service(
+        '3A657F47-D34F-46B3-B1EC-698E29B6B829',
+        [
+            characteristic1
+        ]
+    )
+    server.add_services([service1])
+
+    await client.power_on()
+    await server.power_on()
+    connection = await client.connect(server.random_address)
+    peer = Peer(connection)
+
+    await peer.discover_services()
+    c = peer.get_services_by_uuid(service1.uuid)
+    assert(len(c) == 1)
+    s = c[0]
+    await s.discover_characteristics()
+    c = s.get_characteristics_by_uuid(characteristic1.uuid)
+    assert(len(c) == 1)
+    c1 = c[0]
+
+    v1 = await c1.read_value()
+    assert(v1 == v)
+
+    a1 = PackedCharacteristicAdapter(c1, '>I')
+    v1 = await a1.read_value()
+    assert(v1 == struct.unpack('>I', v)[0])
+
+    b = bytes([0x55, 0x66, 0x77, 0x88])
+    await a1.write_value(struct.unpack('>I', b)[0])
+    await async_barrier()
+    assert(characteristic1.value == b)
+    v1 = await a1.read_value()
+    assert(v1 == struct.unpack('>I', b)[0])
+
+
+# -----------------------------------------------------------------------------
+@pytest.mark.asyncio
 async def test_subscribe_notify():
     [client, server] = TwoDevices().devices
 
@@ -330,6 +477,7 @@ async def test_subscribe_notify():
 # -----------------------------------------------------------------------------
 async def async_main():
     await test_read_write()
+    await test_read_write2()
     await test_subscribe_notify()
 
 # -----------------------------------------------------------------------------
@@ -338,4 +486,6 @@ if __name__ == '__main__':
     test_UUID()
     test_ATT_Error_Response()
     test_ATT_Read_By_Group_Type_Request()
+    test_CharacteristicValue()
+    test_CharacteristicAdapter()
     asyncio.run(async_main())