diff --git a/bumble/controller.py b/bumble/controller.py
index 983692f..1153ec0 100644
--- a/bumble/controller.py
+++ b/bumble/controller.py
@@ -101,10 +101,10 @@ class Connection:
     transport: int
     link_type: int
 
-    def __post_init__(self):
+    def __post_init__(self) -> None:
         self.assembler = HCI_AclDataPacketAssembler(self.on_acl_pdu)
 
-    def on_hci_acl_data_packet(self, packet):
+    def on_hci_acl_data_packet(self, packet: hci.HCI_AclDataPacket) -> None:
         self.assembler.feed_packet(packet)
         self.controller.send_hci_packet(
             HCI_Number_Of_Completed_Packets_Event(
@@ -112,15 +112,81 @@ class Connection:
             )
         )
 
-    def on_acl_pdu(self, data):
+    def on_acl_pdu(self, pdu: bytes) -> None:
         if self.link:
             self.link.send_acl_data(
-                self.controller, self.peer_address, self.transport, data
+                self.controller, self.peer_address, self.transport, pdu
             )
 
 
 # -----------------------------------------------------------------------------
 class Controller:
+    hci_sink: Optional[TransportSink] = None
+
+    central_connections: dict[
+        Address, Connection
+    ]  # Connections where this controller is the central
+    peripheral_connections: dict[
+        Address, Connection
+    ]  # Connections where this controller is the peripheral
+    classic_connections: dict[Address, Connection]  # Connections in BR/EDR
+    central_cis_links: dict[int, CisLink]  # CIS links by handle
+    peripheral_cis_links: dict[int, CisLink]  # CIS links by handle
+
+    hci_version: int = HCI_VERSION_BLUETOOTH_CORE_5_0
+    hci_revision: int = 0
+    lmp_version: int = HCI_VERSION_BLUETOOTH_CORE_5_0
+    lmp_subversion: int = 0
+    lmp_features: bytes = bytes.fromhex(
+        '0000000060000000'
+    )  # BR/EDR Not Supported, LE Supported (Controller)
+    manufacturer_name: int = 0xFFFF
+    acl_data_packet_length: int = 27
+    total_num_acl_data_packets: int = 64
+    le_acl_data_packet_length: int = 27
+    total_num_le_acl_data_packets: int = 64
+    iso_data_packet_length: int = 960
+    total_num_iso_data_packets: int = 64
+    event_mask: int = 0
+    event_mask_page_2: int = 0
+    supported_commands: bytes = bytes.fromhex(
+        '2000800000c000000000e4000000a822000000000000040000f7ffff7f000000'
+        '30f0f9ff01008004002000000000000000000000000000000000000000000000'
+    )
+    le_event_mask: int = 0
+    advertising_parameters: Optional[hci.HCI_LE_Set_Advertising_Parameters_Command] = (
+        None
+    )
+    le_features: bytes = bytes.fromhex('ff49010000000000')
+    le_states: bytes = bytes.fromhex('ffff3fffff030000')
+    advertising_channel_tx_power: int = 0
+    filter_accept_list_size: int = 8
+    filter_duplicates: bool = False
+    resolving_list_size: int = 8
+    supported_max_tx_octets: int = 27
+    supported_max_tx_time: int = 10000
+    supported_max_rx_octets: int = 27
+    supported_max_rx_time: int = 10000
+    suggested_max_tx_octets: int = 27
+    suggested_max_tx_time: int = 0x0148
+    default_phy: dict[str, int]
+    le_scan_type: int = 0
+    le_scan_interval: int = 0x10
+    le_scan_window: int = 0x10
+    le_scan_enable: int = 0
+    le_scan_own_address_type: int = Address.RANDOM_DEVICE_ADDRESS
+    le_scanning_filter_policy: int = 0
+    le_scan_response_data: Optional[bytes] = None
+    le_address_resolution: bool = False
+    le_rpa_timeout: int = 0
+    sync_flow_control: bool = False
+    local_name: str = 'Bumble'
+    advertising_interval: int = 2000
+    advertising_data: Optional[bytes] = None
+    advertising_timer_handle: Optional[asyncio.Handle] = None
+
+    _random_address: 'Address' = Address('00:00:00:00:00:00')
+
     def __init__(
         self,
         name: str,
@@ -128,75 +194,20 @@ class Controller:
         host_sink: Optional[TransportSink] = None,
         link: Optional[LocalLink] = None,
         public_address: Optional[Union[bytes, str, Address]] = None,
-    ):
+    ) -> None:
         self.name = name
-        self.hci_sink = None
         self.link = link
+        self.central_connections = {}
+        self.peripheral_connections = {}
+        self.classic_connections = {}
+        self.central_cis_links = {}
+        self.peripheral_cis_links = {}
+        self.default_phy = {
+            'all_phys': 0,
+            'tx_phys': 0,
+            'rx_phys': 0,
+        }
 
-        self.central_connections: dict[Address, Connection] = (
-            {}
-        )  # Connections where this controller is the central
-        self.peripheral_connections: dict[Address, Connection] = (
-            {}
-        )  # Connections where this controller is the peripheral
-        self.classic_connections: dict[Address, Connection] = (
-            {}
-        )  # Connections in BR/EDR
-        self.central_cis_links: dict[int, CisLink] = {}  # CIS links by handle
-        self.peripheral_cis_links: dict[int, CisLink] = {}  # CIS links by handle
-
-        self.hci_version = HCI_VERSION_BLUETOOTH_CORE_5_0
-        self.hci_revision = 0
-        self.lmp_version = HCI_VERSION_BLUETOOTH_CORE_5_0
-        self.lmp_subversion = 0
-        self.lmp_features = bytes.fromhex(
-            '0000000060000000'
-        )  # BR/EDR Not Supported, LE Supported (Controller)
-        self.manufacturer_name = 0xFFFF
-        self.acl_data_packet_length = 27
-        self.total_num_acl_data_packets = 64
-        self.le_acl_data_packet_length = 27
-        self.total_num_le_acl_data_packets = 64
-        self.iso_data_packet_length = 960
-        self.total_num_iso_data_packets = 64
-        self.event_mask = 0
-        self.event_mask_page_2 = 0
-        self.supported_commands = bytes.fromhex(
-            '2000800000c000000000e4000000a822000000000000040000f7ffff7f000000'
-            '30f0f9ff01008004002000000000000000000000000000000000000000000000'
-        )
-        self.le_event_mask = 0
-        self.advertising_parameters = None
-        self.le_features = bytes.fromhex('ff49010000000000')
-        self.le_states = bytes.fromhex('ffff3fffff030000')
-        self.advertising_channel_tx_power = 0
-        self.filter_accept_list_size = 8
-        self.filter_duplicates = False
-        self.resolving_list_size = 8
-        self.supported_max_tx_octets = 27
-        self.supported_max_tx_time = 10000  # microseconds
-        self.supported_max_rx_octets = 27
-        self.supported_max_rx_time = 10000  # microseconds
-        self.suggested_max_tx_octets = 27
-        self.suggested_max_tx_time = 0x0148  # microseconds
-        self.default_phy = bytes([0, 0, 0])
-        self.le_scan_type = 0
-        self.le_scan_interval = 0x10
-        self.le_scan_window = 0x10
-        self.le_scan_enable = 0
-        self.le_scan_own_address_type = Address.RANDOM_DEVICE_ADDRESS
-        self.le_scanning_filter_policy = 0
-        self.le_scan_response_data = None
-        self.le_address_resolution = False
-        self.le_rpa_timeout = 0
-        self.sync_flow_control = False
-        self.local_name = 'Bumble'
-
-        self.advertising_interval = 2000  # Fixed for now
-        self.advertising_data = None
-        self.advertising_timer_handle = None
-
-        self._random_address = Address('00:00:00:00:00:00')
         if isinstance(public_address, Address):
             self._public_address = public_address
         elif public_address is not None:
@@ -215,44 +226,44 @@ class Controller:
         if link:
             link.add_controller(self)
 
-        self.terminated = asyncio.get_running_loop().create_future()
+        self.terminated: asyncio.Future[Any] = (
+            asyncio.get_running_loop().create_future()
+        )
 
     @property
-    def host(self):
+    def host(self) -> Optional[TransportSink]:
         return self.hci_sink
 
     @host.setter
-    def host(self, host):
+    def host(self, host: Optional[TransportSink]) -> None:
         '''
         Sets the host (sink) for this controller, and set this controller as the
         controller (sink) for the host
         '''
         self.set_packet_sink(host)
-        if host:
-            host.controller = self
 
-    def set_packet_sink(self, sink):
+    def set_packet_sink(self, sink: Optional[TransportSink]) -> None:
         '''
         Method from the Packet Source interface
         '''
         self.hci_sink = sink
 
     @property
-    def public_address(self):
+    def public_address(self) -> Address:
         return self._public_address
 
     @public_address.setter
-    def public_address(self, address):
+    def public_address(self, address: Union[Address, str]) -> None:
         if isinstance(address, str):
             address = Address(address)
         self._public_address = address
 
     @property
-    def random_address(self):
+    def random_address(self) -> Address:
         return self._random_address
 
     @random_address.setter
-    def random_address(self, address):
+    def random_address(self, address: Union[Address, str]) -> None:
         if isinstance(address, str):
             address = Address(address)
         self._random_address = address
@@ -262,29 +273,29 @@ class Controller:
             self.link.on_address_changed(self)
 
     # Packet Sink protocol (packets coming from the host via HCI)
-    def on_packet(self, packet):
+    def on_packet(self, packet: bytes) -> None:
         self.on_hci_packet(HCI_Packet.from_bytes(packet))
 
-    def on_hci_packet(self, packet):
+    def on_hci_packet(self, packet: HCI_Packet) -> None:
         logger.debug(
             f'{color("<<<", "blue")} [{self.name}] '
             f'{color("HOST -> CONTROLLER", "blue")}: {packet}'
         )
 
         # If the packet is a command, invoke the handler for this packet
-        if packet.hci_packet_type == HCI_COMMAND_PACKET:
+        if isinstance(packet, hci.HCI_Command):
             self.on_hci_command_packet(packet)
-        elif packet.hci_packet_type == HCI_EVENT_PACKET:
-            self.on_hci_event_packet(packet)
-        elif packet.hci_packet_type == HCI_ACL_DATA_PACKET:
+        elif isinstance(packet, hci.HCI_AclDataPacket):
             self.on_hci_acl_data_packet(packet)
+        elif isinstance(packet, hci.HCI_Event):
+            self.on_hci_event_packet(packet)
         else:
             logger.warning(f'!!! unknown packet type {packet.hci_packet_type}')
 
-    def on_hci_command_packet(self, command):
+    def on_hci_command_packet(self, command: hci.HCI_Command) -> None:
         handler_name = f'on_{command.name.lower()}'
         handler = getattr(self, handler_name, self.on_hci_command)
-        result = handler(command)
+        result: Optional[bytes] = handler(command)
         if isinstance(result, bytes):
             self.send_hci_packet(
                 HCI_Command_Complete_Event(
@@ -294,10 +305,10 @@ class Controller:
                 )
             )
 
-    def on_hci_event_packet(self, _event):
+    def on_hci_event_packet(self, _event: HCI_Packet) -> None:
         logger.warning('!!! unexpected event packet')
 
-    def on_hci_acl_data_packet(self, packet):
+    def on_hci_acl_data_packet(self, packet: hci.HCI_AclDataPacket) -> None:
         # Look for the connection to which this data belongs
         connection = self.find_connection_by_handle(packet.connection_handle)
         if connection is None:
@@ -309,7 +320,7 @@ class Controller:
         # Pass the packet to the connection
         connection.on_hci_acl_data_packet(packet)
 
-    def send_hci_packet(self, packet):
+    def send_hci_packet(self, packet: HCI_Packet) -> None:
         logger.debug(
             f'{color(">>>", "green")} [{self.name}] '
             f'{color("CONTROLLER -> HOST", "green")}: {packet}'
@@ -318,7 +329,7 @@ class Controller:
             self.host.on_packet(bytes(packet))
 
     # This method allows the controller to emulate the same API as a transport source
-    async def wait_for_termination(self):
+    async def wait_for_termination(self) -> None:
         await self.terminated
 
     ############################################################
@@ -345,15 +356,17 @@ class Controller:
                 handle = max_handle + 1
         return handle
 
-    def find_le_connection_by_address(self, address):
+    def find_le_connection_by_address(self, address: Address) -> Optional[Connection]:
         return self.central_connections.get(address) or self.peripheral_connections.get(
             address
         )
 
-    def find_classic_connection_by_address(self, address):
+    def find_classic_connection_by_address(
+        self, address: Address
+    ) -> Optional[Connection]:
         return self.classic_connections.get(address)
 
-    def find_connection_by_handle(self, handle):
+    def find_connection_by_handle(self, handle: int) -> Optional[Connection]:
         for connection in itertools.chain(
             self.central_connections.values(),
             self.peripheral_connections.values(),
@@ -363,19 +376,19 @@ class Controller:
                 return connection
         return None
 
-    def find_central_connection_by_handle(self, handle):
+    def find_central_connection_by_handle(self, handle: int) -> Optional[Connection]:
         for connection in self.central_connections.values():
             if connection.handle == handle:
                 return connection
         return None
 
-    def find_peripheral_connection_by_handle(self, handle):
+    def find_peripheral_connection_by_handle(self, handle: int) -> Optional[Connection]:
         for connection in self.peripheral_connections.values():
             if connection.handle == handle:
                 return connection
         return None
 
-    def find_classic_connection_by_handle(self, handle):
+    def find_classic_connection_by_handle(self, handle: int) -> Optional[Connection]:
         for connection in self.classic_connections.values():
             if connection.handle == handle:
                 return connection
@@ -386,7 +399,7 @@ class Controller:
             handle
         )
 
-    def on_link_central_connected(self, central_address):
+    def on_link_central_connected(self, central_address: Address) -> None:
         '''
         Called when an incoming connection occurs from a central on the link
         '''
@@ -424,7 +437,7 @@ class Controller:
             )
         )
 
-    def on_link_disconnected(self, peer_address, reason):
+    def on_link_disconnected(self, peer_address: Address, reason: int) -> None:
         '''
         Called when an active disconnection occurs from a peer
         '''
@@ -456,8 +469,10 @@ class Controller:
             logger.warning(f'!!! No peripheral connection found for {peer_address}')
 
     def on_link_peripheral_connection_complete(
-        self, le_create_connection_command, status
-    ):
+        self,
+        le_create_connection_command: hci.HCI_LE_Create_Connection_Command,
+        status: int,
+    ) -> None:
         '''
         Called by the link when a connection has been made or has failed to be made
         '''
@@ -500,7 +515,9 @@ class Controller:
             )
         )
 
-    def on_link_disconnection_complete(self, disconnection_command, status):
+    def on_link_disconnection_complete(
+        self, disconnection_command: hci.HCI_Disconnect_Command, status: int
+    ) -> None:
         '''
         Called when a disconnection has been completed
         '''
@@ -526,7 +543,9 @@ class Controller:
             logger.debug(f'PERIPHERAL Connection removed: {connection}')
             del self.peripheral_connections[connection.peer_address]
 
-    def on_link_encrypted(self, peer_address, _rand, _ediv, _ltk):
+    def on_link_encrypted(
+        self, peer_address: Address, _rand: int, _ediv: int, _ltk: bytes
+    ) -> None:
         # For now, just setup the encryption without asking the host
         if connection := self.find_le_connection_by_address(peer_address):
             self.send_hci_packet(
@@ -535,7 +554,9 @@ class Controller:
                 )
             )
 
-    def on_link_acl_data(self, sender_address, transport, data):
+    def on_link_acl_data(
+        self, sender_address: Address, transport: PhysicalTransport, data: bytes
+    ) -> None:
         # Look for the connection to which this data belongs
         if transport == PhysicalTransport.LE:
             connection = self.find_le_connection_by_address(sender_address)
@@ -550,7 +571,7 @@ class Controller:
         acl_packet = HCI_AclDataPacket(connection.handle, 2, 0, len(data), data)
         self.send_hci_packet(acl_packet)
 
-    def on_link_advertising_data(self, sender_address: Address, data: bytes):
+    def on_link_advertising_data(self, sender_address: Address, data: bytes) -> None:
         # Ignore if we're not scanning
         if self.le_scan_enable == 0:
             return
@@ -677,7 +698,9 @@ class Controller:
     # Classic link connections
     ############################################################
 
-    def on_classic_connection_request(self, peer_address, link_type):
+    def on_classic_connection_request(
+        self, peer_address: Address, link_type: int
+    ) -> None:
         self.send_hci_packet(
             HCI_Connection_Request_Event(
                 bd_addr=peer_address,
@@ -686,7 +709,9 @@ class Controller:
             )
         )
 
-    def on_classic_connection_complete(self, peer_address, status):
+    def on_classic_connection_complete(
+        self, peer_address: Address, status: int
+    ) -> None:
         if status == HCI_SUCCESS:
             # Allocate (or reuse) a connection handle
             peer_address = peer_address
@@ -730,7 +755,7 @@ class Controller:
                 )
             )
 
-    def on_classic_disconnected(self, peer_address, reason):
+    def on_classic_disconnected(self, peer_address: Address, reason: int) -> None:
         # Send a disconnection complete event
         if connection := self.classic_connections.get(peer_address):
             self.send_hci_packet(
@@ -746,7 +771,7 @@ class Controller:
         else:
             logger.warning(f'!!! No classic connection found for {peer_address}')
 
-    def on_classic_role_change(self, peer_address, new_role):
+    def on_classic_role_change(self, peer_address: Address, new_role: int) -> None:
         self.send_hci_packet(
             HCI_Role_Change_Event(
                 status=HCI_SUCCESS,
@@ -757,7 +782,7 @@ class Controller:
 
     def on_classic_sco_connection_complete(
         self, peer_address: Address, status: int, link_type: int
-    ):
+    ) -> None:
         if status == HCI_SUCCESS:
             # Allocate (or reuse) a connection handle
             connection_handle = self.allocate_connection_handle()
@@ -794,13 +819,13 @@ class Controller:
     ############################################################
     # Advertising support
     ############################################################
-    def on_advertising_timer_fired(self):
+    def on_advertising_timer_fired(self) -> None:
         self.send_advertising_data()
         self.advertising_timer_handle = asyncio.get_running_loop().call_later(
             self.advertising_interval / 1000.0, self.on_advertising_timer_fired
         )
 
-    def start_advertising(self):
+    def start_advertising(self) -> None:
         # Stop any ongoing advertising before we start again
         self.stop_advertising()
 
@@ -809,33 +834,35 @@ class Controller:
             self.on_advertising_timer_fired
         )
 
-    def stop_advertising(self):
+    def stop_advertising(self) -> None:
         if self.advertising_timer_handle is not None:
             self.advertising_timer_handle.cancel()
             self.advertising_timer_handle = None
 
-    def send_advertising_data(self):
+    def send_advertising_data(self) -> None:
         if self.link and self.advertising_data:
             self.link.send_advertising_data(self.random_address, self.advertising_data)
 
     @property
-    def is_advertising(self):
+    def is_advertising(self) -> bool:
         return self.advertising_timer_handle is not None
 
     ############################################################
     # HCI handlers
     ############################################################
-    def on_hci_command(self, command):
+    def on_hci_command(self, command: hci.HCI_Command) -> Optional[bytes]:
         logger.warning(color(f'--- Unsupported command {command}', 'red'))
         return bytes([HCI_UNKNOWN_HCI_COMMAND_ERROR])
 
-    def on_hci_create_connection_command(self, command):
+    def on_hci_create_connection_command(
+        self, command: hci.HCI_Create_Connection_Command
+    ) -> Optional[bytes]:
         '''
         See Bluetooth spec Vol 4, Part E - 7.1.5 Create Connection command
         '''
 
         if self.link is None:
-            return
+            return None
         logger.debug(f'Connection request to {command.bd_addr}')
 
         # Check that we don't already have a pending connection
@@ -847,7 +874,7 @@ class Controller:
                     command_opcode=command.op_code,
                 )
             )
-            return
+            return None
 
         self.link.classic_connect(self, command.bd_addr)
 
@@ -859,8 +886,11 @@ class Controller:
                 command_opcode=command.op_code,
             )
         )
+        return None
 
-    def on_hci_disconnect_command(self, command):
+    def on_hci_disconnect_command(
+        self, command: hci.HCI_Disconnect_Command
+    ) -> Optional[bytes]:
         '''
         See Bluetooth spec Vol 4, Part E - 7.1.6 Disconnect Command
         '''
@@ -904,7 +934,7 @@ class Controller:
         elif cis_link := (
             self.central_cis_links.get(handle) or self.peripheral_cis_links.get(handle)
         ):
-            if self.link:
+            if self.link and cis_link.acl_connection:
                 self.link.disconnect_cis(
                     initiator_controller=self,
                     peer_address=cis_link.acl_connection.peer_address,
@@ -913,13 +943,17 @@ class Controller:
                 )
             # Spec requires handle to be kept after disconnection.
 
-    def on_hci_accept_connection_request_command(self, command):
+        return None
+
+    def on_hci_accept_connection_request_command(
+        self, command: hci.HCI_Accept_Connection_Request_Command
+    ) -> Optional[bytes]:
         '''
         See Bluetooth spec Vol 4, Part E - 7.1.8 Accept Connection Request command
         '''
 
         if self.link is None:
-            return
+            return None
         self.send_hci_packet(
             HCI_Command_Status_Event(
                 status=HCI_SUCCESS,
@@ -928,14 +962,17 @@ class Controller:
             )
         )
         self.link.classic_accept_connection(self, command.bd_addr, command.role)
+        return None
 
-    def on_hci_enhanced_setup_synchronous_connection_command(self, command):
+    def on_hci_enhanced_setup_synchronous_connection_command(
+        self, command: hci.HCI_Enhanced_Setup_Synchronous_Connection_Command
+    ) -> Optional[bytes]:
         '''
         See Bluetooth spec Vol 4, Part E - 7.1.45 Enhanced Setup Synchronous Connection command
         '''
 
         if self.link is None:
-            return
+            return None
 
         if not (
             connection := self.find_classic_connection_by_handle(
@@ -949,7 +986,7 @@ class Controller:
                     command_opcode=command.op_code,
                 )
             )
-            return
+            return None
 
         self.send_hci_packet(
             HCI_Command_Status_Event(
@@ -961,14 +998,17 @@ class Controller:
         self.link.classic_sco_connect(
             self, connection.peer_address, HCI_Connection_Complete_Event.LinkType.ESCO
         )
+        return None
 
-    def on_hci_enhanced_accept_synchronous_connection_request_command(self, command):
+    def on_hci_enhanced_accept_synchronous_connection_request_command(
+        self, command: hci.HCI_Enhanced_Accept_Synchronous_Connection_Request_Command
+    ) -> Optional[bytes]:
         '''
         See Bluetooth spec Vol 4, Part E - 7.1.46 Enhanced Accept Synchronous Connection Request command
         '''
 
         if self.link is None:
-            return
+            return None
 
         if not (connection := self.find_classic_connection_by_address(command.bd_addr)):
             self.send_hci_packet(
@@ -978,7 +1018,7 @@ class Controller:
                     command_opcode=command.op_code,
                 )
             )
-            return
+            return None
 
         self.send_hci_packet(
             HCI_Command_Status_Event(
@@ -990,8 +1030,11 @@ class Controller:
         self.link.classic_accept_sco_connection(
             self, connection.peer_address, HCI_Connection_Complete_Event.LinkType.ESCO
         )
+        return None
 
-    def on_hci_sniff_mode_command(self, command: hci.HCI_Sniff_Mode_Command):
+    def on_hci_sniff_mode_command(
+        self, command: hci.HCI_Sniff_Mode_Command
+    ) -> Optional[bytes]:
         '''
         See Bluetooth spec Vol 4, Part E - 7.2.2 Sniff Mode command
         '''
@@ -1003,7 +1046,7 @@ class Controller:
                     command_opcode=command.op_code,
                 )
             )
-            return
+            return None
 
         self.send_hci_packet(
             hci.HCI_Command_Status_Event(
@@ -1020,8 +1063,11 @@ class Controller:
                 interval=2,
             )
         )
+        return None
 
-    def on_hci_exit_sniff_mode_command(self, command: hci.HCI_Exit_Sniff_Mode_Command):
+    def on_hci_exit_sniff_mode_command(
+        self, command: hci.HCI_Exit_Sniff_Mode_Command
+    ) -> Optional[bytes]:
         '''
         See Bluetooth spec Vol 4, Part E - 7.2.3 Exit Sniff Mode command
         '''
@@ -1034,7 +1080,7 @@ class Controller:
                     command_opcode=command.op_code,
                 )
             )
-            return
+            return None
 
         self.send_hci_packet(
             hci.HCI_Command_Status_Event(
@@ -1051,14 +1097,17 @@ class Controller:
                 interval=2,
             )
         )
+        return None
 
-    def on_hci_switch_role_command(self, command: hci.HCI_Switch_Role_Command):
+    def on_hci_switch_role_command(
+        self, command: hci.HCI_Switch_Role_Command
+    ) -> Optional[bytes]:
         '''
         See Bluetooth spec Vol 4, Part E - 7.2.8 Switch Role command
         '''
 
         if self.link is None:
-            return
+            return None
         self.send_hci_packet(
             HCI_Command_Status_Event(
                 status=HCI_SUCCESS,
@@ -1067,22 +1116,29 @@ class Controller:
             )
         )
         self.link.classic_switch_role(self, command.bd_addr, command.role)
+        return None
 
-    def on_hci_set_event_mask_command(self, command):
+    def on_hci_set_event_mask_command(
+        self, command: hci.HCI_Set_Event_Mask_Command
+    ) -> Optional[bytes]:
         '''
         See Bluetooth spec Vol 4, Part E - 7.3.1 Set Event Mask Command
         '''
-        self.event_mask = command.event_mask
+        self.event_mask = int.from_bytes(
+            command.event_mask, byteorder='little', signed=False
+        )
         return bytes([HCI_SUCCESS])
 
-    def on_hci_reset_command(self, _command):
+    def on_hci_reset_command(self, _command: hci.HCI_Reset_Command) -> Optional[bytes]:
         '''
         See Bluetooth spec Vol 4, Part E - 7.3.2 Reset Command
         '''
         # TODO: cleanup what needs to be reset
         return bytes([HCI_SUCCESS])
 
-    def on_hci_write_local_name_command(self, command):
+    def on_hci_write_local_name_command(
+        self, command: hci.HCI_Write_Local_Name_Command
+    ) -> Optional[bytes]:
         '''
         See Bluetooth spec Vol 4, Part E - 7.3.11 Write Local Name Command
         '''
@@ -1097,7 +1153,9 @@ class Controller:
                 pass
         return bytes([HCI_SUCCESS])
 
-    def on_hci_read_local_name_command(self, _command):
+    def on_hci_read_local_name_command(
+        self, _command: hci.HCI_Read_Local_Name_Command
+    ) -> Optional[bytes]:
         '''
         See Bluetooth spec Vol 4, Part E - 7.3.12 Read Local Name Command
         '''
@@ -1107,19 +1165,25 @@ class Controller:
 
         return bytes([HCI_SUCCESS]) + local_name
 
-    def on_hci_read_class_of_device_command(self, _command):
+    def on_hci_read_class_of_device_command(
+        self, _command: hci.HCI_Read_Class_Of_Device_Command
+    ) -> Optional[bytes]:
         '''
         See Bluetooth spec Vol 4, Part E - 7.3.25 Read Class of Device Command
         '''
         return bytes([HCI_SUCCESS, 0, 0, 0])
 
-    def on_hci_write_class_of_device_command(self, _command):
+    def on_hci_write_class_of_device_command(
+        self, _command: hci.HCI_Write_Class_Of_Device_Command
+    ) -> Optional[bytes]:
         '''
         See Bluetooth spec Vol 4, Part E - 7.3.26 Write Class of Device Command
         '''
         return bytes([HCI_SUCCESS])
 
-    def on_hci_read_synchronous_flow_control_enable_command(self, _command):
+    def on_hci_read_synchronous_flow_control_enable_command(
+        self, _command: hci.HCI_Read_Synchronous_Flow_Control_Enable_Command
+    ) -> Optional[bytes]:
         '''
         See Bluetooth spec Vol 4, Part E - 7.3.36 Read Synchronous Flow Control Enable
         Command
@@ -1130,7 +1194,9 @@ class Controller:
             ret = 0
         return bytes([HCI_SUCCESS, ret])
 
-    def on_hci_write_synchronous_flow_control_enable_command(self, command):
+    def on_hci_write_synchronous_flow_control_enable_command(
+        self, command: hci.HCI_Write_Synchronous_Flow_Control_Enable_Command
+    ) -> Optional[bytes]:
         '''
         See Bluetooth spec Vol 4, Part E - 7.3.37 Write Synchronous Flow Control Enable
         Command
@@ -1144,7 +1210,9 @@ class Controller:
             ret = HCI_INVALID_HCI_COMMAND_PARAMETERS_ERROR
         return bytes([ret])
 
-    def on_hci_set_controller_to_host_flow_control_command(self, _command):
+    def on_hci_set_controller_to_host_flow_control_command(
+        self, _command: hci.HCI_Set_Controller_To_Host_Flow_Control_Command
+    ) -> Optional[bytes]:
         '''
         See Bluetooth spec Vol 4, Part E - 7.3.38 Set Controller To Host Flow Control
         Command
@@ -1153,7 +1221,9 @@ class Controller:
         # TODO: respect the passed in values.
         return bytes([HCI_SUCCESS])
 
-    def on_hci_host_buffer_size_command(self, _command):
+    def on_hci_host_buffer_size_command(
+        self, _command: hci.HCI_Host_Buffer_Size_Command
+    ) -> Optional[bytes]:
         '''
         See Bluetooth spec Vol 4, Part E - 7.3.39 Host Buffer Size Command
         '''
@@ -1161,40 +1231,54 @@ class Controller:
         # TODO: respect the passed in values.
         return bytes([HCI_SUCCESS])
 
-    def on_hci_write_extended_inquiry_response_command(self, _command):
+    def on_hci_write_extended_inquiry_response_command(
+        self, _command: hci.HCI_Write_Extended_Inquiry_Response_Command
+    ) -> Optional[bytes]:
         '''
         See Bluetooth spec Vol 4, Part E - 7.3.56 Write Extended Inquiry Response
         Command
         '''
         return bytes([HCI_SUCCESS])
 
-    def on_hci_write_simple_pairing_mode_command(self, _command):
+    def on_hci_write_simple_pairing_mode_command(
+        self, _command: hci.HCI_Write_Simple_Pairing_Mode_Command
+    ) -> Optional[bytes]:
         '''
         See Bluetooth spec Vol 4, Part E - 7.3.59 Write Simple Pairing Mode Command
         '''
         return bytes([HCI_SUCCESS])
 
-    def on_hci_set_event_mask_page_2_command(self, command):
+    def on_hci_set_event_mask_page_2_command(
+        self, command: hci.HCI_Set_Event_Mask_Page_2_Command
+    ) -> Optional[bytes]:
         '''
         See Bluetooth spec Vol 4, Part E - 7.3.69 Set Event Mask Page 2 Command
         '''
-        self.event_mask_page_2 = command.event_mask_page_2
+        self.event_mask_page_2 = int.from_bytes(
+            command.event_mask_page_2, byteorder='little', signed=False
+        )
         return bytes([HCI_SUCCESS])
 
-    def on_hci_read_le_host_support_command(self, _command):
+    def on_hci_read_le_host_support_command(
+        self, _command: hci.HCI_Read_LE_Host_Support_Command
+    ) -> Optional[bytes]:
         '''
         See Bluetooth spec Vol 4, Part E - 7.3.78 Write LE Host Support Command
         '''
         return bytes([HCI_SUCCESS, 1, 0])
 
-    def on_hci_write_le_host_support_command(self, _command):
+    def on_hci_write_le_host_support_command(
+        self, _command: hci.HCI_Write_LE_Host_Support_Command
+    ) -> Optional[bytes]:
         '''
         See Bluetooth spec Vol 4, Part E - 7.3.79 Write LE Host Support Command
         '''
         # TODO / Just ignore for now
         return bytes([HCI_SUCCESS])
 
-    def on_hci_write_authenticated_payload_timeout_command(self, command):
+    def on_hci_write_authenticated_payload_timeout_command(
+        self, command: hci.HCI_Write_Authenticated_Payload_Timeout_Command
+    ) -> Optional[bytes]:
         '''
         See Bluetooth spec Vol 4, Part E - 7.3.94 Write Authenticated Payload Timeout
         Command
@@ -1202,7 +1286,9 @@ class Controller:
         # TODO
         return struct.pack('<BH', HCI_SUCCESS, command.connection_handle)
 
-    def on_hci_read_local_version_information_command(self, _command):
+    def on_hci_read_local_version_information_command(
+        self, _command: hci.HCI_Read_Local_Version_Information_Command
+    ) -> Optional[bytes]:
         '''
         See Bluetooth spec Vol 4, Part E - 7.4.1 Read Local Version Information Command
         '''
@@ -1216,19 +1302,25 @@ class Controller:
             self.lmp_subversion,
         )
 
-    def on_hci_read_local_supported_commands_command(self, _command):
+    def on_hci_read_local_supported_commands_command(
+        self, _command: hci.HCI_Read_Local_Supported_Commands_Command
+    ) -> Optional[bytes]:
         '''
         See Bluetooth spec Vol 4, Part E - 7.4.2 Read Local Supported Commands Command
         '''
         return bytes([HCI_SUCCESS]) + self.supported_commands
 
-    def on_hci_read_local_supported_features_command(self, _command):
+    def on_hci_read_local_supported_features_command(
+        self, _command: hci.HCI_Read_Local_Supported_Features_Command
+    ) -> Optional[bytes]:
         '''
         See Bluetooth spec Vol 4, Part E - 7.4.3 Read Local Supported Features Command
         '''
         return bytes([HCI_SUCCESS]) + self.lmp_features[:8]
 
-    def on_hci_read_local_extended_features_command(self, command):
+    def on_hci_read_local_extended_features_command(
+        self, command: hci.HCI_Read_Local_Extended_Features_Command
+    ) -> Optional[bytes]:
         '''
         See Bluetooth spec Vol 4, Part E - 7.4.4 Read Local Extended Features Command
         '''
@@ -1249,7 +1341,9 @@ class Controller:
             + self.lmp_features[command.page_number * 8 : (command.page_number + 1) * 8]
         )
 
-    def on_hci_read_buffer_size_command(self, _command):
+    def on_hci_read_buffer_size_command(
+        self, _command: hci.HCI_Read_Buffer_Size_Command
+    ) -> Optional[bytes]:
         '''
         See Bluetooth spec Vol 4, Part E - 7.4.5 Read Buffer Size Command
         '''
@@ -1262,7 +1356,9 @@ class Controller:
             0,
         )
 
-    def on_hci_read_bd_addr_command(self, _command):
+    def on_hci_read_bd_addr_command(
+        self, _command: hci.HCI_Read_BD_ADDR_Command
+    ) -> Optional[bytes]:
         '''
         See Bluetooth spec Vol 4, Part E - 7.4.6 Read BD_ADDR Command
         '''
@@ -1275,7 +1371,7 @@ class Controller:
 
     def on_hci_le_set_default_subrate_command(
         self, command: hci.HCI_LE_Set_Default_Subrate_Command
-    ):
+    ) -> Optional[bytes]:
         '''
         See Bluetooth spec Vol 6, Part E - 7.8.123 LE Set Event Mask Command
         '''
@@ -1291,7 +1387,7 @@ class Controller:
 
     def on_hci_le_subrate_request_command(
         self, command: hci.HCI_LE_Subrate_Request_Command
-    ):
+    ) -> Optional[bytes]:
         '''
         See Bluetooth spec Vol 6, Part E - 7.8.124 LE Subrate Request command
         '''
@@ -1323,14 +1419,20 @@ class Controller:
         )
         return None
 
-    def on_hci_le_set_event_mask_command(self, command):
+    def on_hci_le_set_event_mask_command(
+        self, command: hci.HCI_LE_Set_Event_Mask_Command
+    ) -> Optional[bytes]:
         '''
         See Bluetooth spec Vol 4, Part E - 7.8.1 LE Set Event Mask Command
         '''
-        self.le_event_mask = command.le_event_mask
+        self.le_event_mask = int.from_bytes(
+            command.le_event_mask, byteorder='little', signed=False
+        )
         return bytes([HCI_SUCCESS])
 
-    def on_hci_le_read_buffer_size_command(self, _command):
+    def on_hci_le_read_buffer_size_command(
+        self, _command: hci.HCI_LE_Read_Buffer_Size_Command
+    ) -> Optional[bytes]:
         '''
         See Bluetooth spec Vol 4, Part E - 7.8.2 LE Read Buffer Size Command
         '''
@@ -1341,7 +1443,9 @@ class Controller:
             self.total_num_le_acl_data_packets,
         )
 
-    def on_hci_le_read_buffer_size_v2_command(self, _command):
+    def on_hci_le_read_buffer_size_v2_command(
+        self, _command: hci.HCI_LE_Read_Buffer_Size_V2_Command
+    ) -> Optional[bytes]:
         '''
         See Bluetooth spec Vol 4, Part E - 7.8.2 LE Read Buffer Size Command
         '''
@@ -1354,49 +1458,63 @@ class Controller:
             self.total_num_iso_data_packets,
         )
 
-    def on_hci_le_read_local_supported_features_command(self, _command):
+    def on_hci_le_read_local_supported_features_command(
+        self, _command: hci.HCI_LE_Read_Local_Supported_Features_Command
+    ) -> Optional[bytes]:
         '''
         See Bluetooth spec Vol 4, Part E - 7.8.3 LE Read Local Supported Features
         Command
         '''
         return bytes([HCI_SUCCESS]) + self.le_features
 
-    def on_hci_le_set_random_address_command(self, command):
+    def on_hci_le_set_random_address_command(
+        self, command: hci.HCI_LE_Set_Random_Address_Command
+    ) -> Optional[bytes]:
         '''
         See Bluetooth spec Vol 4, Part E - 7.8.4 LE Set Random Address Command
         '''
         self.random_address = command.random_address
         return bytes([HCI_SUCCESS])
 
-    def on_hci_le_set_advertising_parameters_command(self, command):
+    def on_hci_le_set_advertising_parameters_command(
+        self, command: hci.HCI_LE_Set_Advertising_Parameters_Command
+    ) -> Optional[bytes]:
         '''
         See Bluetooth spec Vol 4, Part E - 7.8.5 LE Set Advertising Parameters Command
         '''
         self.advertising_parameters = command
         return bytes([HCI_SUCCESS])
 
-    def on_hci_le_read_advertising_physical_channel_tx_power_command(self, _command):
+    def on_hci_le_read_advertising_physical_channel_tx_power_command(
+        self, _command: hci.HCI_LE_Read_Advertising_Physical_Channel_Tx_Power_Command
+    ) -> Optional[bytes]:
         '''
         See Bluetooth spec Vol 4, Part E - 7.8.6 LE Read Advertising Physical Channel
         Tx Power Command
         '''
         return bytes([HCI_SUCCESS, self.advertising_channel_tx_power])
 
-    def on_hci_le_set_advertising_data_command(self, command):
+    def on_hci_le_set_advertising_data_command(
+        self, command: hci.HCI_LE_Set_Advertising_Data_Command
+    ) -> Optional[bytes]:
         '''
         See Bluetooth spec Vol 4, Part E - 7.8.7 LE Set Advertising Data Command
         '''
         self.advertising_data = command.advertising_data
         return bytes([HCI_SUCCESS])
 
-    def on_hci_le_set_scan_response_data_command(self, command):
+    def on_hci_le_set_scan_response_data_command(
+        self, command: hci.HCI_LE_Set_Scan_Response_Data_Command
+    ) -> Optional[bytes]:
         '''
         See Bluetooth spec Vol 4, Part E - 7.8.8 LE Set Scan Response Data Command
         '''
         self.le_scan_response_data = command.scan_response_data
         return bytes([HCI_SUCCESS])
 
-    def on_hci_le_set_advertising_enable_command(self, command):
+    def on_hci_le_set_advertising_enable_command(
+        self, command: hci.HCI_LE_Set_Advertising_Enable_Command
+    ) -> Optional[bytes]:
         '''
         See Bluetooth spec Vol 4, Part E - 7.8.9 LE Set Advertising Enable Command
         '''
@@ -1407,7 +1525,9 @@ class Controller:
 
         return bytes([HCI_SUCCESS])
 
-    def on_hci_le_set_scan_parameters_command(self, command):
+    def on_hci_le_set_scan_parameters_command(
+        self, command: hci.HCI_LE_Set_Scan_Parameters_Command
+    ) -> Optional[bytes]:
         '''
         See Bluetooth spec Vol 4, Part E - 7.8.10 LE Set Scan Parameters Command
         '''
@@ -1417,25 +1537,29 @@ class Controller:
         self.le_scan_type = command.le_scan_type
         self.le_scan_interval = command.le_scan_interval
         self.le_scan_window = command.le_scan_window
-        self.le_scan_own_address_type = command.own_address_type
+        self.le_scan_own_address_type = hci.AddressType(command.own_address_type)
         self.le_scanning_filter_policy = command.scanning_filter_policy
         return bytes([HCI_SUCCESS])
 
-    def on_hci_le_set_scan_enable_command(self, command):
+    def on_hci_le_set_scan_enable_command(
+        self, command: hci.HCI_LE_Set_Scan_Enable_Command
+    ) -> Optional[bytes]:
         '''
         See Bluetooth spec Vol 4, Part E - 7.8.11 LE Set Scan Enable Command
         '''
-        self.le_scan_enable = command.le_scan_enable
-        self.filter_duplicates = command.filter_duplicates
+        self.le_scan_enable = bool(command.le_scan_enable)
+        self.filter_duplicates = bool(command.filter_duplicates)
         return bytes([HCI_SUCCESS])
 
-    def on_hci_le_create_connection_command(self, command):
+    def on_hci_le_create_connection_command(
+        self, command: hci.HCI_LE_Create_Connection_Command
+    ) -> Optional[bytes]:
         '''
         See Bluetooth spec Vol 4, Part E - 7.8.12 LE Create Connection Command
         '''
 
         if not self.link:
-            return
+            return None
 
         logger.debug(f'Connection request to {command.peer_address}')
 
@@ -1448,7 +1572,7 @@ class Controller:
                     command_opcode=command.op_code,
                 )
             )
-            return
+            return None
 
         # Initiate the connection
         self.link.connect(self.random_address, command)
@@ -1461,41 +1585,54 @@ class Controller:
                 command_opcode=command.op_code,
             )
         )
+        return None
 
-    def on_hci_le_create_connection_cancel_command(self, _command):
+    def on_hci_le_create_connection_cancel_command(
+        self, _command: hci.HCI_LE_Create_Connection_Cancel_Command
+    ) -> Optional[bytes]:
         '''
         See Bluetooth spec Vol 4, Part E - 7.8.13 LE Create Connection Cancel Command
         '''
         return bytes([HCI_SUCCESS])
 
-    def on_hci_le_read_filter_accept_list_size_command(self, _command):
+    def on_hci_le_read_filter_accept_list_size_command(
+        self, _command: hci.HCI_LE_Read_Filter_Accept_List_Size_Command
+    ) -> Optional[bytes]:
         '''
         See Bluetooth spec Vol 4, Part E - 7.8.14 LE Read Filter Accept List Size
         Command
         '''
         return bytes([HCI_SUCCESS, self.filter_accept_list_size])
 
-    def on_hci_le_clear_filter_accept_list_command(self, _command):
+    def on_hci_le_clear_filter_accept_list_command(
+        self, _command: hci.HCI_LE_Clear_Filter_Accept_List_Command
+    ) -> Optional[bytes]:
         '''
         See Bluetooth spec Vol 4, Part E - 7.8.15 LE Clear Filter Accept List Command
         '''
         return bytes([HCI_SUCCESS])
 
-    def on_hci_le_add_device_to_filter_accept_list_command(self, _command):
+    def on_hci_le_add_device_to_filter_accept_list_command(
+        self, _command: hci.HCI_LE_Add_Device_To_Filter_Accept_List_Command
+    ) -> Optional[bytes]:
         '''
         See Bluetooth spec Vol 4, Part E - 7.8.16 LE Add Device To Filter Accept List
         Command
         '''
         return bytes([HCI_SUCCESS])
 
-    def on_hci_le_remove_device_from_filter_accept_list_command(self, _command):
+    def on_hci_le_remove_device_from_filter_accept_list_command(
+        self, _command: hci.HCI_LE_Remove_Device_From_Filter_Accept_List_Command
+    ) -> Optional[bytes]:
         '''
         See Bluetooth spec Vol 4, Part E - 7.8.17 LE Remove Device From Filter Accept
         List Command
         '''
         return bytes([HCI_SUCCESS])
 
-    def on_hci_le_read_remote_features_command(self, command):
+    def on_hci_le_read_remote_features_command(
+        self, command: hci.HCI_LE_Read_Remote_Features_Command
+    ) -> Optional[bytes]:
         '''
         See Bluetooth spec Vol 4, Part E - 7.8.21 LE Read Remote Features Command
         '''
@@ -1510,7 +1647,7 @@ class Controller:
                     command_opcode=command.op_code,
                 )
             )
-            return
+            return None
 
         # First, say that the command is pending
         self.send_hci_packet(
@@ -1529,17 +1666,24 @@ class Controller:
                 le_features=bytes.fromhex('dd40000000000000'),
             )
         )
+        return None
 
-    def on_hci_le_rand_command(self, _command):
+    def on_hci_le_rand_command(
+        self, _command: hci.HCI_LE_Rand_Command
+    ) -> Optional[bytes]:
         '''
         See Bluetooth spec Vol 4, Part E - 7.8.23 LE Rand Command
         '''
         return bytes([HCI_SUCCESS]) + struct.pack('Q', random.randint(0, 1 << 64))
 
-    def on_hci_le_enable_encryption_command(self, command):
+    def on_hci_le_enable_encryption_command(
+        self, command: hci.HCI_LE_Enable_Encryption_Command
+    ) -> Optional[bytes]:
         '''
         See Bluetooth spec Vol 4, Part E - 7.8.24 LE Enable Encryption Command
         '''
+        if not self.link:
+            return None
 
         # Check the parameters
         if not (
@@ -1569,13 +1713,17 @@ class Controller:
 
         return None
 
-    def on_hci_le_read_supported_states_command(self, _command):
+    def on_hci_le_read_supported_states_command(
+        self, _command: hci.HCI_LE_Read_Supported_States_Command
+    ) -> Optional[bytes]:
         '''
         See Bluetooth spec Vol 4, Part E - 7.8.27 LE Read Supported States Command
         '''
         return bytes([HCI_SUCCESS]) + self.le_states
 
-    def on_hci_le_read_suggested_default_data_length_command(self, _command):
+    def on_hci_le_read_suggested_default_data_length_command(
+        self, _command: hci.HCI_LE_Read_Suggested_Default_Data_Length_Command
+    ) -> Optional[bytes]:
         '''
         See Bluetooth spec Vol 4, Part E - 7.8.34 LE Read Suggested Default Data Length
         Command
@@ -1587,7 +1735,9 @@ class Controller:
             self.suggested_max_tx_time,
         )
 
-    def on_hci_le_write_suggested_default_data_length_command(self, command):
+    def on_hci_le_write_suggested_default_data_length_command(
+        self, command: hci.HCI_LE_Write_Suggested_Default_Data_Length_Command
+    ) -> Optional[bytes]:
         '''
         See Bluetooth spec Vol 4, Part E - 7.8.35 LE Write Suggested Default Data Length
         Command
@@ -1597,33 +1747,43 @@ class Controller:
         )
         return bytes([HCI_SUCCESS])
 
-    def on_hci_le_read_local_p_256_public_key_command(self, _command):
+    def on_hci_le_read_local_p_256_public_key_command(
+        self, _command: hci.HCI_LE_Read_Local_P_256_Public_Key_Command
+    ) -> Optional[bytes]:
         '''
         See Bluetooth spec Vol 4, Part E - 7.8.36 LE Read P-256 Public Key Command
         '''
         # TODO create key and send HCI_LE_Read_Local_P-256_Public_Key_Complete event
         return bytes([HCI_SUCCESS])
 
-    def on_hci_le_add_device_to_resolving_list_command(self, _command):
+    def on_hci_le_add_device_to_resolving_list_command(
+        self, _command: hci.HCI_LE_Add_Device_To_Resolving_List_Command
+    ) -> Optional[bytes]:
         '''
         See Bluetooth spec Vol 4, Part E - 7.8.38 LE Add Device To Resolving List
         Command
         '''
         return bytes([HCI_SUCCESS])
 
-    def on_hci_le_clear_resolving_list_command(self, _command):
+    def on_hci_le_clear_resolving_list_command(
+        self, _command: hci.HCI_LE_Clear_Resolving_List_Command
+    ) -> Optional[bytes]:
         '''
         See Bluetooth spec Vol 4, Part E - 7.8.40 LE Clear Resolving List Command
         '''
         return bytes([HCI_SUCCESS])
 
-    def on_hci_le_read_resolving_list_size_command(self, _command):
+    def on_hci_le_read_resolving_list_size_command(
+        self, _command: hci.HCI_LE_Read_Resolving_List_Size_Command
+    ) -> Optional[bytes]:
         '''
         See Bluetooth spec Vol 4, Part E - 7.8.41 LE Read Resolving List Size Command
         '''
         return bytes([HCI_SUCCESS, self.resolving_list_size])
 
-    def on_hci_le_set_address_resolution_enable_command(self, command):
+    def on_hci_le_set_address_resolution_enable_command(
+        self, command: hci.HCI_LE_Set_Address_Resolution_Enable_Command
+    ) -> Optional[bytes]:
         '''
         See Bluetooth spec Vol 4, Part E - 7.8.44 LE Set Address Resolution Enable
         Command
@@ -1637,7 +1797,9 @@ class Controller:
             ret = HCI_INVALID_HCI_COMMAND_PARAMETERS_ERROR
         return bytes([ret])
 
-    def on_hci_le_set_resolvable_private_address_timeout_command(self, command):
+    def on_hci_le_set_resolvable_private_address_timeout_command(
+        self, command: hci.HCI_LE_Set_Resolvable_Private_Address_Timeout_Command
+    ) -> Optional[bytes]:
         '''
         See Bluetooth spec Vol 4, Part E - 7.8.45 LE Set Resolvable Private Address
         Timeout Command
@@ -1645,7 +1807,9 @@ class Controller:
         self.le_rpa_timeout = command.rpa_timeout
         return bytes([HCI_SUCCESS])
 
-    def on_hci_le_read_maximum_data_length_command(self, _command):
+    def on_hci_le_read_maximum_data_length_command(
+        self, _command: hci.HCI_LE_Read_Maximum_Data_Length_Command
+    ) -> Optional[bytes]:
         '''
         See Bluetooth spec Vol 4, Part E - 7.8.46 LE Read Maximum Data Length Command
         '''
@@ -1658,7 +1822,9 @@ class Controller:
             self.supported_max_rx_time,
         )
 
-    def on_hci_le_read_phy_command(self, command):
+    def on_hci_le_read_phy_command(
+        self, command: hci.HCI_LE_Read_PHY_Command
+    ) -> Optional[bytes]:
         '''
         See Bluetooth spec Vol 4, Part E - 7.8.47 LE Read PHY Command
         '''
@@ -1670,94 +1836,118 @@ class Controller:
             HCI_LE_1M_PHY,
         )
 
-    def on_hci_le_set_default_phy_command(self, command):
+    def on_hci_le_set_default_phy_command(
+        self, command: hci.HCI_LE_Set_Default_PHY_Command
+    ) -> Optional[bytes]:
         '''
         See Bluetooth spec Vol 4, Part E - 7.8.48 LE Set Default PHY Command
         '''
-        self.default_phy = {
-            'all_phys': command.all_phys,
-            'tx_phys': command.tx_phys,
-            'rx_phys': command.rx_phys,
-        }
+        self.default_phy['all_phys'] = command.all_phys
+        self.default_phy['tx_phys'] = command.tx_phys
+        self.default_phy['rx_phys'] = command.rx_phys
         return bytes([HCI_SUCCESS])
 
-    def on_hci_le_set_advertising_set_random_address_command(self, _command):
+    def on_hci_le_set_advertising_set_random_address_command(
+        self, _command: hci.HCI_LE_Set_Advertising_Set_Random_Address_Command
+    ) -> Optional[bytes]:
         '''
         See Bluetooth spec Vol 4, Part E - 7.8.52 LE Set Advertising Set Random Address
         Command
         '''
         return bytes([HCI_SUCCESS])
 
-    def on_hci_le_set_extended_advertising_parameters_command(self, _command):
+    def on_hci_le_set_extended_advertising_parameters_command(
+        self, _command: hci.HCI_LE_Set_Extended_Advertising_Parameters_Command
+    ) -> Optional[bytes]:
         '''
         See Bluetooth spec Vol 4, Part E - 7.8.53 LE Set Extended Advertising Parameters
         Command
         '''
         return bytes([HCI_SUCCESS, 0])
 
-    def on_hci_le_set_extended_advertising_data_command(self, _command):
+    def on_hci_le_set_extended_advertising_data_command(
+        self, _command: hci.HCI_LE_Set_Extended_Advertising_Data_Command
+    ) -> Optional[bytes]:
         '''
         See Bluetooth spec Vol 4, Part E - 7.8.54 LE Set Extended Advertising Data
         Command
         '''
         return bytes([HCI_SUCCESS])
 
-    def on_hci_le_set_extended_scan_response_data_command(self, _command):
+    def on_hci_le_set_extended_scan_response_data_command(
+        self, _command: hci.HCI_LE_Set_Extended_Scan_Response_Data_Command
+    ) -> Optional[bytes]:
         '''
         See Bluetooth spec Vol 4, Part E - 7.8.55 LE Set Extended Scan Response Data
         Command
         '''
         return bytes([HCI_SUCCESS])
 
-    def on_hci_le_set_extended_advertising_enable_command(self, _command):
+    def on_hci_le_set_extended_advertising_enable_command(
+        self, _command: hci.HCI_LE_Set_Extended_Advertising_Enable_Command
+    ) -> Optional[bytes]:
         '''
         See Bluetooth spec Vol 4, Part E - 7.8.56 LE Set Extended Advertising Enable
         Command
         '''
         return bytes([HCI_SUCCESS])
 
-    def on_hci_le_read_maximum_advertising_data_length_command(self, _command):
+    def on_hci_le_read_maximum_advertising_data_length_command(
+        self, _command: hci.HCI_LE_Read_Maximum_Advertising_Data_Length_Command
+    ) -> Optional[bytes]:
         '''
         See Bluetooth spec Vol 4, Part E - 7.8.57 LE Read Maximum Advertising Data
         Length Command
         '''
         return struct.pack('<BH', HCI_SUCCESS, 0x0672)
 
-    def on_hci_le_read_number_of_supported_advertising_sets_command(self, _command):
+    def on_hci_le_read_number_of_supported_advertising_sets_command(
+        self, _command: hci.HCI_LE_Read_Number_Of_Supported_Advertising_Sets_Command
+    ) -> Optional[bytes]:
         '''
         See Bluetooth spec Vol 4, Part E - 7.8.58 LE Read Number of Supported
         Advertising Set Command
         '''
         return struct.pack('<BB', HCI_SUCCESS, 0xF0)
 
-    def on_hci_le_set_periodic_advertising_parameters_command(self, _command):
+    def on_hci_le_set_periodic_advertising_parameters_command(
+        self, _command: hci.HCI_LE_Set_Periodic_Advertising_Parameters_Command
+    ) -> Optional[bytes]:
         '''
         See Bluetooth spec Vol 4, Part E - 7.8.61 LE Set Periodic Advertising Parameters
         Command
         '''
         return bytes([HCI_SUCCESS])
 
-    def on_hci_le_set_periodic_advertising_data_command(self, _command):
+    def on_hci_le_set_periodic_advertising_data_command(
+        self, _command: hci.HCI_LE_Set_Periodic_Advertising_Data_Command
+    ) -> Optional[bytes]:
         '''
         See Bluetooth spec Vol 4, Part E - 7.8.62 LE Set Periodic Advertising Data
         Command
         '''
         return bytes([HCI_SUCCESS])
 
-    def on_hci_le_set_periodic_advertising_enable_command(self, _command):
+    def on_hci_le_set_periodic_advertising_enable_command(
+        self, _command: hci.HCI_LE_Set_Periodic_Advertising_Enable_Command
+    ) -> Optional[bytes]:
         '''
         See Bluetooth spec Vol 4, Part E - 7.8.63 LE Set Periodic Advertising Enable
         Command
         '''
         return bytes([HCI_SUCCESS])
 
-    def on_hci_le_read_transmit_power_command(self, _command):
+    def on_hci_le_read_transmit_power_command(
+        self, _command: hci.HCI_LE_Read_Transmit_Power_Command
+    ) -> Optional[bytes]:
         '''
         See Bluetooth spec Vol 4, Part E - 7.8.74 LE Read Transmit Power Command
         '''
         return struct.pack('<BBB', HCI_SUCCESS, 0, 0)
 
-    def on_hci_le_set_cig_parameters_command(self, command):
+    def on_hci_le_set_cig_parameters_command(
+        self, command: hci.HCI_LE_Set_CIG_Parameters_Command
+    ) -> Optional[bytes]:
         '''
         See Bluetooth spec Vol 4, Part E - 7.8.97 LE Set CIG Parameter Command
         '''
@@ -1781,12 +1971,14 @@ class Controller:
             '<BBB', HCI_SUCCESS, command.cig_id, len(handles)
         ) + b''.join([struct.pack('<H', handle) for handle in handles])
 
-    def on_hci_le_create_cis_command(self, command):
+    def on_hci_le_create_cis_command(
+        self, command: hci.HCI_LE_Create_CIS_Command
+    ) -> Optional[bytes]:
         '''
         See Bluetooth spec Vol 4, Part E - 7.8.99 LE Create CIS Command
         '''
         if not self.link:
-            return
+            return None
 
         for cis_handle, acl_handle in zip(
             command.cis_connection_handle, command.acl_connection_handle
@@ -1815,8 +2007,11 @@ class Controller:
                 command_opcode=command.op_code,
             )
         )
+        return None
 
-    def on_hci_le_remove_cig_command(self, command):
+    def on_hci_le_remove_cig_command(
+        self, command: hci.HCI_LE_Remove_CIG_Command
+    ) -> Optional[bytes]:
         '''
         See Bluetooth spec Vol 4, Part E - 7.8.100 LE Remove CIG Command
         '''
@@ -1831,12 +2026,14 @@ class Controller:
 
         return struct.pack('<BH', status, command.cig_id)
 
-    def on_hci_le_accept_cis_request_command(self, command):
+    def on_hci_le_accept_cis_request_command(
+        self, command: hci.HCI_LE_Accept_CIS_Request_Command
+    ) -> Optional[bytes]:
         '''
         See Bluetooth spec Vol 4, Part E - 7.8.101 LE Accept CIS Request Command
         '''
         if not self.link:
-            return
+            return None
 
         if not (
             pending_cis_link := self.peripheral_cis_links.get(command.connection_handle)
@@ -1859,10 +2056,11 @@ class Controller:
                 command_opcode=command.op_code,
             )
         )
+        return None
 
     def on_hci_le_setup_iso_data_path_command(
         self, command: hci.HCI_LE_Setup_ISO_Data_Path_Command
-    ) -> bytes:
+    ) -> Optional[bytes]:
         '''
         See Bluetooth spec Vol 4, Part E - 7.8.109 LE Setup ISO Data Path Command
         '''
@@ -1883,7 +2081,7 @@ class Controller:
 
     def on_hci_le_remove_iso_data_path_command(
         self, command: hci.HCI_LE_Remove_ISO_Data_Path_Command
-    ) -> bytes:
+    ) -> Optional[bytes]:
         '''
         See Bluetooth spec Vol 4, Part E - 7.8.110 LE Remove ISO Data Path Command
         '''
@@ -1909,7 +2107,7 @@ class Controller:
 
     def on_hci_le_set_host_feature_command(
         self, _command: hci.HCI_LE_Set_Host_Feature_Command
-    ):
+    ) -> Optional[bytes]:
         '''
         See Bluetooth spec Vol 4, Part E - 7.8.115 LE Set Host Feature command
         '''
diff --git a/bumble/hci.py b/bumble/hci.py
index 9943ff0..0bb7586 100644
--- a/bumble/hci.py
+++ b/bumble/hci.py
@@ -3441,6 +3441,17 @@ class HCI_Write_Synchronous_Flow_Control_Enable_Command(HCI_Command):
     synchronous_flow_control_enable: int = field(metadata=metadata(1))
 
 
+# -----------------------------------------------------------------------------
+@HCI_Command.command
+@dataclasses.dataclass
+class HCI_Set_Controller_To_Host_Flow_Control_Command(HCI_Command):
+    '''
+    See Bluetooth spec @ 7.3.38 Set Controller To Host Flow Control command
+    '''
+
+    flow_control_enable: int = field(metadata=metadata(1))
+
+
 # -----------------------------------------------------------------------------
 @HCI_Command.command
 @dataclasses.dataclass
@@ -4338,6 +4349,15 @@ class HCI_LE_Write_Suggested_Default_Data_Length_Command(HCI_Command):
     suggested_max_tx_time: int = field(metadata=metadata(2))
 
 
+# -----------------------------------------------------------------------------
+@HCI_Command.command
+@dataclasses.dataclass
+class HCI_LE_Read_Local_P_256_Public_Key_Command(HCI_Command):
+    '''
+    See Bluetooth spec @ 7.8.36 LE LE Read Local P-256 Public Key command
+    '''
+
+
 # -----------------------------------------------------------------------------
 @HCI_Command.command
 @dataclasses.dataclass
@@ -4365,6 +4385,15 @@ class HCI_LE_Clear_Resolving_List_Command(HCI_Command):
     '''
 
 
+# -----------------------------------------------------------------------------
+@HCI_Command.command
+@dataclasses.dataclass
+class HCI_LE_Read_Resolving_List_Size_Command(HCI_Command):
+    '''
+    See Bluetooth spec @ 7.8.41 LE Read Resolving List Size command
+    '''
+
+
 # -----------------------------------------------------------------------------
 @HCI_Command.command
 @dataclasses.dataclass
@@ -5028,6 +5057,15 @@ class HCI_LE_Periodic_Advertising_Terminate_Sync_Command(HCI_Command):
     sync_handle: int = field(metadata=metadata(2))
 
 
+# -----------------------------------------------------------------------------
+@HCI_Command.command
+@dataclasses.dataclass
+class HCI_LE_Read_Transmit_Power_Command(HCI_Command):
+    '''
+    See Bluetooth spec @ 7.8.74 LE Read Transmit Power command
+    '''
+
+
 # -----------------------------------------------------------------------------
 @HCI_Command.command
 @dataclasses.dataclass
diff --git a/examples/run_controller.py b/examples/run_controller.py
index 2b7f743..d25d32f 100644
--- a/examples/run_controller.py
+++ b/examples/run_controller.py
@@ -19,6 +19,7 @@ import asyncio
 import sys
 
 import bumble.logging
+from bumble import hci
 from bumble.controller import Controller
 from bumble.device import Device
 from bumble.gatt import (
@@ -61,7 +62,7 @@ async def main() -> None:
             host_sink=hci_transport.sink,
             link=link,
         )
-        controller1.random_address = sys.argv[1]
+        controller1.random_address = hci.Address(sys.argv[1])
 
         # Create a second controller using the same link
         controller2 = Controller('C2', link=link)