Merge pull request #867 from zxzxwu/fix-import-error

Fix missing ClassVar import

.gitignore

@@ -17,3 +17,6 @@ venv/
 .venv/
 # snoop logs
 out/
+# macOS
+.DS_Store
+._*

apps/usb_probe.py

@@ -26,6 +26,8 @@
 # -----------------------------------------------------------------------------
 # Imports
 # -----------------------------------------------------------------------------
+from typing import Any
+
 import click
 import usb1
 
@@ -166,13 +168,16 @@ def is_bluetooth_hci(device):
 # -----------------------------------------------------------------------------
 @click.command()
 @click.option('--verbose', is_flag=True, default=False, help='Print more details')
-def main(verbose):
+@click.option('--hci-only', is_flag=True, default=False, help='only show HCI device')
+@click.option('--manufacturer', help='filter by manufacturer')
+@click.option('--product', help='filter by product')
+def main(verbose: bool, manufacturer: str, product: str, hci_only: bool):
     bumble.logging.setup_basic_logging('WARNING')
 
     load_libusb()
     with usb1.USBContext() as context:
         bluetooth_device_count = 0
-        devices = {}
+        devices: dict[tuple[Any, Any], list[str | None]] = {}
 
         for device in context.getDeviceIterator(skip_on_error=True):
             device_class = device.getDeviceClass()
@@ -234,6 +239,14 @@ def main(verbose):
                         f'{basic_transport_name}/{device_serial_number}'
                     )
 
+            # Filter
+            if product and device_product != product:
+                continue
+            if manufacturer and device_manufacturer != manufacturer:
+                continue
+            if not is_bluetooth_hci(device) and hci_only:
+                continue
+
             # Print the results
             print(
                 color(

bumble/att.py

@@ -29,7 +29,7 @@ import enum
 import functools
 import inspect
 import struct
-from collections.abc import Awaitable, Callable
+from collections.abc import Awaitable, Callable, Sequence
 from typing import (
     TYPE_CHECKING,
     ClassVar,
@@ -72,34 +72,36 @@ ATT_PSM = 0x001F
 EATT_PSM = 0x0027
 
 class Opcode(hci.SpecableEnum):
-    ATT_ERROR_RESPONSE              = 0x01
-    ATT_EXCHANGE_MTU_REQUEST        = 0x02
-    ATT_EXCHANGE_MTU_RESPONSE       = 0x03
-    ATT_FIND_INFORMATION_REQUEST    = 0x04
-    ATT_FIND_INFORMATION_RESPONSE   = 0x05
-    ATT_FIND_BY_TYPE_VALUE_REQUEST  = 0x06
-    ATT_FIND_BY_TYPE_VALUE_RESPONSE = 0x07
-    ATT_READ_BY_TYPE_REQUEST        = 0x08
-    ATT_READ_BY_TYPE_RESPONSE       = 0x09
-    ATT_READ_REQUEST                = 0x0A
-    ATT_READ_RESPONSE               = 0x0B
-    ATT_READ_BLOB_REQUEST           = 0x0C
-    ATT_READ_BLOB_RESPONSE          = 0x0D
-    ATT_READ_MULTIPLE_REQUEST       = 0x0E
-    ATT_READ_MULTIPLE_RESPONSE      = 0x0F
-    ATT_READ_BY_GROUP_TYPE_REQUEST  = 0x10
-    ATT_READ_BY_GROUP_TYPE_RESPONSE = 0x11
-    ATT_WRITE_REQUEST               = 0x12
-    ATT_WRITE_RESPONSE              = 0x13
-    ATT_WRITE_COMMAND               = 0x52
-    ATT_SIGNED_WRITE_COMMAND        = 0xD2
-    ATT_PREPARE_WRITE_REQUEST       = 0x16
-    ATT_PREPARE_WRITE_RESPONSE      = 0x17
-    ATT_EXECUTE_WRITE_REQUEST       = 0x18
-    ATT_EXECUTE_WRITE_RESPONSE      = 0x19
-    ATT_HANDLE_VALUE_NOTIFICATION   = 0x1B
-    ATT_HANDLE_VALUE_INDICATION     = 0x1D
-    ATT_HANDLE_VALUE_CONFIRMATION   = 0x1E
+    ATT_ERROR_RESPONSE                  = 0x01
+    ATT_EXCHANGE_MTU_REQUEST            = 0x02
+    ATT_EXCHANGE_MTU_RESPONSE           = 0x03
+    ATT_FIND_INFORMATION_REQUEST        = 0x04
+    ATT_FIND_INFORMATION_RESPONSE       = 0x05
+    ATT_FIND_BY_TYPE_VALUE_REQUEST      = 0x06
+    ATT_FIND_BY_TYPE_VALUE_RESPONSE     = 0x07
+    ATT_READ_BY_TYPE_REQUEST            = 0x08
+    ATT_READ_BY_TYPE_RESPONSE           = 0x09
+    ATT_READ_REQUEST                    = 0x0A
+    ATT_READ_RESPONSE                   = 0x0B
+    ATT_READ_BLOB_REQUEST               = 0x0C
+    ATT_READ_BLOB_RESPONSE              = 0x0D
+    ATT_READ_MULTIPLE_REQUEST           = 0x0E
+    ATT_READ_MULTIPLE_RESPONSE          = 0x0F
+    ATT_READ_BY_GROUP_TYPE_REQUEST      = 0x10
+    ATT_READ_BY_GROUP_TYPE_RESPONSE     = 0x11
+    ATT_READ_MULTIPLE_VARIABLE_REQUEST  = 0x20
+    ATT_READ_MULTIPLE_VARIABLE_RESPONSE = 0x21
+    ATT_WRITE_REQUEST                   = 0x12
+    ATT_WRITE_RESPONSE                  = 0x13
+    ATT_WRITE_COMMAND                   = 0x52
+    ATT_SIGNED_WRITE_COMMAND            = 0xD2
+    ATT_PREPARE_WRITE_REQUEST           = 0x16
+    ATT_PREPARE_WRITE_RESPONSE          = 0x17
+    ATT_EXECUTE_WRITE_REQUEST           = 0x18
+    ATT_EXECUTE_WRITE_RESPONSE          = 0x19
+    ATT_HANDLE_VALUE_NOTIFICATION       = 0x1B
+    ATT_HANDLE_VALUE_INDICATION         = 0x1D
+    ATT_HANDLE_VALUE_CONFIRMATION       = 0x1E
 
 ATT_REQUESTS = [
     Opcode.ATT_EXCHANGE_MTU_REQUEST,
@@ -110,9 +112,10 @@ ATT_REQUESTS = [
     Opcode.ATT_READ_BLOB_REQUEST,
     Opcode.ATT_READ_MULTIPLE_REQUEST,
     Opcode.ATT_READ_BY_GROUP_TYPE_REQUEST,
+    Opcode.ATT_READ_MULTIPLE_VARIABLE_REQUEST,
     Opcode.ATT_WRITE_REQUEST,
     Opcode.ATT_PREPARE_WRITE_REQUEST,
-    Opcode.ATT_EXECUTE_WRITE_REQUEST
+    Opcode.ATT_EXECUTE_WRITE_REQUEST,
 ]
 
 ATT_RESPONSES = [
@@ -125,9 +128,10 @@ ATT_RESPONSES = [
     Opcode.ATT_READ_BLOB_RESPONSE,
     Opcode.ATT_READ_MULTIPLE_RESPONSE,
     Opcode.ATT_READ_BY_GROUP_TYPE_RESPONSE,
+    Opcode.ATT_READ_MULTIPLE_VARIABLE_RESPONSE,
     Opcode.ATT_WRITE_RESPONSE,
     Opcode.ATT_PREPARE_WRITE_RESPONSE,
-    Opcode.ATT_EXECUTE_WRITE_RESPONSE
+    Opcode.ATT_EXECUTE_WRITE_RESPONSE,
 ]
 
 class ErrorCode(hci.SpecableEnum):
@@ -185,6 +189,18 @@ ATT_INSUFFICIENT_RESOURCES_ERROR           = ErrorCode.INSUFFICIENT_RESOURCES
 ATT_DEFAULT_MTU = 23
 
 HANDLE_FIELD_SPEC    = {'size': 2, 'mapper': lambda x: f'0x{x:04X}'}
+_SET_OF_HANDLES_METADATA = hci.metadata({
+                'parser': lambda data, offset: (
+                    len(data),
+                    [
+                        struct.unpack_from('<H', data, i)[0]
+                        for i in range(offset, len(data), 2)
+                    ],
+                ),
+                'serializer': lambda handles: b''.join(
+                    [struct.pack('<H', handle) for handle in handles]
+                ),
+            })
 
 # fmt: on
 # pylint: enable=line-too-long
@@ -554,7 +570,7 @@ class ATT_Read_Multiple_Request(ATT_PDU):
     See Bluetooth spec @ Vol 3, Part F - 3.4.4.7 Read Multiple Request
     '''
 
-    set_of_handles: bytes = dataclasses.field(metadata=hci.metadata("*"))
+    set_of_handles: Sequence[int] = dataclasses.field(metadata=_SET_OF_HANDLES_METADATA)
 
 
 # -----------------------------------------------------------------------------
@@ -635,6 +651,55 @@ class ATT_Read_By_Group_Type_Response(ATT_PDU):
         return result
 
 
+# -----------------------------------------------------------------------------
+@ATT_PDU.subclass
+@dataclasses.dataclass
+class ATT_Read_Multiple_Variable_Request(ATT_PDU):
+    '''
+    See Bluetooth spec @ Vol 3, Part F - 3.4.4.11 Read Multiple Variable Request
+    '''
+
+    set_of_handles: Sequence[int] = dataclasses.field(metadata=_SET_OF_HANDLES_METADATA)
+
+
+# -----------------------------------------------------------------------------
+@ATT_PDU.subclass
+@dataclasses.dataclass
+class ATT_Read_Multiple_Variable_Response(ATT_PDU):
+    '''
+    See Bluetooth spec @ Vol 3, Part F - 3.4.4.12 Read Multiple Variable Response
+    '''
+
+    @classmethod
+    def _parse_length_value_tuples(
+        cls, data: bytes, offset: int
+    ) -> tuple[int, list[tuple[int, bytes]]]:
+        length_value_tuple_list: list[tuple[int, bytes]] = []
+        while offset < len(data):
+            length = struct.unpack_from('<H', data, offset)[0]
+            length_value_tuple_list.append(
+                (length, data[offset + 2 : offset + 2 + length])
+            )
+            offset += 2 + length
+        return (len(data), length_value_tuple_list)
+
+    length_value_tuple_list: Sequence[tuple[int, bytes]] = dataclasses.field(
+        metadata=hci.metadata(
+            {
+                'parser': lambda data, offset: ATT_Read_Multiple_Variable_Response._parse_length_value_tuples(
+                    data, offset
+                ),
+                'serializer': lambda length_value_tuple_list: b''.join(
+                    [
+                        struct.pack('<H', length) + value
+                        for length, value in length_value_tuple_list
+                    ]
+                ),
+            }
+        )
+    )
+
+
 # -----------------------------------------------------------------------------
 @ATT_PDU.subclass
 @dataclasses.dataclass

bumble/avctp.py

@@ -235,7 +235,7 @@ class Protocol:
             )
             + payload
         )
-        self.l2cap_channel.send_pdu(pdu)
+        self.l2cap_channel.write(pdu)
 
     def send_command(self, transaction_label: int, pid: int, payload: bytes) -> None:
         logger.debug(

bumble/avdtp.py

@@ -268,7 +268,7 @@ class MediaPacketPump:
                         await self.clock.sleep(delay)
 
                     # Emit
-                    rtp_channel.send_pdu(bytes(packet))
+                    rtp_channel.write(bytes(packet))
                     logger.debug(
                         f'{color(">>> sending RTP packet:", "green")} {packet}'
                     )
@@ -1519,7 +1519,7 @@ class Protocol(utils.EventEmitter):
                 header = bytes([first_header_byte])
 
             # Send one packet
-            self.l2cap_channel.send_pdu(header + payload[:max_fragment_size])
+            self.l2cap_channel.write(header + payload[:max_fragment_size])
 
             # Prepare for the next packet
             payload = payload[max_fragment_size:]
@@ -1829,7 +1829,7 @@ class Stream:
 
     def send_media_packet(self, packet: MediaPacket) -> None:
         assert self.rtp_channel
-        self.rtp_channel.send_pdu(bytes(packet))
+        self.rtp_channel.write(bytes(packet))
 
     async def configure(self) -> None:
         if self.state != State.IDLE:

bumble/device.py

@@ -1383,10 +1383,7 @@ class Peer:
     def create_service_proxy(
         self, proxy_class: type[_PROXY_CLASS]
     ) -> _PROXY_CLASS | None:
-        if proxy := proxy_class.from_client(self.gatt_client):
-            return cast(_PROXY_CLASS, proxy)
-
-        return None
+        return proxy_class.from_client(self.gatt_client)
 
     async def discover_service_and_create_proxy(
         self, proxy_class: type[_PROXY_CLASS]
@@ -1406,7 +1403,7 @@ class Peer:
     async def request_name(self) -> str:
         return await self.connection.request_remote_name()
 
-    async def __aenter__(self):
+    async def __aenter__(self) -> Self:
         await self.discover_services()
         for service in self.services:
             await service.discover_characteristics()

bumble/drivers/rtk.py

@@ -77,6 +77,7 @@ class RtlProjectId(enum.IntEnum):
     PROJECT_ID_8852A = 18
     PROJECT_ID_8852B = 20
     PROJECT_ID_8852C = 25
+    PROJECT_ID_8761C = 51
 
 
 RTK_PROJECT_ID_TO_ROM = {
@@ -92,6 +93,7 @@ RTK_PROJECT_ID_TO_ROM = {
     18: RTK_ROM_LMP_8852A,
     20: RTK_ROM_LMP_8852A,
     25: RTK_ROM_LMP_8852A,
+    51: RTK_ROM_LMP_8761A,
 }
 
 # List of USB (VendorID, ProductID) for Realtek-based devices.
@@ -123,6 +125,10 @@ RTK_USB_PRODUCTS = {
     (0x2550, 0x8761),
     (0x2B89, 0x8761),
     (0x7392, 0xC611),
+    # Realtek 8761CUV
+    (0x0B05, 0x1BF6),
+    (0x0BDA, 0xC761),
+    (0x7392, 0xF611),
     # Realtek 8821AE
     (0x0B05, 0x17DC),
     (0x13D3, 0x3414),
@@ -363,6 +369,15 @@ class Driver(common.Driver):
             fw_name="rtl8761bu_fw.bin",
             config_name="rtl8761bu_config.bin",
         ),
+        # 8761CU
+        DriverInfo(
+            rom=RTK_ROM_LMP_8761A,
+            hci=(0x0E, 0x00),
+            config_needed=False,
+            has_rom_version=True,
+            fw_name="rtl8761cu_fw.bin",
+            config_name="rtl8761cu_config.bin",
+        ),
         # 8822C
         DriverInfo(
             rom=RTK_ROM_LMP_8822B,
@@ -420,9 +435,17 @@ class Driver(common.Driver):
     @staticmethod
     def find_driver_info(hci_version, hci_subversion, lmp_subversion):
         for driver_info in Driver.DRIVER_INFOS:
-            if driver_info.rom == lmp_subversion and driver_info.hci == (
-                hci_subversion,
-                hci_version,
+            if driver_info.rom == lmp_subversion and (
+                driver_info.hci
+                == (
+                    hci_subversion,
+                    hci_version,
+                )
+                or driver_info.hci
+                == (
+                    hci_subversion,
+                    0x0,
+                )
             ):
                 return driver_info
 

bumble/gatt.py

@@ -29,7 +29,7 @@ import functools
 import logging
 import struct
 from collections.abc import Iterable, Sequence
-from typing import TypeVar
+from typing import ClassVar, TypeVar
 
 from bumble.att import Attribute, AttributeValue, AttributeValueV2
 from bumble.colors import color
@@ -403,7 +403,7 @@ class TemplateService(Service):
     to expose their UUID as a class property
     '''
 
-    UUID: UUID
+    UUID: ClassVar[UUID]
 
     def __init__(
         self,

bumble/gatt_client.py

@@ -34,11 +34,14 @@ from datetime import datetime
 from typing import (
     TYPE_CHECKING,
     Any,
+    ClassVar,
     Generic,
     TypeVar,
     overload,
 )
 
+from typing_extensions import Self
+
 from bumble import att, core, l2cap, utils
 from bumble.colors import color
 from bumble.core import UUID, InvalidStateError
@@ -249,10 +252,10 @@ class ProfileServiceProxy:
     Base class for profile-specific service proxies
     '''
 
-    SERVICE_CLASS: type[TemplateService]
+    SERVICE_CLASS: ClassVar[type[TemplateService]]
 
     @classmethod
-    def from_client(cls, client: Client) -> ProfileServiceProxy | None:
+    def from_client(cls, client: Client) -> Self | None:
         return ServiceProxy.from_client(cls, client, cls.SERVICE_CLASS.UUID)
 
 
@@ -285,8 +288,6 @@ class Client:
             self._bearer_id = (
                 f'[0x{bearer.connection.handle:04X}|CID=0x{bearer.source_cid:04X}]'
             )
-            # Fill the mtu.
-            bearer.on_att_mtu_update(att.ATT_DEFAULT_MTU)
             self.connection = bearer.connection
         else:
             bearer.on(bearer.EVENT_DISCONNECTION, self.on_disconnection)

bumble/gatt_server.py

@@ -115,7 +115,6 @@ class Server(utils.EventEmitter):
                 channel.connection.handle,
                 channel.source_cid,
             )
-            channel.att_mtu = att.ATT_DEFAULT_MTU
             channel.sink = lambda pdu: self.on_gatt_pdu(
                 channel, att.ATT_PDU.from_bytes(pdu)
             )
@@ -777,6 +776,18 @@ class Server(utils.EventEmitter):
             error_code=att.ATT_ATTRIBUTE_NOT_FOUND_ERROR,
         )
 
+        if (
+            request.starting_handle == 0x0000
+            or request.starting_handle > request.ending_handle
+        ):
+            response = att.ATT_Error_Response(
+                request_opcode_in_error=request.op_code,
+                attribute_handle_in_error=request.starting_handle,
+                error_code=att.ATT_INVALID_HANDLE_ERROR,
+            )
+            self.send_response(bearer, response)
+            return
+
         attributes: list[tuple[int, bytes]] = []
         for attribute in (
             attribute
@@ -977,6 +988,94 @@ class Server(utils.EventEmitter):
 
         self.send_response(bearer, response)
 
+    @utils.AsyncRunner.run_in_task()
+    async def on_att_read_multiple_request(
+        self, bearer: att.Bearer, request: att.ATT_Read_Multiple_Request
+    ):
+        '''
+        See Bluetooth spec Vol 3, Part F - 3.4.4.7 Read Multiple Request.
+        '''
+        response: att.ATT_PDU
+
+        pdu_space_available = bearer.att_mtu - 1
+        values: list[bytes] = []
+
+        for handle in request.set_of_handles:
+            if not (attribute := self.get_attribute(handle)):
+                response = att.ATT_Error_Response(
+                    request_opcode_in_error=request.op_code,
+                    attribute_handle_in_error=handle,
+                    error_code=att.ATT_ATTRIBUTE_NOT_FOUND_ERROR,
+                )
+                self.send_response(bearer, response)
+                return
+            # No need to catch permission errors here, since these attributes
+            # must all be world-readable
+            attribute_value = await attribute.read_value(bearer)
+            # Check the attribute value size
+            max_attribute_size = min(bearer.att_mtu - 1, 251)
+            if len(attribute_value) > max_attribute_size:
+                # We need to truncate
+                attribute_value = attribute_value[:max_attribute_size]
+
+            # Check if there is enough space
+            entry_size = len(attribute_value)
+            if pdu_space_available < entry_size:
+                break
+
+            # Add the attribute to the list
+            values.append(attribute_value)
+            pdu_space_available -= entry_size
+
+        response = att.ATT_Read_Multiple_Response(set_of_values=b''.join(values))
+        self.send_response(bearer, response)
+
+    @utils.AsyncRunner.run_in_task()
+    async def on_att_read_multiple_variable_request(
+        self, bearer: att.Bearer, request: att.ATT_Read_Multiple_Variable_Request
+    ):
+        '''
+        See Bluetooth spec Vol 3, Part F - 3.4.4.11 Read Multiple Variable Request.
+        '''
+        response: att.ATT_PDU
+
+        pdu_space_available = bearer.att_mtu - 1
+        length_value_tuple_list: list[tuple[int, bytes]] = []
+
+        for handle in request.set_of_handles:
+            if not (attribute := self.get_attribute(handle)):
+                response = att.ATT_Error_Response(
+                    request_opcode_in_error=request.op_code,
+                    attribute_handle_in_error=handle,
+                    error_code=att.ATT_ATTRIBUTE_NOT_FOUND_ERROR,
+                )
+                self.send_response(bearer, response)
+                return
+            # No need to catch permission errors here, since these attributes
+            # must all be world-readable
+            attribute_value = await attribute.read_value(bearer)
+            length = len(attribute_value)
+            # Check the attribute value size
+            max_attribute_size = min(bearer.att_mtu - 3, 251)
+            if len(attribute_value) > max_attribute_size:
+                # We need to truncate
+                attribute_value = attribute_value[:max_attribute_size]
+
+            # Check if there is enough space
+            entry_size = 2 + len(attribute_value)
+
+            # Add the attribute to the list
+            length_value_tuple_list.append((length, attribute_value))
+            pdu_space_available -= entry_size
+
+            if pdu_space_available <= 0:
+                break
+
+        response = att.ATT_Read_Multiple_Variable_Response(
+            length_value_tuple_list=length_value_tuple_list
+        )
+        self.send_response(bearer, response)
+
     @utils.AsyncRunner.run_in_task()
     async def on_att_write_request(
         self, bearer: att.Bearer, request: att.ATT_Write_Request

bumble/hci.py

@@ -2090,9 +2090,9 @@ class Address:
     RANDOM_IDENTITY_ADDRESS = AddressType.RANDOM_IDENTITY
 
     # Type declarations
-    NIL: Address
-    ANY: Address
-    ANY_RANDOM: Address
+    NIL: ClassVar[Address]
+    ANY: ClassVar[Address]
+    ANY_RANDOM: ClassVar[Address]
 
     # pylint: disable-next=unnecessary-lambda
     ADDRESS_TYPE_SPEC = {'size': 1, 'mapper': lambda x: Address.address_type_name(x)}
@@ -2204,38 +2204,38 @@ class Address:
 
         self.address_type = address_type
 
-    def clone(self):
+    def clone(self) -> Address:
         return Address(self.address_bytes, self.address_type)
 
     @property
-    def is_public(self):
+    def is_public(self) -> bool:
         return self.address_type in (
             self.PUBLIC_DEVICE_ADDRESS,
             self.PUBLIC_IDENTITY_ADDRESS,
         )
 
     @property
-    def is_random(self):
+    def is_random(self) -> bool:
         return not self.is_public
 
     @property
-    def is_resolved(self):
+    def is_resolved(self) -> bool:
         return self.address_type in (
             self.PUBLIC_IDENTITY_ADDRESS,
             self.RANDOM_IDENTITY_ADDRESS,
         )
 
     @property
-    def is_resolvable(self):
+    def is_resolvable(self) -> bool:
         return self.address_type == self.RANDOM_DEVICE_ADDRESS and (
             self.address_bytes[5] >> 6 == 1
         )
 
     @property
-    def is_static(self):
+    def is_static(self) -> bool:
         return self.is_random and (self.address_bytes[5] >> 6 == 3)
 
-    def to_string(self, with_type_qualifier=True):
+    def to_string(self, with_type_qualifier: bool = True) -> str:
         '''
         String representation of the address, MSB first, with an optional type
         qualifier.
@@ -2245,23 +2245,23 @@ class Address:
             return result
         return result + '/P'
 
-    def __bytes__(self):
+    def __bytes__(self) -> bytes:
         return self.address_bytes
 
-    def __hash__(self):
+    def __hash__(self) -> int:
         return hash(self.address_bytes)
 
-    def __eq__(self, other):
+    def __eq__(self, other: Any) -> bool:
         return (
             isinstance(other, Address)
             and self.address_bytes == other.address_bytes
             and self.is_public == other.is_public
         )
 
-    def __str__(self):
+    def __str__(self) -> str:
         return self.to_string()
 
-    def __repr__(self):
+    def __repr__(self) -> str:
         return f'Address({self.to_string(False)}/{self.address_type_name(self.address_type)})'
 
 
@@ -2300,10 +2300,10 @@ class HCI_Packet:
     Abstract Base class for HCI packets
     '''
 
-    hci_packet_type: ClassVar[int]
+    hci_packet_type: int
 
-    @staticmethod
-    def from_bytes(packet: bytes) -> HCI_Packet:
+    @classmethod
+    def from_bytes(cls, packet: bytes) -> HCI_Packet:
         packet_type = packet[0]
 
         if packet_type == HCI_COMMAND_PACKET:
@@ -2323,7 +2323,7 @@ class HCI_Packet:
 
         return HCI_CustomPacket(packet)
 
-    def __init__(self, name):
+    def __init__(self, name: str) -> None:
         self.name = name
 
     def __bytes__(self) -> bytes:
@@ -2335,7 +2335,7 @@ class HCI_Packet:
 
 # -----------------------------------------------------------------------------
 class HCI_CustomPacket(HCI_Packet):
-    def __init__(self, payload):
+    def __init__(self, payload: bytes) -> None:
         super().__init__('HCI_CUSTOM_PACKET')
         self.hci_packet_type = payload[0]
         self.payload = payload
@@ -7452,6 +7452,7 @@ class HCI_Vendor_Event(HCI_Event):
 
 
 # -----------------------------------------------------------------------------
+@dataclasses.dataclass
 class HCI_AclDataPacket(HCI_Packet):
     '''
     See Bluetooth spec @ 5.4.2 HCI ACL Data Packets
@@ -7459,8 +7460,14 @@ class HCI_AclDataPacket(HCI_Packet):
 
     hci_packet_type = HCI_ACL_DATA_PACKET
 
-    @staticmethod
-    def from_bytes(packet: bytes) -> HCI_AclDataPacket:
+    connection_handle: int
+    pb_flag: int
+    bc_flag: int
+    data_total_length: int
+    data: bytes
+
+    @classmethod
+    def from_bytes(cls, packet: bytes) -> HCI_AclDataPacket:
         # Read the header
         h, data_total_length = struct.unpack_from('<HH', packet, 1)
         connection_handle = h & 0xFFF
@@ -7469,25 +7476,22 @@ class HCI_AclDataPacket(HCI_Packet):
         data = packet[5:]
         if len(data) != data_total_length:
             raise InvalidPacketError('invalid packet length')
-        return HCI_AclDataPacket(
-            connection_handle, pb_flag, bc_flag, data_total_length, data
+        return cls(
+            connection_handle=connection_handle,
+            pb_flag=pb_flag,
+            bc_flag=bc_flag,
+            data_total_length=data_total_length,
+            data=data,
         )
 
-    def __bytes__(self):
+    def __bytes__(self) -> bytes:
         h = (self.pb_flag << 12) | (self.bc_flag << 14) | self.connection_handle
         return (
             struct.pack('<BHH', HCI_ACL_DATA_PACKET, h, self.data_total_length)
             + self.data
         )
 
-    def __init__(self, connection_handle, pb_flag, bc_flag, data_total_length, data):
-        self.connection_handle = connection_handle
-        self.pb_flag = pb_flag
-        self.bc_flag = bc_flag
-        self.data_total_length = data_total_length
-        self.data = data
-
-    def __str__(self):
+    def __str__(self) -> str:
         return (
             f'{color("ACL", "blue")}: '
             f'handle=0x{self.connection_handle:04x}, '
@@ -7498,6 +7502,7 @@ class HCI_AclDataPacket(HCI_Packet):
 
 
 # -----------------------------------------------------------------------------
+@dataclasses.dataclass
 class HCI_SynchronousDataPacket(HCI_Packet):
     '''
     See Bluetooth spec @ 5.4.3 HCI SCO Data Packets
@@ -7505,8 +7510,13 @@ class HCI_SynchronousDataPacket(HCI_Packet):
 
     hci_packet_type = HCI_SYNCHRONOUS_DATA_PACKET
 
-    @staticmethod
-    def from_bytes(packet: bytes) -> HCI_SynchronousDataPacket:
+    connection_handle: int
+    packet_status: int
+    data_total_length: int
+    data: bytes
+
+    @classmethod
+    def from_bytes(cls, packet: bytes) -> HCI_SynchronousDataPacket:
         # Read the header
         h, data_total_length = struct.unpack_from('<HB', packet, 1)
         connection_handle = h & 0xFFF
@@ -7516,8 +7526,11 @@ class HCI_SynchronousDataPacket(HCI_Packet):
             raise InvalidPacketError(
                 f'invalid packet length {len(data)} != {data_total_length}'
             )
-        return HCI_SynchronousDataPacket(
-            connection_handle, packet_status, data_total_length, data
+        return cls(
+            connection_handle=connection_handle,
+            packet_status=packet_status,
+            data_total_length=data_total_length,
+            data=data,
         )
 
     def __bytes__(self) -> bytes:
@@ -7527,18 +7540,6 @@ class HCI_SynchronousDataPacket(HCI_Packet):
             + self.data
         )
 
-    def __init__(
-        self,
-        connection_handle: int,
-        packet_status: int,
-        data_total_length: int,
-        data: bytes,
-    ) -> None:
-        self.connection_handle = connection_handle
-        self.packet_status = packet_status
-        self.data_total_length = data_total_length
-        self.data = data
-
     def __str__(self) -> str:
         return (
             f'{color("SCO", "blue")}: '
@@ -7556,7 +7557,7 @@ class HCI_IsoDataPacket(HCI_Packet):
     See Bluetooth spec @ 5.4.5 HCI ISO Data Packets
     '''
 
-    hci_packet_type: ClassVar[int] = HCI_ISO_DATA_PACKET
+    hci_packet_type = HCI_ISO_DATA_PACKET
 
     connection_handle: int
     data_total_length: int

bumble/hid.py

@@ -312,11 +312,11 @@ class HID(ABC, utils.EventEmitter):
 
     def send_pdu_on_ctrl(self, msg: bytes) -> None:
         assert self.l2cap_ctrl_channel
-        self.l2cap_ctrl_channel.send_pdu(msg)
+        self.l2cap_ctrl_channel.write(msg)
 
     def send_pdu_on_intr(self, msg: bytes) -> None:
         assert self.l2cap_intr_channel
-        self.l2cap_intr_channel.send_pdu(msg)
+        self.l2cap_intr_channel.write(msg)
 
     def send_data(self, data: bytes) -> None:
         if self.role == HID.Role.HOST:

bumble/host.py

@@ -732,6 +732,16 @@ class Host(utils.EventEmitter):
             )
             packet_queue.enqueue(acl_packet, connection_handle)
 
+    def send_sco_sdu(self, connection_handle: int, sdu: bytes) -> None:
+        self.send_hci_packet(
+            hci.HCI_SynchronousDataPacket(
+                connection_handle=connection_handle,
+                packet_status=0,
+                data_total_length=len(sdu),
+                data=sdu,
+            )
+        )
+
     def send_l2cap_pdu(self, connection_handle: int, cid: int, pdu: bytes) -> None:
         self.send_acl_sdu(connection_handle, bytes(L2CAP_PDU(cid, pdu)))
 

bumble/l2cap.py

@@ -20,6 +20,7 @@ from __future__ import annotations
 import asyncio
 import dataclasses
 import enum
+import itertools
 import logging
 import struct
 from collections import deque
@@ -302,11 +303,9 @@ class EnhancedControlField(ControlField):
 
 @dataclasses.dataclass
 class InformationEnhancedControlField(EnhancedControlField):
-    tx_seq: int = 0
+    tx_seq: int
+    sar: int
     req_seq: int = 0
-    segmentation_and_reassembly: int = (
-        EnhancedControlField.SegmentationAndReassembly.UNSEGMENTED
-    )
     final: int = 1
 
     frame_type = EnhancedControlField.FieldType.I_FRAME
@@ -316,15 +315,15 @@ class InformationEnhancedControlField(EnhancedControlField):
         return cls(
             tx_seq=(data[0] >> 1) & 0b0111111,
             final=(data[0] >> 7) & 0b1,
-            req_seq=(data[1] & 0b001111111),
-            segmentation_and_reassembly=(data[1] >> 6) & 0b11,
+            req_seq=(data[1] & 0b00111111),
+            sar=(data[1] >> 6) & 0b11,
         )
 
     def __bytes__(self) -> bytes:
         return bytes(
             [
                 self.frame_type | (self.tx_seq << 1) | (self.final << 7),
-                self.req_seq | (self.segmentation_and_reassembly << 6),
+                self.req_seq | (self.sar << 6),
             ]
         )
 
@@ -889,27 +888,38 @@ class EnhancedRetransmissionProcessor(Processor):
     class _PendingPdu:
         payload: bytes
         tx_seq: int
+        sar: InformationEnhancedControlField.SegmentationAndReassembly
+        sdu_length: int = 0
         req_seq: int = 0
 
         def __bytes__(self) -> bytes:
             return (
                 bytes(
                     InformationEnhancedControlField(
-                        tx_seq=self.tx_seq, req_seq=self.req_seq
+                        tx_seq=self.tx_seq,
+                        req_seq=self.req_seq,
+                        sar=self.sar,
                     )
                 )
+                + (
+                    struct.pack('<H', self.sdu_length)
+                    if self.sar
+                    == InformationEnhancedControlField.SegmentationAndReassembly.START
+                    else b''
+                )
                 + self.payload
             )
 
-    _expected_ack_seq: int = 0
+    _last_acked_tx_seq: int = 0
+    _last_acked_rx_seq: int = 0
     _next_tx_seq: int = 0
-    _last_tx_seq: int = 0
     _req_seq_num: int = 0
-    _next_seq_num: int = 0
     _remote_is_busy: bool = False
+    _in_sdu: bytes = b''
 
     _num_receiver_ready_polls_sent: int = 0
     _pending_pdus: list[_PendingPdu]
+    _tx_window: list[_PendingPdu]
     _monitor_handle: asyncio.TimerHandle | None = None
     _receiver_ready_poll_handle: asyncio.TimerHandle | None = None
 
@@ -917,12 +927,6 @@ class EnhancedRetransmissionProcessor(Processor):
     monitor_timeout: float
     retransmission_timeout: float
 
-    @classmethod
-    def _num_frames_between(cls, low: int, high: int) -> int:
-        if high < low:
-            high += cls.MAX_SEQ_NUM
-        return high - low
-
     def __init__(
         self,
         channel: ClassicChannel,
@@ -935,6 +939,7 @@ class EnhancedRetransmissionProcessor(Processor):
         self.peer_mps = peer_mps
         self.peer_tx_window_size = peer_tx_window_size
         self._pending_pdus = []
+        self._tx_window = []
         self.monitor_timeout = spec.monitor_timeout
         self.channel = channel
         self.retransmission_timeout = spec.retransmission_timeout
@@ -972,12 +977,9 @@ class EnhancedRetransmissionProcessor(Processor):
 
     def _send_receiver_ready_poll(self) -> None:
         self._num_receiver_ready_polls_sent += 1
-        self.channel.send_pdu(
-            SupervisoryEnhancedControlField(
-                supervision_function=SupervisoryEnhancedControlField.SupervisoryFunction.RR,
-                final=1,
-                req_seq=self._next_seq_num,
-            )
+        self._send_s_frame(
+            supervision_function=SupervisoryEnhancedControlField.SupervisoryFunction.RR,
+            final=1,
         )
 
     def _get_next_tx_seq(self) -> int:
@@ -987,12 +989,35 @@ class EnhancedRetransmissionProcessor(Processor):
 
     @override
     def send_sdu(self, sdu: bytes) -> None:
-        if len(sdu) > self.peer_mps:
-            raise InvalidArgumentError(
-                f'SDU size({len(sdu)}) exceeds channel MPS {self.peer_mps}'
+        if len(sdu) <= self.peer_mps:
+            pdu = self._PendingPdu(
+                payload=sdu,
+                tx_seq=self._get_next_tx_seq(),
+                req_seq=self._req_seq_num,
+                sar=InformationEnhancedControlField.SegmentationAndReassembly.UNSEGMENTED,
             )
-        pdu = self._PendingPdu(payload=sdu, tx_seq=self._get_next_tx_seq())
-        self._pending_pdus.append(pdu)
+            self._pending_pdus.append(pdu)
+        else:
+            for offset in range(0, len(sdu), self.peer_mps):
+                payload = sdu[offset : offset + self.peer_mps]
+                if offset == 0:
+                    sar = (
+                        InformationEnhancedControlField.SegmentationAndReassembly.START
+                    )
+                elif offset + len(payload) >= len(sdu):
+                    sar = InformationEnhancedControlField.SegmentationAndReassembly.END
+                else:
+                    sar = (
+                        InformationEnhancedControlField.SegmentationAndReassembly.CONTINUATION
+                    )
+                pdu = self._PendingPdu(
+                    payload=payload,
+                    tx_seq=self._get_next_tx_seq(),
+                    req_seq=self._req_seq_num,
+                    sar=sar,
+                    sdu_length=len(sdu),
+                )
+                self._pending_pdus.append(pdu)
         self._process_output()
 
     @override
@@ -1000,17 +1025,37 @@ class EnhancedRetransmissionProcessor(Processor):
         control_field = EnhancedControlField.from_bytes(pdu)
         self._update_ack_seq(control_field.req_seq, control_field.final != 0)
         if isinstance(control_field, InformationEnhancedControlField):
-            if control_field.tx_seq != self._next_seq_num:
+            if control_field.tx_seq != self._req_seq_num:
+                logger.error(
+                    "tx_seq != self._req_seq_num, tx_seq: %d, self._req_seq_num: %d",
+                    control_field.tx_seq,
+                    self._req_seq_num,
+                )
                 return
-            self._next_seq_num = (self._next_seq_num + 1) % self.MAX_SEQ_NUM
-            self._req_seq_num = self._next_seq_num
+            self._req_seq_num = (control_field.tx_seq + 1) % self.MAX_SEQ_NUM
 
-            ack_frame = SupervisoryEnhancedControlField(
-                supervision_function=SupervisoryEnhancedControlField.SupervisoryFunction.RR,
-                req_seq=self._next_seq_num,
-            )
-            self.channel.send_pdu(ack_frame)
-            self.channel.on_sdu(pdu[2:])
+            if (
+                control_field.sar
+                == InformationEnhancedControlField.SegmentationAndReassembly.START
+            ):
+                # Drop Control Field(2) + SDU Length(2)
+                self._in_sdu += pdu[4:]
+            else:
+                # Drop Control Field(2)
+                self._in_sdu += pdu[2:]
+            if control_field.sar in (
+                InformationEnhancedControlField.SegmentationAndReassembly.END,
+                InformationEnhancedControlField.SegmentationAndReassembly.UNSEGMENTED,
+            ):
+                self.channel.on_sdu(self._in_sdu)
+                self._in_sdu = b''
+
+            # If sink doesn't trigger any I-frame, ack this frame.
+            if self._req_seq_num != self._last_acked_rx_seq:
+                self._send_s_frame(
+                    supervision_function=SupervisoryEnhancedControlField.SupervisoryFunction.RR,
+                    final=0,
+                )
         elif isinstance(control_field, SupervisoryEnhancedControlField):
             self._remote_is_busy = (
                 control_field.supervision_function
@@ -1022,56 +1067,66 @@ class EnhancedRetransmissionProcessor(Processor):
                 SupervisoryEnhancedControlField.SupervisoryFunction.RNR,
             ):
                 if control_field.poll:
-                    self.channel.send_pdu(
-                        SupervisoryEnhancedControlField(
-                            supervision_function=SupervisoryEnhancedControlField.SupervisoryFunction.RR,
-                            final=1,
-                            req_seq=self._next_seq_num,
-                        )
+                    self._send_s_frame(
+                        supervision_function=SupervisoryEnhancedControlField.SupervisoryFunction.RR,
+                        final=1,
                     )
             else:
                 # TODO: Handle Retransmission.
                 pass
 
     def _process_output(self) -> None:
-        if self._remote_is_busy or self._monitor_handle:
+        if self._remote_is_busy:
+            logger.debug("Remote is busy")
+            return
+        if self._monitor_handle:
+            logger.debug("Monitor handle is not None")
             return
 
-        for pdu in self._pending_pdus:
-            if self._num_unacked_frames >= self.peer_tx_window_size:
-                return
-            self._send_pdu(pdu)
-            self._last_tx_seq = pdu.tx_seq
+        pdu_to_send = self.peer_tx_window_size - len(self._tx_window)
+        for pdu in itertools.islice(self._pending_pdus, pdu_to_send):
+            self._send_i_frame(pdu)
+        self._pending_pdus = self._pending_pdus[pdu_to_send:]
 
-    @property
-    def _num_unacked_frames(self) -> int:
-        if not self._pending_pdus:
-            return 0
-        return self._num_frames_between(self._expected_ack_seq, self._last_tx_seq + 1)
-
-    def _send_pdu(self, pdu: _PendingPdu) -> None:
+    def _send_i_frame(self, pdu: _PendingPdu) -> None:
         pdu.req_seq = self._req_seq_num
 
         self._start_receiver_ready_poll()
+        self._tx_window.append(pdu)
         self.channel.send_pdu(bytes(pdu))
+        self._last_acked_rx_seq = self._req_seq_num
+
+    def _send_s_frame(
+        self,
+        supervision_function: SupervisoryEnhancedControlField.SupervisoryFunction,
+        final: int,
+    ) -> None:
+        self.channel.send_pdu(
+            SupervisoryEnhancedControlField(
+                supervision_function=supervision_function,
+                final=final,
+                req_seq=self._req_seq_num,
+            )
+        )
+        self._last_acked_rx_seq = self._req_seq_num
 
     def _update_ack_seq(self, new_seq: int, is_poll_response: bool) -> None:
-        num_frames_acked = self._num_frames_between(self._expected_ack_seq, new_seq)
-        if num_frames_acked > self._num_unacked_frames:
+        num_frames_acked = (new_seq - self._last_acked_tx_seq) % self.MAX_SEQ_NUM
+        if num_frames_acked > len(self._tx_window):
             logger.error(
                 "Received acknowledgment for %d frames but only %d frames are pending",
                 num_frames_acked,
-                self._num_unacked_frames,
+                len(self._tx_window),
             )
             return
         if is_poll_response and self._monitor_handle:
             self._monitor_handle.cancel()
             self._monitor_handle = None
 
-        del self._pending_pdus[:num_frames_acked]
-        self._expected_ack_seq = new_seq
+        del self._tx_window[:num_frames_acked]
+        self._last_acked_tx_seq = new_seq
         if (
-            self._expected_ack_seq == self._next_tx_seq
+            self._last_acked_tx_seq == self._next_tx_seq
             and self._receiver_ready_poll_handle
         ):
             self._receiver_ready_poll_handle.cancel()
@@ -1592,7 +1647,9 @@ class LeCreditBasedChannel(utils.EventEmitter):
         self.connection_result = None
         self.disconnection_result = None
         self.drained = asyncio.Event()
-        self.att_mtu = 0  # Filled by GATT client or server later.
+        # Core Specification Vol 3, Part G, 5.3.1 ATT_MTU
+        # ATT_MTU shall be set to the minimum of the MTU field values of the two devices.
+        self.att_mtu = min(mtu, peer_mtu)
 
         self.drained.set()
 

bumble/pandora/l2cap.py

@@ -278,7 +278,7 @@ class L2CAPService(L2CAPServicer):
             if not l2cap_channel:
                 return SendResponse(error=COMMAND_NOT_UNDERSTOOD)
             if isinstance(l2cap_channel, ClassicChannel):
-                l2cap_channel.send_pdu(request.data)
+                l2cap_channel.write(request.data)
             else:
                 l2cap_channel.write(request.data)
             return SendResponse(success=empty_pb2.Empty())

bumble/profiles/battery_service.py

@@ -16,35 +16,28 @@
 # -----------------------------------------------------------------------------
 # Imports
 # -----------------------------------------------------------------------------
+from collections.abc import Callable
 
-from bumble.gatt import (
-    GATT_BATTERY_LEVEL_CHARACTERISTIC,
-    GATT_BATTERY_SERVICE,
-    Characteristic,
-    CharacteristicValue,
-    TemplateService,
-)
-from bumble.gatt_adapters import (
-    PackedCharacteristicAdapter,
-    PackedCharacteristicProxyAdapter,
-)
-from bumble.gatt_client import CharacteristicProxy, ProfileServiceProxy
+from bumble import device, gatt, gatt_adapters, gatt_client
 
 
 # -----------------------------------------------------------------------------
-class BatteryService(TemplateService):
-    UUID = GATT_BATTERY_SERVICE
+class BatteryService(gatt.TemplateService):
+    UUID = gatt.GATT_BATTERY_SERVICE
     BATTERY_LEVEL_FORMAT = 'B'
 
-    battery_level_characteristic: Characteristic[int]
+    battery_level_characteristic: gatt.Characteristic[int]
 
-    def __init__(self, read_battery_level):
-        self.battery_level_characteristic = PackedCharacteristicAdapter(
-            Characteristic(
-                GATT_BATTERY_LEVEL_CHARACTERISTIC,
-                Characteristic.Properties.READ | Characteristic.Properties.NOTIFY,
-                Characteristic.READABLE,
-                CharacteristicValue(read=read_battery_level),
+    def __init__(self, read_battery_level: Callable[[device.Connection], int]) -> None:
+        self.battery_level_characteristic = gatt_adapters.PackedCharacteristicAdapter(
+            gatt.Characteristic(
+                gatt.GATT_BATTERY_LEVEL_CHARACTERISTIC,
+                properties=(
+                    gatt.Characteristic.Properties.READ
+                    | gatt.Characteristic.Properties.NOTIFY
+                ),
+                permissions=gatt.Characteristic.READABLE,
+                value=gatt.CharacteristicValue(read=read_battery_level),
             ),
             pack_format=BatteryService.BATTERY_LEVEL_FORMAT,
         )
@@ -52,19 +45,17 @@ class BatteryService(TemplateService):
 
 
 # -----------------------------------------------------------------------------
-class BatteryServiceProxy(ProfileServiceProxy):
+class BatteryServiceProxy(gatt_client.ProfileServiceProxy):
     SERVICE_CLASS = BatteryService
 
-    battery_level: CharacteristicProxy[int] | None
+    battery_level: gatt_client.CharacteristicProxy[int]
 
-    def __init__(self, service_proxy):
+    def __init__(self, service_proxy: gatt_client.ServiceProxy) -> None:
         self.service_proxy = service_proxy
 
-        if characteristics := service_proxy.get_characteristics_by_uuid(
-            GATT_BATTERY_LEVEL_CHARACTERISTIC
-        ):
-            self.battery_level = PackedCharacteristicProxyAdapter(
-                characteristics[0], pack_format=BatteryService.BATTERY_LEVEL_FORMAT
-            )
-        else:
-            self.battery_level = None
+        self.battery_level = gatt_adapters.PackedCharacteristicProxyAdapter(
+            service_proxy.get_required_characteristic_by_uuid(
+                gatt.GATT_BATTERY_LEVEL_CHARACTERISTIC
+            ),
+            pack_format=BatteryService.BATTERY_LEVEL_FORMAT,
+        )

bumble/profiles/heart_rate_service.py

@@ -18,40 +18,30 @@
 # -----------------------------------------------------------------------------
 from __future__ import annotations
 
+import dataclasses
+import enum
 import struct
-from enum import IntEnum
+from collections.abc import Callable, Sequence
+from typing import Any
 
-from bumble import core
-from bumble.att import ATT_Error
-from bumble.gatt import (
-    GATT_BODY_SENSOR_LOCATION_CHARACTERISTIC,
-    GATT_HEART_RATE_CONTROL_POINT_CHARACTERISTIC,
-    GATT_HEART_RATE_MEASUREMENT_CHARACTERISTIC,
-    GATT_HEART_RATE_SERVICE,
-    Characteristic,
-    CharacteristicValue,
-    TemplateService,
-)
-from bumble.gatt_adapters import (
-    DelegatedCharacteristicAdapter,
-    PackedCharacteristicAdapter,
-    SerializableCharacteristicAdapter,
-)
-from bumble.gatt_client import CharacteristicProxy, ProfileServiceProxy
+from typing_extensions import Self
+
+from bumble import att, core, device, gatt, gatt_adapters, gatt_client, utils
 
 
 # -----------------------------------------------------------------------------
-class HeartRateService(TemplateService):
-    UUID = GATT_HEART_RATE_SERVICE
+class HeartRateService(gatt.TemplateService):
+    UUID = gatt.GATT_HEART_RATE_SERVICE
+
     HEART_RATE_CONTROL_POINT_FORMAT = 'B'
     CONTROL_POINT_NOT_SUPPORTED = 0x80
     RESET_ENERGY_EXPENDED = 0x01
 
-    heart_rate_measurement_characteristic: Characteristic[HeartRateMeasurement]
-    body_sensor_location_characteristic: Characteristic[BodySensorLocation]
-    heart_rate_control_point_characteristic: Characteristic[int]
+    heart_rate_measurement_characteristic: gatt.Characteristic[HeartRateMeasurement]
+    body_sensor_location_characteristic: gatt.Characteristic[BodySensorLocation]
+    heart_rate_control_point_characteristic: gatt.Characteristic[int]
 
-    class BodySensorLocation(IntEnum):
+    class BodySensorLocation(utils.OpenIntEnum):
         OTHER = 0
         CHEST = 1
         WRIST = 2
@@ -60,82 +50,90 @@ class HeartRateService(TemplateService):
         EAR_LOBE = 5
         FOOT = 6
 
+    @dataclasses.dataclass
     class HeartRateMeasurement:
-        def __init__(
-            self,
-            heart_rate,
-            sensor_contact_detected=None,
-            energy_expended=None,
-            rr_intervals=None,
-        ):
-            if heart_rate < 0 or heart_rate > 0xFFFF:
+        heart_rate: int
+        sensor_contact_detected: bool | None = None
+        energy_expended: int | None = None
+        rr_intervals: Sequence[float] | None = None
+
+        class Flag(enum.IntFlag):
+            INT16_HEART_RATE = 1 << 0
+            SENSOR_CONTACT_DETECTED = 1 << 1
+            SENSOR_CONTACT_SUPPORTED = 1 << 2
+            ENERGY_EXPENDED_STATUS = 1 << 3
+            RR_INTERVAL = 1 << 4
+
+        def __post_init__(self) -> None:
+            if self.heart_rate < 0 or self.heart_rate > 0xFFFF:
                 raise core.InvalidArgumentError('heart_rate out of range')
 
-            if energy_expended is not None and (
-                energy_expended < 0 or energy_expended > 0xFFFF
+            if self.energy_expended is not None and (
+                self.energy_expended < 0 or self.energy_expended > 0xFFFF
             ):
                 raise core.InvalidArgumentError('energy_expended out of range')
 
-            if rr_intervals:
-                for rr_interval in rr_intervals:
+            if self.rr_intervals:
+                for rr_interval in self.rr_intervals:
                     if rr_interval < 0 or rr_interval * 1024 > 0xFFFF:
                         raise core.InvalidArgumentError('rr_intervals out of range')
 
-            self.heart_rate = heart_rate
-            self.sensor_contact_detected = sensor_contact_detected
-            self.energy_expended = energy_expended
-            self.rr_intervals = rr_intervals
-
         @classmethod
-        def from_bytes(cls, data):
+        def from_bytes(cls, data: bytes) -> Self:
             flags = data[0]
             offset = 1
 
-            if flags & 1:
-                hr = struct.unpack_from('<H', data, offset)[0]
+            if flags & cls.Flag.INT16_HEART_RATE:
+                heart_rate = struct.unpack_from('<H', data, offset)[0]
                 offset += 2
             else:
-                hr = struct.unpack_from('B', data, offset)[0]
+                heart_rate = struct.unpack_from('B', data, offset)[0]
                 offset += 1
 
-            if flags & (1 << 2):
-                sensor_contact_detected = flags & (1 << 1) != 0
+            if flags & cls.Flag.SENSOR_CONTACT_SUPPORTED:
+                sensor_contact_detected = flags & cls.Flag.SENSOR_CONTACT_DETECTED != 0
             else:
                 sensor_contact_detected = None
 
-            if flags & (1 << 3):
+            if flags & cls.Flag.ENERGY_EXPENDED_STATUS:
                 energy_expended = struct.unpack_from('<H', data, offset)[0]
                 offset += 2
             else:
                 energy_expended = None
 
-            if flags & (1 << 4):
+            rr_intervals: Sequence[float] | None = None
+            if flags & cls.Flag.RR_INTERVAL:
                 rr_intervals = tuple(
-                    struct.unpack_from('<H', data, offset + i * 2)[0] / 1024
-                    for i in range((len(data) - offset) // 2)
+                    struct.unpack_from('<H', data, i)[0] / 1024
+                    for i in range(offset, len(data), 2)
                 )
-            else:
-                rr_intervals = ()
 
-            return cls(hr, sensor_contact_detected, energy_expended, rr_intervals)
+            return cls(
+                heart_rate=heart_rate,
+                sensor_contact_detected=sensor_contact_detected,
+                energy_expended=energy_expended,
+                rr_intervals=rr_intervals,
+            )
 
-        def __bytes__(self):
+        def __bytes__(self) -> bytes:
+            flags = 0
             if self.heart_rate < 256:
-                flags = 0
                 data = struct.pack('B', self.heart_rate)
             else:
-                flags = 1
+                flags |= self.Flag.INT16_HEART_RATE
                 data = struct.pack('<H', self.heart_rate)
 
             if self.sensor_contact_detected is not None:
-                flags |= ((1 if self.sensor_contact_detected else 0) << 1) | (1 << 2)
+                flags |= self.Flag.SENSOR_CONTACT_SUPPORTED
+                if self.sensor_contact_detected:
+                    flags |= self.Flag.SENSOR_CONTACT_DETECTED
 
             if self.energy_expended is not None:
-                flags |= 1 << 3
+                flags |= self.Flag.ENERGY_EXPENDED_STATUS
                 data += struct.pack('<H', self.energy_expended)
 
-            if self.rr_intervals:
-                flags |= 1 << 4
+            if self.rr_intervals is not None:
+                flags |= self.Flag.RR_INTERVAL
                 data += b''.join(
                     [
                         struct.pack('<H', int(rr_interval * 1024))
@@ -145,57 +143,67 @@ class HeartRateService(TemplateService):
 
             return bytes([flags]) + data
 
-        def __str__(self):
-            return (
-                f'HeartRateMeasurement(heart_rate={self.heart_rate},'
-                f' sensor_contact_detected={self.sensor_contact_detected},'
-                f' energy_expended={self.energy_expended},'
-                f' rr_intervals={self.rr_intervals})'
-            )
-
     def __init__(
         self,
-        read_heart_rate_measurement,
-        body_sensor_location=None,
-        reset_energy_expended=None,
+        read_heart_rate_measurement: Callable[
+            [device.Connection], HeartRateMeasurement
+        ],
+        body_sensor_location: HeartRateService.BodySensorLocation | None = None,
+        reset_energy_expended: Callable[[device.Connection], Any] | None = None,
     ):
-        self.heart_rate_measurement_characteristic = SerializableCharacteristicAdapter(
-            Characteristic(
-                GATT_HEART_RATE_MEASUREMENT_CHARACTERISTIC,
-                Characteristic.Properties.NOTIFY,
-                0,
-                CharacteristicValue(read=read_heart_rate_measurement),
-            ),
-            HeartRateService.HeartRateMeasurement,
+        self.heart_rate_measurement_characteristic = (
+            gatt_adapters.SerializableCharacteristicAdapter(
+                gatt.Characteristic(
+                    uuid=gatt.GATT_HEART_RATE_MEASUREMENT_CHARACTERISTIC,
+                    properties=gatt.Characteristic.Properties.NOTIFY,
+                    permissions=gatt.Characteristic.Permissions(0),
+                    value=gatt.CharacteristicValue(read=read_heart_rate_measurement),
+                ),
+                HeartRateService.HeartRateMeasurement,
+            )
         )
-        characteristics = [self.heart_rate_measurement_characteristic]
+        characteristics: list[gatt.Characteristic] = [
+            self.heart_rate_measurement_characteristic
+        ]
 
         if body_sensor_location is not None:
-            self.body_sensor_location_characteristic = Characteristic(
-                GATT_BODY_SENSOR_LOCATION_CHARACTERISTIC,
-                Characteristic.Properties.READ,
-                Characteristic.READABLE,
-                bytes([int(body_sensor_location)]),
+            self.body_sensor_location_characteristic = (
+                gatt_adapters.EnumCharacteristicAdapter(
+                    gatt.Characteristic(
+                        uuid=gatt.GATT_BODY_SENSOR_LOCATION_CHARACTERISTIC,
+                        properties=gatt.Characteristic.Properties.READ,
+                        permissions=gatt.Characteristic.READABLE,
+                        value=body_sensor_location,
+                    ),
+                    cls=self.BodySensorLocation,
+                    length=1,
+                )
             )
             characteristics.append(self.body_sensor_location_characteristic)
 
         if reset_energy_expended:
 
-            def write_heart_rate_control_point_value(connection, value):
+            def write_heart_rate_control_point_value(
+                connection: device.Connection, value: bytes
+            ) -> None:
                 if value == self.RESET_ENERGY_EXPENDED:
                     if reset_energy_expended is not None:
                         reset_energy_expended(connection)
                 else:
-                    raise ATT_Error(self.CONTROL_POINT_NOT_SUPPORTED)
+                    raise att.ATT_Error(self.CONTROL_POINT_NOT_SUPPORTED)
 
-            self.heart_rate_control_point_characteristic = PackedCharacteristicAdapter(
-                Characteristic(
-                    GATT_HEART_RATE_CONTROL_POINT_CHARACTERISTIC,
-                    Characteristic.Properties.WRITE,
-                    Characteristic.WRITEABLE,
-                    CharacteristicValue(write=write_heart_rate_control_point_value),
-                ),
-                pack_format=HeartRateService.HEART_RATE_CONTROL_POINT_FORMAT,
+            self.heart_rate_control_point_characteristic = (
+                gatt_adapters.PackedCharacteristicAdapter(
+                    gatt.Characteristic(
+                        uuid=gatt.GATT_HEART_RATE_CONTROL_POINT_CHARACTERISTIC,
+                        properties=gatt.Characteristic.Properties.WRITE,
+                        permissions=gatt.Characteristic.WRITEABLE,
+                        value=gatt.CharacteristicValue(
+                            write=write_heart_rate_control_point_value
+                        ),
+                    ),
+                    pack_format=HeartRateService.HEART_RATE_CONTROL_POINT_FORMAT,
+                )
             )
             characteristics.append(self.heart_rate_control_point_characteristic)
 
@@ -203,50 +211,51 @@ class HeartRateService(TemplateService):
 
 
 # -----------------------------------------------------------------------------
-class HeartRateServiceProxy(ProfileServiceProxy):
+class HeartRateServiceProxy(gatt_client.ProfileServiceProxy):
     SERVICE_CLASS = HeartRateService
 
-    heart_rate_measurement: (
-        CharacteristicProxy[HeartRateService.HeartRateMeasurement] | None
-    )
+    heart_rate_measurement: gatt_client.CharacteristicProxy[
+        HeartRateService.HeartRateMeasurement
+    ]
     body_sensor_location: (
-        CharacteristicProxy[HeartRateService.BodySensorLocation] | None
+        gatt_client.CharacteristicProxy[HeartRateService.BodySensorLocation] | None
     )
-    heart_rate_control_point: CharacteristicProxy[int] | None
+    heart_rate_control_point: gatt_client.CharacteristicProxy[int] | None
 
-    def __init__(self, service_proxy):
+    def __init__(self, service_proxy: gatt_client.ServiceProxy) -> None:
         self.service_proxy = service_proxy
 
-        if characteristics := service_proxy.get_characteristics_by_uuid(
-            GATT_HEART_RATE_MEASUREMENT_CHARACTERISTIC
-        ):
-            self.heart_rate_measurement = SerializableCharacteristicAdapter(
-                characteristics[0], HeartRateService.HeartRateMeasurement
+        self.heart_rate_measurement = (
+            gatt_adapters.SerializableCharacteristicProxyAdapter(
+                service_proxy.get_required_characteristic_by_uuid(
+                    gatt.GATT_HEART_RATE_MEASUREMENT_CHARACTERISTIC
+                ),
+                HeartRateService.HeartRateMeasurement,
             )
-        else:
-            self.heart_rate_measurement = None
+        )
 
         if characteristics := service_proxy.get_characteristics_by_uuid(
-            GATT_BODY_SENSOR_LOCATION_CHARACTERISTIC
+            gatt.GATT_BODY_SENSOR_LOCATION_CHARACTERISTIC
         ):
-            self.body_sensor_location = DelegatedCharacteristicAdapter(
-                characteristics[0],
-                decode=lambda value: HeartRateService.BodySensorLocation(value[0]),
+            self.body_sensor_location = gatt_adapters.EnumCharacteristicProxyAdapter(
+                characteristics[0], cls=HeartRateService.BodySensorLocation, length=1
             )
         else:
             self.body_sensor_location = None
 
         if characteristics := service_proxy.get_characteristics_by_uuid(
-            GATT_HEART_RATE_CONTROL_POINT_CHARACTERISTIC
+            gatt.GATT_HEART_RATE_CONTROL_POINT_CHARACTERISTIC
         ):
-            self.heart_rate_control_point = PackedCharacteristicAdapter(
-                characteristics[0],
-                pack_format=HeartRateService.HEART_RATE_CONTROL_POINT_FORMAT,
+            self.heart_rate_control_point = (
+                gatt_adapters.PackedCharacteristicProxyAdapter(
+                    characteristics[0],
+                    pack_format=HeartRateService.HEART_RATE_CONTROL_POINT_FORMAT,
+                )
             )
         else:
             self.heart_rate_control_point = None
 
-    async def reset_energy_expended(self):
+    async def reset_energy_expended(self) -> None:
         if self.heart_rate_control_point is not None:
             return await self.heart_rate_control_point.write_value(
                 HeartRateService.RESET_ENERGY_EXPENDED

bumble/rfcomm.py

@@ -800,7 +800,7 @@ class Multiplexer(utils.EventEmitter):
 
     def send_frame(self, frame: RFCOMM_Frame) -> None:
         logger.debug(f'>>> Multiplexer sending {frame}')
-        self.l2cap_channel.send_pdu(frame)
+        self.l2cap_channel.write(bytes(frame))
 
     def on_pdu(self, pdu: bytes) -> None:
         frame = RFCOMM_Frame.from_bytes(pdu)

bumble/sdp.py

@@ -847,7 +847,7 @@ class Client:
             self.pending_request = request
 
             try:
-                self.channel.send_pdu(bytes(request))
+                self.channel.write(bytes(request))
                 return await self.pending_response
             finally:
                 self.pending_request = None
@@ -1061,7 +1061,7 @@ class Server:
 
     def send_response(self, response):
         logger.debug(f'{color(">>> Sending SDP Response", "blue")}: {response}')
-        self.channel.send_pdu(response)
+        self.channel.write(response)
 
     def match_services(self, search_pattern: DataElement) -> dict[int, Service]:
         # Find the services for which the attributes in the pattern is a subset of the

docs/mkdocs/src/platforms/linux.md

@@ -63,7 +63,7 @@ HCI sockets provide a way to send/receive HCI packets to/from a Bluetooth contro
 See the [HCI Socket Transport page](../transports/hci_socket.md) for details on the `hci-socket` tansport syntax.
 
 The HCI device referenced by an `hci-socket` transport (`hci<X>`, where `<X>` is an integer, with `hci0` being the first controller device, and so on) must be in the `DOWN` state before it can be opened as a transport.
-You can bring a HCI controller `UP` or `DOWN` with `hciconfig hci<X> up` and `hciconfig hci<X> up`.
+You can bring a HCI controller `UP` or `DOWN` with `hciconfig hci<X> up` and `hciconfig hci<X> down`.
 
 !!! tip "HCI Socket Permissions"
     By default, when running as a regular user, you won't have the permission to use

examples/heart_rate_server.py

@@ -71,8 +71,8 @@ async def main() -> None:
                 rr_intervals=random.choice(
                     (
                         (
-                            random.randint(900, 1100) / 1000,
-                            random.randint(900, 1100) / 1000,
+                            random.randint(900, 1100) // 1000,
+                            random.randint(900, 1100) // 1000,
                         ),
                         None,
                     )

examples/run_hfp_gateway.py

@@ -100,13 +100,9 @@ def on_sco_packet(packet: hci.HCI_SynchronousDataPacket):
     if source_file and (pcm_data := source_file.read(packet.data_total_length)):
         assert ag_protocol
         host = ag_protocol.dlc.multiplexer.l2cap_channel.connection.device.host
-        host.send_hci_packet(
-            hci.HCI_SynchronousDataPacket(
-                connection_handle=packet.connection_handle,
-                packet_status=0,
-                data_total_length=len(pcm_data),
-                data=pcm_data,
-            )
+        host.send_sco_sdu(
+            connection_handle=packet.connection_handle,
+            sdu=pcm_data,
         )
 
 

rust/pytests/wrapper/drivers.rs

@@ -17,6 +17,6 @@ use pyo3::PyResult;
 
 #[pyo3_asyncio::tokio::test]
 async fn realtek_driver_info_all_drivers() -> PyResult<()> {
-    assert_eq!(12, DriverInfo::all_drivers()?.len());
+    assert_eq!(13, DriverInfo::all_drivers()?.len());
     Ok(())
 }

tests/battery_service_test.py

@@ -0,0 +1,34 @@
+# Copyright 2021-2026 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.
+
+
+import pytest
+
+from bumble import device as device_module
+from bumble.profiles import battery_service
+
+from . import test_utils
+
+
+# -----------------------------------------------------------------------------
+@pytest.mark.asyncio
+async def test_read_battery_level():
+    devices = await test_utils.TwoDevices.create_with_connection()
+    service = battery_service.BatteryService(lambda _: 1)
+    devices[0].add_service(service)
+
+    async with device_module.Peer(devices.connections[1]) as peer:
+        client = peer.create_service_proxy(battery_service.BatteryServiceProxy)
+        assert client
+        assert await client.battery_level.read_value() == 1

tests/gatt_test.py

@@ -28,7 +28,7 @@ from unittest.mock import ANY, AsyncMock, Mock
 import pytest
 from typing_extensions import Self
 
-from bumble import gatt_client, l2cap
+from bumble import att, gatt_client, l2cap
 from bumble.att import (
     ATT_ATTRIBUTE_NOT_FOUND_ERROR,
     ATT_PDU,
@@ -1638,6 +1638,104 @@ async def test_eatt_connection_failure():
         await gatt_client.Client.connect_eatt(devices.connections[0])
 
 
+# -----------------------------------------------------------------------------
+@pytest.mark.asyncio
+async def test_read_multiple() -> None:
+    devices = await TwoDevices.create_with_connection()
+
+    characteristic1 = Characteristic(
+        '0001', Characteristic.Properties.READ, Characteristic.READABLE, b'1234'
+    )
+
+    characteristic2 = Characteristic(
+        '0002',
+        Characteristic.Properties.READ,
+        Characteristic.READABLE,
+        b'5678',
+    )
+
+    service = Service('0000', [characteristic1, characteristic2])
+    devices[1].add_service(service)
+
+    client = devices.connections[0].gatt_client
+    server = devices[1].gatt_server
+
+    await client.discover_services()
+    characteristics = await client.discover_characteristics(
+        [characteristic1.uuid, characteristic2.uuid], None
+    )
+    response = await client.send_request(
+        att.ATT_Read_Multiple_Request(
+            set_of_handles=[c.handle for c in characteristics]
+        )
+    )
+    assert isinstance(response, att.ATT_Read_Multiple_Response)
+    assert response.set_of_values == b'12345678'
+
+    response = await client.send_request(
+        att.ATT_Read_Multiple_Request(
+            set_of_handles=[
+                next(
+                    handle
+                    for handle in range(0x0001, 0xFFFF)
+                    if not server.get_attribute(handle)
+                )
+            ]
+        )
+    )
+    assert isinstance(response, att.ATT_Error_Response)
+    assert response.error_code == att.ATT_ATTRIBUTE_NOT_FOUND_ERROR
+
+
+# -----------------------------------------------------------------------------
+@pytest.mark.asyncio
+async def test_read_multiple_variable() -> None:
+    devices = await TwoDevices.create_with_connection()
+
+    characteristic1 = Characteristic(
+        '0001', Characteristic.Properties.READ, Characteristic.READABLE, b'1234'
+    )
+
+    characteristic2 = Characteristic(
+        '0002',
+        Characteristic.Properties.READ,
+        Characteristic.READABLE,
+        b'99',
+    )
+
+    service = Service('0000', [characteristic1, characteristic2])
+    devices[1].add_service(service)
+
+    client = devices.connections[0].gatt_client
+    server = devices[1].gatt_server
+
+    await client.discover_services()
+    characteristics = await client.discover_characteristics(
+        [characteristic1.uuid, characteristic2.uuid], None
+    )
+    response = await client.send_request(
+        att.ATT_Read_Multiple_Variable_Request(
+            set_of_handles=[c.handle for c in characteristics]
+        )
+    )
+    assert isinstance(response, att.ATT_Read_Multiple_Variable_Response)
+    assert response.length_value_tuple_list == [(4, b'1234'), (2, b'99')]
+
+    response = await client.send_request(
+        att.ATT_Read_Multiple_Variable_Request(
+            set_of_handles=[
+                next(
+                    handle
+                    for handle in range(0x0001, 0xFFFF)
+                    if not server.get_attribute(handle)
+                )
+            ]
+        )
+    )
+    assert isinstance(response, att.ATT_Error_Response)
+    assert response.error_code == att.ATT_ATTRIBUTE_NOT_FOUND_ERROR
+
+
 # -----------------------------------------------------------------------------
 if __name__ == '__main__':
     logging.basicConfig(level=os.environ.get('BUMBLE_LOGLEVEL', 'INFO').upper())

tests/heart_rate_service_test.py

@@ -0,0 +1,89 @@
+# Copyright 2021-2026 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.
+
+import asyncio
+import itertools
+from collections.abc import Sequence
+
+import pytest
+
+from bumble import device as device_module
+from bumble.profiles import heart_rate_service
+
+from . import test_utils
+
+
+# -----------------------------------------------------------------------------
+@pytest.mark.asyncio
+@pytest.mark.parametrize(
+    "heart_rate, sensor_contact_detected, energy_expanded, rr_intervals",
+    itertools.product(
+        (1, 1000), (True, False, None), (2, None), ((3.0, 4.0, 5.0), None)
+    ),
+)
+async def test_read_measurement(
+    heart_rate: int,
+    sensor_contact_detected: bool | None,
+    energy_expanded: int | None,
+    rr_intervals: Sequence[int] | None,
+):
+    devices = await test_utils.TwoDevices.create_with_connection()
+    measurement = heart_rate_service.HeartRateService.HeartRateMeasurement(
+        heart_rate, sensor_contact_detected, energy_expanded, rr_intervals
+    )
+    service = heart_rate_service.HeartRateService(lambda _: measurement)
+    devices[0].add_service(service)
+
+    async with device_module.Peer(devices.connections[1]) as peer:
+        client = peer.create_service_proxy(heart_rate_service.HeartRateServiceProxy)
+        assert client
+        assert await client.heart_rate_measurement.read_value() == measurement
+
+
+# -----------------------------------------------------------------------------
+@pytest.mark.asyncio
+async def test_read_body_sensor_location():
+    devices = await test_utils.TwoDevices.create_with_connection()
+    measurement = heart_rate_service.HeartRateService.HeartRateMeasurement(0)
+    location = heart_rate_service.HeartRateService.BodySensorLocation.FINGER
+    service = heart_rate_service.HeartRateService(
+        lambda _: measurement,
+        body_sensor_location=location,
+    )
+    devices[0].add_service(service)
+
+    async with device_module.Peer(devices.connections[1]) as peer:
+        client = peer.create_service_proxy(heart_rate_service.HeartRateServiceProxy)
+        assert client
+        assert client.body_sensor_location
+        assert await client.body_sensor_location.read_value() == location
+
+
+# -----------------------------------------------------------------------------
+@pytest.mark.asyncio
+async def test_reset_energy_expended() -> None:
+    devices = await test_utils.TwoDevices.create_with_connection()
+    measurement = heart_rate_service.HeartRateService.HeartRateMeasurement(1)
+    reset_energy_expended = asyncio.Queue[None]()
+    service = heart_rate_service.HeartRateService(
+        lambda _: measurement,
+        reset_energy_expended=lambda _: reset_energy_expended.put_nowait(None),
+    )
+    devices[0].add_service(service)
+
+    async with device_module.Peer(devices.connections[1]) as peer:
+        client = peer.create_service_proxy(heart_rate_service.HeartRateServiceProxy)
+        assert client
+        await client.reset_energy_expended()
+        await reset_energy_expended.get()

tests/l2cap_test.py

@@ -239,20 +239,7 @@ async def transfer_payload(
     channels[1].sink = received.put_nowait
     sdu_lengths = (21, 70, 700, 5523)
 
-    if isinstance(channels[1], l2cap.LeCreditBasedChannel):
-        mps = channels[1].mps
-    elif isinstance(
-        processor := channels[1].processor, l2cap.EnhancedRetransmissionProcessor
-    ):
-        mps = processor.mps
-    else:
-        mps = channels[1].mtu
-
-    messages = [
-        bytes([i % 8 for i in range(sdu_length)])
-        for sdu_length in sdu_lengths
-        if sdu_length <= mps
-    ]
+    messages = [bytes([i % 8 for i in range(sdu_length)]) for sdu_length in sdu_lengths]
     for message in messages:
         channels[0].write(message)
         if isinstance(channels[0], l2cap.LeCreditBasedChannel):
@@ -334,20 +321,26 @@ async def test_mtu():
 
 # -----------------------------------------------------------------------------
 @pytest.mark.asyncio
-async def test_enhanced_retransmission_mode():
+@pytest.mark.parametrize("mtu,", (50, 255, 256, 1000))
+async def test_enhanced_retransmission_mode(mtu: int):
     devices = TwoDevices()
     await devices.setup_connection()
 
     server_channels = asyncio.Queue[l2cap.ClassicChannel]()
     server = devices.devices[1].create_l2cap_server(
         spec=l2cap.ClassicChannelSpec(
-            mode=l2cap.TransmissionMode.ENHANCED_RETRANSMISSION
+            mode=l2cap.TransmissionMode.ENHANCED_RETRANSMISSION,
+            mtu=mtu,
+            mps=256,
         ),
         handler=server_channels.put_nowait,
     )
     client_channel = await devices.connections[0].create_l2cap_channel(
         spec=l2cap.ClassicChannelSpec(
-            server.psm, mode=l2cap.TransmissionMode.ENHANCED_RETRANSMISSION
+            server.psm,
+            mode=l2cap.TransmissionMode.ENHANCED_RETRANSMISSION,
+            mtu=mtu,
+            mps=1024,
         )
     )
     server_channel = await server_channels.get()