aioble: Use DeviceDisconnectedError for disconnected guards.

Replace ValueError("Not connected") with DeviceDisconnectedError in
the is_connected() guards in L2CAPChannel.__init__,
DeviceConnection.exchange_mtu, and Characteristic.indicate.  Callers
already catch DeviceDisconnectedError for disconnect handling; the
ValueError was not semantically correct and required string matching
to distinguish from other ValueErrors.

Also make L2CAPDisconnectedError a subclass of DeviceDisconnectedError
so that mid-operation L2CAP disconnections are caught by the same
handler (e.g. in the l2cap_file_server example).

Signed-off-by: Andrew Leech <andrew.leech@planetinnovation.com.au>

Author: pi-anl

micropython/bluetooth/aioble/aioble/device.py

@@ -273,7 +273,7 @@ def timeout(self, timeout_ms):
 
     async def exchange_mtu(self, mtu=None, timeout_ms=1000):
         if not self.is_connected():
-            raise ValueError("Not connected")
+            raise DeviceDisconnectedError
 
         if mtu:
             ble.config(mtu=mtu)

micropython/bluetooth/aioble/aioble/l2cap.py

@@ -6,7 +6,7 @@
 import asyncio
 
 from .core import ble, log_error, register_irq_handler
-from .device import DeviceConnection
+from .device import DeviceConnection, DeviceDisconnectedError
 
 
 _IRQ_L2CAP_ACCEPT = const(22)
@@ -63,7 +63,7 @@ def _l2cap_shutdown():
 
 
 # The channel was disconnected during a send/recvinto/flush.
-class L2CAPDisconnectedError(Exception):
+class L2CAPDisconnectedError(DeviceDisconnectedError):
     pass
 
 
@@ -75,7 +75,7 @@ class L2CAPConnectionError(Exception):
 class L2CAPChannel:
     def __init__(self, connection):
         if not connection.is_connected():
-            raise ValueError("Not connected")
+            raise L2CAPDisconnectedError
 
         if connection._l2cap_channel:
             raise ValueError("Already has channel")

micropython/bluetooth/aioble/aioble/server.py

@@ -15,7 +15,7 @@
     register_irq_handler,
     GattError,
 )
-from .device import DeviceConnection, DeviceTimeout
+from .device import DeviceConnection, DeviceDisconnectedError, DeviceTimeout
 
 _registered_characteristics = {}
 
@@ -263,7 +263,7 @@ async def indicate(self, connection, data=None, timeout_ms=1000):
         if self._indicate_connection is not None:
             raise ValueError("In progress")
         if not connection.is_connected():
-            raise ValueError("Not connected")
+            raise DeviceDisconnectedError
 
         self._indicate_connection = connection
         self._indicate_status = None