diff --git a/fwupd.py b/fwupd.py
index 87ab7f5..9c62a27 100644
--- a/fwupd.py
+++ b/fwupd.py
@@ -17,7 +17,7 @@ PING_RETRIES = 20
 
 def checksum(s, data):
     for c in data:
-        s += ord(c)
+        s += c
     return s & 0xFFFFFFFF
 
 
@@ -99,7 +99,7 @@ parser.add_argument(
     "--interface",
     help="communication interface, default: %(default)s",
     type=str.lower,
-    choices=("ble", "serial", "tcp", "blefleet"),
+    choices=("ble", "serial", "tcp", "blefleet", "bleak"),
     default="ble",
 )
 
@@ -149,6 +149,12 @@ elif args.interface == "blefleet":
     except:
         exit("BLE is not supported on your system !")
     link = BLELink()
+elif args.interface == "bleak":
+    try:
+        from py9b.link.bleak import BleakLink
+    except:
+        exit("BLE is not supported on your system !")
+    link = BleakLink()
 else:
     exit("!!! BUG !!! Unknown interface selected: " + args.interface)
 
diff --git a/py9b/command/base.py b/py9b/command/base.py
index 3d2af4f..5b468b6 100644
--- a/py9b/command/base.py
+++ b/py9b/command/base.py
@@ -7,7 +7,7 @@ class InvalidResponse(Exception):
 
 
 class BaseCommand(object):
-    def __init__(self, src=BT.HOST, dst=0, cmd=0, arg=0, data="", has_response=True):
+    def __init__(self, src=BT.HOST, dst=0, cmd=0, arg=0, data=bytearray(), has_response=True):
         self.has_response = has_response
         self.request = PKT(src, dst, cmd, arg, data)
 
diff --git a/py9b/link/bleak.py b/py9b/link/bleak.py
index bac8987..7e27273 100644
--- a/py9b/link/bleak.py
+++ b/py9b/link/bleak.py
@@ -92,7 +92,9 @@ class BleakLink(BaseLink):
         fut.result(10)
 
     async def _connect(self, port):
-        self._client = BleakClient(port[1], device=self.device)
+        if isinstance(port, tuple):
+            port = port[1]
+        self._client = BleakClient(port, device=self.device)
         await self._client.connect()
         print("connected")
         await self._client.start_notify(_tx_char_uuid, self._data_received)
diff --git a/py9b/transport/base.py b/py9b/transport/base.py
index e3eb316..0e45f13 100644
--- a/py9b/transport/base.py
+++ b/py9b/transport/base.py
@@ -31,7 +31,7 @@ class BaseTransport(object):
     def recv(self):
         raise NotImplementedError()
 
-    def send(self, src, dst, cmd, arg, data=""):
+    def send(self, src, dst, cmd, arg, data=bytearray()):
         raise NotImplementedError()
 
     def execute(self, command):
diff --git a/py9b/transport/packet.py b/py9b/transport/packet.py
index cc7a21d..4e87df7 100644
--- a/py9b/transport/packet.py
+++ b/py9b/transport/packet.py
@@ -3,7 +3,7 @@ from .base import BaseTransport as BT
 
 
 class BasePacket(object):
-    def __init__(self, src=0, dst=0, cmd=0, arg=0, data=""):
+    def __init__(self, src=0, dst=0, cmd=0, arg=0, data=bytearray()):
         self.src = src
         self.dst = dst
         self.cmd = cmd