diff --git a/.gitignore b/.gitignore
index f92a110..0068633 100644
--- a/.gitignore
+++ b/.gitignore
@@ -110,6 +110,7 @@ celerybeat.pid
 .venv
 env/
 venv/
+venv3/
 ENV/
 env.bak/
 venv.bak/
diff --git a/PyGrowatt/growatt_framer.py b/PyGrowatt/growatt_framer.py
index 2af4a25..177158a 100644
--- a/PyGrowatt/growatt_framer.py
+++ b/PyGrowatt/growatt_framer.py
@@ -39,7 +39,7 @@ class GrowattV6Framer(ModbusSocketFramer):
         * The -1 is to account for the uid byte
     """
 
-    def __init__(self, decoder, client=None, key="Growatt"):
+    def __init__(self, decoder, client=None, key=b'Growatt'):
         """ Initializes a new instance of the framer
 
         :param decoder: The decoder factory implementation to use
@@ -54,7 +54,7 @@ def _process(self, callback, error=False):
         data = self.getRawFrame() if error else self.getFrame()
         # data contains the function_code, then encrypted payload
         payload = self._xor(data[1:])
-        data = data[0] + payload
+        data = bytes([data[0]]) + payload
         result = self.decoder.decode(data)
         if result is None:
             raise ModbusIOException("Unable to decode request")
@@ -123,7 +123,7 @@ def buildPacket(self, message):
         return packet
 
     def _xor(self, data):
-        decrypted = ''
+        decrypted = b''
         for i in range(0, len(data)):
-            decrypted += chr(ord(data[i]) ^ ord(self._key[i % len(self._key)]))
+            decrypted += bytes([data[i] ^ self._key[i % len(self._key)]])
         return decrypted
diff --git a/test/test_Growatt.py b/test/test_Growatt.py
index 799e90d..3cff31e 100644
--- a/test/test_Growatt.py
+++ b/test/test_Growatt.py
@@ -7,23 +7,23 @@
 
 
 def _xor(data):
-    key = "Growatt"
-    decrypted = ""
+    key = b'Growatt'
+    decrypted = b''
     for i in range(0, len(data)):
-        decrypted += chr(ord(data[i]) ^ ord(key[i % len(key)]))
+        decrypted += bytes([data[i] ^ key[i % len(key)]])
     return decrypted
 
 
 class TestGrowattBufferedEnergyRequest(TestCase):
     def test_decode(self):
         data = binascii.unhexlify(
-            "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
+            b'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
 
         request = Growatt.GrowattBufferedEnergyRequest()
         request.decode(_xor(data))
 
-        self.assertEqual(request.wifi_serial, 'ABC1D2345E')
-        self.assertEqual(request.inverter_serial, 'WXY9Z87654')
+        self.assertEqual(request.wifi_serial, b'ABC1D2345E')
+        self.assertEqual(request.inverter_serial, b'WXY9Z87654')
 
         self.assertEqual(request.year, 20)
         self.assertEqual(request.month, 12)
@@ -68,11 +68,11 @@ def test_encode(self):
         store = ModbusSlaveContext(di=block, co=block, hr=block, ir=block)
 
         buffered_input_register = ModbusSparseDataBlock([0] * 100)
-        store.register(0x50, 'bi', buffered_input_register)
+        store.register(0x50, b'bi', buffered_input_register)
 
         # Initialize the Request
         data = binascii.unhexlify(
-            "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
+            b'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
         request = Growatt.GrowattBufferedEnergyRequest()
         request.decode(data)
 
@@ -88,222 +88,222 @@ def test_decode(self):
         request = Growatt.GrowattQueryRequest()
 
         # From "2020-12-20 09/33/35.531467_0x19_192.168.1.108.dat"
-        data = binascii.unhexlify("06302c4625464773472a7761747447726f7761747447726f7761747447726f73617545")
+        data = binascii.unhexlify(b'06302c4625464773472a7761747447726f7761747447726f7761747447726f73617545')
         request.decode(_xor(data))
-        self.assertEqual(request.wifi_serial, 'ABC1D2345E')
+        self.assertEqual(request.wifi_serial, b'ABC1D2345E')
         self.assertEqual(request.config_id, 4)
         self.assertEqual(request.config_length, 1)
-        self.assertEqual(request.config_value, '1')
+        self.assertEqual(request.config_value, b'1')
 
         # From "2020-12-20 09/33/37.137908_0x19_192.168.1.108.dat"
-        data = binascii.unhexlify("06302c4625464773472a7761747447726f7761747447726f7761747447726f72617545")
+        data = binascii.unhexlify(b'06302c4625464773472a7761747447726f7761747447726f7761747447726f72617545')
         request.decode(_xor(data))
-        self.assertEqual(request.wifi_serial, 'ABC1D2345E')
+        self.assertEqual(request.wifi_serial, b'ABC1D2345E')
         self.assertEqual(request.config_id, 5)
         self.assertEqual(request.config_length, 1)
-        self.assertEqual(request.config_value, '1')
+        self.assertEqual(request.config_value, b'1')
 
         # From "2020-12-20 09/33/38.317449_0x19_192.168.1.108.dat"
-        data = binascii.unhexlify("06302c4625464773472a7761747447726f7761747447726f7761747447726f7161764775")
+        data = binascii.unhexlify(b'06302c4625464773472a7761747447726f7761747447726f7761747447726f7161764775')
         request.decode(_xor(data))
-        self.assertEqual(request.wifi_serial, 'ABC1D2345E')
+        self.assertEqual(request.wifi_serial, b'ABC1D2345E')
         self.assertEqual(request.config_id, 6)
         self.assertEqual(request.config_length, 2)
-        self.assertEqual(request.config_value, '32')
+        self.assertEqual(request.config_value, b'32')
 
         # From "2020-12-20 09/33/39.442625_0x19_192.168.1.108.dat"
-        data = binascii.unhexlify("06302c4625464773472a7761747447726f7761747447726f7761747447726f7061752c")
+        data = binascii.unhexlify(b'06302c4625464773472a7761747447726f7761747447726f7761747447726f7061752c')
         request.decode(_xor(data))
-        self.assertEqual(request.wifi_serial, 'ABC1D2345E')
+        self.assertEqual(request.wifi_serial, b'ABC1D2345E')
         self.assertEqual(request.config_id, 7)
         self.assertEqual(request.config_length, 1)
-        self.assertEqual(request.config_value, 'X')
+        self.assertEqual(request.config_value, b'X')
 
         # From "2020-12-20 09/33/40.467802_0x19_192.168.1.108.dat"
         data = binascii.unhexlify(
-            "06302c4625464773472a7761747447726f7761747447726f7761747447726f7f617e3505315e335347407237")
+            b'06302c4625464773472a7761747447726f7761747447726f7761747447726f7f617e3505315e335347407237')
         request.decode(_xor(data))
-        self.assertEqual(request.wifi_serial, 'ABC1D2345E')
+        self.assertEqual(request.wifi_serial, b'ABC1D2345E')
         self.assertEqual(request.config_id, 8)
         self.assertEqual(request.config_length, 10)
-        self.assertEqual(request.config_value, 'ABC1D2345E')
+        self.assertEqual(request.config_value, b'ABC1D2345E')
 
         # From "2020-12-20 09/33/41.593722_0x19_192.168.1.108.dat"
-        data = binascii.unhexlify("06302c4625464773472a7761747447726f7761747447726f7761747447726f7e61702c1f2a37")
+        data = binascii.unhexlify(b'06302c4625464773472a7761747447726f7761747447726f7761747447726f7e61702c1f2a37')
         request.decode(_xor(data))
-        self.assertEqual(request.wifi_serial, 'ABC1D2345E')
+        self.assertEqual(request.wifi_serial,b'ABC1D2345E')
         self.assertEqual(request.config_id, 9)
         self.assertEqual(request.config_length, 4)
-        self.assertEqual(request.config_value, 'XXXX')
+        self.assertEqual(request.config_value, b'XXXX')
 
         # From "2020-12-20 09/33/42.720057_0x19_192.168.1.108.dat"
-        data = binascii.unhexlify("06302c4625464773472a7761747447726f7761747447726f7761747447726f7d617544")
+        data = binascii.unhexlify(b'06302c4625464773472a7761747447726f7761747447726f7761747447726f7d617544')
         request.decode(_xor(data))
-        self.assertEqual(request.wifi_serial, 'ABC1D2345E')
+        self.assertEqual(request.wifi_serial, b'ABC1D2345E')
         self.assertEqual(request.config_id, 10)
         self.assertEqual(request.config_length, 1)
-        self.assertEqual(request.config_value, '0')
+        self.assertEqual(request.config_value, b'0')
 
         # From "2020-12-20 09/33/43.744657_0x19_192.168.1.108.dat"
         data = binascii.unhexlify(
-            "06302c4625464773472a7761747447726f7761747447726f7761747447726f7c616957644356454f45427f5c5c5952415b26021f5819191868515747594557")
+            b'06302c4625464773472a7761747447726f7761747447726f7761747447726f7c616957644356454f45427f5c5c5952415b26021f5819191868515747594557')
         request.decode(_xor(data))
-        self.assertEqual(request.wifi_serial, 'ABC1D2345E')
+        self.assertEqual(request.wifi_serial, b'ABC1D2345E')
         self.assertEqual(request.config_id, 11)
         self.assertEqual(request.config_length, 29)
-        self.assertEqual(request.config_value, '##192.168.3.35/app/xml/#8081#')
+        self.assertEqual(request.config_value, b'##192.168.3.35/app/xml/#8081#')
 
         # From "2020-12-20 09/33/44.870469_0x19_192.168.1.108.dat"
         data = binascii.unhexlify(
-            "06302c4625464773472a7761747447726f7761747447726f7761747447726f7b617b2c1f2a372f392c2c1f2a372f392c2c")
+            b'06302c4625464773472a7761747447726f7761747447726f7761747447726f7b617b2c1f2a372f392c2c1f2a372f392c2c')
         request.decode(_xor(data))
-        self.assertEqual(request.wifi_serial, 'ABC1D2345E')
+        self.assertEqual(request.wifi_serial, b'ABC1D2345E')
         self.assertEqual(request.config_id, 12)
         self.assertEqual(request.config_length, 15)
-        self.assertEqual(request.config_value, 'XXXXXXXXXXXXXXX')
+        self.assertEqual(request.config_value, b'XXXXXXXXXXXXXXX')
 
         # From "2020-12-20 09/33/45.996974_0x19_192.168.1.108.dat"
-        data = binascii.unhexlify("06302c4625464773472a7761747447726f7761747447726f7761747447726f7a61764571")
+        data = binascii.unhexlify(b'06302c4625464773472a7761747447726f7761747447726f7761747447726f7a61764571')
         request.decode(_xor(data))
-        self.assertEqual(request.wifi_serial, 'ABC1D2345E')
+        self.assertEqual(request.wifi_serial, b'ABC1D2345E')
         self.assertEqual(request.config_id, 13)
         self.assertEqual(request.config_length, 2)
-        self.assertEqual(request.config_value, '16')
+        self.assertEqual(request.config_value, b'16')
 
         # From "2020-12-20 09/33/47.040342_0x19_192.168.1.108.dat"
         data = binascii.unhexlify(
-            "06302c4625464773472a7761747447726f7761747447726f7761747447726f79617f457e404146574c5a725c5e")
+            b'06302c4625464773472a7761747447726f7761747447726f7761747447726f79617f457e404146574c5a725c5e')
         request.decode(_xor(data))
-        self.assertEqual(request.wifi_serial, 'ABC1D2345E')
+        self.assertEqual(request.wifi_serial, b'ABC1D2345E')
         self.assertEqual(request.config_id, 14)
         self.assertEqual(request.config_length, 11)
-        self.assertEqual(request.config_value, '192.168.5.1')
+        self.assertEqual(request.config_value, b'192.168.5.1')
 
         # From "2020-12-20 09/33/48.146565_0x19_192.168.1.108.dat"
-        data = binascii.unhexlify("06302c4625464773472a7761747447726f7761747447726f7761747447726f7861764c77")
+        data = binascii.unhexlify(b'06302c4625464773472a7761747447726f7761747447726f7761747447726f7861764c77')
         request.decode(_xor(data))
-        self.assertEqual(request.wifi_serial, 'ABC1D2345E')
+        self.assertEqual(request.wifi_serial, b'ABC1D2345E')
         self.assertEqual(request.config_id, 15)
         self.assertEqual(request.config_length, 2)
-        self.assertEqual(request.config_value, '80')
+        self.assertEqual(request.config_value, b'80')
 
         # From "2020-12-20 09/33/49.274950_0x19_192.168.1.108.dat"
         data = binascii.unhexlify(
-            "06302c4625464773472a7761747447726f7761747447726f7761747447726f6761654177485f455b4d457d375a4d23374e7f46")
+            b'06302c4625464773472a7761747447726f7761747447726f7761747447726f6761654177485f455b4d457d375a4d23374e7f46')
         request.decode(_xor(data))
-        self.assertEqual(request.wifi_serial, 'ABC1D2345E')
+        self.assertEqual(request.wifi_serial, b'ABC1D2345E')
         self.assertEqual(request.config_id, 16)
         self.assertEqual(request.config_length, 17)
-        self.assertEqual(request.config_value, '50:02:91:E5:BC:84')
+        self.assertEqual(request.config_value, b'50:02:91:E5:BC:84')
 
         # From "2020-12-20 09/33/50.400144_0x19_192.168.1.108.dat"
         data = binascii.unhexlify(
-            "06302c4625464773472a7761747447726f7761747447726f7761747447726f666179457e404146574c5a765c5e4759")
+            b'06302c4625464773472a7761747447726f7761747447726f7761747447726f666179457e404146574c5a765c5e4759')
         request.decode(_xor(data))
-        self.assertEqual(request.wifi_serial, 'ABC1D2345E')
+        self.assertEqual(request.wifi_serial, b'ABC1D2345E')
         self.assertEqual(request.config_id, 17)
         self.assertEqual(request.config_length, 13)
-        self.assertEqual(request.config_value, '192.168.1.108')
+        self.assertEqual(request.config_value, b'192.168.1.108')
 
         # From "2020-12-20 09/33/51.525851_0x19_192.168.1.108.dat"
-        data = binascii.unhexlify("06302c4625464773472a7761747447726f7761747447726f7761747447726f65617041754556")
+        data = binascii.unhexlify(b'06302c4625464773472a7761747447726f7761747447726f7761747447726f65617041754556')
         request.decode(_xor(data))
-        self.assertEqual(request.wifi_serial, 'ABC1D2345E')
+        self.assertEqual(request.wifi_serial, b'ABC1D2345E')
         self.assertEqual(request.config_id, 18)
         self.assertEqual(request.config_length, 4)
-        self.assertEqual(request.config_value, '5279')
+        self.assertEqual(request.config_value, b'5279')
 
         # From "2020-12-20 09/33/52.551080_0x19_192.168.1.108.dat"
-        data = binascii.unhexlify("06302c4625464773472a7761747447726f7761747447726f7761747447726f646174")
+        data = binascii.unhexlify(b'06302c4625464773472a7761747447726f7761747447726f7761747447726f646174')
         request.decode(_xor(data))
-        self.assertEqual(request.wifi_serial, 'ABC1D2345E')
+        self.assertEqual(request.wifi_serial, b'ABC1D2345E')
         self.assertEqual(request.config_id, 19)
         self.assertEqual(request.config_length, 0)
-        self.assertEqual(request.config_value, '')
+        self.assertEqual(request.config_value, b'')
 
         # From "2020-12-20 09/33/53.676882_0x19_192.168.1.108.dat"
         data = binascii.unhexlify(
-            "06302c4625464773472a7761747447726f7761747447726f7761747447726f6361602c1f2a372f392c2c1f2a372f392c2c1f2a372f39")
+            b'06302c4625464773472a7761747447726f7761747447726f7761747447726f6361602c1f2a372f392c2c1f2a372f392c2c1f2a372f39')
         request.decode(_xor(data))
-        self.assertEqual(request.wifi_serial, 'ABC1D2345E')
+        self.assertEqual(request.wifi_serial, b'ABC1D2345E')
         self.assertEqual(request.config_id, 20)
         self.assertEqual(request.config_length, 20)
-        self.assertEqual(request.config_value, 'XXXXXXXXXXXXXXXXXXXX')
+        self.assertEqual(request.config_value, b'XXXXXXXXXXXXXXXXXXXX')
 
         # From "2020-12-20 09/33/54.802842_0x19_192.168.1.108.dat"
-        data = binascii.unhexlify("06302c4625464773472a7761747447726f7761747447726f7761747447726f62617345694541404f43")
+        data = binascii.unhexlify(b'06302c4625464773472a7761747447726f7761747447726f7761747447726f62617345694541404f43')
         request.decode(_xor(data))
-        self.assertEqual(request.wifi_serial, 'ABC1D2345E')
+        self.assertEqual(request.wifi_serial, b'ABC1D2345E')
         self.assertEqual(request.config_id, 21)
         self.assertEqual(request.config_length, 7)
-        self.assertEqual(request.config_value, '1.7.7.7')
+        self.assertEqual(request.config_value, b'1.7.7.7')
 
         # From "2020-12-20 09/33/56.648984_0x19_192.168.1.108.dat"
         data = binascii.unhexlify(
-            "06302c4625464773472a7761747447726f7761747447726f7761747447726f686167467743585a51435977434f45524e417e485a4e")
+            b'06302c4625464773472a7761747447726f7761747447726f7761747447726f686167467743585a51435977434f45524e417e485a4e')
         request.decode(_xor(data))
-        self.assertEqual(request.wifi_serial, 'ABC1D2345E')
+        self.assertEqual(request.wifi_serial, b'ABC1D2345E')
         self.assertEqual(request.config_id, 31)
         self.assertEqual(request.config_length, 19)
-        self.assertEqual(request.config_value, '2017-07-01 23:59:59')
+        self.assertEqual(request.config_value, b'2017-07-01 23:59:59')
 
 
 class TestGrowattQueryResponse(TestCase):
     def test_decode(self):
         # From "2020-12-12 09/58/27.027356_0x19.dat"
         # First packet from server_thread.growatt
-        data = binascii.unhexlify("06302c4625464773472a7761747447726f7761747447726f7761747447726f736161")
+        data = binascii.unhexlify(b'06302c4625464773472a7761747447726f7761747447726f7761747447726f736161')
         response = Growatt.GrowattQueryResponse()
         response.decode(_xor(data))
-        self.assertEqual(response.wifi_serial, 'ABC1D2345E')
+        self.assertEqual(response.wifi_serial, b'ABC1D2345E')
         self.assertEqual(response.first_config, 0x04)
         self.assertEqual(response.last_config, 0x15)
 
         # From "2020-12-12 09/58/38.293196_0x19.dat"
         # After client responses received to first packet from server_thread.growatt
-        data = binascii.unhexlify("06302c4625464773472a7761747447726f7761747447726f7761747447726f68616b")
+        data = binascii.unhexlify(b'06302c4625464773472a7761747447726f7761747447726f7761747447726f68616b')
         response = Growatt.GrowattQueryResponse()
         response.decode(_xor(data))
-        self.assertEqual(response.wifi_serial, 'ABC1D2345E')
+        self.assertEqual(response.wifi_serial,b'ABC1D2345E')
         self.assertEqual(response.first_config, 0x1F)
         self.assertEqual(response.last_config, 0x1F)
 
     def test_encode(self):
         # Build "2020-12-12 09/58/27.027356_0x19.dat" from values
-        response = Growatt.GrowattQueryResponse(wifi_serial='ABC1D2345E', first_config=0x04, last_config=0x15)
+        response = Growatt.GrowattQueryResponse(wifi_serial=b'ABC1D2345E', first_config=0x04, last_config=0x15)
         data = response.encode()
         self.assertEqual(_xor(data),
-                         binascii.unhexlify("06302c4625464773472a7761747447726f7761747447726f7761747447726f736161"))
+                         binascii.unhexlify(b'06302c4625464773472a7761747447726f7761747447726f7761747447726f736161'))
 
         # Build "2020-12-12 09/58/38.293196_0x19.dat" from values
-        response = Growatt.GrowattQueryResponse(wifi_serial='ABC1D2345E', first_config=0x1F, last_config=0x1F)
+        response = Growatt.GrowattQueryResponse(wifi_serial=b'ABC1D2345E', first_config=0x1F, last_config=0x1F)
         data = response.encode()
         self.assertEqual(_xor(data),
-                         binascii.unhexlify("06302c4625464773472a7761747447726f7761747447726f7761747447726f68616b"))
+                         binascii.unhexlify(b'06302c4625464773472a7761747447726f7761747447726f7761747447726f68616b'))
 
 
 class TestGrowattConfigRequest(TestCase):
     def test_decode(self):
         data = binascii.unhexlify(
-            "06302c4625464773472a7761747447726f7761747447726f7761747447726f6861674677405f5a50465976404f47504e4474485f44")
+            b'06302c4625464773472a7761747447726f7761747447726f7761747447726f6861674677405f5a50465976404f47504e4474485f44')
         request = Growatt.GrowattConfigRequest()
         request.decode(_xor(data))
-        self.assertEqual(request.wifi_serial, 'ABC1D2345E')
+        self.assertEqual(request.wifi_serial, b'ABC1D2345E')
         self.assertEqual(request.config_id, 0x1F)
         self.assertEqual(request.config_length, 19)
-        self.assertEqual(request.config_value, '2020-12-12 01:03:03')
+        self.assertEqual(request.config_value, b'2020-12-12 01:03:03')
 
-        data = binascii.unhexlify("06302c4625464773472a7761747447726f7761747447726f7761747447726f6861")
+        data = binascii.unhexlify(b'06302c4625464773472a7761747447726f7761747447726f7761747447726f6861')
         request = Growatt.GrowattConfigRequest()
         request.decode(_xor(data))
-        self.assertEqual(request.wifi_serial, 'ABC1D2345E')
+        self.assertEqual(request.wifi_serial, b'ABC1D2345E')
         self.assertEqual(request.config_id, 0x1F)
         self.assertEqual(request.config_length, 0)
-        self.assertEqual(request.config_value, '')
+        self.assertEqual(request.config_value,b'')
 
     def test_execute(self):
         data = binascii.unhexlify(
-            "06302c4625464773472a7761747447726f7761747447726f7761747447726f6861674677405f5a50465975424f47514e4774485a4076f4")
+            b'06302c4625464773472a7761747447726f7761747447726f7761747447726f6861674677405f5a50465975424f47514e4774485a4076f4')
 
         # ----------------------------------------------------------------------- #
         # initialize the data store
@@ -312,53 +312,53 @@ def test_execute(self):
         store = ModbusSlaveContext(di=block, co=block, hr=block, ir=block)
 
         holding_register = ModbusSparseDataBlock([0] * 100)
-        store.register(0x18, 'h', holding_register)
+        store.register(0x18,b'h', holding_register)
 
         request = Growatt.GrowattConfigRequest()
         Growatt.GrowattConfigRequest.decode(request, _xor(data))
         Growatt.GrowattConfigRequest.execute(request, store)
 
-        self.assertEqual(request.config_value, "2020-12-20 00:33:57")
+        self.assertEqual(request.config_value, b'2020-12-20 00:33:57')
 
 
 class TestGrowattConfigResponse(TestCase):
     def test_encode(self):
         # From "2020-12-20 09/33/57.875549_0x18_47.91.67.66.dat"
-        response = Growatt.GrowattConfigResponse(wifi_serial='ABC1D2345E',
+        response = Growatt.GrowattConfigResponse(wifi_serial=b'ABC1D2345E',
                                                  config_id=31,
                                                  config_length=19,
-                                                 config_value='2020-12-20 00:33:57')
+                                                 config_value=b'2020-12-20 00:33:57')
         data = response.encode()
 
         self.assertEqual(binascii.hexlify(_xor(data)),
-                         "06302c4625464773472a7761747447726f7761747447726f7761747447726f6861674677405f5a50465975424f47514e4774485a40")
+                         b'06302c4625464773472a7761747447726f7761747447726f7761747447726f6861674677405f5a50465975424f47514e4774485a40')
 
 
 class TestGrowattPingResponse(TestCase):
     def test_encode(self):
-        response = Growatt.GrowattPingResponse(wifi_serial='ABC1D2345E')
+        response = Growatt.GrowattPingResponse(wifi_serial=b'ABC1D2345E')
         data = response.encode()
 
-        self.assertEqual(binascii.hexlify(_xor(data)), "06302c4625464773472a7761747447726f7761747447726f776174744772")
+        self.assertEqual(binascii.hexlify(_xor(data)), b'06302c4625464773472a7761747447726f7761747447726f776174744772')
 
 
 class TestGrowattAnnounceRequest(TestCase):
     def test_decode(self):
         data = binascii.unhexlify(
-            "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")
+            b'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')
         request = Growatt.GrowattAnnounceRequest()
         request.decode(_xor(data))
 
-        self.assertEqual(request.wifi_serial, 'XGD3A1968B')
-        self.assertEqual(request.device_serial, 'XTD7A19031')
+        self.assertEqual(request.wifi_serial, b'XGD3A1968B')
+        self.assertEqual(request.device_serial, b'XTD7A19031')
         self.assertEqual(request.active_rate, 100)
         self.assertEqual(request.reactive_rate, 0)
         self.assertEqual(request.power_factor, 10000)
         self.assertEqual(request.p_max, 50000)
         self.assertEqual(request.v_normal, 1000)
-        # self.assertEqual(request.fw_version, 'AK1.0')
-        # self.assertEqual(request.control_fw_version, 'ZAAA')
-        self.assertEqual(request.device_type, '   PV Inverter  ')
+        # self.assertEqual(request.fw_version,b'AK1.0')
+        # self.assertEqual(request.control_fw_version,b'ZAAA')
+        self.assertEqual(request.device_type, b'   PV Inverter  ')
         self.assertEqual(request.year, 2021)
         self.assertEqual(request.month, 1)
         self.assertEqual(request.day, 9)
@@ -368,7 +368,7 @@ def test_decode(self):
 
     def test_execute(self):
         data = binascii.unhexlify(
-            "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")
+            b'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')
 
         # ----------------------------------------------------------------------- #
         # initialize the data store
diff --git a/test/test_growatt_framer.py b/test/test_growatt_framer.py
index 9904bb8..e634c69 100644
--- a/test/test_growatt_framer.py
+++ b/test/test_growatt_framer.py
@@ -63,9 +63,9 @@ def test_build_packet(self):
         framer = GrowattV6Framer(decoder)
 
         # Ping frame
-        message = GrowattPingResponse(wifi_serial='XGD3A1968B')
+        message = GrowattPingResponse(wifi_serial=b'XGD3A1968B')
         message.transaction_id = 2
         message.unit_id = 1
         message.protocol_id = 6
         self.assertEqual(binascii.hexlify(framer.buildPacket(message)),
-                         "00020006002001161f352b4420454d714a2d7761747447726f7761747447726f77617474477267ca")
\ No newline at end of file
+                         b'00020006002001161f352b4420454d714a2d7761747447726f7761747447726f77617474477267ca')
\ No newline at end of file