From 1d3a44c9f0043c5c1cf45c408976ae295385a8bf Mon Sep 17 00:00:00 2001
From: Stefan Allius <stefan.allius@t-online.de>
Date: Fri, 12 Apr 2024 18:57:48 +0200
Subject: [PATCH] first self-sufficient island support

- add Sequence class to handle the sequence of packets
- send response for received packets directly
- don't forward responses anymore
- addapt tests to new behavior
---
 app/src/gen3plus/solarman_v5.py | 125 +++++++++++++++++++++-----------
 app/tests/test_solarman.py      | 109 +++++++++++++++++-----------
 2 files changed, 151 insertions(+), 83 deletions(-)

diff --git a/app/src/gen3plus/solarman_v5.py b/app/src/gen3plus/solarman_v5.py
index fc189b3..86b64f1 100644
--- a/app/src/gen3plus/solarman_v5.py
+++ b/app/src/gen3plus/solarman_v5.py
@@ -1,7 +1,7 @@
 import struct
 # import json
 import logging
-# import time
+import time
 from datetime import datetime
 
 if __name__ == "app.src.gen3plus.solarman_v5":
@@ -19,6 +19,32 @@ else:  # pragma: no cover
 logger = logging.getLogger('msg')
 
 
+class Sequence():
+    def __init__(self, server_side: bool):
+        self.rcv_idx = 0
+        self.snd_idx = 0
+        self.server_side = server_side
+
+    def set_recv(self, val: int):
+        if self.server_side:
+            self.rcv_idx = val >> 8
+            self.snd_idx = val & 0xff
+        else:
+            self.rcv_idx = val & 0xff
+            self.snd_idx = val >> 8
+
+    def get_send(self):
+        self.snd_idx += 1
+        self.snd_idx &= 0xff
+        if self.server_side:
+            return (self.rcv_idx << 8) | self.snd_idx
+        else:
+            return (self.snd_idx << 8) | self.rcv_idx
+
+    def __str__(self):
+        return f'{self.rcv_idx:02x}:{self.snd_idx:02x}'
+
+
 class SolarmanV5(Message):
 
     def __init__(self, server_side: bool):
@@ -26,7 +52,7 @@ class SolarmanV5(Message):
 
         self.header_len = 11  # overwrite construcor in class Message
         self.control = 0
-        self.serial = 0
+        self.seq = Sequence(server_side)
         self.snr = 0
         self.db = InfosG3P()
         self.switch = {
@@ -160,6 +186,13 @@ class SolarmanV5(Message):
             type += 'S'
         return switch.get(type, '???')
 
+    def _timestamp(self):   # pragma: no cover
+        # utc as epoche
+        return int(time.time())
+
+    def _heartbeat(self) -> int:
+        return 60
+
     def __parse_header(self, buf: bytes, buf_len: int) -> None:
 
         if (buf_len < self.header_len):  # enough bytes for complete header?
@@ -168,10 +201,10 @@ class SolarmanV5(Message):
         result = struct.unpack_from('<BHHHL', buf, 0)
 
         # store parsed header values in the class
-        start = result[0]    # len of complete message
+        start = result[0]            # start byte
         self.data_len = result[1]    # len of variable id string
         self.control = result[2]
-        self.serial = result[3]
+        self.seq.set_recv(result[3])
         self.snr = result[4]
 
         if start != 0xA5:
@@ -194,6 +227,7 @@ class SolarmanV5(Message):
                     self._recv_buffer = bytearray()
 
             return False
+
         check = sum(buf[1:buf_len-2]) & 0xff
         if check != crc:
             self.inc_counter('Invalid_Msg_Format')
@@ -204,6 +238,36 @@ class SolarmanV5(Message):
 
         return True
 
+    def __build_header(self, ctrl) -> None:
+        '''build header for new transmit message'''
+        self.send_msg_ofs = len(self._send_buffer)
+
+        self._send_buffer += struct.pack(
+            '<BHHHL', 0xA5, 0, ctrl, self.seq.get_send(), self.snr)
+        fnc = self.switch.get(ctrl, self.msg_unknown)
+        logger.info(self.__flow_str(self.server_side, 'tx') +
+                    f' Ctl: {int(ctrl):#04x} Msg: {fnc.__name__!r}')
+
+    def __finish_send_msg(self) -> None:
+        '''finish the transmit message, set lenght and checksum'''
+        _len = len(self._send_buffer) - self.send_msg_ofs
+        struct.pack_into('<H', self._send_buffer, self.send_msg_ofs+1, _len-11)
+        check = sum(self._send_buffer[self.send_msg_ofs+1:self.send_msg_ofs +
+                                      _len]) & 0xff
+        self._send_buffer += struct.pack('<BB', check, 0x15)    # crc & stop
+
+    def _update_header(self, _forward_buffer):
+        '''update header for message before forwarding, 
+        set sequence and checksum'''
+        _len = len(_forward_buffer)
+        struct.pack_into('<H', _forward_buffer, 1,
+                         _len-13)
+        struct.pack_into('<H', _forward_buffer, 5,
+                         self.seq.get_send())
+
+        check = sum(_forward_buffer[1:_len-2]) & 0xff
+        struct.pack_into('<B', _forward_buffer, _len-2, check)
+
     def __dispatch_msg(self) -> None:
         fnc = self.switch.get(self.control, self.msg_unknown)
         if self.unique_id:
@@ -220,41 +284,7 @@ class SolarmanV5(Message):
         self._recv_buffer = self._recv_buffer[(self.header_len +
                                                self.data_len+2):]
         self.header_valid = False
-    '''
-    def modbus(self, data):
-        POLY = 0xA001
 
-        crc = 0xFFFF
-        for byte in data:
-            crc ^= byte
-            for _ in range(8):
-                crc = ((crc >> 1) ^ POLY
-                if (crc & 0x0001)
-                else crc >> 1)
-        return crc
-
-    def validate_modbus_crc(self, frame):
-        # Calculate crc with all but the last 2 bytes of
-        # the frame (they contain the crc)
-        calc_crc = 0xFFFF
-        for pos in frame[:-2]:
-            calc_crc ^= pos
-            for i in range(8):
-                if (calc_crc & 1) != 0:
-                    calc_crc >>= 1
-                    calc_crc ^= 0xA001  # bitwise 'or' with modbus magic
-                                        # number (0xa001 == bitwise
-                                        # reverse of 0x8005)
-                else:
-                    calc_crc >>= 1
-
-        # Compare calculated crc with the one supplied in the frame....
-        frame_crc, = struct.unpack('<H', frame[-2:])
-        if calc_crc == frame_crc:
-            return 1
-        else:
-            return 0
-    '''
     '''
     Message handler methods
     '''
@@ -280,6 +310,11 @@ class SolarmanV5(Message):
 
         self.__process_data(ftype)
         self.forward(self._recv_buffer, self.header_len+self.data_len+2)
+        self.__build_header(0x1110)
+        self._send_buffer += struct.pack('<BBLL', ftype, 1,
+                                         self._timestamp(),
+                                         self._heartbeat())
+        self.__finish_send_msg()
 
     def msg_dev_rsp(self):
         self.msg_response()
@@ -299,9 +334,13 @@ class SolarmanV5(Message):
         dt = datetime.fromtimestamp(total)
         logger.info(f'ts: {dt.strftime("%Y-%m-%d %H:%M:%S")}')
 
-        ftype &= 0x7f  # mask bit 7  (0x80)
-        self.__process_data(ftype)
+        self.__process_data(ftype & 0x7f)  # mask bit 7  (0x80)
         self.forward(self._recv_buffer, self.header_len+self.data_len+2)
+        self.__build_header(0x1210)
+        self._send_buffer += struct.pack('<BBLL', ftype, 1,
+                                         self._timestamp(),
+                                         self._heartbeat())
+        self.__finish_send_msg()
 
     def __process_data(self, ftype):
         inv_update = False
@@ -343,6 +382,11 @@ class SolarmanV5(Message):
 
     def msg_hbeat_ind(self):
         self.forward(self._recv_buffer, self.header_len+self.data_len+2)
+        self.__build_header(0x1710)
+        self._send_buffer += struct.pack('<BBLL', 0, 1,
+                                         self._timestamp(),
+                                         self._heartbeat())
+        self.__finish_send_msg()
 
     def msg_hbeat_rsp(self):
         self.msg_response()
@@ -359,7 +403,6 @@ class SolarmanV5(Message):
 
         dt = datetime.fromtimestamp(ts)
         logger.info(f'ts: {dt.strftime("%Y-%m-%d %H:%M:%S")}')
-        self.forward(self._recv_buffer, self.header_len+self.data_len+2)
 
     def at_command_ind(self):
         self.inc_counter('AT_Command')
diff --git a/app/tests/test_solarman.py b/app/tests/test_solarman.py
index 6743540..73b7123 100644
--- a/app/tests/test_solarman.py
+++ b/app/tests/test_solarman.py
@@ -1,4 +1,7 @@
-import pytest, json
+import pytest
+import struct
+import time
+from datetime import datetime
 from app.src.gen3plus.solarman_v5 import SolarmanV5
 from app.src.config import Config
 from app.src.infos import Infos, Register
@@ -6,6 +9,9 @@ from app.src.infos import Infos, Register
 # initialize the proxy statistics
 Infos.static_init()
 
+timestamp = int(time.time())  # 1712861197
+heartbeat = 60         
+
 class MemoryStream(SolarmanV5):
     def __init__(self, msg, chunks = (0,), server_side: bool = True):
         super().__init__(server_side)
@@ -19,6 +25,12 @@ class MemoryStream(SolarmanV5):
         self.db.stat['proxy']['Invalid_Msg_Format'] = 0
         self.db.stat['proxy']['AT_Command'] = 0
 
+    def _timestamp(self):
+        return timestamp
+    
+    def _heartbeat(self) -> int:
+        return heartbeat
+    
 
     def append_msg(self, msg):
         self.__msg += msg
@@ -42,9 +54,6 @@ class MemoryStream(SolarmanV5):
             pass     
         return copied_bytes
     
-    def _timestamp(self):
-        return 1700260990000
-    
     def _SolarmanV5__flush_recv_msg(self) -> None:
         super()._SolarmanV5__flush_recv_msg()
         self.msg_count += 1
@@ -60,6 +69,16 @@ def get_inv_no() -> bytes:
 def get_invalid_sn():
     return b'R170000000000002'
 
+def total():
+    ts = timestamp
+    # convert int to little-endian bytes
+    return struct.pack('<L',ts)
+
+def hb():
+    hb = heartbeat
+    # convert int to little-endian bytes
+    return struct.pack('<L',hb)
+
 def correct_checksum(buf):
     checksum = sum(buf[1:]) & 0xff
     return checksum.to_bytes(length=1)
@@ -90,8 +109,9 @@ def DeviceIndMsg(): # 0x4110
 
 @pytest.fixture
 def DeviceRspMsg():  # 0x1110
-    msg  = b'\xa5\x0a\x00\x10\x11\x10\x84' +get_sn()  +b'\x01\x01\x69\x6f\x09'
-    msg += b'\x66\x78\x00\x00\x00'               
+    msg  = b'\xa5\x0a\x00\x10\x11\x01\x01' +get_sn()  +b'\x02\x01'
+    msg += total()  
+    msg += hb()
     msg += correct_checksum(msg)
     msg += b'\x15'
     return msg
@@ -158,7 +178,7 @@ def InvalidChecksum(): # 0x4110
 
 @pytest.fixture
 def InverterIndMsg():  # 0x4210
-    msg  = b'\xa5\x99\x01\x10\x42\xe6\x9e' +get_sn()  +b'\x01\xb0\x02\xbc\xc8'
+    msg  = b'\xa5\x99\x01\x10\x42\x01\x02' +get_sn()  +b'\x01\xb0\x02\xbc\xc8'
     msg += b'\x24\x32\x6c\x1f\x00\x00\xa0\x47\xe4\x33\x01\x00\x03\x08\x00\x00'
     msg += b'\x59\x31\x37\x45\x37\x41\x30\x46\x30\x31\x30\x42\x30\x31\x33\x45'
     msg += b'\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00'
@@ -290,8 +310,9 @@ def InverterIndMsg2000():  # 0x4210 rated Power 2000W
 
 @pytest.fixture
 def InverterRspMsg():  # 0x1210
-    msg  = b'\xa5\x0a\x00\x10\x12\x10\x84' +get_sn()  +b'\x01\x01\x69\x6f\x09'
-    msg += b'\x66\x78\x00\x00\x00'               
+    msg  = b'\xa5\x0a\x00\x10\x12\x02\02' +get_sn()  +b'\x01\x01'
+    msg += total()  
+    msg += hb()
     msg += correct_checksum(msg)
     msg += b'\x15'
     return msg
@@ -314,8 +335,9 @@ def HeartbeatIndMsg():  # 0x4710
 
 @pytest.fixture
 def HeartbeatRspMsg():  # 0x1710
-    msg  = b'\xa5\x0a\x00\x10\x17\x10\x84' +get_sn()  +b'\x00\x01\x22\x71\x09'
-    msg += b'\x66\x78\x00\x00\x00'               
+    msg  = b'\xa5\x0a\x00\x10\x17\x11\x84' +get_sn()  +b'\x00\x01'
+    msg += total()  
+    msg += hb()
     msg += correct_checksum(msg)
     msg += b'\x15'
     return msg
@@ -349,7 +371,7 @@ def test_read_message(DeviceIndMsg):
     assert m.snr == 2070233889
     assert m.unique_id == None
     assert m.control == 0x4110
-    assert m.serial == 0x0100
+    assert str(m.seq) == '01:00'
     assert m.data_len == 0xd4
     assert m._recv_buffer==b''
     assert m._send_buffer==b''
@@ -370,7 +392,7 @@ def test_invalid_start_byte(InvalidStartByte, DeviceIndMsg):
     assert m.snr == 2070233889
     assert m.unique_id == 0
     assert m.control == 0x4110
-    assert m.serial == 0x0100
+    assert str(m.seq) == '01:00'
     assert m.data_len == 0xd4
     assert m._recv_buffer==b''
     assert m._send_buffer==b''
@@ -390,7 +412,7 @@ def test_invalid_stop_byte(InvalidStopByte):
     assert m.snr == 2070233889
     assert m.unique_id == 0
     assert m.control == 0x4110
-    assert m.serial == 0x0100
+    assert str(m.seq) == '01:00'
     assert m.data_len == 0xd4
     assert m._recv_buffer==b''
     assert m._send_buffer==b''
@@ -410,7 +432,7 @@ def test_invalid_stop_byte2(InvalidStopByte, DeviceIndMsg):
     assert m.snr == 2070233889
     assert m.unique_id == 0
     assert m.control == 0x4110
-    assert m.serial == 0x0100
+    assert str(m.seq) == '01:00'
     assert m.data_len == 0xd4
     assert m._recv_buffer==DeviceIndMsg
     assert m._send_buffer==b''
@@ -424,7 +446,7 @@ def test_invalid_stop_byte2(InvalidStopByte, DeviceIndMsg):
     assert m.snr == 2070233889
     assert m.unique_id == None
     assert m.control == 0x4110
-    assert m.serial == 0x0100
+    assert str(m.seq) == '01:00'
     assert m.data_len == 0xd4
     assert m._recv_buffer==b''
     assert m._send_buffer==b''
@@ -446,7 +468,7 @@ def test_invalid_stop_start_byte(InvalidStopByte, InvalidStartByte):
     assert m.snr == 2070233889
     assert m.unique_id == 0
     assert m.control == 0x4110
-    assert m.serial == 0x0100
+    assert str(m.seq) == '01:00'
     assert m.data_len == 0xd4
     assert m._recv_buffer==b''
     assert m._send_buffer==b''
@@ -466,7 +488,7 @@ def test_invalid_checksum(InvalidChecksum, DeviceIndMsg):
     assert m.snr == 2070233889
     assert m.unique_id == 0
     assert m.control == 0x4110
-    assert m.serial == 0x0100
+    assert str(m.seq) == '01:00'
     assert m.data_len == 0xd4
     assert m._recv_buffer==DeviceIndMsg
     assert m._send_buffer==b''
@@ -480,7 +502,7 @@ def test_invalid_checksum(InvalidChecksum, DeviceIndMsg):
     assert m.snr == 2070233889
     assert m.unique_id == None
     assert m.control == 0x4110
-    assert m.serial == 0x0100
+    assert str(m.seq) == '01:00'
     assert m.data_len == 0xd4
     assert m._recv_buffer==b''
     assert m._send_buffer==b''
@@ -488,7 +510,7 @@ def test_invalid_checksum(InvalidChecksum, DeviceIndMsg):
     assert m.db.stat['proxy']['Invalid_Msg_Format'] == 1
     m.close()
 
-def test_read_message_twice(ConfigNoTsunInv1, DeviceIndMsg):
+def test_read_message_twice(ConfigNoTsunInv1, DeviceIndMsg, DeviceRspMsg):
     ConfigNoTsunInv1
     m = MemoryStream(DeviceIndMsg, (0,))
     m.append_msg(DeviceIndMsg)
@@ -499,10 +521,13 @@ def test_read_message_twice(ConfigNoTsunInv1, DeviceIndMsg):
     assert m.snr == 2070233889
     assert m.unique_id == '2070233889'
     assert m.control == 0x4110
-    assert m.serial == 0x0100
+    assert str(m.seq) == '01:01'
     assert m.data_len == 0xd4
+    assert m._send_buffer==DeviceRspMsg
     assert m._forward_buffer==b''
     assert m.db.stat['proxy']['Invalid_Msg_Format'] == 0
+    
+    m._send_buffer = bytearray(0) # clear send buffer for next test    
     m.read()         # read complete msg, and dispatch msg
     assert not m.header_valid  # must be invalid, since msg was handled and buffer flushed
     assert m.msg_count == 2
@@ -510,8 +535,9 @@ def test_read_message_twice(ConfigNoTsunInv1, DeviceIndMsg):
     assert m.snr == 2070233889
     assert m.unique_id == '2070233889'
     assert m.control == 0x4110
-    assert m.serial == 0x0100
+    assert str(m.seq) == '01:01'
     assert m.data_len == 0xd4
+    assert m._send_buffer==DeviceRspMsg
     assert m._forward_buffer==b''
     assert m.db.stat['proxy']['Invalid_Msg_Format'] == 0
     m.close()
@@ -528,7 +554,7 @@ def test_read_message_in_chunks(DeviceIndMsg):
     assert m.snr == 2070233889
     assert m.unique_id == 0 # should be None ?
     assert m.control == 0x4110
-    assert m.serial == 0x0100
+    assert str(m.seq) == '01:00'
     assert m.data_len == 0xd4
     assert m.db.stat['proxy']['Invalid_Msg_Format'] == 0
     m.read()    # read rest of message
@@ -552,7 +578,7 @@ def test_read_message_in_chunks2(ConfigTsunInv1, DeviceIndMsg):
     assert m.snr == 2070233889
     assert m.unique_id == '2070233889'
     assert m.control == 0x4110
-    assert m.serial == 0x0100
+    assert str(m.seq) == '01:01'
     assert m.data_len == 0xd4
     assert m.msg_count == 1
     assert m.db.stat['proxy']['Invalid_Msg_Format'] == 0
@@ -563,7 +589,7 @@ def test_read_message_in_chunks2(ConfigTsunInv1, DeviceIndMsg):
     assert m.db.stat['proxy']['Invalid_Msg_Format'] == 0
     m.close()
 
-def test_read_two_messages(ConfigTsunAllowAll, DeviceIndMsg, InverterIndMsg):
+def test_read_two_messages(ConfigTsunAllowAll, DeviceIndMsg, DeviceRspMsg, InverterIndMsg, InverterRspMsg):
     ConfigTsunAllowAll
     m = MemoryStream(DeviceIndMsg, (0,))
     m.append_msg(InverterIndMsg)
@@ -574,14 +600,13 @@ def test_read_two_messages(ConfigTsunAllowAll, DeviceIndMsg, InverterIndMsg):
     assert m.snr == 2070233889
     assert m.unique_id == '2070233889'
     assert m.control == 0x4110
-    assert m.serial == 0x0100
+    assert str(m.seq) == '01:01'
     assert m.data_len == 0xd4
     assert m.msg_count == 1
     assert m.db.stat['proxy']['Invalid_Msg_Format'] == 0
     assert m._forward_buffer==DeviceIndMsg
-    assert m._send_buffer==b''
-    # assert m._send_buffer==MsgContactResp
-
+    assert m._send_buffer==DeviceRspMsg
+ 
     m._send_buffer = bytearray(0) # clear send buffer for next test  
     m._init_new_client_conn()
     assert m._send_buffer==b''
@@ -597,11 +622,11 @@ def test_read_two_messages(ConfigTsunAllowAll, DeviceIndMsg, InverterIndMsg):
     assert m.snr == 2070233889
     assert m.unique_id == '2070233889'
     assert m.control == 0x4210
-    assert m.serial == 0x9ee6
+    assert str(m.seq) == '02:02'
     assert m.data_len == 0x199
     assert m.db.stat['proxy']['Invalid_Msg_Format'] == 0
     assert m._forward_buffer==InverterIndMsg
-    assert m._send_buffer==b''
+    assert m._send_buffer==InverterRspMsg
 
     m._send_buffer = bytearray(0) # clear send buffer for next test    
     m._init_new_client_conn()
@@ -618,7 +643,7 @@ def test_unkown_message(ConfigTsunInv1, UnknownMsg):
     assert m.snr == 2070233889
     assert m.unique_id == '2070233889'
     assert m.control == 0x5110
-    assert m.serial == 0x8410
+    assert str(m.seq) == '84:10'
     assert m.data_len == 0x0a
     assert m._recv_buffer==b''
     assert m._send_buffer==b''
@@ -636,11 +661,11 @@ def test_device_rsp(ConfigTsunInv1, DeviceRspMsg):
     assert m.snr == 2070233889
     assert m.unique_id == '2070233889'
     assert m.control == 0x1110
-    assert m.serial == 0x8410
+    assert str(m.seq) == '01:01'
     assert m.data_len == 0x0a
     assert m._recv_buffer==b''
     assert m._send_buffer==b''
-    assert m._forward_buffer==DeviceRspMsg
+    assert m._forward_buffer==b''  # DeviceRspMsg
     assert m.db.stat['proxy']['Invalid_Msg_Format'] == 0
     m.close()
 
@@ -654,15 +679,15 @@ def test_inverter_rsp(ConfigTsunInv1, InverterRspMsg):
     assert m.snr == 2070233889
     assert m.unique_id == '2070233889'
     assert m.control == 0x1210
-    assert m.serial == 0x8410
+    assert str(m.seq) == '02:02'
     assert m.data_len == 0x0a
     assert m._recv_buffer==b''
     assert m._send_buffer==b''
-    assert m._forward_buffer==InverterRspMsg
+    assert m._forward_buffer==b''  # InverterRspMsg
     assert m.db.stat['proxy']['Invalid_Msg_Format'] == 0
     m.close()
 
-def test_heartbeat_ind(ConfigTsunInv1, HeartbeatIndMsg):
+def test_heartbeat_ind(ConfigTsunInv1, HeartbeatIndMsg, HeartbeatRspMsg):
     ConfigTsunInv1
     m = MemoryStream(HeartbeatIndMsg, (0,))
     m.read()         # read complete msg, and dispatch msg
@@ -672,10 +697,10 @@ def test_heartbeat_ind(ConfigTsunInv1, HeartbeatIndMsg):
     assert m.snr == 2070233889
     # assert m.unique_id == '2070233889'
     assert m.control == 0x4710
-    assert m.serial == 0x8410
+    assert str(m.seq) == '84:11'  # value after sending response
     assert m.data_len == 0x01
     assert m._recv_buffer==b''
-    assert m._send_buffer==b''
+    assert m._send_buffer==HeartbeatRspMsg
     assert m._forward_buffer==HeartbeatIndMsg
     assert m.db.stat['proxy']['Invalid_Msg_Format'] == 0
     m.close()
@@ -690,11 +715,11 @@ def test_heartbeat_rsp(ConfigTsunInv1, HeartbeatRspMsg):
     assert m.snr == 2070233889
     assert m.unique_id == '2070233889'
     assert m.control == 0x1710
-    assert m.serial == 0x8410
+    assert str(m.seq) == '11:84'  # value after sending response
     assert m.data_len == 0x0a
     assert m._recv_buffer==b''
     assert m._send_buffer==b''
-    assert m._forward_buffer==HeartbeatRspMsg
+    assert m._forward_buffer==b''  # HeartbeatRspMsg
     assert m.db.stat['proxy']['Invalid_Msg_Format'] == 0
     m.close()
 
@@ -708,7 +733,7 @@ def test_at_command_ind(ConfigTsunInv1, AtCommandIndMsg):
     assert m.snr == 2070233889
     # assert m.unique_id == '2070233889'
     assert m.control == 0x4510
-    assert m.serial == 0x8410
+    assert str(m.seq) == '84:10'
     assert m.data_len == 0x01
     assert m._recv_buffer==b''
     assert m._send_buffer==b''