diff --git a/README.md b/README.md
index 697ea87..3552aec 100644
--- a/README.md
+++ b/README.md
@@ -179,10 +179,9 @@ A combination with a red question mark should work, but I have not checked it in
 
 <table align="center">
   <tr><th align="center">Micro Inverter Model</th><th align="center">Fw. 1.00.06</th><th align="center">Fw. 1.00.17</th><th align="center">Fw. 1.00.20</th><th align="center">Fw. 1.1.00.0B</th></tr>
-  <tr><td>GEN3 micro inverters (single MPPT):<br>MS300, MS350, MS400</td><td align="center">❓</td><td align="center">❓</td><td align="center">❓</td><td align="center">➖</td></tr>
-  <tr><td>GEN3 micro inverters (dual MPPT):<br>MS600, MS700, MS800</td><td align="center">✔️</td><td align="center">✔️</td><td align="center">✔️</td><td align="center">➖</td></tr>
-  <tr><td>GEN3 PLUS micro inverters:<br>MS1600, MS1800, MS2000</td><td align="center">➖</td><td align="center">➖</td><td align="center">➖</td><td align="center">✔️</td></tr>
-  <tr><td>Balcony micro inverters:<br>MS400-D, MS800-D, MS2000-D</td><td align="center">❓</td><td align="center">❓</td><td align="center">❓</td><td align="center">❓</td></tr>
+  <tr><td>GEN3 micro inverters (single MPPT):<br>MS300, MS350, MS400<br>MS400-D</td><td align="center">❓</td><td align="center">❓</td><td align="center">❓</td><td align="center">➖</td></tr>
+  <tr><td>GEN3 micro inverters (dual MPPT):<br>MS600, MS700, MS800<br>MS600-D, MS800-D</td><td align="center">✔️</td><td align="center">✔️</td><td align="center">✔️</td><td align="center">➖</td></tr>
+  <tr><td>GEN3 PLUS micro inverters:<br>MS1600, MS1800, MS2000<br>MS2000-D</td><td align="center">➖</td><td align="center">➖</td><td align="center">➖</td><td align="center">✔️</td></tr>
   <tr><td>TITAN micro inverters:<br>TSOL-MP3000, MP2250, MS3000</td><td align="center">❓</td><td align="center">❓</td><td align="center">❓</td><td align="center">❓</td></tr>
 </table>
 
diff --git a/app/src/gen3plus/solarman_v5.py b/app/src/gen3plus/solarman_v5.py
index ac2ce61..5c8e588 100644
--- a/app/src/gen3plus/solarman_v5.py
+++ b/app/src/gen3plus/solarman_v5.py
@@ -58,10 +58,10 @@ class SolarmanV5(Message):
         self.switch = {
 
             0x4210: self.msg_data_ind,   # real time data
-            0x1210: self.msg_data_rsp,   # at least every 5 minutes
+            0x1210: self.msg_response,   # at least every 5 minutes
 
             0x4710: self.msg_hbeat_ind,  # heatbeat
-            0x1710: self.msg_hbeat_rsp,  # every 2 minutes
+            0x1710: self.msg_response,   # every 2 minutes
 
             # every 3 hours comes a sync seuqence:
             # 00:00:00  0x4110   device data     ftype: 0x02
@@ -72,18 +72,18 @@ class SolarmanV5(Message):
             # 00:00:07  0x4310   wifi data       ftype: 0x01    sub-id 0x0018: 0c   # noqa: E501
             # 00:00:08  0x4810   options?        ftype: 0x01
 
-            0x4110: self.msg_dev_ind,    # device data, sync start
-            0x1110: self.msg_dev_rsp,    # every 3 hours
+            0x4110: self.msg_dev_ind,     # device data, sync start
+            0x1110: self.msg_response,    # every 3 hours
 
-            0x4310: self.msg_forward,    # regulary after 3-6 hours
-            0x1310: self.msg_forward,
-            0x4810: self.msg_forward,    # sync end
-            0x1810: self.msg_forward,
+            0x4310: self.msg_sync_start,  # regulary after 3-6 hours
+            0x1310: self.msg_response,
+            0x4810: self.msg_sync_end,    # sync end
+            0x1810: self.msg_response,
 
             #
-            # AT cmd
-            0x4510: self.at_command_ind,  # from server
-            0x1510: self.msg_forward,     # from inverter
+            # MODbus or AT cmd
+            0x4510: self.msg_command_req,  # from server
+            0x1510: self.msg_response,     # from inverter
         }
 
     '''
@@ -285,63 +285,23 @@ class SolarmanV5(Message):
                                                self.data_len+2):]
         self.header_valid = False
 
-    '''
-    Message handler methods
-    '''
-    def msg_unknown(self):
-        logger.warning(f"Unknow Msg: ID:{int(self.control):#04x}")
-        self.inc_counter('Unknown_Msg')
-        self.msg_forward()
-
-    def msg_forward(self):
-        self.forward(self._recv_buffer, self.header_len+self.data_len+2)
-
-    def msg_dev_ind(self):
-        data = self._recv_buffer[self.header_len:]
-        result = struct.unpack_from('<BLLL', data, 0)
-        ftype = result[0]  # always 2
-        total = result[1]
-        tim = result[2]
-        res = result[3]  # always zero
-        logger.info(f'frame type:{ftype:02x} total:{total}s'
-                    f' timer:{tim:08x}s  null:{res}')
-        dt = datetime.fromtimestamp(total)
-        logger.info(f'ts: {dt.strftime("%Y-%m-%d %H:%M:%S")}')
-
-        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,
+    def __send_ack_rsp(self, msgtype, ftype, ack=1):
+        self.__build_header(msgtype)
+        self._send_buffer += struct.pack('<BBLL', ftype, ack,
                                          self._timestamp(),
                                          self._heartbeat())
         self.__finish_send_msg()
 
-    def msg_dev_rsp(self):
-        self.msg_response()
-
-    def msg_data_ind(self):
-        data = self._recv_buffer
-        result = struct.unpack_from('<BLLLLL', data, self.header_len)
-        ftype = result[0]  # 1 or 0x81
-        total = result[1]
-        tim = result[2]
-        offset = result[3]
-        unkn = result[4]
-        cnt = result[5]
-        logger.info(f'ftype:{ftype:02x} total:{total}s'
-                    f' timer:{tim:08x}s  ofs:{offset}'
-                    f' ??: {unkn:08x} cnt:{cnt}')
-        dt = datetime.fromtimestamp(total)
-        logger.info(f'ts: {dt.strftime("%Y-%m-%d %H:%M:%S")}')
-
-        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())
+    def send_at_cmd(self, AT_cmd: str) -> None:
+        self.__build_header(0x4510)
+        self._send_buffer += struct.pack(f'<BHLLL{len(AT_cmd)}sc', 1, 2,
+                                         0, 0, 0, AT_cmd.encode('utf-8'),
+                                         b'\r')
         self.__finish_send_msg()
 
+    def __forward_msg(self):
+        self.forward(self._recv_buffer, self.header_len+self.data_len+2)
+
     def __process_data(self, ftype):
         inv_update = False
         ctrl_update = False
@@ -377,19 +337,81 @@ class SolarmanV5(Message):
                 Model = Version.split('_')[0]
                 self.db.set_db_def_value(Register.CHIP_MODEL, Model)
 
-    def msg_data_rsp(self):
-        self.msg_response()
+    '''
+    Message handler methods
+    '''
+    def msg_unknown(self):
+        logger.warning(f"Unknow Msg: ID:{int(self.control):#04x}")
+        self.inc_counter('Unknown_Msg')
+        self.__forward_msg()
+
+    def msg_dev_ind(self):
+        data = self._recv_buffer[self.header_len:]
+        result = struct.unpack_from('<BLLL', data, 0)
+        ftype = result[0]  # always 2
+        total = result[1]
+        tim = result[2]
+        res = result[3]  # always zero
+        logger.info(f'frame type:{ftype:02x} total:{total}s'
+                    f' timer:{tim:08x}s  null:{res}')
+        dt = datetime.fromtimestamp(total)
+        logger.info(f'ts: {dt.strftime("%Y-%m-%d %H:%M:%S")}')
+
+        self.__process_data(ftype)
+        self.__forward_msg()
+        self.__send_ack_rsp(0x1110, ftype)
+
+    def msg_data_ind(self):
+        data = self._recv_buffer
+        result = struct.unpack_from('<BLLLLL', data, self.header_len)
+        ftype = result[0]  # 1 or 0x81
+        total = result[1]
+        tim = result[2]
+        offset = result[3]
+        unkn = result[4]
+        cnt = result[5]
+        logger.info(f'ftype:{ftype:02x} total:{total}s'
+                    f' timer:{tim:08x}s  ofs:{offset}'
+                    f' ??: {unkn:08x} cnt:{cnt}')
+        dt = datetime.fromtimestamp(total)
+        logger.info(f'ts: {dt.strftime("%Y-%m-%d %H:%M:%S")}')
+
+        self.__process_data(ftype & 0x7f)  # mask bit 7  (0x80)
+        self.__forward_msg()
+        self.__send_ack_rsp(0x1210, ftype)
+
+    def msg_sync_start(self):
+        data = self._recv_buffer[self.header_len:]
+        result = struct.unpack_from('<B', data, 0)
+        ftype = result[0]
+
+        self.__forward_msg()
+        self.__send_ack_rsp(0x1310, ftype)
+
+    def msg_command_req(self):
+        data = self._recv_buffer[self.header_len:]
+        result = struct.unpack_from('<B', data, 0)
+        ftype = result[0]
+
+        self.inc_counter('AT_Command')
+        self.__forward_msg()
+        self.__send_ack_rsp(0x1510, ftype)
 
     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()
+        data = self._recv_buffer[self.header_len:]
+        result = struct.unpack_from('<B', data, 0)
+        ftype = result[0]
 
-    def msg_hbeat_rsp(self):
-        self.msg_response()
+        self.__forward_msg()
+        self.__send_ack_rsp(0x1710, ftype)
+
+    def msg_sync_end(self):
+        data = self._recv_buffer[self.header_len:]
+        result = struct.unpack_from('<B', data, 0)
+        ftype = result[0]
+
+        self.__forward_msg()
+        self.__send_ack_rsp(0x1810, ftype)
 
     def msg_response(self):
         data = self._recv_buffer[self.header_len:]
@@ -403,7 +425,3 @@ class SolarmanV5(Message):
 
         dt = datetime.fromtimestamp(ts)
         logger.info(f'ts: {dt.strftime("%Y-%m-%d %H:%M:%S")}')
-
-    def at_command_ind(self):
-        self.inc_counter('AT_Command')
-        self.msg_forward()
diff --git a/app/tests/test_solarman.py b/app/tests/test_solarman.py
index 73b7123..28af3ea 100644
--- a/app/tests/test_solarman.py
+++ b/app/tests/test_solarman.py
@@ -344,8 +344,18 @@ def HeartbeatRspMsg():  # 0x1710
 
 @pytest.fixture
 def AtCommandIndMsg():  # 0x4510
-    msg  = b'\xa5\x01\x00\x10\x45\x10\x84' +get_sn()
-    msg += b'\x00'               
+    msg  = b'\xa5\x27\x00\x10\x45\x02\x01' +get_sn() +b'\x01\x02\x00'
+    msg += b'\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00'           
+    msg += b'AT+TIME=214028,1,60,120\r'
+    msg += correct_checksum(msg)
+    msg += b'\x15'
+    return msg
+
+@pytest.fixture
+def AtCommandRspMsg():  # 0x1510
+    msg  = b'\xa5\x0a\x00\x10\x15\x03\x01' +get_sn()  +b'\x01\x01'
+    msg += total()  
+    msg += hb()
     msg += correct_checksum(msg)
     msg += b'\x15'
     return msg
@@ -723,7 +733,7 @@ def test_heartbeat_rsp(ConfigTsunInv1, HeartbeatRspMsg):
     assert m.db.stat['proxy']['Invalid_Msg_Format'] == 0
     m.close()
 
-def test_at_command_ind(ConfigTsunInv1, AtCommandIndMsg):
+def test_at_command_ind(ConfigTsunInv1, AtCommandIndMsg, AtCommandRspMsg):
     ConfigTsunInv1
     m = MemoryStream(AtCommandIndMsg, (0,))
     m.read()         # read complete msg, and dispatch msg
@@ -733,10 +743,10 @@ def test_at_command_ind(ConfigTsunInv1, AtCommandIndMsg):
     assert m.snr == 2070233889
     # assert m.unique_id == '2070233889'
     assert m.control == 0x4510
-    assert str(m.seq) == '84:10'
-    assert m.data_len == 0x01
+    assert str(m.seq) == '01:03'
+    assert m.data_len == 39
     assert m._recv_buffer==b''
-    assert m._send_buffer==b''
+    assert m._send_buffer==AtCommandRspMsg
     assert m._forward_buffer==AtCommandIndMsg
     assert m.db.stat['proxy']['Invalid_Msg_Format'] == 0
     assert m.db.stat['proxy']['AT_Command'] == 1
@@ -804,3 +814,18 @@ def test_build_logger_modell(ConfigTsunAllowAll, DeviceIndMsg):
     assert 'LSW5BLE_17_02B0_1.05' == m.db.get_db_value(Register.COLLECTOR_FW_VERSION, 0).rstrip('\00')
     assert 'LSW5BLE' == m.db.get_db_value(Register.CHIP_MODEL, 0)
     m.close()
+
+def test_AT_cmd(ConfigTsunAllowAll, DeviceIndMsg, DeviceRspMsg, AtCommandIndMsg):
+    ConfigTsunAllowAll
+    m = MemoryStream(DeviceIndMsg)
+    m.read()
+    assert m._recv_buffer==b''
+    assert m._send_buffer==DeviceRspMsg
+    assert m._forward_buffer==DeviceIndMsg
+    m._send_buffer = bytearray(0) # clear send buffer for next test    
+    m._forward_buffer = bytearray(0) # clear send buffer for next test    
+    m.send_at_cmd('AT+TIME=214028,1,60,120')
+    assert m._recv_buffer==b''
+    assert m._send_buffer==AtCommandIndMsg
+    assert m._forward_buffer==b''
+    m.close()