usb connection improved

laser_control/protocol.py

@@ -427,8 +427,8 @@ class Protocol:
             )
 
         words = _unpack_words(data)
-        expected_crc = _payload_checksum(list(words[1:14]))
-        if words[14] != expected_crc:
+        if not Protocol.has_valid_response_crc(data):
+            expected_crc = _payload_checksum(list(words[1:14]))
             raise CRCError(expected=expected_crc, received=words[14])
 
         return Measurements(
@@ -448,6 +448,15 @@ class Protocol:
             timestamp=datetime.now(),
         )
 
+    @staticmethod
+    def has_valid_response_crc(data: bytes) -> bool:
+        """Return True when a telemetry frame has the expected length and CRC."""
+        if len(data) != GET_DATA_TOTAL_LENGTH:
+            return False
+        words = _unpack_words(data)
+        expected_crc = _payload_checksum(list(words[1:14]))
+        return words[14] == expected_crc
+
     @staticmethod
     def decode_status(data: bytes) -> tuple[DeviceState, int]:
         """Decode the two-byte firmware status response into flags and detail."""