fix bug

Author: anla-xu

pymycobot/common.py

@@ -395,7 +395,6 @@ def _process_received(self, data, genre, arm=6):
         unique_data = [ProtocolCode.GET_BASIC_INPUT, ProtocolCode.GET_DIGITAL_INPUT]
         if cmd_id == ProtocolCode.GET_DIGITAL_INPUT and arm == 14:
             data_pos = header_i + 4
-            data_len -= 1
         elif cmd_id in unique_data:
             if arm == 12:
                 data_pos = header_i + 6