错误描述：
error: cannot convert ‘USBSerial*’ to ‘HardwareSerial*’ in assignment.

解决办法：
https://github.com/ROBOTIS-GIT/OpenCR/issues/120
https://github.com/ROBOTIS-GIT/OpenCR/blob/master/arduino/opencr_arduino/opencr/libraries/turtlebot3_ros_lib/ArduinoHardware.h