CAN bus, CANopen only adds application layer protocol on the basis of CAN bus. Just as telephone lines (relative to CAN bus) can communicate by telephone, they all transmit sound through electrical signals, but the languages (application layer protocols) are different, some speak Chinese and some speak English. CANopen bus or even application layer protocol on CAN bus (such as Chinese) (relative to telephone line); CAN bus has other application layer protocols, such as DeviceNET, SEA J 1939 and other well-known application layer protocols.