Research Of The Higher Layer Protocol CANopen And Its Implementation On The Modularized CAN Bus Controller

As a kind of general, reliable and economical platform, CAN bus has been used for a long time, which appears in automobile, mechanical engineering and many other application fields. CAN bus chips, however, only provide with the function of CAN physical layer and CAN data link layer of OSI communication model. Common users have to deal with the data link layer with the result that Can chips cannot meet the requirement of configuration and product interlinkage in industrial control networks. The corresponding application layer protocol has to be made in order to constitute the complete industrial field bus systems based on CAN chips. With this purpose, CiA (CAN in Automation) established the higher layer protocol CANopen, which has been put forward to Europe Standard Committee as a kind of new industrial field bus standard. This thesis analyzed the CANopen application layer in detail. It explained the core of CANopen---object dictionary, all kind of communication objects, the allocation of COB-ID and some device profiles. In addition, a kind of modularized CAN bus controller was designed. This controller took the form of two-level structure, i.e. the system bus and I/O bus was designed separately and the whole controller had two parts: CAN node control module and I/O module. The two parts communicated with each other through RS-485. The users can configure the I/O modules freely to constitute a complete CAN node. With this controller, the CAN bus can contain more I/O ports with less nodes, so the real time performance of the bus is guaranteed. At the end of the thesis, the CANopen slave protocol was realized in this modularized controller. The function of CANopen network management and communication was implemented. And this thesis made some attempt to modify the CANopen application protocol to improve the real time performance of CAN bus.