Research On The CAN Bus Technology Based On CANopen Protocol And μC/OS-Ⅱ

As an application layer protocol of CAN bus, CANopen protocol utilizes the features of real time and reliability of CAN bus and achieves standardization and interoperability. It has been widely accepted and applied in various distributed automatic control systems in industry. Therefore research and development of field-bus communication equipment based on CANopen protocol can arouse domestic industry's concern on the CANopen technology, and it will have significant meaning in terms of accelerating the development of self-intellectual property products.This paper first outlines the development process of CAN bus and its high level protocols. According to the hierarchical structure, the important content of CAN protocol and CANopen kernel are analyzed in detail. The function and implementation of CANopen protocol's four category communication objects are studied in depth.The hardware design based on MC9S12XF512 chip comprises MSCAN interface circuit, RS232 serial communication circuit, BDM download interface circuit and LCD liquid crystal display circuit. MSCAN controller which is integrated in the MCU connects the dual-channel optocoupler HCPL-2630 and high-speed CAN transceiver TJA1040.They work together to constitute the CAN Bus communications interface circuits. The whole frame of software design based on MC9S12XF512 andμC/OS-II includes three layers according to the data flow. They are hardware driver layer,μC/OS-II system layer,the implementation and application of CANopen protocol. The CANopen communication function is embedded into theμC/OS-II. So the task scheduling and management capabilities of embedded system could be used in dealing with complex multi-task and make the whole system stable and reliable in operation.Through constructing a master-slave CANopen network, the communication mechanism and related parameters are tested and the experiment shows the CANopen node has a good completeness of the agreed standards, CiA DS301. The four categories of communication object's function are verified through analyzing the CAN frame data. The experiment shows that the CANopen master-slave nodes can connect with each other and exchange CAN message successfully. The communication process is proved to be effective and reliable.