Research And Design Of Protocol Converter Base On RS232/485 And CAN Bus

Fieldbus is the technology which is used to realize bidirectional, serial, multi-node digital communication between field device and field device, or control room. Field bus is used in manufacture field. The difference of field bus in protocol standard brings complexity to practice and influence the opening and interoperability of bus. In this case, it need protocol converter to interconnect different buses. So this thesis designs the protocol converter to interconnect traditional RS485 network and CAN bus. It is used to data collecting system, through RS232 interface it connects to computer and configures dynamically parameter of two buses.Firstly, aiming at the limitation of the real-time capability of CAN Bus, based on analyzing communication principle of CAN Bus that includes format of message, structure of the frame and wrong type etc, the thesis brings the method that distributed dynamic priority forward to change real-time capability. Secondly, this thesis designs the hardware of RS232/RS485 protocol converter that include core module, CAN interface, RS485 interface, RS232 interface and power supply of system. In the power supply of system, the design adopts AT89S51 as CPU dealing data, SJA1000 as CPU of CAN bus and P82C250 as transceiver of CAN bus sending and receiving data. Finally, based on the hardware, the program of each function is designed, including the main program module, CAN communication module, RS485 communication module, RS232 communication module and Human-Computer Interaction program connecting to PC by RS232. In CAN communication module and RS485 communication module, it adopts interrupt mode to receive data, inquiry mode to send data. Human-Computer Interaction program can make protocol converter become main node of network to manage CAN bus and RS485 and configure parameter dynamically.The protocol converter in the thesis can be applied to some monitoring system for example temperature monitoring of cable. Also, it can connect RS485 network with CAN bus network, complete collecting data of two buses and it lays function for protocol converter applying to more industry field in the future.