Design Of CAN Repeater And CAN-LIN Gateway Based On CAN Bus

At present, LINbus and CANbus are widely used in the car bodynetwork. the developing technology of car body network such as FlexRay,MOST that can be used on the media and navigation,Bluetooth that iscompatible with computer network and wireless LAN which belongs to thewireless network technology.This paper introduces the CAN/LIN bus and the application.Main Characteristics of CAN: Serial,realtime multi-master bussystem Transmission rates up to 1 Mbit/s Content based addressing Bus allocation:non destructive arbitration Two compatible data formats Self monitoring,error recognition,error correction Implementation by many manufacturersLIN (Local Interconnect Network) was designed for low cost networksin automotive domain. LIN aims on the introduction of hierarchicalnetworks in automotive-networks. Goal is to increase quality and to reducecosts. LIN reduces the set of existing low-end multiplex solutions. Thisleads to reduction in cost, development time, production, service inautomotive electronics.Main Characteristics of LIN: Single Master-Multiple Slaves concept Low cost silicon device(standard UART/SCI Basis) No crystals or resonators necessary in slaves Deterministic communication Low cost solution due to single wire Maximum length of bus line=40mMaximum number of nodes=16 Transmission rates up to 19.2kbit/sThis paper introduced the application of CAN bus and LIN bus invehicle,present the low cost CAN/LIN mixed net for vehicle,and designa gateway for the conversion between CAN data and LIN data,which madethe full share of data in vehicle possible.89C51 is 8-bit COMS MCU which is low voltage and low powerconsumption,high-performance.SJA1000 mostly accomplish thecommunication protocol, PCA82C250 is an transceiver and the interfacebetween CAN controller and the physics bus. TJA 1020 transceiver whichbaudrateat20Kmaximum-speed.The master node constantly supervise the data coming from theCANbus, if there are data, the master node read them, configures the node,form LIN message pattern and then send them which include head-frameand handshake message,command data and receiving feedback in formation.The slave-node receive the handshake message, carryout thedata commandand result feedback.The CAN repeater is one of the main devices in the system,if the initialparameter can be configured well, then the CAN repeater not only can havethe function of message transmit, but also the function of filtration。Expanded the communication distance,increase the number of node,hangethe rate of the communication in different network and improve thereliability.It includes two CANbus communication channel ports,the one CANbuschannel and then other CANbus channel, which forward the two CANbuschannel data. Isolation interface, electrical isolation completely in the twoCANbus channel protect it from electromagnetic interference and protectthe system circuit from influence of internet,improve the reliability. Hardware buffer storage not to lose the frameThe compatibility of the two communication protocol Two network at different communication rate are connectedCan repeater include MCU89C51 and two CAN controllers. 89C51 isthe MCU which supervise the whole repeater.the two can controllerinterface circuitinclude can controller,can transceiver.The main function of Can repeater is data buffer and data forwardMechanism of data forward is that if the first CANbus transmits the data,MCU receives them and stores them in the databuffer of MCU 51 and thencalls subprogram to send datas which were receivered ago to the otherCANbus,vice versa.Hereby, the program should setup two transceiver buffers. Thetransmitting buffer of the first CANbus is the same receiving buffer of theother CANbus in physical address,and shared the area of MCU storage.And for the same reason, the receiving buffer of the first CANbus is thesame transmitting buffer of the other CANbus in physical address andshared the area of MCU storage.The software programs include: CAN1/2INI CAN1/2RECRECEIVE1/2 SEND1/2. The main function of the CAN1/2REC is tosupervise the FIFO of the two CANcontrollers. If the FIFO in one of them isnot empty,then call subprogram to forward data to the other CANbus.This designment testifies the feasibility of using CAN/LIN gateway,CAN repeater in car body network and data communication in different busnetwork can be made. We will put emphasis on the research ofcommunication between different bus network such as MOST, FlaxRay inthenextstep.