| With the continuous improvement and development of Beidou satellite navigation system and vehicle Internet of Things,the application of integrated Beidou positioning receiver in vehicle field is becoming more and more mature.By receiving Beidou satellite navigation signal to determine vehicle position,speed and direction,it provides important technical support in the fields of vehicle navigation,vehicle management and intelligent driving.At the same time,the demand of vehicle network system for vehicle receiver is increasing,and the traditional integrated serial port has low flexibility and difficulty in expansion.MOST and CAN bus have the defects of high cost and high network complexity.Wireless communication and other transmission methods are susceptible to interference and have low stability.Traditional data transmission methods can no longer meet the demand.Therefore,it is urgent to build a flexible,efficient,stable and reliable data transmission method to solve the above problems.Based on the advantages of high reliability,low cost,easy expansion and high flexibility of the underlying bus LIN as a data transmission carrier,this paper builds and implements a high-performance LIN bus-based vehicle-mounted IoT data transmission system,which effectively improves the efficient and stable transmission of vehicle-mounted receiver data,and can provide reference for high-performance vehicle-mounted IoT data transmission.The main research work of this paper is as follows:(1)The LIN bus controller is designed and optimized.According to the output data format and characteristics of Beidou positioning receiver,the feasibility of transmitting the data based on LIN2.2 protocol is analyzed and verified.The LIN bus controller is designed and optimized according to the LIN2.2 protocol,which is suitable for the output data transmission of the Beidou positioning receiver.The controller module is designed based on Verilog language.Compared with the traditional LIN bus controller,the optimization is as follows:First,the hardware implements the filter to reduce the workload of software operation;the second is to optimize the state machine of the slave node,which can complete the frame header detection and reception at the same time in the process of receiving frame data,and can be used for transmission conditions such as vehicle restart.It overcomes the defect that the slave node of the traditional LIN bus controller cannot recognize the new frame header in the process of receiving frame data,and is suitable for data transmission of the vehicle receiver.(2)A vehicle Beidou positioning receiver data transmission network system based on LIN bus controller is built.Aiming at the output position update frequency,single update data size and format of the Beidou positioning receiver,the communication protocol packet structure,the number of data transmission frames and the number of data bytes required for each frame are constructed.The network construction of the host and slave software level(API)is designed and completed,and the LIN host schedule is designed.(3)Hardware implementation of the vehicle receiver transmission network using LIN bus controller.Two FPGAs are used to implement the host and slave of the designed LIN bus controller,and the vehicle transmission network system based on LIN is constructed with BDS positioning receiver and single-line transmission board to verify the correctness of data transmission from the host node of the navigation receiver to the slave node of the vehicle display.In the process of receiving the frame data of the slave node,the host suddenly terminates the sending frame data and restarts the frame head transmission.The performance of the traditional LIN module,CAN bus and the optimized LIN module in bit error rate,transmission speed,packet loss rate and I/O resource occupation is compared.(3)Hardware implementation and verification of vehicle receiver data transmission network based on LIN bus controller.Based on the dual FPGA board,the LIN bus controller master and slave are realized.The vehicle transmission network system based on LIN is constructed with the Beidou positioning receiver and the single line transmission board,which verifies the correctness of the data transmission between the host node of the Beidou positioning receiver and the slave node of the vehicle display.The performance of this design,traditional LIN module and CAN bus in bit error rate,transmission speed,packet loss rate and I/O resource occupation are compared and analyzed.The experimental results show that the vehicle receiver data transmission network system built in this paper can complete the expected function of the design,provide reference for vehicle receiver data transmission,and provide research basis for BDS-3 vehicle receiver in vehicle navigation,vehicle management and intelligent driving. |
