Vehicle Terminal Based On OBD-? Interface

Vehicle networking technology is used to solve the problems of traffic control, vehicle condition remote diagnosis, vehicle tracking and positioning, official vehicle management, vehicle service and so on. In this thesis, the application technology of OBD-? standard interface was studied, and an embedded vehicle terminal system based on OBD-? interface was designed to achieve large vehicle status data acquisition, processing and sharing.In this thesis, CAN, SAE J1850 and KW2000 vehicle bus technology, and diagnostic model of OBD-? standard were studied and a general solution of intelligent terminal device based on STM32 MCU and OBD-? interface, using Beidou position and 3G communication technology, was proposed. The vehicle status data transmitted from CAN, J1850 or KW2000 vehicle bus interface circuit which connected with the STM32F103C8T6 MCU, to the WCDMA module which is use to send data to the data server by 3G wireless network when after the processing by MCU and fusion with the Beidou positioning data. The system auxiliary circuit includes power management circuit, FLASH memory circuit, humancomputer interaction circuit, and etc.By using the integrated development environment Keil ?Vision5 MDK, real-time operating system ?C/OS-? was transplanted to STM32 MCU, and the peripheral driver and vehicle bus protocol driver software were developed. The data transceiver control of OBD-? interface data, interpretation of Beidou data with NMEA protocol, network management and data transmission of 3G communication module were implemented. The application software system which includes OBD-? interface protocol adaptation unit, data backup unit, establishment of the wireless network link unit, data transmission unit and so on, was developed with multi-task modular design after the allocation of hardware resource and the deployment of application software.By using OBD-? simulator, the terminal equipment was tested in Laboratory. The test equipment could adapt the various protocols simulator configured, send and receive data through OBD-? interface accurately, and connect to the server automatically according to the state of the 3G network signal. The test indicated that the design of software and hardware system can meet the requirements of large data transmission and sharing for Internet of Vehicles and works stably.