Design Of Automobile Combination Meter Based On CAN Bus

At present, along with extensive utilization of Very-Large-Scale Integration(VLSI) in vehicle electronics area and quickly upgrading on-board network system, the vehicle instruments also require to be more comprehensive, intuitive and accurate to display various data and information. The demands from vehicle drivers about the humane and real-time performance of the instruments are also increasing. The traditional mechanical,electrical or analog type vehicle instruments become unable to cope with the complex and variable modern traffic environment. At the same time, the data bus communication technology can effectively simplify the wiring required for data transmission, reducing the weight of the whole vehicle. Therefore, utilization of CAN bus communication technology in the development of modern vehicle instrument has become an inevitable trend.This paper at first briefly introduces the development and current situation in the field of vehicle instruments, and analyzes the advantages and disadvantages of the four types of vehicle instruments, i.e., the mechanical movement type, electrical type, analog type and full digital type, then it puts forward the main contents of this paper based on the current situation. The basic principle and technical specifications of the CAN communication protocol are then introduced to some extent.The major part of this paper involves the integrated system design scheme, hardware circuit design and software design. The system design scheme was based on analysis of the basic design principles of vehicle instruments, so as to aim on the main functions of the system that need to be achieved. The hardware circuit design utilised a STM32F103RBT6 chip as the main controller of instrument system, adopted a TFT-LCD as the display screen of the vehicle instruments, selected the chips for each module according to the principle of modular design, and designed the corresponding hardware circuit. The software design task was divided into blocks based on the principle of modular design, the corresponding flow diagram of each block was then produced, the software was developed and thenrepeatedly optimized in order to improve the efficiency. The hardware circuit and software program were considered at the same time in a coordinated manner.Finally, this paper also analyzed interference of the system and carried EMC design,tested the operation of the combined instrument group. By analyzing of the interference source, coupling path and sensitive elements, it respectively took the interference measures on the hardware and software of the system, which effectively improved its stability and anti-interference. The software was loaded into a test platform of the vehicle instruments using computer and gone through comprehensive debugging and testing process in order to ensure the design is feasible and practical.