Abstract: A design scheme of a car light control system based on CAN bus is given. The hardware design and software design of the car light control system are introduced. The overall structure, hardware configuration, and software functions of the system are described in detail. Tests show that the system has a simple structure and reliable performance, and has broad application prospects.
introduction
CAN (Controller Area Network) is a vehicle-specific serial data communication bus developed by the German Bosch company for the automotive industry in the early 1980s, meeting the SAE (Society of Automo bileEngineer) class C high-speed vehicle network (≤1Mb / s ) Requirements, suitable for information transmission and control of power transmission and chassis electronic systems, so it is also suitable for information transmission and control of general vehicle electronic systems.
Compared with the traditional technology, the CAN bus has the following characteristics: ①Adopting non-destructive arbitration technology, the node that obtains arbitration priority will continue to transmit the message, and the message will not be destroyed or an error occurs by another node; ② The CAN bus uses a short frame structure, each The effective data of one frame is 8 bytes, the data transmission time is short, the probability of interference is low, and the retransmission time is short; ③ CAN uses CRC (Cyclic Redundancy Check) check for each frame of data to ensure high reliability of data transmission. Suitable for use in a high-interference environment; ④ CAN uses balanced differential signals to transmit data. When the communication rate is 5kb / s, the direct communication distance can be up to 10km. When the communication distance is 40m, the communication rate can be up to 1Mb / s. The field offset effect is formed; ⑤ The repeated laying of automobile wiring harnesses can be avoided, effectively reducing the number of automobile wiring harnesses, improving reliability, and reducing costs. Therefore, the use of CAN bus for the design of the car light system can improve the performance of the car.
1 Car light function and system design
Figure 1 is the headlight lighting and signal system, which is composed of lighting and signal light groups, including headlights (high beam lights, low beam lights), turn signals, fog lights, brake lights, ceiling lights, position lights, reverse lights and License plate lights and so on, different types of lights have different functions and different installation locations. According to the location of the car lights, it can be divided into four groups of left and right rear lights, right front and right rear lighting and signal light groups, as well as interior light groups, so you can set the control module, left front module, left rear module and right front module in the CAN communication network , The rear right module and the interior lighting module, a total of 6 nodes, and its car light system structure diagram is shown in Figure 2. Among them, the control module sends control commands to other 5 modules by monitoring the change of the switch state. After receiving the control commands belonging to this module, the lights of the corresponding positions are controlled respectively. Because CAN is a priority-based event triggering protocol, according to the different driving safety levels, the priority of each node in the system must be set in sequence. It should be emphasized that the switch control module is a system control command sending module, which has the highest safety requirements and has the highest priority. The left and right rear modules involve brake-related lights such as braking, and its priority is second only to the switch. Control module.
Figure 1 Car lamp lighting and signal system
Figure 2 CAN bus light system structure
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