| The advanced driver assistance system(ADAS)uses various sensors installed in the vehicle to identify and detect situations inside or outside the vehicle,thereby alerting drivers to potential dangers and enhancing safety.The assisted driving system has experienced reversing whistle warnings,reversing radar warnings,reversing image assisted parking,automatic parking and other development stages.Among them,ADAS research based on image sensors has received extensive attention from countries around the world,and has invested a large number of funds to carry out research and development of related systems.Many cameras will be installed on cars for ADAS.Under this background,this article carries on the certain research based on advanced driving assistance system of ASX340AT image sensor,and develops a high performance,low cost,low power consumption ADAS camera.First of all,this topic draws the overall framework and functional block diagram of the camera,and uses Allegro design software to design each module of the peripheral circuit of CMOS image sensor ASX340AT.The power module circuit design selects a wide voltage input switching regulator(DC-DC)power chip,which has the characteristics of high conversion efficiency and low power consumption.In order to meet the power requirements,the secondary circuit also uses a small package of DC-DC power chip.From the EMC point of favoring the product,the clock module circuit design selects the passive crystal oscillator to provide the oscillation frequency for the system,and the generated clock signal is connected in series with the RC filter circuit to reduce the interference of the external circuit to the clock signal.Second,the design of the image sensor module requires careful reading of the corresponding manual to understand the configuration of each pin so as to ensure the accuracy and certainty of the circuit.The image sensors include an SOC Sensor and a RAW Sensor.The SOC Sensor has an ISP processor inside itself and can output the processed image data.The ASX340AT image sensor that this design adopts is SOC Sensor,its integrated ISP system inside,has the function of image processing,the resolution is 640*480.Select the configuration code of the SPI Flash chip memory system,and use ORCAD Capture software to complete the drawing of each module circuit.PCB design software is used to design the circuit board and to ensure the integrity of the signal,a classical 4-layer board press-fit structure is adopted,and reasonable line width,line spacing,and line length are used to connect components.Copper is laid on a large area in the power and ground layers,which facilitates the heat dissipation of the PCB and provides a complete reference plane for the return path of the signal.Strict design requirements ensure that ADAS cameras can meet electromagnetic compatibility requirements.Finally,camera board and image effects are debugged and tested.Commissioning is divided into hardware debugging and software debugging.The hardware platform adopts the development tool of the MCU and the software debug adopts the ?C bus protocol software package compiled in C language.Through the combination of software and hardware,the two-wire serial synchronous serial ?C bus communication is used to change the internal register-related parameters of the CMOS image sensor in order to achieve the best image display effect.Debugging includes not only the debugging of the image output effect but also the calibration of the image center so that the geometric center of the camera coincides with the optical center.According to the actual needs of the development project,the camera module was mainly tested for EMC and image quality.Through rigorous testing,we have developed a competitive product. |
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