[Car basic knowledge]The design of reversing radar, reversing visual, reversing multimedia visual ranging terminal

Abstract: This article describes a new type ofcarReversing radarproduct(Reversing multimedia visual ranging terminal)Hardware/software development and design.Firstly, it introduces its advantages and working principle compared with the current products.Car TVFor the display platform, it combines the infrared reversing distance measurement module, the character overlay module, and the main control module for hardware design and software development. Keywords: Ultrasonic distance measurement; Rear-view camera system; Character superimposition signal processing introduction At present, two new technologies have emerged for reversing: ultrasonic distance measurement and rear-view camera.

　　

Both the reversing radar and the rear view camera have their advantages and disadvantages. The former has the advantage of accurately judging the distance. However, ultrasonic waves cannot sense the ditches, cliffs, protruding steel bars, bamboo poles, etc. behind the car. This is also a dead end in reversing safety; The image of the reader is intuitive and true, but the precise distance cannot be obtained. How to combine the advantages of the two and eliminate the shortcomings of the two is a key problem to be solved by the reversing multimedia visual ranging terminal.

The reversing multimedia visual distance measurement terminal uses the latest ultrasonic distance measurement technology, character generation and superposition technology, and video display technology to realize the combination of reversing distance measurement and image monitoring functions. It is a kind of detection and monitoring for object distance behind the vehicle. The electronic equipment of the image behind the car has three major functions:

The first function: Ultrasonic distance measurement-------Embedded ultrasonic distance measurement makes parking distance measurement accurate.

The second function: Rear-view camera system ------ Take pictures of the scene behind the car, intuitive and without blind spots. The third function: Car TV------display the image of the scene behind the car and the distance of obstacles behind the car, and can connect to VCDDVD, watch TV programs, and provide entertainment and leisure. Hardware circuit design The reversing multimedia visual ranging terminal is operated byswitchPower supply, ultrasonic probe, ultrasonic distance measurement, OSD display controller, camera probe, and car TV (see Figure 1). The OSD display controller is composed of microprocessor W87E58, character overlay uPD6453, clock chip DS12C887, keyboard, ultrasonic Ranging interface circuit CON4, character superimposition interface CON2, RS-485 interface circuit, indicator lights D1 and D4, buzzer drive circuit S2 andbuzzerU5 driver and switching circuit composition. The clock chip is used to generate the time signal, which enters the CPU through the parallel bus; the ultrasonic ranging signal enters the CPU through the interface CON4; the character superimposition signal is output from the CPU to the character superimposition controller, and the character superimposition controller completes the superposition of time, distance information and video . The keyboard is used for time adjustment and function setting; the indicator lights D1 and D4 are used to indicate the working status; the buzzer circuit is used for reporting.

Figure 1 Block diagram of the reversing and ranging monitor The working principle of the reversing multimedia visual ranging terminal is: it will come from the rear of the carbumperThe installed ultrasonic signal is connected to the OSD display controller, and at the same time the camera probe signal in the video monitoring subsystem is connected to the OSD display controller, through the automatic switching circuit, character overlay and micro-processing of the OSD display controller installed in the car The output of the OSD display controller is connected to the monitor again, so as to realize the functions of automatic image switching, monitoring, ultrasonic reversing distance measurement, and automatic alarm. The OSD display superimposer uses a dedicated OSD chip to achieve character superposition: the input video signal is synchronized and separated first, and the line and field synchronization signals are separated as the OSD reference signal, and then the OSD chip outputs the red primary color voltage Vr and the green primary color voltage Vg , The blue color voltage Vb signal is encoded, and the video signal generated after encoding is synchronized with the input video signal. The two video signals are switched at a high speed. The keying pulse of the switch is a signal, that is, as long as there is a character signal, it is switched to the video signal encoded by the character signal. As a result, the image of the input video signal is keyed, and the keyed part is composed of the characters. Signal replaced.

Its advantage is: it can be installed on any kind of vehicle for reversing. When reversing, the driver can clearly see the scene behind the car from the monitor without opening the door; the CCD color or black-and-white wide-angle camera probe has an angle of 80° and a horizontal distance of 0.3 to 1.5 meters; the rear scene is displayed as an upright image, without distortion, No geometric distortion; working voltage is DC12V, which can be shared with car power supply.

System software design The OSD display controller of the reversing multimedia visual ranging terminal adopts the microprocessor W87E58, and the software adopts C language programming. Figure 2 shows the flow of images and ranging data behind the vehicle.

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