Research And Design On The Hardware Platform Of The Visual Reversing System

With the gradually rising of living standard of people, the automobile industry is more and more civilian. When people are enjoying their rich life, of course, they do not expect traffic accidents. However, in our increasingly crowded cities. the parking space is getting smaller and smaller. The more cars there are. the more novice drivers will appear. For novice drivers. the hardest thing is to back or park their cars in small space. Because car drivers can not see the situation behind their cars. it is difficult to park accurately. In order to see the situation behind their cars, assistant reversing system thus comes into being.So far. there are many car manufacturers who have installed assistant reversing system in some of their models. However, the integrated installation of reversing assistant system is expensive and car models are almost imported models. Thus, it gave birth to a third-party external installation of assistant reversing system.Assistant reversing system mainly uses the technology of reversing radar or reversing version to make a feedback of the situation behind the car to the driver. helping car drivers to reverse. Reversing radars detect situations behind cars through infrared ray. electromagnetic induction or ultrasonic waves, making a feedback of the detection result to drivers through voice or image. Reversing video displays on the monitor in the front of cars through the rear car cameras who collect images.This article designs and implements a hardware platform of visual reversing system. This platform collects and receives video signals of vehicle-bone cameras installed behind the cars through video decoding modules. After the decoding, it inputs to the system buffer zone. The system obtains modules with the perspectives, getting the angle signals through CAN bus of the OBD system. The system encodes the processed video information and angle signals by the video coding module and displays in the front of the vehicle-bone monitor in order to achieve a supporting role of reversing.This article first introduces the electromagnetic compatible design theory involved in PCB design of the hardware platform and the rules that the PCB design needs to comply with. On the hardware structure, in this paper, through research and analysis, the author selects the S3C2440 processor of Samsung Company as the core processor and selects the corresponding devices as SDRAM. Nand Flash, power, reset and debug interface devices that peripheral circuits require. For video collection modules, the author uses the SAA7113H chip of the NXP Corporation as the core processing chip; for video display modules, the author uses the CH7026 chip of Chrontel Company as the core processing chip:for angle signal acquisition module, the MCP2510 of the Microchip Company is used as the core processing chip. All the circuit diagrams are mapped and three processing module circuit board are produced.For software system, in view of the many advantages of Linux operating system, Linux is selected as the operating system. The u-boot of the German DENX software engineering center is also used as the boot loading program. Yaffs2 is used in the file system.When the hardware system is built, in order to make the system work, there must be appropriate software to support. First, the system should boot up. In the initial operation period, the operating system needs basic environment set in order to work properly. However, when the hardware is just in power, the hardware devices. memory without being initialized. need a procedure to run before the operating system to set this setting well. The program to finish this function is the boot loading program. In this paper, u-boot boot loading program is transplanted in detail. This system uses the S3C2440 processor of the Samsung Company, but the u-boot program has never provided support for the processor. however, the good news is that it provides a good support for the S3C2410 with the same processor core as ARM920T. Therefore, this article is based on the files transplantation of u-boot supporting for S3C2410. and mainly finds out the difference between them. The main differences between S3C2440 and S3C2410 main lie in the increasing of the camera and AC'97 audio interfaces of S3C2440 and registers of Nand Flash Control device and the chip clock frequency control. Other interfaces are compatible. If the hardware resources are made clear, one can make revises according to the specific differences between the two. This paper elaborates detailed migration steps and key points to modify.On operating system. Linux has a perfect support for S3C2440. Here, the author mainly makes changes to specific circuit connections on the target platform designed by his own. It should be noted that the settings of target platform's machine code should be consistent with that of the u-boot. otherwise it can not guide successfully. Due to the attachment of devices files after the initialization of Linux kernel, these file-based device nodes must have storage space to survive. Therefore, root file system must be built. This article adopts Yaffs2 file system that can provide a good support for the large page memory.On driver programs, the paper introduces the Linux device driver model and the V4L2 driver model. It designs and implements in detail the driver of the video collection module, the video decoding module and the angle signal acquisition module. The core processing chips of Video decoding module SAA7113H and video encoding modules CH7026 are both based on the connection and communication of I2C bus and processor, so the two drivers for the chips operate both through I2C device driver; the core chip MCP2510 of angle signal acquisition module adopts the connection of SPI bus and the processor and driver program simulates the communication timing of the SPI bus.After the video encoding and decoding chip is driven, it just meets the basic data communications. In order to make the video stream be displayed and collected properly, the interface and display interface of the camera of S3C2440 should also be driven. The camera interface driver program uses the means of memory mapping to realize which is highly efficient and exclusive deal is made. The display part is connected by video encoder chip and LCD controller and the achievement of driver program is through the transplantation of LCD driver of Linux that matches the input of the CH7026.Finally, friendly arm Mini2440 evaluation board is used for the test of video collection, video display and angle signal acquisition modules. Results show that the processing ability of the hardware platform and interfaces can meet the requirements of upper layer applications.