毕业设计 外文翻译

毕业设计(论文)外文资料翻译

学院：电子工程学院

专业级：电子信息工程D电子091

学生姓名：环洲书院学号：510920138

指导教师：韩晓春（高级实验师）

2008International Conference on 外文出处：

MultiMedia and Information Technology 附件： 1.外文资料翻译译文； 2.外文原文

指导教师评语：

签名：

年月日

图像采集技术与AVR单片机

摘要

图像采集系统在各种数字图像应用系统中是不可或缺的部分。在本文中,我们开发了一种基于AVR单片机的紧凑的图像采集与处理系统。该系统主要利用AVR单片机ATmega16与低功耗、高性能的数据处理主控制单元。首先，它完成了CMOS光通过I2C接口接收的相机模块C3088初始化。然后，它被用来从LCD 上实时显示C3088和获取图像的采集状态。最后,利用单片机串行通信接口发送数据到电脑,在经过数据处理显示图像。硬件电路和软件系统的设计。

关键词：图像采集，单片机，AVR串行通信，视频监控

一、简介

随着社会的进步和科学的发展,技术与经济,要求更安全的工作和生活环境所倡导的组织和个人对防盗措施都提出了新的要求。作为一个有效的安全保护手段,在视频监控领域中发挥着重要的作用,公共安全等,已经越来越受到广泛关注[1-4]。目前,视频监督和控制已经进入所有域名,我们几乎每天可以看到它的应用。图像采集系统在各种数字图像应用系统中是不可或缺的部分。

AVR单片机是基于可编程GSI和计算机技术的大规模集成电路芯片(5-9]。它的快速数据采集和处理功能以及各种功能模块集成在芯片中在各种场合提供丰富便捷的应用程序。比较CCD、CMOS图像传感器可以将时间序列处理成电路,前端放大器的图像信号和数字部分为一个芯片,因此它的发展是高度强调由行业一向性。目前,随着技术的发展,噪声的CMOS图像传感器已经有效地改善,并且解决能力明显增强。CMOS图像传感器由于其低廉的价格,图像质量,高整合度和相对较少的电力消耗将被广泛应用在视频采集领域。因此,在本文中,我们开发实施的图像数据采集系统是基于AVR单片机的。程序驱动摄影机C3088[10]通过单片机ATmega16获取原始图像数据,通过I2C接口的初始化摄像头协议,并实现数据传输,。该电路具有许多优点如结构简单,方便转移和低CPU占用,它可以降低系统的总成本。

二、系统结构

它以数字化和自动化的水准在传统光学采集系统中安装电气部分数据处理。数据处理单元的原则包括快速数据运算速度,丰富的外围接口和低功耗。根据这些原则,我们采用AVR单片机与高性能的设计,它可以结合获取的信息数据采集仪在CMOS图像传感器前端显示,其结构示意图见图1。该系统采用单片机作为

微控制器,驱动摄像头通过I2C总线,主要是初始化一些寄存器,组成了图像传感器。当初始化完成时,相机输出三个符号包括像素时钟信号同步信号和垂直,生的同步信号。单片机读取原始数据的图像并从相机数据总线通过测试这三个标志信号,暂时存储数据到数据存储器在单片机,然后传输数据到计算机通过串行通信。

图1.系统结构

硬件

选择器在硬件的实现方面对于系统的整体性能是非常重要的。我们可以选择单片机具有较高的性价比和速度,我们也可以选择功能强大的DSP,速度快,多个接口和核心芯片,我们也可以选择ARM微处理器。作为视频采集系统、图像系统中使用的传感器的速度可以由单片机控制。当我们第一次用51系列单芯片微型计算机在设计过程中,我们发现它无法满足数据庞大的吞吐量所需的视频采集。所以我们使用ATmega16系统中可以满足设计要求的系统。单片机被广泛应用于爱特梅尔公司的许多领域如工业生产控制、智能仪器、数据采集和家用电器。这种单片机具有RISC结构。由于其先进的指令集和单时钟周期指令执行时间。当它工作达到16MIPS16兆赫时,它可以减少能耗之间的冲突加快处理速度。执行一个指令只需要一个时钟周期，且速度比传统的单片机快很多，所以它可以胜任高速条件下的A/D采样的控制。但当我们使用DSP，ARM和FPGA／CPLD，它会浪费资源，使系统变得越来越复杂，成本和性能是不合理的。

用于视频捕获设备，无论是CCD或CMOS全部采用光接收元件作为捕获图像的基本措施。核心的CCD/CMOS光接收组件是一个光接收二极管，产生输出电流时，接收光的照射。电流的强度对应光的照射强度。对于周边设备，光接收元件CCD与光接收元件不同，除了光接收二极管。光接收的前部分还包括一个存储单元，用于控制相邻电荷。光接收二极管占多数的面积，即有效的受光面积，CCD光接收组件更大，它可以在相同的条件下获得更强的光信号，并使输出相应的电信号更清楚。由于CMOS图像传感器技术发展很快，每一个光接收元件可以直接集成在CMOS传感器放大器并完成逻辑模数转换。当光接收二极管接收光的照射而产生的模拟电信号，并模拟电信号放大在光接收元件之前转换成相应的数字信号。换句话说，在CMOS传感器，每个光接收组件产品都有最终的数字输出。由于集成度高，体积小，使用方便，内容丰富，图像捕获快速，我们采用CMOS传感器组成的相机模块C3088（OV6620）作为设计的采集设备。

默认的分辨率的摄像头是356×292，所以它非常适合于单芯片微型计算机的操作能力。

该相机模块C3088工作电压为5V，它的引脚20和引脚22与电源连接，和引脚31连接数字地球，与引脚21，引脚15和引脚17连接模拟地球。数据线连接~Y0Y7PA0~PA7单片机的数据线，和uv0~uv7连接PB0~PB7的单片机，和PCLK与PD2，和超链接与PD3，和垂直同步连接PD4。SDA和SCL与PC1，接PC0。现场可编程逻辑器件包括356×292分辨率的图像阵列，模拟信号处理器，双8位模拟数字转换，模拟视频多路转接器，数字格式输出端口，一个模拟视频接口，I2C总线接口及寄存器。该传感器采用基于完整图像的电子曝光控制算法。

单片机采用RS232串行通信与上位计算机的通信。其电路结构是非常简单的，它可以保证系统的稳定和满足系统设计要求。该系统采用RS232连接计算机和视频数据传输。ATmega16采用8位数据位，1位停止位和0个奇偶校验位，其速度可以达到230400bps，和计算机的串行端口速度仅为115200bps，可以满足系统的设计要求。

由于单片机的电压ttl5v和RS232电压12V，双方需要进行电平转换来识别。该系统需要与单片机通过MAX232芯片如图2所示连接。

图2.电压匹配电路

显示的液晶采用ZT018智能全彩液晶。这个模块具有基本的绘图功能,采用通常的微型客车作为接口,因此它可以节省开发时间以及方便发展和转移。它的接口模式包括SPI和I2C,本系统采用I2C接口,只需要两个数据行。

四、软件

C3088由CMOS图像传感器OV6620,它的初始化主要取决于通过I2C对内部寄存器的写入操作。通过软件的初始化设置,视频数字输出可以使用不同的格式并和其他寄存器进行初始化。因为最初的时钟频率的C3088相机模块是17.73mhz,当它工作在16位数据输出模式,其PCLK时钟周期是112ns和当它工

作在8位数据输出模式,其PCLK时钟周期是56ns。晶体振荡所采用的单片机是16兆赫和单周期是62.5ns。所以单片机可以不遵循视频的速度。它必须通过写寄存器0x11降低时钟频率PCLK,设置低5位的寄存器在“1”可以减少PCLK 至69.25千赫,可以适合单片机处理较低的速度。

数据输出格式通常的CMOS图像传感器是原始数据输出格式。由于CMOS 光传感器单元具有三种颜色不同的响应灵敏度，响应是非线性的。它是相对于亮度，加上材料。因此，图像传感器的原始数据应校正和补偿。不同厂家的产品补偿曲线是不同的，所以我们应该设计不同的补偿算法。现场可编程逻辑器件不仅可以输出的原始数据格式的R，G和B，并将色彩补偿算法在芯片中，并能输出YUV和YCrCb视频输出格式符合CCIR601标准。

相机通过初始化工作在最低频率。单片机可将数据存储在单片机数据存储器时，它读取原始数据，并将所获得的程序转换为BMP格式的数据，并将数据传送给计算机进行存储和显示。

串行通信是一种通信模式，可以通过比特传输二进制数据，因此传输线所需要的是很少的数量，这是非常适合的分级控制系统，分层控制系统，分布式控制系统和远程通信。由于分布式控制系统被广泛应用在现代的计算机控制系统，因此它往往需要一个主计算机控制多台下位机，与计算机和单片机成为一个重要的问题之间的通信。单芯片的微型计算机的程序流程图如图3所示。计算机程序流程图如图4所示。

图3.程序流程图的数据采集和发送

图4.程序流程图的数据接收和处理

五、结论

视频数据的采集和存储技术日复一日发展很快，识别技术，数字电视和实时监测和控制的行业前景很好。相机的图像采集系统基于AVR单片机和C3088简化了系统的结构。该系统具有清晰的图像，可满足实时显示的要求，可广泛应用于工业自动化监控网络视频。

Image Acquisition Technology with AVR Single Chip Microcomputer

Xiao Chen

Department of Electronic Information Engineering,

Nanjing University of Information Science and Technology

Nanjing210044,China

rainofsun@https://www.360docs.net/doc/451116139.html,

Abstract—The image acquisition system is one of indispensable parts in various kinds of digital image application system.In this article,we developed a sort of video camera compact image acquisition and processing system based on AVR single chip microcomputer.The system utilises AVR single chip microcomputer ATmega16with low power consumption and high performance as the data processing main control unit.Firstly,it completes the initialisation of CMOS light-receiving camera module C3088through I2C interface.Then it is used to acquire image from C3088and the acquisition states are displayed on LCD real time.Finally,the single chip microcomputer utilises serial communication interface to send data to the computer, which displays the image after data processing.The hardware circuit and the software programs of the system are designed.

Keywords-Image acquisition;single chip microcomputer;AVR;serial communication; video surveillance

I.INTRODUCTION

With the progress of society and the development of science,technology and economy,the demands for more security in working and living environment has been advocated by both organizations and individuals,which puts forward new requirements for anti-theft measures.As an effective means of security protection, video monitoring plays an important role in fields of public security,etc.,and has drawn increasing and extensive attentions[1-4].At present,Video supervision and control has entered into all domains,and we can see its applications almost everyday. The image acquisition system is one of indispensable parts in various kinds of digital image application system.

AVR single chip microcomputer is the integrated chip based on programmable GSI and computer technology[5-9].Its quick data acquisition and processing function and various function modules integrated in the chip offer abundant conveniences for its applications in various https://www.360docs.net/doc/451116139.html,paring with CCD,the CMOS image sensor could integrate the time sequence processing circuit,the front-end amplifier of image signals and digital part into one chip,so its development is highly emphasised by the industry all along.At present,with the development of technology and technique,the yawp of CMOS image sensor has been improved effectively and its resolving capability has been obviously enhanced.CMOS image sensor will be extensively applied in the video acquisition domain because of its cheap price,applied image quality,high integration degree and relatively little power consumption.Therefore,in this article,we develop the implementation program of video data acquisition system

based on A VR single chip microcomputer.The program drives the camera C3088[10] through single chip microcomputer ATmega16to obtain the original image data acquired by the camera,and implement data transmission and initialisation of camera through I2C interface protocol.This circuit has many advantages such as simple structure,convenient transfer and low CPU occupation rate,and it can reduce the total cost of the System.

II.SYSTEM STRUCTURE

It can realize the digitalization and automatization of leveling to install the electric parts of data process in traditional optical acquisition system.The principles of data processing unit include quick data operation speed,abundant peripheral interfaces and low power consumption.According to these principles,we adopt AVR single chip microcomputer with high performance in the design,which can combine with the information acquired by the data acquisition apparatus CMOS image sensor in the front end,and its structure sketch is seen in Fig.1.The system adopt single chip microcomputer as the micro-controller to drive the camera through I2C bus,which mainly initializes some registers which composes the image sensor of the camera.When the initialization of camera is completed,the camera outputs three symbol signals including pixel clock,raw synchronous signal and vertical synchronous signal.The single chip microcomputer read the original data of image from the camera data bus through testing these three symbol signals and temporarily stores the data into the data memorizer in single chip microcomputer,and then transmit the data to the computer through serial communication.

III.HARDWARE

The selection of apparatus in the implementation of hardware is very important for the performance of the whole system.We can select the single chip microcomputer with high cost performance and high speed,and we can also select the DSP with powerful function,quick speed,multiple interfaces and good stability as the core chip,and we can also select ARM microprocessor.As the video acquisition system,the image sensor speed used in the system can be controlled by the single chip microcomputer.When we first used51series ingle chip microcomputer in the design process,we found it couldn't fulfill the throughput of large data needed by the video acquisition.So we use ATmega16in the system which can fulfill the design requirement of the system.The single chip microcomputer of ATMEL Company is extensively applied in many domains such as industrial production control,intelligent instruments,data acquisition and home electric appliances.This kind of single chip microcomputer has the structure of RISC.Because of its advanced instruction set and

single clock period instruction execution time,the performance of AVR single chip microcomputer can achieve16MIPS when it works in16MHz,which can reduce the conflict between power consumption and processing speed.The execution of one instruction only needs one clock cycle,and the speed is much quicker than traditional single chip microcomputer,so it can be competent for the control of A/D sampling under the condition of high speed.But when we use DSP,ARM or FPGA/CPLD,it will waste the resources and make the system become more complex,and the cost performance is not so reasonable.

For the video capture equipments,whether CCD or CMOS all adopt the light-receiving component as the basic measure to capture images.The core of CCD/CMOS light receiving component is a light-receiving diode which can produce output current when receiving light irradiation.The intensity of the current is corresponding to the intensity of the irradiation.For the peripheral equipments,the light receiving component of CCD is different to the light receiving component of CMOS,and except for the light receiving diode.The light-receiving component of the former also includes one storage unit which is used to control the neighboring charge. The light-receiving diode occupies most areas,i.e.the effective light-receiving area of the CCD light-receiving component is bigger,and it can receive stronger light signal under same condition,and the corresponding output electric signals are more clear. Because the CMOS image sensor technology develops very quickly,every light-receiving component in CMOS sensor can directly integrate the amplifier and the analog-to-digital conversion logic.When the light-receiving diode receives light irradiation and produces analog electric signals,and the signals are amplified by the amplifier in the light receiving component firstly and then converted into corresponding digital signals.In another words,in the CMOS sensor,every light-receiving component can product final digital output.Because of high integration degree,small volume,convenient use and abundant image content effect captured,we adopt the camera C3088module composed by CMOS sensor(OV6620) as the acquisition equipment in the design.The default resolving capability of the camera is356*292,so it is very fit for the single chip microcomputer with low operation ability.

The work voltage of the camera module C3088is5V,and its pin20and pin22 connect with the power supply,and the pin31connects with the digital earth,and the pin21,pin15and pin17connect with the analog earth.Data lines Y0~Y7connect PA0~PA7of the single chip microcomputer,and data lines UV0~UV7connect with PB0~PB7of the single chip microcomputer,and PCLK connects with PD2,and HREF connects with PD3,and VSYNC connects with PD4.SDA connects with PC1, and SCL connects with PC0.OV6620includes the image array with the resolving capability of356*292,an analog signal processor,double8bits analog-to-digital conversion,analog video multiple routes commutator,digital output format port,an analog video port,I2C bus interface and its register.The sensor uses the electric exposal control algorithm based on complete image.

The single chip microcomputer selects RS232serial communication to communicate with the computer.Its circuit structure is very simple,which can ensure

the stability of the system and fulfill the design requirement of the system.RS232is one of communication interfaces on personal computer,and it is the asynchronous transmission standard interface constituted by the Electronic Industries Association (EIA).This system adopts RS232to connect with computer and transmit video data. The ATmega16adopts8bits data bit,1bit stop bit and0parity bit,and its speed can achieve230400bps,and speed of the serial port of the computer is only115200bps, which can fulfill the design requirement of the system.

Because the voltage of the SCM is TTL5V and the voltage of the RS232is-12V, so both sides need level conversion to identify the other.The system needs to connect with single chip microcomputer through the chip MAX232as shown in Fig.2.

The display of LCD adopts ZT018intelligent true color LCD.This module possesses basic plotting function which adopts usual microbus as the interface,so it can save development time and offer large convenience for the development and transfer.Its interface modes include SPI and I2C,and this system adopts I2C interface which only needs two data lines.

IV.SFOTWARE

C3088is composed by CMOS image sensor OV6620,and its initialization mainly depends on the write-operation to interior registers through I2C.Through the initialization setting of the software,the video digital output can use different formats and initialize other registers.Because the initial clock frequency of the C3088camera module is17.73MHz,when it works in the16bits data output mode,its PCLK clock cycle is112ns and when it works in the8bits data output mode,its PCLK clock cycle is56ns.The crystal oscillation adopted by the single chip microcomputer is16MHz and the single order cycle is62.5ns.So the single chip microcomputer can not follow the speed of the video.It must reduce the PCLK clock frequency through writing the register0x11,and to set the low5bits of the register in"1"can reduce PCLK to 69.25KHz,which can fit for the single chip microcomputer processing with low speed.

The data output format of the usual CMOS image sensor is the original data output format.Because the CMOS optical sensor unit has different response sensitivities to three sorts of color,and the response is nonlinear.It is relative to the

brightness,plus and materials.So the original data of the image sensor should be emendated and compensated.The product compensation curves of different factories are different,so we should design different compensation algorithms.OV6620can not only output original data formats of R,G and B,and integrate color compensate algorithms in the chip,and it can output the video output formats of YUV and YCrCb according with the standard of CCIR601.

The camera works in the lowest frequency through initialization.The single chip microcomputer can store the data in the data memorizer of single chip microcomputer when it read a raw of data,and it converts the data acquired by the program into the format of BMP,and transmits the data to the computer for storage and display.

The serial communication is a sort of communication mode which can transmit binary system data by bit,so the quantity of the transmission lines needed by it is very few,and it is very fit for grading control system,layer-division control system, distributed control system and remote communication.Because the distributed control system is extensively applied in the modern computer control system,so it often needs one main computer to control multiple slave-computers,and the communication between the computer and single chip microcomputer becomes into an important problem.The program flow chart of single chip microcomputer is shown in Fig.3.The program flow chart of computer is shown in Fig.4.

V.CONCLUSION

The acquisition and storage of video data is the accidence of the video technology,and in the day that the video technology develops very quickly,the identification technology,digital TV and real-time supervision and control are the industries with very good foreground.The camera image acquisition system based on AVR single chip microcomputer and C3088simplifies the structure of the system.The system has clear image,and it can fulfill the requirement of real-time display and be extensively applied in network video and industrial automatic supervision. ACKNOWLEDGMENT

The work is supported by the Basic Research Program(Natural Science Foundation)of Jiangsu Province of China(Granted No.BK2007601),"Qing Lan Gong Cheng"program of Jiangsu Province of China and the Natural Science Foundation of Jiangsu Higher Education Institutions of China(Granted No. 06KJB510048).

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