Abstract : After briefly introducing PECOS technology and its characteristics, the main components of the embedded video surveillance system are defined in combination with the basic requirements of the embedded video surveillance system. The serial communication component program example is given in combination with the PECOS standard. Finally, several key issues in component-based program design are discussed. 0. Introduction With the increasing maturity of digital video compression technology, embedded video surveillance has become the mainstream of today's monitoring technology. However, due to the continuous increase in system functions, the continuous change in programming environment, and the imperfect early requirements analysis and design, the difficulty of system upgrade and maintenance has been increasing [1]. Every small change may cause the entire system to be recompiled, linked and debugged, which consumes a lot of manpower, material resources and time. Therefore, component-based design is required. In order to simplify the component development process, a set of standard methods is needed to build, manage and maintain components. In view of the problems encountered in the development of current network video applications, such as the weak reusability of software, the instability of IP network transmission and the diversity of network bandwidth, the best solution is to build the application on the basis of components. The commonly used component models (mainly COM/DCOM, CORBA, JavaBeans, etc.) require a lot of underlying infrastructure support at runtime and mainly run on non-embedded platforms [2]. The popular embedded component models abroad are mainly the CCOM model sponsored by the Belgian IWT Association, the Koala component model used by Philips for consumer electronics, and the Delta System platform of Keyin Jingcheng Company, which is in its initial stage in China. These models are undisclosed technologies limited to internal use within the company and require corresponding CASE tools [3]. Based on the above analysis, this paper designs the monitoring componentization and selects ABB's PECOS component model for field devices as the componentization standard to develop the entire system. 1. Introduction to PECOS Technology The elements in the PECOS component model include components, interfaces, and connectors. There are three types of components: active components with their own control thread; passive components that do not have their own control thread and are scheduled by active components [4]; and event components whose functions are triggered by an event. These three types of components can be used in combination. The interface indicates that the component provides data to other components or needs data from other components. This includes the type (e.g., floating-point), direction (in, out, in/out), and range of the data to be transmitted. The connector is responsible for connecting interfaces with compatible types, directions, and ranges. 1.1 PECOS Component Behavior An application can be comprehensively described using CoCo and target language classes. The connected object is called the RTE runtime environment. RTE is the standard library provided by PECOS. The advantage of RTE is application independence. PECOS components are also platform independent and can be shared in different projects. A specific application can be divided into the following four layers: RTOS, RTE, Generated Classes, and User classes. 1.2 Characteristics of the PECOS Component Model User Language Independence Interfaces and components are described using Interface Definition Language (IDL) and Component Definition Language (CDL), separating the model from the specific implementation. Theoretically, it can be mapped to multiple languages ​​such as C, C++, and Java. Portability Embedded systems have diverse hardware environments, so the portability of the component model is very important. In this model, good portability is achieved by encapsulating the underlying interfaces. Maintainability of Components Maintainability of components is achieved through interface inheritance and optional interfaces. Compared with other component programming technologies, PECOS has good cross-platform performance and is independent of programming languages. It has good openness, scalability and real-time performance. Therefore, we choose CORBA as the component standard to program the whole system in a componentized manner. 2. Main functional components of the embedded monitoring system The remote monitoring system based on embedded Web is mainly composed of three parts: field data acquisition equipment, embedded Web server and remote monitoring host [5]. The field data acquisition equipment is responsible for field data acquisition and transmitting data according to a certain protocol standard; the embedded Web server is responsible for collecting and publishing field data, and the monitoring host obtains data in real time through Ethernet, thereby achieving the goal of remote monitoring. For the whole system, according to the functional requirements, based on the principles of global scalability, reusability, advanced technology and reliability, the system design is divided into several component modules such as Web Server component, CGI component, serial communication component, data storage component, alarm component, etc. The interface is divided according to service and encapsulated in the component according to function, striving for clear, simple and easy-to-maintain system components. The relationships between these components are shown in Figure 1: [align=center] Figure 1 Main Functional Components of the Embedded Monitoring System[/align] The Web Server component refers to a program module that implements the basic content of the TCP/IP protocol (such as the HTTP protocol), can respond to and process user requests, and realize adversarial communication. Through the implementation of TCP/IP related protocols, the Web server has the ability to interact with the browser, can process client user requests, transmit network messages and return results to the browser, and can also work with other applications. Since Boa is a small, single-task HTTP server with open source code, good stability, and strong real-time performance, Boa is selected as the Web Server in this system. The CGI component refers to a program module with independent functions designed according to the CGI standard. It is a standard interface for the embedded web server to interact with external extended applications. Through it, data from field devices is transmitted to the embedded web server in real time, thereby realizing dynamic data interaction between remote clients and field devices. The data storage component refers to a functional module that can save field-collected data and provide read and write methods for other functional components. The alarm component refers to a program module that can provide alarm functions. Among these components, the WebServer component and the CGI program component are combined with the serial communication component, the data storage component and the alarm component to complete the functions of data acquisition, storage, display and alarm. 3. Serial Communication Component Example The serial communication component module is used as an example to illustrate how to implement its function using PECOS. The serial communication component refers to an independent program module that completes the serial communication function. This module mainly includes hardware devices such as PTZ cameras. Camera control mainly includes controlling its focal length, lens concavity and convexity, and aperture; PTZ control mainly includes controlling its automatic rotation and direction, which completes the data transmission from the field device, i.e., the PTZ camera, to the CGI component [6]. It works together with the CGI program component to complete the data update of the embedded web server. The following is the interface definition language IDL definition of the serial communication component module. Constants and data definitions are omitted here. Only the overall framework of the entire module is provided. Module SerialPort { interface Camera { SetFocus(in int FocusValue, out int Result); // Set focal length value SetLens(in int LensValue, out int Result); // Set lens convergence and divergence values ​​SetAperture(in int ApertureValue, out int Result); // Set aperture value