Development and Research of Embedded Controller of Instrument System

Development and Research of Embedded Controller of Instrument System

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The application of embedded systems in the field of instrumentation has become a trend in the development of the instrumentation industry by combining traditional instrumentation, Internet, and microprocessor.

This paper first introduces the embedded controller based on the Embedded Intelligent Instrument remote monitoring system, and then combined with the embedded controller, the author elaborated on the application of UML-RT and platform ideas in the design of embedded controller system, the detailed steps and contents of the embedded controller design are given.

1 Introduction

With the rapid development of instruments, computer and network technologies are also developing rapidly. PC has grown from high speed to steady development. The emergence and wide application of embedded systems, this has brought computers and networks into the post-PC era. The remote monitoring system based on embedded smart meters is one of the important development directions of industrial control networks. The embedded controller is a key device that can achieve remote monitoring of intelligent instruments and a bridge between industrial control instruments and the Internet.

2. General Introduction to Controllers

Design of the Structure of embedded smart instruments and their connection to the Internet 1.

Figure 1 remote monitoring system based on embedded smart meters

An embedded controller is a control system used to execute independent functions and process data in a complex way. It is built into an industrial instrument and consists of three parts: high-speed processors, embedded Web servers, and industrial instrumentation interfaces. The embedded controller uses high-speed processors as the core, and works with other chips to control electronic devices or devices. It can complete various automated processing tasks such as monitoring and control. The embedded controller is a good basic access device, which is connected to the instrument through the interface of the industrial instrument. The embedded controller integrates Web functions into the entire device based on TCP/IP data transmission. With a browser, the customer can easily communicate with the Controller, view and set process parameters for on-site intelligent instruments, and disable and enable the control object.

Embedded Controller is the core of the Remote Monitoring System Based on Embedded instruments. embedded controller is a typical embedded system. The system design of embedded controllers follows the related theories of embedded system design. System design should consider the structure of software and hardware as a unified and coordinated whole. Embedded systems tend to use high Platform and object-oriented UML-RT for system analysis and design. Therefore, when designing an embedded controller, we adopt UML-RT and Platform to enable the embedded controller to have an elastic architecture, which can easily and quickly change or expand functions to meet the system requirements.

3 Requirement Analysis of embedded Controllers

We use the use case diagram of UML to analyze the requirements of embedded controllers. The use case diagram describes the functions of the system hardware and software from the user's point of view. According to the previous description of the functions of the embedded controller, we can obtain the system use case diagram, as shown in figure 2. There are seven different use cases and two different roles.

Figure 2 example of an Embedded Controller

User roles can view data, set data, enable and disable control objects (smart meters), control objects can receive and send data, and enable and disable operation commands accordingly. The data processing center is responsible for data encapsulation, transmission, computing, and other data processing.

4. platform division and Design

After completing the system requirement analysis, we began to divide the system structure of the platform, the system structure of the platform refers to the definition of interfaces between different levels and the assignment of functions of the upper and lower layers. Each layer has its own system structure. The hierarchical structure is divided by functions and logic order. When dividing the system structure, we need to comprehensively balance the following problems:

1. In essence, it refers to the attributes of the Platform, including the conceptual structure, some interfaces and functional features, that Platform Users see when using the platform for development. The concept and function regard it as a hierarchical structure consisting of multiple levels, which is conducive to a correct understanding of the embedded controller and the development platform itself. What should be transparent and what should not be transparent. The advantage of transparency is that it can simplify the design at this level.

2. In general, many functions can be either placed on the upper or lower layers, and they are equivalent to logical functions. The upper-and lower-layer allocation ratio depends on ease of use, complexity, and existing hardware conditions.

3. It is also an important issue to design and implement the system structure. For example, for a three-tier structure, you can choose from top to bottom, from bottom to top, and from the middle. The system structure of the embedded controller platform is shown in figure 3.

We divide the embedded controller system into three abstract layers: The architecture platform (ARC platform), The Application Programming Interface platform (API platform), and the customized application platform (ASP ). The ARC platform includes microprocessor storage systems, interface circuits, I/O channels, and internal connections between chips. The microprocessor system is composed of S3C2410 microprocessor, FLASH, SDRAM, CS8900A network control chip, and other "microarchitectures. The API platform includes the RTOS real-time operating system, embedded Web servers, and device drivers. The API platform is a software abstraction layer that encapsulates the implementation details of the ARC platform. The API platform provides interface services and groups these interfaces by category. For example, you need to know whether RTOS provides the preemptive task scheduling interface and the HTTP and TCP/IP interfaces provided by embedded Web servers. The ASP Platform provides the user's direct operation interface and specialized application services, such as allowing users to view and set the control parameters of smart meters through a browser.

Figure 3 platform Division

Each platform has corresponding QoS requirements. The ARC platform requires power consumption, storage capacity, processing speed, and communication capabilities. Chips such as S3C2410 and CS8900A can meet these requirements. The API platform also requires the number of running tasks and task switching time. Embedded Web servers and embedded Linux can meet these requirements. The ASP Platform requires real-time parameter viewing and parameter setting. Using Java Applet can do this well.

Divide the platform of the embedded controller system, and put forward the corresponding service quality parameters for each platform so that we have a global concept for the entire design at the initial stage of the design, since each platform is relatively independent of each other, it will be able to adapt to new design requirements and design modifications in the future.

Design of Embedded Controller Based on UML-RT

After dividing the platform of the embedded controller, we can use the symbol system of the UML-RT to model the embedded controller system. We divide the modeling process into two stages. The first stage is to consider the external interface of the system. The second stage is to consider the Internal Platform modeling of the system.

In the first stage, the modeling of the embedded controller is shown in Figure 4. According to the requirement analysis of the previous use case diagram, the system has two ports to interact with the environment: one is to communicate with the control object, that is, the intelligent meter. One is to interact with users. To support interaction with users and control object communication, we define two containers (capsule) u: User InteRFace and t: Transfer Data. The p: Process Data container is used to Process Data. Containers can contain the relevant software and hardware structure, data transmission can be performed through the parallel port and serial port, this transfer and processor coupling is very tight, we use UML-RT extension Symbol Representation. Similarly, SW p1 indicates the program that processes and controls object communication on the processor P1. We can also refine u: User Interface and p: Process Data in this way.

Figure 4 first-stage representation of an Embedded Controller

On the basis of the first stage, we can build a platform based on the platform division. Modeling of the system's ARC platform 5 is shown.

Figure 5 UML-RT Modeling on ARC Platform

Figure 5 shows the basic components of the ARC platform and their topology. This graph can be used to further model objects. This model provides a framework that can easily add, move, replace, and modify elements in the framework. The port of the UML-RT can effectively represent an interface between model elements.

The API platform is located between the ARC platform and ASP platform, including RTOS embedded Web servers and device drivers. From the perspective of UML-RT, API platform is the communication pipeline between ARC container and ASP container. Here, the ARC container and the ASP container are directly connected through the connector.

The ARC Proxy receives the call information from the port of the ASP container, and sends this information to the appropriate device driver through the rtos api, so that the device driver can communicate with the ARC platform. Asynchronous or synchronous communication can be performed in this way. Drivers are closely related to RTOS. Modeling on the ASP platform can also be performed in a similar way.

To sum up, combined with UML-RT and Platform for embedded controller design, we can see that they can be very good for Embedded Software and Hardware abstract, provide good documentation. The system architecture based on UML-RT and Platform design has good adaptability to the new design requirements and design changes in the design process. Designers can detect and correct errors as soon as possible.