Windows CE embedded Navigation System (Overview of embedded systems)

1.1 Overview of embedded systems 1.1.1 definition and composition of Embedded Systems

Embedded systems are application-oriented, computer-based, and can be used to reduce hardware and software. They are suitable for application systems, dedicated computer systems with special requirements for functions, reliability, cost, volume, and power consumption. The essential difference between an embedded system and a general computer system is that the system applications are different. an embedded system embeds a computer system into an object system. This object may be a huge machine or a small handheld device. users do not care about the existence of this computer system. Embedded systems involve computer technology, microelectronics technology, electronic technology, communication and software, and other industries. They are a Knowledge Integration System with intensive technologies, capital-intensive, highly dispersed, and constantly innovated.

Embedded systems generally include four parts: embedded microprocessor, peripheral hardware devices, embedded operating systems and applications. Any embedded system includes both hardware and software. The Hardware includes the microprocessor, memory, I/O port, and graphics controller. Software includes operating system software and application software. application software controls the operation and behavior of embedded systems, while the operating system provides necessary underlying support for applications. Figure 1.1 shows the composition of a typical embedded hardware platform [3].

Figure 1.1 Composition of the embedded hardware platform

1.1.2 embedded system hardware

The core component of an embedded system is an embedded processor. According to incomplete statistics, there are more than 1000 types of embedded microprocessor in the world, and more than 30 popular architectures. In recent years, the main development direction of embedded microprocessor is small size, high performance, low power consumption. The division of professional work is becoming more and more obvious. There are professional IP (intellectual property core, Intellectual Property core) suppliers, such as arm and MIPS. By providing high-quality and high-performance embedded microprocessor kernels, various Semiconductor manufacturers produce chips for various application fields. Generally, an embedded microprocessor can be divided into four categories: Microprocessor Unit (MPU), microcontroller unit (MCU), and digital signal processor, DSP and embedded on-Chip Systems (SOC ).

Embedded processors generally have the following four features:

(1) strong support for real-time multi-task operating systems. Multi-task execution and short interrupt response time can be implemented to minimize the execution time of internal code and real-time kernel.

(2) has a powerful storage area protection function. The software structure of the embedded system is generally modular. To avoid the crossover of errors between software modules, a powerful storage zone protection function needs to be designed, which is also conducive to software fault diagnosis.

(3) The processor structure is scalable. It can quickly develop embedded microprocessor that meets various applications and high performance.

(4) low power consumption. Especially for Embedded Systems of portable wireless and mobile computing and communication devices, the power consumption can reach MW or even μW.

1.1.3 Embedded System Software

Embedded System Software generally consists of embedded operating systems and application software. An operating system is a system program that connects computer hardware and applications. The operating system has two basic functions: making computer hardware easy to use and efficiently organizing and correctly using computer resources. The operating system has four main tasks: process management, inter-process communication and synchronization, memory management, and I/O resource management.

Embedded operating systems can be divided into real-time operating systems and time-sharing operating systems. A real-time operating system is an operating system that supports real-time control of the system. The first task of a real-time operating system is to schedule all available resources to complete real-time control tasks. The second task is to improve the efficiency of computer use, it is important that task scheduling is used to respond to important events correctly within the specified time. For a time-based operating system, the execution of the software is not strictly required. The delay or timing errors generally do not cause disastrous consequences. For real-time operating systems, the main task is to process events in real time. Although the events may arrive at unpredictable times, the software must randomly, respond within a strict time limit (system response time ). Even if the system is under a peak load, the system's time response exceeds the limit, which means a fatal failure. In addition, the real-time operating system is characterized by system certainty, that is, the system can make accurate estimates of the best and worst cases of operation.

According to the survey, there are more than 200 embedded systems around the world. Since 1980s, some commercial embedded operating systems have emerged, most of which are developed for proprietary systems. With the development of the embedded field, a variety of embedded operating systems have emerged one after another. There are many commercial embedded operating systems and a large number of open source embedded operating systems. Common embedded operating systems include: vxWorks, neculeus, WinCE, embedded Linux, μ c/OS and μC/OS-II, palmos, QNX, Delta OS, hopen OS, PSOs, etc. The application software of embedded systems is a computer software based on the embedded hardware platform and can complete user's expected tasks in a specific field of practice. Your tasks may require time and precision. Some applications require the support of embedded operating systems, but do not require specialized operating systems in simple application scenarios.

1.1.4 features of Embedded Systems

Embedded systems are user-oriented, product-oriented, and application-oriented. They must be combined with specific applications to have advantages. Embedded systems are very specific and must be tailored to application requirements to meet the functional, reliability, cost, volume, and other requirements of the application system. In an embedded system, specific applications determine the requirements for hardware and software, such as chips, memory, I/O extensions, operating systems, and application programming [3].

Compared with general computer systems, embedded computer systems have the following features:

(1) embedded systems are applicable to specific system applications. Most embedded processors are specially designed for specific applications. They have the characteristics of low power consumption, small size, and high integration. Generally, they are on-chip systems that contain interfaces of various peripheral devices.

(2) embedded systems involve computer technology, microelectronics technology, electronic technology, communication and software, and other industries, it is a technology-intensive, capital-intensive, highly dispersed, and constantly innovative knowledge integration system.

(3) The hardware and software of the embedded system must be highly customizable. Only in this way can embedded system applications be applied and competitive in terms of product price and performance.

(4) the lifecycle of an embedded system is quite long. After an embedded system is applied to a product, software upgrade can be performed, and its lifecycle is almost the same as that of the product.

(5) embedded systems do not have local system development capabilities. They usually need a set of specialized development tools and environments.

1.1.5 application fields of Embedded Systems

The concept of embedded systems has been put forward for a long time and is mainly used in military and industrial control fields. With the development of digital technology and the emergence of new smaller control chips and more powerful operating systems, embedded systems have been widely used in many fields, such as national defense, industrial control, communication, office automation, and consumer electronics. Today's embedded systems bring about an annual industrial output of more than $1 trillion.

(1) Industrial Process Control: at present, a large number of 8, 16, and 32-bit embedded controllers have been applied in industrial process control, numerical control machine tools, power systems, power grid security, power grid equipment monitoring, petrochemical systems, and other fields. With the development of technology, 32-bit and 64-Bit Microprocessor has gradually become the core of industrial control equipment and will surely achieve greater development in the next few years.

(2) Traffic Management: Embedded System technology has been widely used in vehicle navigation, traffic control, information monitoring and automotive services, mobile Positioning terminals embedded with GPS and GSM modules have been successfully used in various transportation industries.

(3) Information appliances: this will become the largest application field of embedded systems. The networking and intelligence of refrigerators and air conditioners will lead people's lives into a new space. Remote control can be performed through telephone lines and networks even if you are not at home. Embedded Systems will be useful in these devices.

(4) Smart Home Management System: remote automatic meter reading of water, electricity, and gas meters, security, fire prevention, and anti-theft systems. The embedded dedicated control chip will replace the traditional manual inspection, and achieve higher, more accurate and safer performance.

(5) POS network and e-commerce: contactless smatrcard and CSC) the distribution system, public telephone card distribution system, vending machines, and various smart atm terminals will all enter people's lives.

(6) environmental monitoring: including real-time hydrological data monitoring, flood control system and soil and water quality monitoring, dam security, earthquake monitoring network, real-time meteorological information network, water source and air pollution monitoring. In many areas where the environment is harsh and complex, the embedded system will implement unattended monitoring.

With the development of information technology, human beings have entered a new digital age. It is no exaggeration to say that embedded systems have entered all aspects of people's life in modern society ", especially for control applications. For a long period of time, embedded technology will develop rapidly in the consumer electronics field, and embedded products will be more closely integrated with people's daily lives.