Embedded system (Embedded system) is a "special-purpose computer system completely embedded in the controlled device and designed for specific applications". According to the definition of the UK Institution of Electrical Engineers, an embedded system is a control , monitoring or auxiliary equipment, machinery or equipment used in the operation of a plant. Unlike general-purpose computer systems such as personal computers, embedded systems typically perform predefined tasks with specific requirements. Because an embedded system is targeted at a specific task, designers can optimize it to reduce size and cost. Embedded systems are usually mass-produced, so a single cost savings can be scaled up by hundreds or thousands as volumes are produced.

Embedded systems are systems used to control or monitor large-scale equipment such as machines, devices, and factories. The definition of embedded system generally recognized in China is: a special computer system centered on applications, based on computer technology, software and hardware can be tailored, and adapted to the strict requirements of application systems on function, reliability, cost, volume, and power consumption. Typically, an embedded system is an embedded processor control board with a control program stored in ROM. In fact, all devices with digital interfaces, such as watches, microwave ovens, video recorders, cars, etc., use embedded systems, some embedded systems also contain operating systems, but most embedded systems are completely controlled by a single program logic.

The core of an embedded system is composed of one or several microprocessors or single-chip microcomputers pre-programmed to perform a few tasks. Unlike a general-purpose computer, which can run software chosen by the user, software on an embedded system is usually temporary; hence the name "firmware".

features

Embedded system is user-oriented, product-oriented, and application-oriented, and it must be combined with specific applications to have vitality and advantages. Therefore, the meaning of the above three aspects can be understood in this way, that is, the embedded system is closely integrated with the application, it has strong specificity, and must be reasonably cut and utilized in combination with actual system requirements.

◆ Embedded system is the product of combining advanced computer technology, semiconductor technology and electronic technology with specific applications in various industries, which determines that it must be a technology-intensive, capital-intensive, highly decentralized and innovative knowledge integrated system. Therefore, to get involved in the embedded system industry, one must have a correct positioning. For example, the reason why Palm occupies more than 70% of the market in the PDA field is because it is based on personal electronic consumer goods and focuses on the development of graphical interfaces and multi-task management; High real-time and high reliability.

◆ Embedded systems must tailor software and hardware according to application requirements to meet the requirements of the application system's functions, reliability, cost, and volume. Therefore, if we can establish a relatively common software and hardware foundation, and then develop a system that meets various needs on it, it is a better development model. The core of the current embedded system is often a microkernel with only a few K to dozens of K, which needs to be expanded or cut according to actual use, but due to the existence of the microkernel, this expansion can be carried out very smoothly.

In fact, embedded system itself is a very broad term. Any control system with embedded features combined with products can be called embedded system, and sometimes it is difficult to give it an accurate definition. Now when people talk about embedded systems, they refer to a certain extent to the embedded systems with operating systems that have been popular in recent years. This article also follows this point of view when analyzing and looking ahead.

Generally speaking, the architecture of an embedded system can be divided into four parts: processor, memory, input/output (I/O) and software (because the application software and operating system of most embedded devices are closely integrated, here we This is also the biggest difference between embedded systems and general PC operating systems).

There are several reasons for the upsurge of embedded system applications in these years: first, the development of chip technology has made a single chip have stronger processing capabilities, and it has become possible to integrate multiple interfaces. Focus on this. Another reason is the need for applications. Due to the improvement of product reliability, cost, and replacement requirements, embedded systems have gradually emerged from pure hardware implementations and applications implemented using general-purpose computers, and have become a concern in recent years. focus.

From the above definition, we can see several important characteristics of embedded systems:

1. The system kernel is small. Because embedded systems are generally applied to small electronic devices, system resources are relatively limited, so the kernel is much smaller than traditional operating systems. For example, Enea's OSE distributed system has a kernel of only 5K, but the Windows kernel? There is simply no comparison.

2. Strong specificity. Embedded systems are highly personalized, and the software system and hardware are very closely integrated. Generally, the system needs to be transplanted for the hardware. Even in the same brand and the same series of products, it is necessary to continuously adapt to the changes and increases or decreases of the system hardware. to modify. At the same time, for different tasks, it is often necessary to make major changes to the system. The compilation and download of the program must be combined with the system. This modification and the "upgrade" of general software are completely two concepts.

3. The system is streamlined. Embedded systems generally do not have a clear distinction between system software and application software, and do not require their functional design and implementation to be too complicated, which is conducive to controlling system costs and realizing system security.

4. High real-time system software (OS) is the basic requirement of embedded software. And software requires solid-state storage to increase speed; software code requires high quality and high reliability.

5. If embedded software development wants to move toward standardization, it must use a multitasking operating system. The application program of the embedded system can run directly on the chip without an operating system; but in order to reasonably schedule multi-tasks, utilize system resources, system functions and interface with expert library functions, users must choose RTOS (Real-Time Operating System) by themselves Development platform, so as to ensure the real-time performance and reliability of program execution, reduce development time, and ensure software quality.

6. Embedded system development requires development tools and environments. Because it does not have the ability to bootstrap development, users usually cannot modify the program functions even after the design is completed. A set of development tools and environment are required for development. These tools and environments are generally based on software on general-purpose computers. Hardware equipment and various logic analyzers, mixed signal oscilloscopes, etc. When developing, there are often the concepts of host and target machine. The host is used for program development, and the target machine is used as the final execution machine. It needs to be combined alternately during development.

7. Embedded systems are organically combined with specific applications, and upgrades are carried out simultaneously. Therefore, once an embedded system product enters the market, it has a long life cycle.

8. In order to improve the operating speed and system reliability, the software in the embedded system is generally solidified in the memory chip.

Application field

Embedded system technology has very broad application prospects, and its application fields can include:

industrial control

Industrial automation equipment based on embedded chips will achieve considerable development. At present, there are already a large number of 8, 16, and 32-bit embedded microcontrollers in application. Networking is the main way to improve production efficiency and product quality, and reduce human resources. For example, Industrial process control, digital machine tools, power systems, power grid security, power grid equipment monitoring, petrochemical systems. As far as traditional industrial control products are concerned, low-end models often use 8-bit microcontrollers. However, with the development of technology, 32-bit and 64-bit processors have gradually become the core of industrial control equipment, and will surely gain considerable development in the next few years.

traffic management

Embedded system technology has been widely used in vehicle navigation, traffic control, information monitoring and car services. Mobile positioning terminals with embedded GPS modules and GSM modules have been successfully used in various transportation industries. At present, GPS equipment has entered the homes of ordinary people from cutting-edge products. It only costs a few thousand yuan to find your location anytime and anywhere.

Information appliances

This will be called 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. Even if you are not at home, you can also carry out remote control through telephone lines and the Internet. In these devices, embedded systems will be of great use.

Smart home management

Remote automatic meter reading of water, electricity and gas meters, safety fire prevention and anti-theft system, the special control chip embedded in it will replace the traditional manual inspection and achieve higher, more accurate and safer performance. At present, in the field of services, such as remote ordering devices, etc., the advantages of embedded systems have been reflected.

POS network

Public transportation contactless smart card (Contactless Smartcard, CSC) issuance system, public telephone card issuance system, vending machines, and various smart ATM terminals will fully enter people's lives. By then, you can travel all over the world with one card.

Environmental Engineering

Real-time monitoring of hydrological data, flood control system and water and soil quality monitoring, dam safety, earthquake monitoring network, real-time meteorological information network, water source and air pollution monitoring. In many areas with harsh environments and complex terrain conditions, embedded systems will realize unmanned monitoring.