Meet embedded systems
Introduction of Embedded System
The embedded system is composed of hardware and software. It is a device that can operate independently. The software content only includes the software operating environment and its operating system. The hardware content includes signal processor, memory, communication module, etc. Embedded systems are application-centric, based on modern computer technology, and can flexibly tailor software and hardware modules according to user needs (function, reliability, cost, volume, power consumption, environment, etc.).
Summary of main points:
Application-oriented: Emphasize that the goal of embedded systems is to meet the specific needs of users. As far as most complete embedded systems are concerned, users can enjoy their functions directly after turning on the power, without the need for secondary development or only a small amount of configuration operations.
Speciality: Most of the applications of embedded systems have high requirements for reliability and real-time. This determines that the special system serving specific applications is the mainstream mode of embedded systems. It does not emphasize the versatility and availability of the system. Expand. This specificity usually also leads to an embedded system that is a final system with tight integration of software and hardware, because it can more effectively improve the reliability of the entire system and reduce costs, and make it have a better user experience.
Taking modern computer technology as the core: the most basic supporting technology of embedded systems, including integrated circuit design technology, system structure technology, sensing and detection technology, embedded operating system and real-time operating system technology, high resource-constrained systems Reliable software development technology, system formal specification and verification technology, communication technology, low power consumption technology, data analysis, signal processing and control optimization technology in specific application areas, etc. They are formed around the basic principles of computers and integrated into specific special equipment. An embedded system.
Software and hardware can be tailored: Embedded systems target so many application scenarios, and bring very different design index requirements (functional performance, reliability, cost, power consumption), so that in reality it is difficult to have a set of solutions to meet All system requirements, so according to different needs, flexible cutting hardware and software, and build a final system that meets the requirements is an inevitable technical route for the development of embedded technology.
Embedded system features
The hardware and software of the embedded system must be selected according to the specific application tasks, with power consumption, cost, volume, reliability, processing capacity, etc. as indicators. The core of the embedded system is the system software and application software. Due to the limited storage space, the software code is required to be compact and reliable, and there are strict requirements for real-time.
In terms of composition, an embedded system is a computer system that integrates software and hardware, and can work independently; in appearance, the embedded system is like a "programmable" electronic "device"; in terms of function, it It is a controller that controls the target system (host object) and makes it intelligent. From different perspectives of users and developers, compared with ordinary computers, embedded systems have the following characteristics.
(1) Strong specificity. Because embedded systems are usually oriented to a specific application, the hardware and software of the embedded system, especially the software, are designed for a specific user group, and usually have some special characteristics.
(2) Small size. The embedded computer integrates many tasks completed by the board in the general computer system into the chip, which is beneficial to miniaturization and facilitates the embedding of the embedded system into the target system.
(3) Good real-time performance. Embedded systems are widely used in production process control, data collection, transmission and communication, etc., mainly used to control the host object, so there are more or less real-time requirements for embedded systems. For example, for embedded systems in weapons, the real-time requirements of control systems in certain industrial control devices are extremely high. Some systems are not very demanding on real-time performance, for example, handheld computers, which have developed relatively fast in recent years. But overall, real-time is a common requirement for embedded systems, and an important indicator that designers and users should focus on.
(4) Good cutability. From the perspective of the specific characteristics of embedded systems, suppliers of embedded systems should provide a variety of hardware and software for alternative use, and strive to achieve higher performance on the same silicon area, so that specific More competitive in application.
(5) High reliability. Because the computing tasks undertaken by some embedded systems involve major issues such as the critical quality of the controlled product, the safety of personal equipment, and even state secrets, and the host objects of some embedded systems work in unattended situations, such as when the risk is high Monitoring device in industrial environment and harsh field environment. Therefore, compared with ordinary systems, embedded systems have extremely high requirements for reliability.
(6) Low power consumption. There are many embedded systems whose host objects are some small application systems, such as mobile phones, MP3s, digital cameras, etc. These devices cannot be configured with AC power supplies or large-capacity power supplies, so low power consumption has always been the goal pursued by embedded systems .
(7) The embedded system itself does not have self-development capabilities, and must be developed with the help of a general-purpose computer platform. After the design of the embedded system is completed, ordinary users usually have no way to modify the program or hardware structure in it, and they must have a set of development tools and environment.
(8) Embedded systems are usually implemented by "software and hardware collaborative design". Early embedded system design methods often used the principle of "hardware first", that is, in the case of only a rough estimate of software task requirements, first hardware design and implementation, and then software design on this hardware platform. If the traditional design method is adopted, once a problem is found in the test and the design needs to be modified, the entire design process will be re-run, which will have a great impact on the cost and design cycle. The design of the system relies heavily on the designer's experience. Since the 1990s, with the development of related technologies such as electronics and chips, software and hardware collaborative design methods have emerged in the design and implementation of embedded systems, that is, using unified methods and tools to describe, synthesize, and verify software and hardware. Guided by the requirements of the system, through comprehensive analysis of system hardware and software functions and existing resources, collaborative design of hardware and software architecture to maximize the ability of system hardware and software, to avoid the various design and hardware architecture caused by the independent Disadvantages, get high-performance, low-cost optimization design.
development process
1.
With no operating system, with the wide range of embedded microprocessors and microcontrollers throughout the development process of embedded systems, the initial application of embedded systems is generally based on single-chip microcomputers, mostly programmable controllers The form H = | Now, with monitoring, servo, equipment indication and other functions, usually used in various industrial controls and aircraft, missiles and other weapons and equipment, generally does not support the operating system, can only directly control the system through assembly language , And then clear the memory after running. Although these devices have initially possessed the characteristics of embedded applications, they only use 8-bit CPU chips to execute some single-threaded programs, so strictly speaking, the concept of "system" cannot be talked about. The main features of the embedded system at this stage are: relatively simple system structure and function, low processing efficiency, small storage capacity, and almost no user interface. Because this embedded system is easy to use and cheap, it has been widely used in the field of industrial control, but it cannot meet the needs of today's information appliances that have high requirements for execution efficiency and storage capacity.
2. The stage of simple operating system
In the 1980s, with the improvement of the level of microelectronics technology, IC manufacturers began to integrate microprocessors, I / O interfaces, serial interfaces, RAM, ROM and other components required for embedded applications. All integrated into a VLSI (Very Large Scale Integrated Circuit), manufacturing microcontrollers for I / O design, and at one fell swoop become a rising star in the field of embedded systems. At the same time, programmers of embedded systems began to develop embedded application software based on some simple "operating systems", which greatly shortened the development cycle and improved development efficiency. The main features of embedded systems at this stage are: a large number of highly reliable, low-power embedded CPUs (such as PowerPC, etc.), various simple embedded operating systems began to appear and developed rapidly. Although the embedded operating system at this time is relatively simple, it has initially had a certain degree of compatibility and scalability. The kernel is compact and efficient, and is mainly used to control system load and monitor the operation of application programs.
3. Real-time operating system stage
In the 1990s, under the traction of huge demands such as distributed control, flexible manufacturing, digital communications, and information appliances, embedded systems further developed rapidly, while DSP products for real-time signal processing algorithms were toward high speed, high precision, and low power. The direction of consumption. With the improvement of hardware real-time requirements, the software scale of embedded systems has been continuously expanded, and a real-time multi-task operating system (RTOS) has gradually formed, and it has become the mainstream of embedded systems. The main characteristics of the embedded system at this stage are: the real-time performance of the operating system has been greatly improved, it has been able to run on various types of microprocessors, with a high degree of modularity and scalability. At this time, the embedded operating system already has functions such as file and directory management, device management, multitasking, network, and graphical user interface (GUI), and provides a large number of application programs connected to EI (API), which makes the application software Development becomes easier.
4. Facing the Internet stage The
21st century will undoubtedly be an era of networks, and the demand for the application of embedded systems in various network environments will naturally increase. At present, most embedded systems are still isolated from Internet. With the further development of Internet, and the increasingly close integration of Internet technology with information appliances, industrial control technology, etc., the combination of embedded equipment and Internet is the real embedded technology. future.
