1. Embedded systems are usually application-oriented.
The biggest difference between embedded microprocessors and general processors is that most embedded microprocessors work in systems designed for specific user groups. Embedded microprocessor usually has the characteristics of low power consumption, small size and high integration. , which can integrate many tasks completed by the board card in the general processor into the chip, thus contributing to the miniaturization of embedded system design, greatly enhancing the mobility, and becoming more and more closely coupled with the network.
2. Embedded system is the product of the integration of various technologies and industries.
Embedded system can be used in all fields of people's lives, and it is the product of the combination of advanced computer technology, semiconductor technology and electronic technology with specific applications in various industries. This determines that it must be a technology-intensive, capital-intensive and highly decentralized innovative knowledge integration system.
3. The software and hardware design of embedded system is efficient and can be cut.
Embedded system has strict requirements on cost and volume, which requires embedded engineers to design hardware and software efficiently, tailor products and remove redundancy, and strive to achieve higher efficiency in the same silicon chip area, so as to be more competitive in specific applications.
4. Solidification of embedded system software
In order to improve the execution speed and system reliability, the software in embedded systems is generally solidified in memory chips or microcontrollers, rather than stored in carriers such as disks.
5. The combination of product procurement and technology development.
Most general-purpose processor systems are developed by software engineering methods according to the needs of users. Users have complete technical data, which can be maintained and upgraded according to the needs of the application. The embedded system is generally built by purchasing off-the-shelf products and developing independently.
Embedded system is difficult to understand when the teacher speaks. But I believe that nothing is difficult in the world, nothing is impossible to a willing mind!
Basic subjects: C language, computer composition principle, discrete mathematics, data structure, microcontroller, ARM9 embedded system design basis, operating system, compilation principle, etc.
Embedded system itself is a vague definition, but it is generally considered in the industry to be a special computer system which is application-centered, based on computer technology and can be customized to meet the strict requirements of application system on function, reliability, cost, volume and power consumption. In fact, the embedded system we are talking about now is narrow, that is, a system based on an embedded microprocessor (such as ARM) embedded in an object to realize intelligent control, while the generalized embedded system is broader (such as microcontroller system, DSP system, etc. ). I hope these are helpful to you. The above are all my hope support according to my personal understanding.
Embedded system is a kind of "special computer system completely embedded in controlled equipment and designed for specific applications". According to the definition of the British Institute of Electrical Engineers, an embedded system is a device, machine or device used to control, monitor or assist the operation of a factory. Unlike general computer systems such as personal computers, embedded systems usually perform predefined tasks with specific requirements. Because the embedded system is only aimed at a special task, designers can optimize it, reduce its size and reduce its cost.
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Look at the question you asked, it should be that you are interested in embedded systems. In fact, you can teach yourself embedded systems. About how to learn embedded system, I just saw a good article, which was a junior college student who introduced how to learn embedded system by himself and found a job in embedded system. Introduced his learning methods and process, hoping to help you.
Let me introduce myself first. In 2007, I was admitted to a poor private college, majoring in biology. I won't say the specific name of the school. Dropped out of school in 2009. I'm in that school, and the annual tuition is more than 1000, but no one studies at all. I really didn't see any hope, so I dropped out of school.
After dropping out of school, I was also confused. I didn't graduate from junior college. I really don't know what I can do. I'm struggling with what I can do. So I want to find a job for a while after dropping out of school, because I am quiet and quiet, so I am not suitable for applying for entrepreneurship. I want to apply for a job as a technician, but I hit a wall everywhere.
By chance, I heard about the embedded industry. I went to Xinhua Bookstore that day and wanted to find a book to learn computer classification. Later, a girl came up to me and asked me if I studied computer and if I was interested in learning embedded system. Then she introduced me to the hot situation of embedded system, told me how promising it is to learn embedded system, and gave me a leaflet and an advertisement for embedded training. After listening to her introduction, I felt itchy. Indeed, I really want to learn my own skills and eat with my own hands.
After returning home, I checked the embedded system online. Now it is really a hot industry, and it is easy to find a job and the salary is relatively high. I made up my mind to learn embedded technology. So I went to find the information of embedded training. To tell you the truth, I was confused at that time, too. I don't know whether the training can really be as good as they advertised, so I just want to know for a while before making plans.
Later, I learned in Baidu that I saw an article encouraging me. It was an embedded expert who introduced how a friend who had no foundation taught himself how to embed. The article is well written, including how to learn and how to learn. He mentioned that one way is to watch videos, because reading books is so boring and confusing that we can't understand many books. I really agree with this. Often a person can't read a few pages.
I wonder why others can teach themselves, so can I! I want to believe in myself, so I want to teach myself. If I really can't learn, I'll go to training again.
With a clear idea, I went to search for embedded video. Although some embedded videos are found sporadically, they are not systematic. I want to find a video that can tell me how to learn, a set of videos from beginners to skilled people, and a relatively complete material. I'd better have a teacher to teach me, but I can ask if I don't understand.
Later, I found a very good video, which was a video "Zero-based Embedded Employment Course" launched on the website of the IT Learning Alliance (those who like "Zero-based Embedded Employment Course" can copy and paste the address bar of the browser in sina.lt/qKh, and press enter to open it). The tutorial inside is very good and complete, which allows me to learn from the basics. Video is cheaper.
Let me introduce my learning process, hoping to help my friends who have no foundation at all like me.
After receiving the CD they sent me, I began to study. Because there is no foundation, I start with the simplest C language video course. In short, there are still many things I don't understand, so I have to ask them. They were still very enthusiastic and helped me solve it. I studied C language for almost a week, and then I learned the basic commands of linux. I practiced on the linux virtual machine provided by them, typed the basic commands of linux and wrote simple C language code for almost three weeks. I insist on writing some simple codes every day, so I basically mastered the basic operations of C and linux after January.
Next, I went to learn other people's video training courses, which are very complete and not much different from attending training. It seems like two months. I learned the basic principle of ARM and the concept of embedded system, and also mastered the construction of some embedded environments. I also have a deeper understanding of linux and how embedded applications are done, but I only have a little knowledge of drivers. This is more difficult. I want to chew it slowly in the future.
In these two months, I have been studying almost all the time except eating and sleeping. Because I know that I have almost no foundation and am worse than others, I can only continue to work hard. I can't give up. I have to support myself. I must learn this technique well, and then I will sum up the problems I don't understand. After that, I slowly accumulated for a period of time, and I found myself really getting started.
In the last month, I went to see the content about practice, and learned about the specific development process of embedded projects and what kind of knowledge is needed. I began to prepare this knowledge, that is, to learn this video. At the same time, they suggested that I find some topics embedded in the interview to prepare for future job hunting. I went online to find many embedded topics and wrote them down. It took me about 20 days to prepare.
I think I'm getting started, and I can make some simple things. I just want to find a job, so I went to 5 1job to submit my resume crazily. Because of my education, I didn't graduate from junior college. Seriously, no one in the big company wanted me, so I invested in a small private enterprise. I hope my efforts will pay off. I didn't expect an interview in a few days, and the first interview failed. Although I think the written test is very good because of the preparation before, they are strict and need one year's project experience, so they are not selected.
Later, I interviewed several companies one after another, and finally it was worth it. Finally got an interview with a private company in Minhang. This company is relatively small. My post is embedded linux application development and security product application. I think I'm lucky, too. The manager attached great importance to my efforts and decided to hire me. The salary is 3500 a month. Although I know that 3500 can only live a life of food and clothing in Shanghai, I think I have enough. At least I don't have to rely on my parents every day. I can support myself. I think as long as I keep working hard, my salary will definitely double.
I write this article in the hope of giving confidence to friends who have no foundation like me. In fact, we don't need to feel inferior. We are no more stupid than others. We will succeed as long as we are willing to work hard.
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There is no specific specification. Strictly speaking, the main chips can burn programs, as well as microcontrollers, FPGAs, 8086 and so on. Both are embedded systems, but neither microcontroller nor FPGAs are embedded systems, so they are very small. Usually it is a large embedded system composed of ARM, etc.
The microcontroller can also run RTOS, as long as the hardware conditions meet the requirements of the system.
Digital circuit, analog circuit, microcomputer principle, combined language, passing the three-level pc technology by the way,
Then contact the specific single chip microcomputer, 5 1, avr can be used, high numbers must be learned well, and many electronic industries need to use mathematics. I recommend you to learn an embedded operating system-ucosii. As long as you have the foundation of C language, data structure and microcomputer principle, it is easy to get started.
What are the types of embedded systems?
IEEE defines an embedded system as a device for controlling, monitoring or assisting the operation of equipment, machines or factories. Embedded system is "a device for controlling, monitoring or assisting the operation of machines and equipment".
In the field of embedded system in China, the accepted concept of embedded system is that embedded system is application-centered, based on computer technology, and its software and hardware can be tailored, which is suitable for special computer systems with strict requirements on function, reliability, cost, volume and power consumption. It generally consists of four parts: embedded microprocessor, peripheral hardware devices, embedded operating system and user applications, which are used to control, monitor or manage other devices.
Embedded system generally refers to non-PC system, including hardware and software. Hardware includes processor/microprocessor, memory and peripheral devices, I/O port, graphics controller, etc. The software part includes operating system software (OS) (requiring real-time multitasking) and application design. Sometimes designers combine the two kinds of software. The application program controls the operation and behavior of the system; The operating system controls the interaction between applications and hardware.
The core of embedded system is embedded microprocessor. Embedded microprocessors generally have the following four characteristics:
1) has strong support for real-time multiplexing, can complete multiplexing, and has short interrupt response time, thus minimizing the execution time of internal code and real-time kernel.
2) It has powerful storage area protection function. This is because the software structure of embedded system has been modularized. In order to avoid the wrong cross-action between software modules, it is necessary to design a powerful storage protection function, which is also beneficial to software diagnosis.
3) The processor structure of the suite can be extended, so as to develop the embedded microprocessor that meets the highest performance of the application as quickly as possible.
4) Embedded microprocessors must have low power consumption, especially embedded systems powered by batteries used in mobile wireless and mobile computing and communication devices. When necessary, the power consumption is only mW or even μW level.
Compared with general computer systems, embedded computer systems have the following characteristics:
1. Embedded system is usually an application-oriented embedded CPU. The biggest difference between embedded CPU and general CPU is that most of them work in systems designed for specific users. They usually have the characteristics of low power consumption, small size and high integration, and can integrate many tasks completed by the board card in the general CPU into the chip, which is beneficial to the miniaturization of embedded system design, greatly enhances mobility and is more closely coupled with the network.
2. Embedded system is the product of advanced computer technology, semiconductor technology and electronic technology combined with specific applications in various industries. This determines that it must be a technology-intensive, capital-intensive and highly decentralized innovative knowledge integration system.
3. The hardware and software of embedded system must be designed with high efficiency, customization and redundancy, and strive to achieve higher performance on the same silicon chip area, so as to be more competitive in the selection of processors in specific applications.
4. Embedded systems are organically combined with specific applications, and their upgrades are also synchronized with specific products, so once embedded system products enter the market, their life cycle is long.
5. In order to improve the execution speed and system reliability, the software in the embedded system is generally solidified in the memory chip or microcontroller itself, rather than stored in the disk and other carriers.
6. The embedded system itself does not have bootstrap development capability. Even after the design is completed, users usually can't modify the program functions, and they must have a set of development tools and environment to develop.
Embedded system, embedded system has many directions, hardware, linux driver, dsp, fpga. What does your tutor do? Why not learn C programming under linux first? It is very popular now.
Embedded system is urgent! After entering the 2 1 century, with the continuous popularization and development of social informatization, the application of embedded system is more and more extensive. Among them, due to the limitation of power consumption, the design and application of embedded system with its own power supply are limited. Generally speaking, the current consumption of the embedded system is in the mA level during normal operation, but it can be controlled in the μA level in the dormant state. Three orders of magnitude of energy saving is undoubtedly a great temptation for the limited self-provided power supply, so this kind of system basically adopts the dormant activation scheme to realize energy saving and prolong the working life.
At present, there are three main sleep enabling schemes available: event enabling method, timing enabling method and positioning enabling method. The event activation method is mainly used to detect alarms and other occasions. The system is usually in sleep mode. If a specific argument goes beyond the limit, it will stimulate the system to work. This method is generally implemented with corresponding sensors, and the microprocessor also occupies corresponding interrupt resources. The timed activation method is mainly used in the system that works periodically (for example, the data acquisition of three electric meters in a community), and the system regularly reports the collected data according to the time interval set by the timer. This activation mode is also very convenient to realize, just add the interrupt handler of timer in the corresponding microprocessor; Location-enabled methods are mainly used in location-sensitive systems (such as management of valuable assets and automatic doors of parking lots). The system installs detection equipment at specific locations, and if supervisors or equipment leave or enter these specific areas, it will stimulate the system to work. There are many ways to realize location activation. This paper mainly introduces a method to realize location activation by using wireless signals.
The basic principle of 1
In the wireless signal spectrum, the signal in LF band has the characteristics of strong penetration, which can penetrate non-magnetic media such as water, concrete and plastic. (not limited by the line of sight), so it is a better scheme to design the enabling circuit using LF frequency band. The frequency of wireless signal is inversely proportional to the wavelength, and the antenna length depends on the wavelength length. The wavelength of 500 MHz RF signal is 60 cm, and the antenna is very short, which is easy to realize. 125 kHz low frequency signal has a wavelength of 2.4 km, so it is definitely not practical to make such an antenna. Therefore, if the LF band signal is used as the enabling signal, the receiving end will not work by using the electromagnetic field (radio) principle, but directly receive the magic signal, and then use the induced signal in the magnetic field coil for judgment processing, as shown in figure 1. The system mainly consists of two parts: magnetic field transmitter and receiver.
Figure 1 Working principle of magnetic field
MCP2030 is an analog front-end device specially developed by Microchip company for low-frequency wireless magnetic field communication. The device integrates 8 programmable configuration registers and 1 read-only status registers. According to the register configuration, MCP2030 can output demodulation data, carrier clock and magnetic field strength RSSI. The analog receiving circuit of the device has strong sensitivity, and can receive identification 1 mVpp signals and demodulate 8% weakly modulated signals. In order to obtain reliable magnetic field signals, MCP2030 adopts three groups of antennas and three groups of receiving and demodulating circuits. The three groups of antennas point to the mutually perpendicular X, Y and Z axes, so that no matter how the receiver is placed, the magnetic field signal can always be obtained, and the directivity problem of the magnetic field signal is solved. Its structural block diagram is shown in Figure 2.
Fig. 2 structural block diagram of MCP 2030
Fig. 3 MCP2030 with output
MCP2030 integrates the digital sequence filtering component of wireless signal, and can set the digital sequence as required. The device will only respond when it receives a specific digital sequence, so it can effectively avoid the activation phenomenon caused by other signal interference. Fig. 3 shows the case where the wireless digital sequence conforms to the set digital sequence. The specific digital sequence is the carrier signal of "2 ms with 2 ms without". At this time, LFDATA outputs ASK modulation signal after monitoring a specific sequence. If the wireless digital sequence does not conform to the set digital sequence, LFDATA has no output.
MCP2030 has the remarkable advantage of extremely low power consumption. In order to be used in embedded system with its own power supply, three working modes, namely sleep mode, standby mode and working mode, are specially designed and optimized. The sleep mode is controlled by SPI interface commands. After going to sleep, all circuits except registers, storage and SPI function circuits will be turned off to minimize current consumption (0.2 μA). It is necessary to wake up the device from sleep mode by power-on reset and any other SPI command except sleep command. When there is no LF signal at the antenna input, the device will automatically enter standby mode, but all circuits in the device are powered on and can receive input signals. The typical power consumption in standby mode is 4 μ A (three receiving antennas work). When there is a low-frequency signal at the input end of the low-frequency antenna and the internal circuit switches according to the received data, the equipment is in a low-current working mode, and the current consumption in this mode is only13μ a. ..
In addition, the device also supports half-power and no-power operation modes. In the working mode without power supply, the device completely extracts energy from the magnetic field to work; In the half-power mode, the equipment obtains energy from the magnetic field as much as possible, and is powered by the power supply if necessary.
2 Design application
Active RFID tag is an important part of RFID system, which has the advantages of large storage capacity, long communication distance and rich functions, and can be widely used in logistics tracking, valuable asset management and other fields. The main components of its internal circuit are: controller, enable signal detection circuit, RAM/ROM, timer, UHF transceiver, power supply and so on. The enable signal detection circuit can be realized by MCP2030, as shown in fig. 4. Using MCP2030' s ability to recognize and receive the set number sequence, the working state of the tag can be effectively controlled. When the tag arrives at the specific location where the RF-enabled transmitter is installed, MCP2030 outputs the corresponding receiving signal from SPI interface to make the controller exit the sleep state, receive, analyze and process the data, and finally store it in the corresponding location of RAM/ROM. When it is necessary to interact with the reader, the controller communicates through the UHF transceiver, and the controller automatically enters the sleep state after processing, until the next magnetic field enabling signal is received or the timer generates timing interruption.
Fig. 4 Enable signal detection circuit
As shown in fig. 4, MCP2030 is connected to the controller through SPI interfaces, which are defined as LFDATA, SCCLK and MCCS respectively. The interface command consists of 16 control words, and the command format is as follows:
D 13 ~ D 15 is the command type, and MCP2030 determines the meaning of subsequent data according to the command type and performs corresponding operations. Where 0x07 is a data write command and 0x06 is a data read command. If it is a data write or data read command, the following D9 ~ D 12 is the register address, respectively specifying the register address to be operated by the command, D 1 ~ D8 is the register data content, and D0 is the command line check information; The data content of D0 ~ D 12 is meaningless if it is not a command to write or read data.
In order to make MCP2030 work normally, the equipment should be initialized correctly when the system is powered on. Here, the digital filtering sequence of the wireless signal is set to 2 ms, with or without 2 ms, and the automatic channel selection function and the demodulation signal output function are enabled. The initialization program segment is as follows:
void Init_MCP2030(void) {
ShiftOutSpi(0xe 1，0x 4 1)； reg 0 1 1 1 0000 10 10 0000 1
ShiftOutSpi(0xe2，0x 0 1)； reg 1 1 1 1 000 1 0000 0000 1
ShiftOutSpi(0xe4，0x 0 1)； reg 2 1 1 1 00 10 0000 0000 1
ShiftOutSpi(0xe6，0x 0 1)； reg 3 1 1 1 00 1 1 0000 0000 1
ShiftOutSpi(0xe8，0x 0 1)； reg 4 1 1 1 0 100 0000 0000 1
ShiftOutSpi(0xeb，0x 8 1)； reg 5 1 1 1 0 1 1 1 100 0000 1
ShiftOutSpi(0xed，0x3f)； reg 6 1 1 1 0 10 100 1 1 1 1 1 1 1 1
}
The program of controller transmitting data to MCP2030 is realized as follows:
Data is pre-stored in OutData 1 and OutData2.
void shift out SPI(unsigned char outdate 1，unsigned char outdate 2){
Unsigned character I;
SCCLK = 0；
MCCS = 0；
for(I = 0； I<8; i++) {
lf data = outdate 1 & amp； 0x80
outdate 1 = outdate 1？ 1;
SCCLK = 1；
SCCLK = 0；
}
for(I = 0； I<8; i++) {
LFDATA = OutData2 & amp0x80
OutData2=OutData2？ 1;
SCCLK = 1；
SCCLK = 0；
}
MCCS = 1；
}
The program segment for the controller to receive data from MCP2030 is as follows:
Data is stored in AFESpiInDataH and AFESpiInDataL.
void ShiftInSpi(void) {
Unsigned character I;
SCCLK = 0；
MCCS = 0；
for(I = 0； I<8; i++) {
SCCLK = 1；
AFESpiInDataH = AFESpiInDataH & ampLFDATA
AFESpiInDataH=AFESpiInDataH？ 1;
SCCLK = 0；
}
for(I = 0； I<8; i++) {
SCCLK = 1；
AFESpiInDataL = AFESpiInDataL & amp； LFDATA
AFESpiInDataL=AFESpiInDataL？ 1;
SCCLK = 0；
}
MCCS = 1；
}
label
According to the characteristics of MCP2030, its application in active radio frequency tags is introduced. The device not only integrates a 3-channel low-frequency receiving circuit and a 3-direction magnetic field detection receiving circuit, but also has low power consumption, diverse working modes and energy saving, which is very suitable for other embedded system applications that need low-power wireless enabling.
Embedded system problems 1 mov
2 LDR
Only two instructions. Don't you get it?
I didn't learn well in getting started.