Design scheme using ARM7 network car anti-theft system

Overview : The shortcomings of the popular types of conventional anti-theft devices were analyzed, and a new embedded car anti-theft system was successfully researched and successfully produced. The system is developed based on ARM's S3C44B0X microprocessor, which improves the stability and scalability of the system. It uses the network advantage of GPRS to achieve the purpose of remote control, and has other existing functions of the car alarm system to reliably implement the anti-theft control function. .

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introduction

With the improvement of people's living standards, cars have gradually entered the family, but the increasingly rampant cases of car theft are also on the rise. How to effectively prevent car theft is the most concerned issue for car owners. In recent years, science and technology have developed rapidly, and new types of car anti-theft devices combined with various new technologies have emerged. With the development of communication technologies, wireless telecommunications technology has also been applied in the automotive field. Based on S3C44B0X network type car anti-theft control system is an embedded system constructed with ARM 7 microprocessor. It combines traditional anti-theft technology and new GPRS wireless communication technology to realize the existing functions of the existing anti-theft device. Remote control features increase the security, flexibility and reliability of the anti-theft system.

1 system design

1 . 1 System features and functions

After analyzing the characteristics of various types of car anti-theft systems, the S3C44B0X network-based car anti-theft control system is designed, which makes full use of the advantages of GPRS wireless communication technology based on GSM network: ubiquitous, fast access, always online, traffic Billing and other features. At the same time, it also takes advantage of the ARM7 microprocessor: 32-bit core, high-performance, low-cost, low-power RISC microprocessor, there are many cooperative development partners. Due to the increasingly complex functions of the anti-theft system, in order to facilitate the effective development of system programs and the expansion of system functions, embedded systems are used for development, which improves the flexibility, security and reliability of the system. The main functions of the system are as follows:

(1) Based on the GSM global networking function, the GPRS communication network is used to realize the nationwide burglar alarm function.

(2) Intelligent remote control or using a mobile phone to realize the lock and unlock function, convenient and quick access to the anti-theft state and the anti-theft state.

(3) Once the alarm occurs, you can send the message to your mobile phone in a short time, realize the silent automatic alarm, and achieve the unique effect of “I know the thief does not know”.

(4) When the vehicle is robbed or stolen, use the mobile phone to send a control message to the car alarm device to realize power failure or fuel cut, and force the car to stop.

(5) After the anti-theft setting, the car door, the trunk, the hood, or the vehicle are vibrated without the permission of the owner, and the alarm message and the short message can be sent to the owner's mobile phone.

(6) The microcomputer is powered off and cut off, and enters the anti-theft state. The microcomputer is automatically powered off and the fuel is cut off by the microcomputer. The vehicle cannot be started.

(7) After entering the anti-theft state, even if the thief cuts off the power, it can alarm as usual, and the alarm will be sent once every 1 minute, that is, the information will be sent to the mobile phone.

1 . 2 system hardware design

The system hardware is mainly composed of two parts: one is to build an embedded system platform with S3C44B0X microprocessor, the external GPRS module is used as the main control board for automobile anti-theft; the other part is the automotive circuit signal interface board, which is mainly used to obtain The status signal of the car and the transmission of control signals to the car. Figure 1 is a hardware block diagram of the system.

The CPU uses SAMSUNG's ARM7 series chip S3C44B0X. The S3C44B0X has excellent core performance, a rich external interface and low power consumption. The system clock is 66MHz, supports LCD, has 8 memory BANK, the maximum memory can be expanded to 256M, and is convenient to connect various types of memory; can run the operating system without MMU management, can realize more complicated control efficiently and conveniently; In the system we use 2 kinds of memory, a kind of SDRAM, a kind of FLASH;

Figure 1 system hardware block diagram

SDRAM dynamic memory, running fast, but can not save data after power failure, the system is mainly used to run the operating system, applications and various types of data cache, SDAM type, there are various manufacturers of products, performance difference is not too Large, mainly considering the memory capacity, we choose a more general-purpose chip, hynix HY57V641620HC, which is 1M × l6bit × 4bank synchronous DRAM.

FLASH memory runs slower than SDRAM, but can save data after power down. FLASH has two types of NAND and NOR. The NOR is characterized by on-chip execution, so that the application can run directly in the flash memory without having to read the code into the system RAM. The transmission efficiency of NOR is very high, and it is very cost-effective in a small capacity of 1 to 4 MB, but the slower writing and erasing speed greatly affects its performance. The NAND structure provides extremely high cell density, high memory density, and fast write and erase speeds. The difficulty in applying NAND lies in the management of flash and the need for special system interfaces. A universal FALSH (SST39LV160) is also used in the system with a capacity of 2MB, which is mainly used to cure the startup code and control application, and save some system data and the owner's mobile phone number.

Communication with mobile phones, using SIM100 GSM/GPRS module provided by SIMCOM Co., Ltd., this module has a standard AT command interface, which can provide services such as GSM voice, SMS and GPRS Internet access. Remote wireless anti-theft control is implemented by means of short messages in the system.

In the system also added LCD and keyboard, LCD uses 1602, can display 2 lines of characters, 16 letters per line, mainly used to display some prompts and status information, the keyboard is used to set the owner's mobile phone number.

The main control board has an interface with the car control detection board. Through the detection interface, the main control board can obtain the current state of the car, such as the door opening and closing state, the foot brake and the hand brake state, whether the car is started, etc., according to these states. It is convenient for the controller to implement corresponding control on the car. The main control board controls the car through the control interface, mainly the control of the double lamp, the alarm horn and the broken fire.

1 . 3 system software design

The software system for car theft prevention can be divided into two parts: one is the processing of the arming state; the other part is the processing without the arming state.

In the fortified state, when the car is stolen or destroyed, the alarm will sound and light alarm, and send an alarm message to the owner's mobile phone. The owner will make a true and false judgment according to the information: if it is a real alarm, it can alarm and control the car to break the fire at the same time. If it is a false alarm, the alarm can be revoked by the mobile phone and the car is again in anti-theft monitoring state. The fortification state is further divided into audible anti-theft and silent anti-theft. Under the audible anti-theft, if it is stolen, the sound and light alarm at the same time; in the case of silent anti-theft, if it is stolen, only the light alarm, no sound alarm, in two cases, Stolen short messages will be sent to the owner's mobile phone.

In the unarmed state, there will be no alarm. Only in some illegal operation, the owner will be prompted with danger through sound and light. If the car is started, the door is not closed. The overall process of the system software is shown in Figure 2.

Figure 2 The overall process of the system software

3 system key technology

There are two key technologies used in the system, one is GPRS remote wireless data transmission, and the other is FLASH memory reading and writing.

3 . 1 GPRS data transmission process

GPRS remote wireless data transmission is mainly through the serial port to send and receive SMS messages to SIM100 GSM/GPRS. When a text message arrives, SIM100 GSM/GPRS will send "+CMTI: "SM", N" to the serial port of ARM, where N is the SMS number. For example, if N is 5, after the serial port receives the short message, the processing function first parses the ID of the received short message according to the content of "+CMTI: "SM", 5", and packs it into "AT+CMGR= The 5" command is sent to the GPRS module. After about 1~2 seconds, the module will return a confirmation data "AT+CMGR=5". After a while, the module will return the SMS with ID number 5, and its content is: "+CMGR: "RECREAD", "+8613978319414", "04/07/22, 10:54:23+00" #13#10dX# 13#10#13#10 OK". In order to ensure the legality of the control, the program first checks the legality of the sent short message number. Only the content of the short message that matches the set mobile phone number is processed as a control command, and the other short messages are shielded. Prevent erroneous operations.

If the short message is sent through the GPRS module, the ARM system first sends a control command "AT+CMGS=XXXX" to the GPRS module, and the GPRS module returns the message "AT+CMGS=XXXX#13#10>" after receiving the command, waiting for the input to be sent. SMS content. If the content is "Your Car Has Stolen!", the system program first sends the content to the GPRS module through the serial port, and then sends the confirmation command "ctl+z", indicating that the data transmission is completed. After receiving the short message data and confirmation command, the GPRS module immediately returns "AT+CMGS=XXXX#13#10>#13#10 Your Car Has Stolen!#13#10" information to the ARM system, indicating the data and commands sent by the system. Has been received by the GPRS module. Then the GPRS module sends the short message data to the owner's mobile phone. After about 5 seconds, the GPRS module returns to the system whether to send the successful feedback information, if it returns "#13#10+CMGS:19#13#10#13#10 OK#13# 10" indicates successful transmission and ends. If the return "ERROR" indicates that the transmission failed, the system will continue to send the same content SMS in the next round of rotation until the transmission is successful.

3 . 2 FLASH reading and writing technology

Since the FLASH memory of different manufacturers is different in structure and read and write operations, the programming and erasing procedures of the FLASH memory are generally not versatile. The FLASH used by the system is SST39LV160, which can read, write or erase any sector without affecting other parts of the data. The programming instruction for FLASH can only change the binary bit from '1' to '0', and the erase command can make '0' become '1', so the correct operation sequence must be erased first, then programmed, otherwise This will cause the FLASH memory to be reset, causing the operation command to be incomplete. When the FLASH memory is erased, the contents read are all 0XFF.

There are several fixed steps to follow when programming the SST39LV160. Each step begins by writing an address and data command to a particular register of the FLASH memory, which is then automatically programmed or erased by its internal programming or erasing algorithm. For the erase operation, the first step writes data 1 (0XAAAA) to address 1 (0X5555), the second step writes data 2 (0X5555) to address 2 (0X2AAA), and the third step writes data to address 1 (0X5555). 3 (0X8080), this completes the first phase of erasing the sector, and the second phase is almost the same as the first phase, except that the last time is to write data 0X3030 to address 0X10000, and then the program uses a loop to detect Whether the content of the sector has become 0XFF. If the content of the sector becomes 0XFF, then the operation of erasing the sector has been completed, and the next operation can be performed to write the data to the specified address of the FLASH. Write operation is similar to erase, and it also follows several fixed steps. The specific steps should refer to the technical data of the corresponding FLASH chip. The data should be checked after the write operation is performed. If the write is successful, the next byte is written. Otherwise, it waits. If it times out, it exits. Since it takes a certain amount of time to program or erase, the program should judge whether the operation is completed or the operation is correct according to its internal operation detection mechanism to determine whether to perform the next step.

In our system, the system program uses the FLASH No. 17 sector to store the owner's mobile phone number, starting from the first address. Usually the operation procedure for the sector is: first read all the contents of the sector into the SDRAM (4K in total), and then write the telephone number to be written to the 11 units after the first address of the 17 sector, because We don't use all the No. 17 sectors, so we can save the steps of reading 4K content to SDRAM. We only need to start directly to the first address of the 17th sector, 0x10000, and write the mobile phone number of the owner.

4 conclusion

The system adopts embedded development technology, and develops a mobile phone-based car anti-theft system by using S3C44B0X and GPRS communication module. The system can realize remote wireless monitoring function of the car through the owner's mobile phone. It makes full use of the advantages of GPRS network, can be monitored 24 hours a day, low cost, and achieve complete self-service. No matter where you are, you can know the specific conditions of the vehicle through the mobile phone inquiry; you can remotely control the vehicle from the door lock, remote start to command stop. It has been proved by experiments that this is a product with stable performance, safety and high cost performance. The system will further integrate with Global Positioning System (GPS) and Traffic Geographic Information System (GIS) to achieve a more powerful car anti-theft monitoring network.

The author's innovation point: the use of embedded development technology, the use of S3C44B0X and GPRS communication module to develop a mobile phone-based car security system, the system can achieve remote wireless monitoring of the car through the owner's mobile phone.

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