Traditional monitoring systems can be roughly divided into four types: anti-theft and fire alarm monitoring systems, access control systems, attendance or patrol systems, environmental detection systems, video surveillance systems, and currently on the market usually comprehensively monitor a certain area (such as a warehouse) Management is a simple addition of the above four types of monitoring systems, and the sub-systems are relatively independent, and they are not integrated until the upper-level monitoring center. The single networking mode of the system may also cause the system to be less robust and not capable of handling emergencies. In view of such a situation, an intelligent integrated monitoring base station solution based on the 32-bit high-performance processor AT91RM9200 is improved in this paper .
1 System structure
The biggest feature of this base station is the comprehensive integration of various subsystems at the bottom, and the use of PSTN, GPRS and TCP / IC three networking methods. It is an absolute advantage in terms of cost, degree of intelligence, and ease of installation and use. The system structure is shown in Figure 1.
The entire system can be divided into two parts: the upper-level monitoring center and the lower-level monitoring base station. The monitoring base station and the monitoring center are connected by Ethernet or telephone network. In addition, managers can also access the monitoring base station via GPRS. The monitoring base station is connected with front-end temperature and humidity transmitters and other environmental data measurement equipment and access control card readers by RS485 bus, and multiple devices can be mounted according to actual needs. The smoke sensor and infrared alarm are generally in the form of dry contact output, and can be mounted to the digital interface of the base station; the magnetic door lock can also be mounted to the digital interface of the base station through a dedicated access control power supply, in order to reduce video transmission Data volume, the data line of the camera is compressed by the MEPG4 video compression coding device, and then the compressed data stream is read to the base station buffer through the USB main port of the base station, and then sent to the upper monitoring center through the network, which is decoded and read by the upper monitoring center.
This architecture has good scalability, can easily increase or decrease the number of monitoring base stations according to the actual situation, and has little effect on the upper-level monitoring center. In addition, the system has flexible network control management functions, as long as given permissions , Any computer on the network can be used as a monitoring center for remote monitoring, to achieve a hierarchical, networked and distributed monitoring management.
2 Hardware composition and design
In order to realize this scheme as soon as possible, quickly build a prototype, the modular design idea is adopted in the hardware design, the hardware structure diagram is shown in Figure 2.
2.1 Minimal system
The smallest system is the processing center of the base station. The main chip uses Atmel's high-performance embedded chip AT91RM9200 based on the ARM920T core, and the operation speed is up to 200MIPS. AT91RM9200 integrates a wealth of peripheral components, including system peripherals and application (user) peripherals. System peripherals include power management controller (PMC), system timer (ST), real-time clock (RTC), advanced interrupt controller (AIC), parallel I / 0 (PIO) controller, debug unit (DU); application peripheral Including USB host port, USB device port, Ethernet 10 / 100BaseT MAC controller, multimedia flash memory (MMC) card interface, synchronous serial control (SSC), USART, serial peripheral interface (SPI), TWO-wire two-wire interface , Timer / Counter. The AT91RM9200 integrates high-speed on-chip SRAM and a low-latency external bus interface (EBI). The EBI provides a seamless connection to external memory or peripherals mapped in the memory. The EBI has a built-in controller for controlling synchronous DRAM, flash memory and static memory in burst access mode; EBI also provides interfaces with SmartMedia, CompactFlash and NAND Flash. The extensible Flash interface provides convenience for the upgrade and expansion of the entire system.
The main chip is connected with 1 piece of 16 MB Flash and 2 pieces of 16 MB SDRAM to expand the storage space and memory. The storage space and memory size can be further expanded according to the actual application needs.
2.2 Peripheral interface
Peripheral interfaces include 1 USB main port, 2 RS485 serial interfaces, 2 RS232 serial interfaces, 1 Ethernet port, 1 RS232 debugging serial port, 1 JTAG port, 3 dry contact input interfaces, 3 digital channels Quantity output interface, 5 V power input interface.
The USB main port is used for the transmission of the data stream of the video compression module; for the convenience of software design, considering the different RS485 device protocols, two RS485 interfaces are designed, one for connecting the temperature and humidity transmitter of Dalian North Measurement and Control Group, one It is used to connect the RS485 card reader of Guangzhou Micropower Company; two RS232 serial interfaces, one is used to connect the GPRS M0DEM of Shenzhen Baiyi Company, and one is used to connect the embedded modem of Beijing Tianshi Company to achieve GPRS access and The function of accessing the telephone network; one Ethernet port realizes the function of accessing the Ethernet; 3 dry contact input interfaces are used to connect the smoke sensors and passive infrared detectors of Shenzhen Dilek Company; 3 digital output interfaces pass electromagnetic The relay can control door magnetic locks, air conditioners, fire sprinklers, sound and light alarms, etc. according to actual needs.
AT91RM9200 integrates a wealth of peripheral components, so only a small number of chips can be used to design the peripheral interface.
2.3 Video compression module
The video compression module was originally integrated with the base station. Considering the actual application, in some cases, there is no Ethernet, and it can only be connected to the monitoring center through the telephone network. In this case, the video transmission is meaningless, so the video compression module is independent and can be applied and video surveillance is required. On occasion, mount the video compression module to the USB main port of the base station.
In order to shorten the development cycle, the video compression module adopts the multi-format MPEG24 video encoding chip GO7007SB of the American WIS company. GO7007SB adopts a variety of WIS patented technologies, which can easily realize audio / video compression and alarm in multiple formats and standards, dynamic detection, OSD (On Screen Display), embedded web server and other functions. With proper configuration, the output format of the video stream can be MPEG-1, MPEG-2, MPEG-4, H. 263. MJPEG format. The GO7007SB can be connected to the CMOS / CCD image sensor without glue. At the same time, it provides control channels such as EEPROM, SDRAM, USB, and rich peripheral interfaces such as HPI.
GO7007SB only supports digital video interface, and the cost of analog camera is low. You can use Philips video decoding chip SAA711A to convert the analog video data transmitted from the analog camera into a digital video data stream and send it to GO7007SB for compression encoding.
3 Base station software composition and design
There are several versions of the software design of the base station. Here, the video surveillance version and the version for transmitting data from Ethernet are used as examples.
3.1 Main functions of the software
The main functions of the software are as follows:
â‘ Detect and process the data sent by the front-end sensors in real time, and determine whether the condition of the monitored location of the front-end is normal through judgment. If there is an emergency, it will automatically start fire extinguishing, alarm and other devices, and send the relevant situation and data to the administrator of the main control center through the network and SMS.
â‘¡Can receive commands sent from the network in real time, and realize the corresponding functions after automatic processing and judgment of the type of commands (such as querying the sensor and controlling the SMS module); meanwhile, the main control center can receive the relevant information of the front-end sensors through the network data.
â‘¢ Can compress the video data through the video coding module, and send the compressed video data to the monitoring center in real time through the network.
â‘£Users can query the status of sensors in front of the intelligent control terminal through SMS, and can control the access control system. When an emergency occurs, the intelligent control terminal can send an alarm through SMS.
5) The base station can automatically identify and process the data of the access control system, automatically determine the user's authority, record the user's entry and exit, and pass the latest record to the main control center for backup.
3.2 Software architecture
The entire software uses the embedded operating system Linux as the main carrier for the realization of base station functions. Linux is a multi-tasking operating system. There are five main threads in the overall software division. Five threads work in parallel after the system is powered on. The relationship between the five threads is shown in Figure 3.
Items an be used simultaneously, also one of them can be used separately. And can connect two devices simultaneously.
HD Microphone, provides clear and loud sound.
1, True wireless stereo: realizes movement and wireless control and everyone can share music without wrie
2, Comfortable and convenient: Earplug made of food-grade silica gel material in combinalion with the design to avoid falling off, which makes you comfortable and relieved,also the Earbuds can be Dual or Single use.
Photo as below:
Bluetooth Earbuds,Wireless Earbuds,Cordless Earbuds,Wireless Bluetooth Headset
Shenzhen Greater Industry Co., Ltd. , https://www.szgreater.net