Foreword Smart home, also known as smart home, is developing in the direction of wireless remote control, multimedia control, high-speed data transmission, etc. Its key technologies are compatible home controllers and home networks that meet the information transmission needs. At present, the transmission network mostly adopts integrated wiring technology, which limits the application place of the system, and the cost is high. The use of wireless to build a flexible and convenient smart home security monitoring system has become a hot research topic. At present, the wireless communication technologies applied to smart home mainly include: Ir2DA infrared technology, Bluetooth technology and ZigBee technology. IrDA is a short-distance, point-to-point half-duplex communication method. It is inconvenient to use and has a high error rate. It is not suitable for home networking. Bluetooth technology is not suitable for home network applications with more nodes because of limited network capacity and high cost. . In this study, a smart home remote security monitoring system was designed by using ZigBee technology with moderate transmission range, safety and reliability, and large network capacity. 1 system architecture 1. 1 ZigBee network topology selection ZigBee is a short-range, low-complexity, low-power, low-cost two-way wireless communication technology, mainly used in the field of automatic control and remote control. IEEE 802. 15. 4 is the foundation of ZigBee technology, and the ZigBee protocol is simpler and more practical than high-speed personal area networks, Bluetooth or 802.11x wireless LANs. There are three main topologies for ZigBee networks: star, tree, and mesh networks. Mesh network has high fault tolerance, good adaptability and long transmission distance, but its complexity is also the highest; star network has the characteristics of simplicity and low power consumption, simple to use, suitable for small-scale and low-complexity applications of the family. The tree network is somewhere in between. Applying a star network to a smart home can result in a higher price/performance ratio. 1. 2 system composition The system uses a modular design. With the embedded system motherboard as the core, the CMOS camera is used to monitor the key parts, the security information and image MMS are transmitted through the mobile phone, and the household appliances are remotely controlled. The ZigBee module is used to implement the household appliances, the system motherboard and the smoke, temperature and gas. Wireless networking of sensors. The core controller of the system board is a S3C44B0X 32-bit microcontroller that processes and discriminates data, and sends information and commands through the MMS module and the Zig2Bee module. The expansion board is used to connect to home security status sensors such as smoke, infrared, and gas. The MMS module sends the home security status information sent by the system controller to the user's mobile phone, and receives the short message command sent by the user; the ZigBee module is responsible for data cross-linking between the system main board, the expansion board, and the home appliance. The system structure is shown in Figure 1. Figure 1 ZigBee-based smart home security monitoring system 2 system hardware design 2. 1 serial camera The serial port camera uses an optimized serial communication protocol to support packet transmission, allowing the host to configure a smaller buffer, while providing both TTL level and RS232 level output. The command and data transmission between the host and the host are realized by serial communication, and the host can set the state parameters such as baud rate, image resolution, and transmission mode. 2. 2 MMS module design The MMS module has a built-in MMS protocol and is a GSM/GPRS module that integrates SMS and MMS. It uses AT commands for module control and control commands and data transmission via the RS232 interface. It integrates 600 KB of Flash memory space for multiple uploads of images when sending MMS messages.
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