0 Preface
With the improvement of people's living standards and the development of computer technology, communication technology and network technology, smart home has gradually become the development direction of future home life. Smart homes not only provide users with a safe, healthy and comfortable living environment, but also users can remotely monitor their home status and control home electrical equipment. In the smart home system , wireless network technology can provide greater flexibility, mobility, and more in line with the simplicity, flexibility, modularity, scalability and independence of the home network communication characteristics, the application of wireless network technology to the home The network has become a mainstream trend.
As an emerging wireless communication technology, Zigbee's low-speed, low-cost, low-power, self-configuring and flexible network structure is ideal for home networking. Wi-Fi is a wireless networking technology. The main advantage is that it does not require wiring and is not limited by the wiring conditions. Therefore, it is especially suitable for the needs of mobile office users. Wi-Fi technology is used in smart homes to make the home internal network The Internet connection is more convenient, and a Wi-Fi handheld terminal device can directly enter the home gateway to realize remote monitoring and intelligent control of the home appliance. The home gateway in the system is a Wi-Fi-ZigBee web server, which is a conversion interface between the ZigBee protocol, the Wi-Fi protocol and the Ethernet, and is responsible for establishing and managing the wireless sensor network and realizing the communication connection of the external network.
1 Gateway overall design and workflow
The system mainly includes ARM9 processor S3C2440A (home gateway), Zigbee module (coordinator), Wi-Fi module, Zigbee terminal equipment (such as infrared detector, magnetic switch and fire detector and smoke detector, etc.). The structure is shown in Figure 1. Porting the Web server Boa as a home gateway in the ARM9 processor is responsible for the management and remote monitoring of the entire smart home device.
Since many home appliances in smart homes work through the Zigbee wireless sensor network, data must be stored in the processor and data fusion processing is performed on the Zigbee wireless sensor network. The coordinator is responsible for the management and control of the Zigbee network inside the home. . The Wi-Fi module is used to transmit large-capacity information and connect to the Ethernet through a wireless access point (AP) router to communicate with the home network and the Internet.
Figure 1 System structure
The basic process of system processing is as follows: The system is internally composed of Zigbee star network. The control information of the switch status and sensors in the home is freely transmitted in the network, transmitted to the gateway of the Web server via the coordinator (Zigbee module), and then passed by the gateway through Wi- Fi is connected to the external Ethernet via wireless routing, and the user can know the status of the home appliance through the remote user interface; the home gateway can judge and respond to the remote user's control commands through the wireless network, thereby turning on or off the home appliance.
2 Gateway hardware platform design
The gateway hardware circuit is mainly composed of a controller module (S3C2440A), a storage unit (64 MB SDRAM, 64 MB Nand Flash and 2 MB Nor Flash), a communication module (Zigbee module and Wi-Fi module), and a display module (LCD). The hardware circuit block diagram is shown in Figure 2.
Figure 2 system hardware circuit
2. 1 controller module
The controller is the core of the entire embedded home gateway. It is used to configure the Zigbee communication module and receive the data of the Zigbee terminal node. The Wi-Fi protocol is used to connect the gateway to the Internet through the Wi-Fi module. In order to achieve high performance and low power consumption, the embedded gateway is designed with the ARM920T as the core of the 32-bit RISC microprocessor S3C2440A as the main controller. The processor integrates the LCD controller, USBHost, and NAND controller. The rich peripheral resources such as BUS controller, interrupt control, power control, memory control, UART, SPI and GPIO form a hardware platform through external expansion memory, serial port, USB interface and JTAG debugging interface.
2. 2 Zigbee networking module
In the smart home system, Zigbee wireless communication technology is used to form smart home appliances into a star network. The star network is a radial structure. The network commands and data are transmitted through the coordinator. The communication between the terminal devices is also forwarded through the coordinator. The terminal device is not the starting point of communication or the end point of communication.
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