The Key Technology Research On Smart Home System Based On ZigBee Wireless Network

Smart home refers to the combination of the subsystems related to household livelihood using advanced computer technology,network communication technology and integrated wiring technology.Through the overall management, home life will be more comfortable and convenient. Generally,smart home system can be divided into three parts:external network,gateway and internal network.The subject of this article came from project of Jilin Provincial Science and Technology Department and named "Research on key technology of network digital home(20060531)". We introduced advanced embedded Ethernet technology and ZigBee technology to build up a smart home system based on ZigBee wireless network, deeply studied on some key technologies such as wireless networking for household appliances,embedded gateway and local and remote control. The smart home system could meet the basic need of users, within the family, users could change the state of electric appliances by the infrared remote controller;in the remote user center,the user could observe and control status of household appliances.The system mainly included ZigBee wireless network,terminal control unit,gateway(module of Ethernet--serial interface)and remote user center. Among it, ZigBee wireless network was made up of a network coordinator and eight terminal nodes(including wall light, ceiling light,table lamp, television,curtains, air condition,acoustics and pendant lamp of adjustable brightness).ZigBee wireless network constituted home internal network using mesh network,the switch status information of home internal electric appliances and the lighting brightness information of sitting room pendant lamp could be transmitted in the network freely. ZigBee was set up based on the IEEE802.15.4 standard,with some characteristics of small system spending, large network capacity, high scalability and easy to transplant,and so on.ZigBee chip used by system was CC2430,which was produced by Texas Instruments, CC2430 integrated ZigBee radio frequency (RF)front end,memory and microcontroller in a single chip, it would be able to send and receive signals combined with a few external components.Terminal control unit mainly responded to infrared control command and remote user center control command. Infrared remote controller chip was SAA3010T type, the processor of terminal control unit used AT89S51 microcontroller, integrated infrared receiver connected with P3.3 port of MCU (INT1), CC2430 connected with AT89S51 through the serial port. AT89S51 controlled the switch status of home appliances and the lighting brightness according to the received information.Gateway (module of Ethernet--serial interface) was a network connection device which connected home internal network with external network, and made internal network access to external network.Gateway connected internal network by serial interface of the network coordinator, connected external Ethernet through RJ-45 interface, mainly achieved data conversion between Ethernet and serial interface, completed communication between Ethernet and home internal network. Gateway in the system used a 16 bit MCU--MC9S12NE64 as processor which was made in Freescare company, MC9S12NE64 could match TCP/IP protocol stack, and provided RS232 interface, also could achieve data conversion and transmission between Ethernet and serial interface, directly supplied efficient support for specific applications.The implementation of system's communication protocol was key importance to data transmission.The interior of gateway needed to embed TCP/IP protocol to meet that system could connect with Internet; home internal network was ZigBee protocol based on IEEE802.15.4; In addition, in order to enable data transmission security,reliability,bit error rate and retransmission rate lower, we also needed to constitute user's protocol.OpenTCP faced to embedded system, was an open source rightsizing TCP/IP protocol stack. Gateway mainly provided bidirectional data transmission,TFTP,HTTP and other application layer protocol in OpenTCP was not necessary,this paper removed all the application layer protocol, leaving only TCP,IP,ICMP and ARP key protocol, application layer directly faced to user program, the cost of system greatly decreased. ZigBee is a wireless communication protocol which is established based on IEEE802.15.4 standard, using hierarchy structure, the key part of ZigBee protocol stack is network layer, the main responsibility of network layer includes providing mechanism of devices leaving and joining the network, also providing route and security mechanism of data frame transmission. The network layer of ZigBee coordinator is responsible for starting a new network, the formation of network included a number of steps, such as network address distribution, setting up new network, allowing devices to join network, devices joining network, devices quiting network and sending and receiving data,and so on.The user's protocol frame was composed of frame header, data and end of frame, it could be divided into uplink frame and downlink frame according to the functions of frame.Uplink frame mainly transmitted the number of electric appliances and status data of electric appliances or brightness data of lighting,downlink frame mainly transmitted the number of electric appliances and command words.Remote user center achieved the interaction between system and user,which existed in a remote computer in the form of visual interface service program, remote user center received and send IP packets of TCP protocol to accomplish Ethernet communication, thus to achieve controlling household appliances.The main designing language of remote user center used Visual Basic programming language, according to the functional requirements for users, the interface included network communication module, remote control module, remote calling module, graphic display module and other module,and so on, the remote control module could be divided into switch control of terminal electric appliances and brightness control of lighting.In this paper, the application scheme of a smart home system based on ZigBee wireless network was proposed, achieving controlling various of status of household appliances through two access mode, respectively,the home local place and remote. The system introduced ZigBee technology of communication reliability and easy expansion, completing wireless networking communication of household appliances; introduced Ethernet solution scheme of single chip MC9S12NE64 terminal node which was low cost,low consumption,coupled with the extended RS232 interface, it was more suitable upgrading and regeneration of similar systems;infrared technology and remote control were applied in domestic life at the same time, providing users with a more convenient way of life,achieving the real low cost home networking, intelligent management. The development of smart home will not only bring easeful and comfortable life, but also promote the development of social high-new science and technology.