ZigBee Technology

ZigBee technology is a type of short-distance, low complexity, low power consumption, low data rate, and low-cost bidirectional wireless communication technology. It is mainly used for data transmission between various electronic devices with short distances, low power consumption, and not high transmission rates, including typical applications involving periodic data, intermittent data, and low-latency data transmission. ZigBee is an emerging wireless communication technology that features short distance, low power consumption, low cost, and low data rates. The characteristics of smart homes include small data transmission, low bandwidth requirements, but good network real-time performance, short delays, convenient access, long system battery life, strong scalability, and simple maintenance in the later stages. This undoubtedly makes ZigBee technology the preferred choice because its main application areas include industrial control, electronic devices, and building automation, and its characteristics determine that ZigBee technology can meet the requirements of smart home systems well.

1. System Overall Design

Smart home system networks can generally be divided into external networks (such as the Internet), internal networks (ZigBee self-organizing networks), and home gateways. The home gateway is the core part of the system. In this system, the Boa server transplanted on the tiny6410 development board is used as the home gateway, responsible for connecting and protocol conversion between the internal and external networks. Below is an introduction to the internal network, where the internal network refers to the ZigBee self-organizing network, which adopts a tree-shaped or star-shaped network topology according to the home layout. The ZigBee self-organizing network includes various terminal nodes that work with relays to control various home appliances, switches, temperature and humidity sensors, and other devices that need to be monitored in the home, achieving remote monitoring functionality. From a communication perspective, each node is a terminal, and they communicate wirelessly through the ZigBee protocol. Protocol conversion issues between different internal network protocols are not considered here. The overall structural diagram of the smart home system is shown in Figure 1.

2. Smart Home Gateway Design

The home gateway designed in this paper needs to process data from the Internet, requiring the hardware of the home gateway to provide strong network support and support for the TCP/IP protocol. Therefore, an operating system is needed to support multitasking. The home gateway is a functional entity composed of hardware and software, with the Boa server transplanted to an ARM development board used as the gateway. Boa is a single-task small HTTP server with open-source code and superior performance, especially suitable for embedded systems. The structure diagram of the home gateway is shown in Figure 2.

The establishment of the Boa server is relatively simple, with main steps including: decompressing and cross-compiling on the development host, then configuring the server, mainly modifying files; after the configuration is completed, it can be ported. After successful porting and installation, the Boa server software can be run. By running the Boa server and the serial port read-write application program on the built embedded platform, combining static web pages and dynamic CGI programs can enable commands to be sent from the webpage to the embedded server. Through CGI technology, the call between the Web server and the serial port read/write application program can be implemented, achieving a forward process where data (commands) are sent from the webpage to the server and then written into the ZigBee internal network via the serial port. After commands are sent to the ZigBee internal network, the read-write application program reads the ZigBee feedback data (mainly LED status and sensor readings) and stores them in the SQLite database on the ARM board for later use by CGI programs to display on the webpage.

3. ZigBee Home Internal Network Design

From a development trend perspective, wireless self-organizing networks are the future direction of smart home networks. ZigBee is an emerging short-distance, low complexity, low power consumption, low data rate, and low-cost bidirectional wireless communication technology. It is a proposal that bridges wireless tagging technologies and Bluetooth. Compared to various existing wireless communication technologies, ZigBee is one of the lowest power consumption and cost-effective technologies. Considering the scale of smart homes, including the small amount of data transmitted within the network and a large number of nodes, a star-shaped structure is chosen for the internal network topology. The hardware design of ZigBee nodes is relatively simple, using TI"s CC2430 chip, which integrates ZigBee radio frequency (RF) frontend, memory, and microcontroller on a single chip. It uses an MCU (enhanced 8051) with 128KB programmable flash memory, 8KB of RAM, as well as ADC, timers, and an AES128 coprocessor. The data collection unit uses a temperature and humidity composite sensor, DHT11, with calibrated digital signal output. The software system of the home internal network is based on IAR Systems" IAR EmbeddedWorkben