introduction
With the rapid development of Internet technology, wireless sensing technology, and information processing technology, the Internet of Things technology has received more and more attention. In 2003, the United States "Technology Review" proposed that the Internet of Things will be the first ten technologies that will change people's lives in the future. The Internet of Things is based on the computer Internet and is constructed using technologies such as electronic product codes EPC, RFID, wireless data communication, etc. An information network covering everything in the world is a product independent of the integration of EPC system and Internet technology. On the one hand, the Internet of Things can improve economic efficiency and greatly save costs, and on the other hand, it can provide technical impetus for the recovery of the global economy.
ZigBee technology is a group of communication technologies related to networking, security, and application software developed based on the IEEE 802.15.4 wireless standard. It is a short distance, low complexity, low power consumption, low data rate, and low Cost of two-way wireless network technology. The frequency band it uses is 2.4 GHz, which is universal worldwide. The standard defines the network layer and supported application services on the IEEE 802.15.4 physical layer (PHY) and standard media access control layer (MAC). The ZigBee Alliance Alliance ’s The long-term goal is to be able to build a scalable, low-cost embedded infrastructure based on interoperable platforms and configuration files. The construction of the Internet of Things development platform is also very important to promote the transformation of research results and the integration of production, education and research, and provides a simple and feasible way for the ultimate realization of the "Internet of Things".
1 IoT development platform hardware design
The core key of the Internet of Things technology is radio frequency identification technology (RFID). The basic RFID system includes at least a reader and a RFID tag. It has fast reading speed, large storage space, long working distance, and strong penetration. , Strong working environment adaptability, reusable and many other advantages. The RFID tag is composed of a chip and an antenna. Each tag has a unique electronic code. The tag is attached to the object to represent the target object.
Another important technology of the Internet of Things is wireless sensor network technology. ZigBee technology is a short-distance, low complexity, low power consumption, low data rate, low cost two-way wireless network. Zi-gBee technology is economical, reliable, High efficiency and other advantages have good application prospects in the Internet of Things technology.
There are three types of logical devices in the ZigBee network: coordinator, router and terminal device. The ZigBee network consists of a coordinator, multiple routers and multiple terminal devices. There are three main types of ZigBee network topology: star, tree and mesh network structures. The ZigBee protocol specification uses the physical layer (PHY) and media medium access control layer (MAC) defined by IEEE 802.15.4, and on this basis, the network layer (NWK) and application layer (APL) architectures are defined.
ZigBee hardware circuit adopts 2.4GHz IEEE 802.15.4 / ZigBee system-on-chip solution CC2430 / CC2431 wireless single-chip microcomputer developed by TI / Chipcon company. It provides a fully compatible IEEE certified by the ZigBee Alliance for free. 80215.4-2003 protocol specification and ZigBee 2006 protocol specification protocol stack source code and development documents, integrating single-chip emulator, programmer, ZigBee protocol analyzer, picture dot matrix LCD display, high-performance voice circuit, JoysTIck and several The typical analog component is an integrated development master, which realizes the seamless connection of ZigBee development software provided by TI / Chipeon. The CC2430 integrates the excellent performance of the 2.4GHz IEEE 804.15.4 / ZigBee RF transceiver CC2420 and the industry-standard enhanced 8051MCU. It also includes 8KB of SRAM, large-capacity flash memory, and many other powerful features. The CC2430's current consumption in receiver transmission mode is 25 mA, making RFID an ideal solution for applications with very long battery life. The circuit diagram of ZigBee embedded RFID radio frequency identification system is shown in the figure.
Circuit diagram of ZigBee embedded RFID radio frequency identification system
There are also GPS and GPRS modules in the IoT development platform system. The Global Positioning System (Global PosiTIoning System, GPS) is a high-precision radio navigation-based global positioning system based on aerial satellites, anywhere in the world and near-Earth space. It can provide accurate geographic location, vehicle speed and precise time information. The GPS system consists of 3 parts: the space part, the ground control part, and the user equipment part. GPRS is the abbreviation of General Packet Radio Service, which is located between the second generation (2G) and third generation (3G) mobile communication technologies. It provides medium-speed data transfer by using unused TDMA channels in the GSM network. GPRS breaks through the thinking that GSM network can only provide circuit switching. It only realizes packet switching by adding corresponding functional entities and partially transforming the existing base station system. The user data rate obtained is much faster than that of GSM network. The GPRS module uses the mobile phone module and the SIM card to send short messages to the GPS location data to inform the location of the other party's items.
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