The application direction of ZigBee technology is targeted at home automation, building automation, sensor applications, etc. The wireless network communication module of the system uses CC2430, which is a true system-on-chip (SoC) COMS solution that can improve performance and meet the low-cost and low-power consumption requirements of ZigBee-based 2.4GHz ISM band applications. . It also contains a DSSS (Direct Sequence Spread Spectrum) radio frequency transceiver core and an industrial-grade, compact and efficient 8051 controller. The wireless data transmission module uses the DL6200 module. Users only need to have the familiar serial communication knowledge to communicate through the GPRS network.
1 ZigBee’s technical advantages
ZigBee’s technical advantages are shown in the following aspects:
(1) Power saving. Due to the short working cycle, low power consumption for sending and receiving information, and the adoption of sleep mode, ZigBee technology can ensure that 2 AA batteries can support use for up to 6 months to about 2 years. The power consumption corresponding to different applications is naturally different.
(2) Reliable. ZigBee technology adopts a collision avoidance mechanism and reserves dedicated time slots for communication services that require fixed bandwidth to avoid competition and conflicts when sending data. The MAC layer adopts a fully confirmed data transmission mechanism, and each data packet sent must wait for confirmation information from the receiver.
(3) Low cost. The module is cheap and the ZigBee protocol is patent-free.
(4) Short delay. Optimized for latency-sensitive applications, communication latency and activation latency from sleep state are both very short. The typical value of device search delay is 30ms, the typical value of sleep activation delay is 15ms, and the typical value of active device channel access delay is 15ms.
(5) Node communication settings are easy to configure.
(6) Large network capacity. ZigBee can adopt star, mesh, and tree structure networking, and can be connected through any node to form a larger network structure. Theoretically, it can connect up to 64,000 nodes. One ZigBee network can accommodate up to 254 slave devices and one master device, and up to 100 ZigBee networks can exist simultaneously in one area.
(7)Safety. ZigBee provides data integrity checking and authentication functions, and the encryption algorithm uses AES-128. At the same time, each application can flexibly determine its security attributes.
(8) Global versatility and complete openness. The ZigBee standard protocol makes communication between ZigBee devices a breeze.
2 Technical Features of CC2430
The CC2430 chip continues the architecture of the previous CC2420 chip and integrates the ZigBee radio frequency (RF) front-end, memory and microcontroller on a single chip. It uses an 8-bit MCU (8051) with 128KB programmable flash memory and 8KB RAM. It also contains analog-to-digital conversion (ADC), several timers (Timer), AES-128 co-processor, and watchdog timer. (Watchdogtimer), 32kHz crystal oscillator sleep mode timer, power-on reset circuit (PowerOnReset), brownout detection circuit (BrownOutDetection), and 21 programmable I/O pins. The CC2430 chip uses a 0.18?mCMOS process; in receiving and transmitting modes, the current consumption is less than 27mA and 25mA respectively. The CC2430's sleep mode and ultra-short transition to active mode are particularly suitable for applications that require very long battery life.
3 GPRS data transmission module DL6200
The core hardware of the DL6200 module is designed and produced using GPRS chips produced by world-renowned mobile communication product manufacturers, and has high reliability. When using DL6200, you only need to be familiar with serial communication knowledge to communicate through the GPRS network.
There is no need to care about the radio frequency circuit part of the module (using the mobile operator's public network) and related hardware connections; there is no need to care about the AT command set, all operations related to AT response are completed by the DL6200 module inside the module; there is no need to care about the TCP/IP protocol And related knowledge of interconnection network: Since the GPRS module is based on the communication method of the interconnection network, it must deal with the INTERNET network during use. All information exchange with the network is automatically completed internally by the DL6200 module without user participation; no need The user has a fixed IP address alone; has two transmission formats: format and transparent transmission; has general working mode and power-saving working mode; can be directly connected to various configuration software without a dedicated driver; supports bus-type passive data transmission Way.
4 System structure and working principle
4.1 System structure and function
The system consists of two parts: the external network and the internal network. The external network is composed of a GPRS data transmission module and a PC. Information can be transmitted between the two through TTL\RS232\RS485. The system uses the host computer level interface as TTL.
The intranet consists of a PC and a ZigBee wireless data communication module, which are connected through a serial port. ZigBee network consists of three parts: coordinator, router and terminal equipment. Coordinators and routers are called full-function devices FFD, and end devices are called reduced-function devices RFD. Since the system equipment is relatively simple, it adopts a star networking method, and regards window sensors, door sensors, etc. as terminal devices, and the ZigBee wireless module as the coordinator. The system has a simple structure, so no router is required. As shown in Figure 3.
(1) The user sends a text message command to the GPRS data transmission module DL6200 through the external GSM mobile phone. After receiving the command, the DL6200 interprets the command. After the explanation is completed, it is sent to the ZigBee wireless communication module CC2430 in the intranet. The module sends the command to the corresponding terminal device. The terminal device takes corresponding actions after receiving the command.
(2) After receiving the command, the terminal device will first take corresponding actions and respond to the upper layer, and second, transmit the data required by the upper layer to the upper layer device through the CC2430 module. The upper-layer device receives the information from the terminal device and sends it to the user's mobile phone in the form of text messages through DL6200.
(3) When there is an interrupt response, for example, if there is a thief in the home and the alarm device is triggered, the terminal device will send a message to the user as soon as possible to indicate the alarm.
4.2 System hardware design
DL6200 does not need to care about the AT instruction set. There is no need to care about the relevant knowledge of TCP/IP protocol and interconnection network. All information exchange with the network is automatically completed by the DL6200 module. Directly connected to various configuration software without special driver. These features of DL6200 make hardware design easy. Its RXD and TDX must be connected to ZigBee's RX and TX to send and receive data.
4.3 System software design
The system software mainly completes data collection and data sending and receiving through ZigBee network protocol operation, including initialization, transmitting and receiving program design, and monitoring of alarm signals , processing and execution of remote control instructions, etc.
The sending and receiving of the system uses the PingPang sending function
5 Conclusion
The ZigBee wireless module has the advantages of low power consumption and low cost, and can meet the transmission rate required by people. Under the circumstances, it will be popularized in every household in the near future. In addition, the use of wireless networks eliminates the burden of redecoration. Using ZigBee wireless network, you can add or reduce its nodes at any time, and it has the ability to self-organize the network. Therefore, the economic level of goods and the ease of technology have become inevitable conditions for development.