The Design Of WSN Gas-meter Node Based On CC2420

When ZigBee protocol was framed, wireless sensor network touched off a new round of revolutionary upgrade of the electronics world. So many chip manufacturers brought in several Wireless RF modules which matched with ZigBee protocol in succession.Meanwhile, there are also some research groups studied different solutions about it. In this paper, according to the existing drawbacks of China's water, electricity, gas, heat, and other existing public utility meter reading programmer, I proposed this programm which based on CC2420 WSN gas meter reading program. It is focus on the gas meter node development.Based on the design of University of California, Berkeley Wireless communication module of gas meter node used TICC2420,which meet IEEE802.15.4 protocol. CPU adopted TI MSP430F149, which is a typical microchip applying to apparatus.MSP430F149 has 60K ROM and 2K RAM. And it meets the requirements of gas- meter node. MSP430F149 is also an ultra low- power microchip which meets the requirement of ZigBee protocol for low- power.We adopt the software TinyOS which is developed by the University of California at Berkeley. The TinyOS is specifically for wireless sensor networks which developed an embedded operating system. It is based on the components of the framework, the language from nesC . TinyOS has many good components which could be effective in saving development time and provide efficient.Software development tools include Cygwin, UltraEdit, download programming software used MspFet.Gas Meter as a wireless remote meter reading network of the basic unit, asks for a data acquisition capacity, data processing capabilities, communications capabilities, and data storage capacity. It requests its low-cost, low-power, strong ability to adapt to the environment. In this paper, all gas meter designed with data acquisition modules, power management unit, valve control units, liquid crystal display modules, 2.4 G wireless communications modules, data storage unit.Data acquisition unit which is a few gas flow meter units, with the internal gas meter runner and the common reed switches completed together. Gas Meter power using three AA batteries in series power supply. Power management unit is completed with the MSP430F149 internal voltage comparator and 12 of the AD converter .This two detection unit completed jointly with the two external hardware detection module also includes a sub-voltage circuit and super capacitor. Power module design related to the success or failure of a system, so I use an ultra-low-power LDO and effectively reduce the power consumption node. Valve control unit used motor valve with a valve H-bridge motor driver circuit, completed gas meter valves open / close. LCD modules for professional used by blocking the production of liquid crystal screen, on-screen can display "for battery," "Please buy gas", "magnetic interference," and "cumulative gas," "valve opening," "valve clearance". Drive circuit used HT1621B struts LCD driver chips, which have 32-bit SEG, 4 COM. 2.4G wireless communications module is the core chip RF transceiver chip CC2420. It is based on TI's SmartRF03 technology to 0.18 um CMOS process made only very few external components, stable performance and low power consumption. Its selectivity and sensitivity of the index over the IEEE802.15.4 standard requirements to ensure that the short-distance communications effectiveness and reliability. Data storage modules using the AT24C08 ATMEL Corporation (industrial) to achieve the operating voltage of 1.8-5.5 V. This E2PROM has Two Wire I2C Serial Interface, High Reliability, Endurance: 1 Million Cycles,Data Retention: 100 Years,3uA standby Current Lock-Out Write Protect。Because the gas meter nodes are battery-powered, it is necessary to meet the requirements of low-power; the CC2420 is the work of the current up to 18.8 mA. All nodes in the gas meter into dormancy scheduling mechanism. There are four types of slot in the Gas Meter nodes in a cycle: dormancy, upload routing maintenance, time synchronization, and application communication.Nodes in a cycle, it should experience a 3.5 routing maintenance, the fourth time synchronization, communications and the application of two-routing maintenance.Application node communication is the main gas meter application layer of the task. It implements the node data upload, base station orders in response to the jump-news packages.DMTS time synchronization is synchronization mechanism based on the past. Bu it more simple than DMTS synchronization maintenance。Synchronization accuracy is also higher than DMTS synchronization maintenance. Gas Meter node network nodes local clock from the clock, table clocks and network nodes composed of the difference between the local clocks. Clock synchronization to the network, synchronization only change table clock network nodes and the difference between the local clocks. Gas Meter clock network adopt the world standard time, several network clock sources for this district jurisdiction of the base stations. Gas Meter network clock network Table 6 bytes.Routing maintenance divided into upload routing maintenance, and issued routing maintenance. WSN addition to the traditional self-organizing wireless (Ad hoc) network as a dynamic network topology changes, such as the existence of one-way nature of the link, there are many new features. Traditionally, Ad hoc network nodes on the network as the center, and WSN are data-centric network. WSN does not need to safeguard the network between any two nodes of the routing, it is merely the need to preserve sensor nodes and Sink between routing, routing protocol can be relatively simplified. Some times sensor node resources greater restrictions. Sensor nodes with a limited, non-replacement of the power supply, node computing, communications, storage capacity is very limited, and some WSN network nodes do not even have status symbol.PTRP (Pagoda Tree Routing Protocol) routing protocol based on hierarchical thinking of the tower tree routing protocol. It is against gas meter network nodes deployed by the characteristics. Cell site tower top of the tree, the tree in charge of the entire tower all nodes. PTRP routing building process is divided into two phases: 1. The supremacy of the link building process. 2. Register on to the next and routing information. The establishment of the link is initiated by the cell site. PTRP routing maintenance consists of two parts operation, First Find Father, Son nodes, and the second is to update routing table, neighbors Table. PTRP routing maintenance applied to the gas meter on the network, the network cycle gas meter for the distribution of the PTRP routing maintenance upload routing maintenance slot. Upload routing maintenance slot to upload link maintenance, waiting for the new node to join. Under-routing maintenance in communications slot in the application, application communication is completed next-link maintenance.In this paper, based on the last completed a CC2420, a data acquisition function, sleep scheduling, time synchronization, routing generation and maintenance function, the function of the network security protection WSN gas meter bus system. Routing and network security have had a number of tests to achieve the goal of the design. The wireless remote gas meter nodes are also displayed in September 2007 in Beijing ZigBee at the General Assembly, to complete point-to-point data upload, order given at that time did not include dormant nodes scheduling, time synchronization and routing.