Development of intelligent gateway for heterogeneous networks environment monitoring in greenhouse based on Android system

The technologies of Internet of things have been widely applied in the agricultural environmental monitoring in recent years, while multiple transmission networks have been deployed to obtain environmental information. The gateway of internet of things was used for heterogeneous networks access and transmission of data protocol among the networks. In order to realize the unified management of heterogeneous networks that were used for greenhouse environment, an intelligent gateway with Exynos4412 as the core processor was developed, which has high speed operation capability and can be expanded for various communication module interfaces. Correspondingly, an application program worked in the gateway based on Android system was designed, which realized the management process of heterogeneous networks as following: Firstly, on the gateway display interface, user configured the information of the gateway communicating interface, data acquisition unit, and phase description of the sensors data stream. Secondly, the gateway application program established an information configuration file based on XML. Thirdly, after the application program was running again, according to the data stream description in XML configuration file, the gateway program matched the received data stream byte by byte segment in the data receiving tread, then positioned the sensor data in the data stream, parsed and converted the original value to the real value of the monitoring parameter. Fourthly, the data relation between keyword and value was composed to a map and was stored in the SQLite database. Lastly, the data access interface was provided for upper module such as real time data query module and historical data query module. The system was deployed in greenhouse and started running since December 18, 2014, to test three kinds of heterogeneous networks for Zigbee, RS-485 and Wi-Fi. The Zigbee network was used to collect air temperature, air humidity, light intensity, CO2 concentration, soil moisture inside the greenhouse, and data was transmitted to a Zigbee aggregation unit that was linked to the gateway by Serial line. The RS-485 network was used to collect the meteorological information outside the greenhouse such as wind direction, air temperature, air humidity, wind speed, rainfall, UVI, light intensity, and data was transmitted to a 485/232 conversion module which linked to the gateway by Serial line. The Wi-Fi network was used to collect the greenhouse image data from the camera, and data was transmitted wirelessly to the Wi-Fi module in the gateway by using a wireless router. In the gateway application program, the heterogeneous networks channel properties and sensors data protocol was not fixed in the software code, but was configured by user on the interface, also the storage and display of monitoring parameters was synchronous with the configuration. Thus, the application program can save developing time when the system was deployed for similar greenhouse environment monitoring or the nodes in the networks were changed for different use. The running results for at least 14 days showed that the intelligent gateway had corresponded the analysis, storage and display of monitoring parameters to the configuration information. Various monitoring parameters of heterogeneous networks data had been stored, and environmental monitoring data can be updated accurately and history data record can be query accurately on the displaying interface of the gateway. The application model of the system was of good stability and can be further extended to more heterogeneous networks. ©, 2015, Chinese Society of Agricultural Engineering. All right reserved.