Design Of IOT Gateway Based On Linux

As the main access network equipment, the gateway of the Internet of Things (IoT) plays an important role of encapsulating the perceptive information based on sensors into network packets and sending them to the background server. With the capability of comprehensive perception, reliable transmission and intelligent processing, it can be used to substitute the traditional manual work of meter coping for the intelligent monitor, control and management of energy system in the field of building energy efficiency.In this paper, the actual requirements of the building energy monitoring system are first analyzed to give a detailed architecture. Based on this, the functional requirements of the gateway are analyzed and summarized according to the designing standards about the energy data collection equipment. Finally, the architectures of both the hardware and software are presented in detail.In order to facilitate the ongoing maintenance as well as minimize the circuit size, the hardware is designed into two parts, namely, the core board and the expansion board. The core board integrates the master chip AT91SAM9G20, RAM, ROM and power module, whereas the expansion board integrates RS-485data acquisition module, serial console, Ethernet interface,3G network interface, SD card, temperature sensor, USB, RTC and power module.According to the basic structure of embedded system, the software is designed into three levels including the driver level, the operation system layer and the application layer. On the bottom, the driver layer supplies the drivers for watchdog, temperature sensor, network chip and some other devices. The operation system layer includes U-Boot loader, Linux kernel and root file system. This paper mainly focuses on the application layer which is composed by five parts including Sqlite3database, web configuration, data acquisition, soft watchdog and program upgrade service. Among them, Sqlite3database is used to store configuration information of metering devices, web configuration program provides interface for human-computer interaction and update the configuration information combined with program upgrade service. Data acquisition program is mainly used to achieve the six-port data collection and upload the data via Ethernet to the server. In addition, it is also capable of time synchronization, file management, emergency alarm and passive data acquisition. Soft watchdog program monitors the possible getting stuck of data acquisition program and restarts it. Program upgrade service provides a convenient way to upgrade the software by either the local or remote method. Finally. This paper had made a test to the success rate of data acquisition and the trouble-free operation time of gateway. To summarize, the gateway presented in this paper meets the functional requirements fully including data acquisition, data processing, data storage, data updating, system configuration and long-term maintenance.