我国煤矿安全生产形势依然十分严峻，迫切需要开发煤矿重大危险源的在线监测技术，以降低煤矿事故的发生。 煤矿井下监测设备常常采用RS-485或CAN总线方式传输数据，但这种传输方式不能满足长距离传输的要求。大多数矿井通过以太网将监测数据传输到地面监测站，由于以太网和井下监测设备数据传输协议不同，需要添加专用的协议转换节点以实现协议转换。目前，国内使用的转换节点存在功能单一的问题，也就是RS-485或CAN只能转以太网，因此需要研制多功能转换节点，实现多功能转换。 本文以CAN、RS-485和TCP/IP协议为基础，选用不同的硬件，完成了CAN总线和RS-485总线都能与以太网转换的多功能电路设计；选用高性能8位Atmega128 单片机与通用的以太网驱动芯片RTL8019AS，并移植了嵌入式实时操作系统μC/OS-II和LwIP协议栈，实现了以太网传输数据的功能；通过分析RS-485总线协议、传输数据的格式以及RS-485发送、接收过程中使用的函数，编写出RS-485与以太网之间互相传输数据的程序，完成了RS-485与以太网之间的协议转换；在分析CAN总线协议的基础上，通过中断处理把CAN报文处理成以太网数据格式，分别从CAN报文对象、发送报文、接收报文和错误处理这四个方面进行设计，实现了CAN与以太网之间的协议转换；实验证明：该转换节点能够实现井下监测设备和以太网的数据传输。 本文利用多功能转换节点将以太网和井下监测设备使用的网络统一起来，使原来基于普通总线的监测系统无需进行技术改造和升级即可连接到以太网上，保证了产品的延续性；将不同的监测设备统一挂接到煤矿现在已经开始普及的以太网上，形成完善的、统一的煤矿监测监控网络，具有较大的推广应用前景。

The security during the process of coal mining is facing some serious issues. Online monitoring technology for potential hazards in coal mining is urgently needed to be developed to reduce the probability of accidents. RS-485/CAN bus transmission is the common way to transfer the data for coalmine monitoring equipment, but it cannot meet the need for long-distance data transmission. It is a better solution using Ethernet to transfer the observed data to the ground station. A dedicated conversion node protocol should be set up to obtain protocol transformation capabilities because of the differences in communication protocols between Ethernet and the monitoring equipments. However, current conversion node can only transfer the data from RS-485 or CAN to Ethernet. It is necessary to develop a multi-function conversion nodes to get universal conversion. Based on CAN, RS-485 and TCP/IP protocols, our work is to develop a multifunction conversion interface circuits according to the following three steps. Firstly, we completed the communication connection through network by selecting a high-performance 8-bit ATmega128 microcontroller with a common Ethernet driver chip RTL8019AS design gateway and transplanting the embedded real-time operating system μC/OS-II, TCP/IP protocol stack. Secondly, the conversion in protocol between RS-485 and Ethernet could be accomplished by coupling the RS-485 bus protocol, the transmission format of the data, RS-485 transmission function used in the receiving process and a transformation program between RS-485 and TCP/IP. At last, based on the analysis of the CAN bus protocol, the protocol conversion between CAN and Ethernet can be finished by formatting CAN packet data to Ethernet data using interrupt handling and redesigning the CAN message object, send packets received messages and error handling. The multifunctional conversion between Ethernet and coalmine networks in our system worked well in experiment. Instead of transforming and promoting the original hareware or technology, the Ethernet can be combined with the underground network using a multifunctional conversion node on the basis of the original monitoring system with the common bus. This solution keeps the continuity of the products. Our design can be implemented extensively to coal mining by merging the monitoring system and Ethernet TCP/IP network into a comprehensive controlled system.