Design And Implementation Of WTB Communication Card Based On CPCI Bus

Train Communication Network (TCN) architecture is commonly used in train control networks of domestic bullet trains, which is in line with international standards IEC61375-1. As one of the vital equipment of gateway, WTB communication card can transfer data on train buss and organize vehicles into groups. At present, there is less domestic research on it, whose modular application in TCN gateway is relatively scarce. WTB devices of domestic bullet trains are almost supported by foreign manufacturers, which control the core technologies. Therefore, it is practically significant to research and develop a suitable WTB communication card for TCN gateway.On the basis of analyzing the train bus applications and WTB devices (gateway) development status around the world, a design of WTB communication card was proposed. The card was applied to gateway devices with CPCI backplane buses, on which the CPU card communicated with WTB card. WTB communication card was designed with FPGA+CPCI architecture. The core function of WTB node controller was achieved by FPGA, where a Nios Ⅱ soft-core processor running WTB inauguration and regulation tasks was embedded. CPCI interface was achieved by a PCI bridge chip, which made the communication card interconnect with other CPCI devices. Real Time Protocol (RTP) service software has been developed on VxWorks operating system, which can provide effective link layer access to application layer.According to the WTB network layer reference model, the design of Medium Attachment Unit (MAU) was firstly introduced. In order to ensure the signal quality of the communication card, the overshoot of transmitting signals was optimized. Then some analysis of main functions of link layer was done. And the implementation of Manchester codec module and redundant control module was introduced in details. Considering that the telegraph timing needed to be accurate, the timing mechanism of Nios Ⅱ system on chip and VxWorks operating system were compared and analyzed, ensuring accurate telegraph timing of inauguration. Finally, a platform which included a standard gateway as reference was set up in lab. Signal quality, load capacity and CPCI communication function were tested. A multi-nodes network test has verified the WTB inauguration and RTP service software functions, and the results met the requirements of IEC61375-1standard.