The Design Of Data Acquisition Module On Ethernet Based On OpenTCP

The data acquisition board based on interior bus and the acquisition terminal based on exterior communication bus are often used in the industrial production and intellectualized system research area to gather all kinds of data. These acquisition methods transmit data in a short distance, so it is hard to use them to interconect the acquisition equipments in different scene and transmit data in a long distance. With development of the ethernet technology and embedded technical,more and more research focus on the embedded ethernet technology. The method is inserting the Ethernet protocol in acquisition chip and transimiting the data on Ethernet, so the transmission could be father. The data acquisition and processing system based on Ethernet build on the existing Ethernet network, and it could work together with any application platforms based on Ethernet. Compared with the traditional data acquisition technology based on bus, it has many advantages such as extensible, flexible, long distence trasmission and high speend.The paper use Freescale's 16-bits MCU MC9S12NE64 and OpenTCP Ethernet protocol to design a single-chip data acquisition module and realize a Ethernet data acquisition terminal. At first, the paper used MC9S12NE64 to carry out a TCP server. Then used the ATD module and SCI module of MC9S12NE64 to gather data. Finally, the data acquisition terminal gathered could be transmited on Ethernet through the OpenTCP protocol embedded in MC9S12NE64.MC9S12NE64 is a 16-bit microcontroller, with third-party TCP/IP protocol stack match, and then use Metrowerks CodeWarrior development tools of the rapid design, may realize the low cost terminal node Ethernet solution. It has high integration, simple structure and high flexibility. The software can be configured characteristics and realize large amounts of data acquisition and high-speed data transmission directly to the specific application of efficient support. The paper made a single-chip TCP server with embedding the modified OpenTCP in MC9S12NE64. Compared with the multi-chip design it has many advantages such as small size, simple structure, high integration and reliability.Currently,there are different types of popular network protocol, although each has its own advantages, but only TCP/IP allows full connectivity with the Internet, it is more focused on the Internet data transmission between equipments. The TCP/IP protocol stack, run on General computer is too complicated and demand large system resources. Embedded systems are generally in order to meet a specific demand, and network support requirements are relatively low. Any agreement on the need to add the corresponding module, without the use of complete TCP/IP protocol, we shall, in accordance with the needs, reduct the TCP/IP protocol appropriately.The paper, comparing several embedded protocol stack, choose OpenTCP protocol stack. OpenTCP protocol is free so it could reduce the cost of the research. The code of the OpenTCP is open, so researchers can modify it based on their need. As the CPU processing power and storage capacity of MC9S12NE64 is limited, the paper made some changes on OpenTCP protocol with characteristics of processors MC9S12NE64. This paper cutted down the unuseful protocols, such as HTTP and TFTP, of OpenTCP and hold the useful protocols such as TCP server, ICMP ping, ARP and IP. With the cutting of the protocol, the code reduced more than a half and the time used to processing OpenTCP is also reduced.The Ethernet parameter should be embedded into Ethernet data acquisition terminal before Ethernet connection. The popular method to embed the Ethernet parameter is setting the Ethernet parameter in programme. But it is hard to modify the Ethernet parameter because it needs the developer to modify the Ethernet parameter in programme and download the programme into the data acquisition terminal again. The paper found a way to modify the Ethernet parameter conveniently. To save the Ethernet parameter in an EEPROM connected to MC9S12NE64. The Ethernet parameter is loaded form the EEPROM and used for Ethernet connection when acquisition terminal is turned on. When Ethernet parameter is needed to be modified, using the SCI interface to link the data acquisition terminal to a computer. So user can use computer to modify the Ethernet parameter in EEPROM depend on a parameter modify communication protocol defined by the paper. The paper defined a parameter modify communication protocol for the communication security between computer an acquisition terminal. This method of parameter modification makes the work to modify the Ethernet parameter easyer. Modifying the Ethernet parameter through SCI communication is more convenient than modify the Ethernet parameter through programme, because it just need to operate on the parameter modification interface on coputer rather than to understand the code. The existing Ethernet data acquisition terminals are generally used for Ethernet-serial port communication. The Ethernet data acquisition terminal of the paper can gather three kinds of data, they are serial port datda, analog data, I/O port state. The paper defined a data acquisition protocol, which is used for communication between data acquisition terminal and control terminal, based on Ethernet protocol.The data acquisition protocol defines two work mode, once acquisition and series acquisition, and port selection mode. The paper is not simply patch up the data acquisition and Ethernet but carry out a bidirectional and more functional data acquisition system.The paper proposes a data acquisition terminal on Ethernet based on MCPS12NE64 and OpenTCP protocol. Not only the system realizes the data acquisition and Ethernet transmission but also actualize the parameter modification and three kinds of data acquisition. The data acquisition terminal can gather analog data, I/O state data and series port data through SCI module, ATD module and I/O port of MC9S12NE64. The data acquisition terminal has been embedded OpenTCP protocol and realized Ethernet function based on the EPHY and EMAC module of MC9S12NE64. The paper defined data acquisition protocol and parameter modification protocol to make data acquisition terminal achieving the data acquisition and parameter modification function.