Study On The Remote Meter Reading System Transmitting Data Based On Ethernet

The remote meter reading system is a new mode in which meter data can be read without people on the spot. It can effectively solve the problems such as low efficiency, high cost and high error rate.The data transmission is the most important part in a remote meter reading system, based on advantages and disadvantages of current data tansmission methods, a remote meter reading system in which meter data is transmitted based on Ethernet is presented. For Ethernet technology has many advantages such as good compatibility and extensive technical support, the research in this field is significative.This system consists of three main modules: data collection and display module, data transmission module and software on the epigynous computer. In data collection and display module, the 8-bit MCU W78E58 is used to collect four paths of data including hot water, cold water, gas and electricity, the collected data is diplayed on LCD and stored in EEPROM 93C46 to avoid data lost cased by accidental poweroff. The data transmission module consists of the Ethernet interface and simplized TCP/IP protocol stack on W78E58. The hardware part of the Ethernet interface is made up of W78E58, Ethernet controller RTL8019AS and extended 32K SRAM, the Ethernet interface driver is realized through operation on local and remote DMA in RTL8019AS. For the limited resource of 8-bit MCU, TCP/IP protocol stack on W78E58 only has protocols including ARP, ICMP, IP, TCP and UDP. In addition, these protocols are simplized according to the functions this system need to have. In ARP protolcol, the buffering table is cancelled, only ARP request and reply function is reserved. In ICMP protocol, only Ping function is reserved. In IP protocol, the routing and packet segment function is cancelled, only packet send and receive function is reserved. In TCP protocol, the state machine, slip window mechanism and timing to retransmit mechanism are simplized, and the number of connection is reduced. Software on the epigynous computer is realized in enviorment of DELPHI, it has functions including connection test and instant meter data display. The testing result shows that this system has basic functions of meter reading and data transmission.