Abstract
The remote temperature reading system is a new mode in which temperature 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 temperature reading system ,based on advantages and disadvantages of current data transmission methods, a remote temperature reading system in which data is transmitted based on Ethernet is presented. For Ethernet technology has many advantages such as good compatibility、 extensive technical support ,and the research in this field is significative.
This system consists of three main modules : data collection module.data transmission module and software on the computer. In data collection module, the 8-bit MCU ATmega32 is used to collect data and stored in EEPROM to avoid data lost cased by accidental power off.
the data transmission module consists of the Ethernet interface and simple TCP/IP protocol stack on ATmega32.The hardware part of the Ethernet interface is made up of ATmega32, Ethernet controller Enc28j60. For the limited resource of 8-bit MCU, TCP/IP protocol stack on ATmega32 only has protocols including ARP, ICMP, IP, TCP and UDP. In addition, these protocols are simple according to the functions this system need to have. 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 simple, and the number of connection is reduced. Software on the computer is realized in the environment of VC++, it has functions including connection test and instant data display. The testing result shows that this system has basic functions of temperature reading and data transmission.
Keywords: remote temperature reading system; Ethernet; TCP/IP protocols