The Research On Network Embedded System Based On PIC MCU

The rapid development of information technology brings people into a Post-PC era,portable and real time information processing embedded system combined with the Internet will be a great popularity.It can transmit information conveniently and cheaply to places all over the world with the perfect combination of embedded systems with the Internet.The main topic of this paper is to research a dedicated and economic,pithiness and high reliable network embedded system. The system can realize the function of remote monitoring through the Internet,and this system includes a high performance temperature and humidity sensor to implement data acquisition and real time transmission.It has the advantage of convenience and practicability by the NAT hole punching technology and client application.The paper describes the process of research from bottom to top.First,this paper introduces the design of the hardware and the development of device drivers of the embedded system.The MCU(Micro Controller Unit) of the system is the high performance PIC18F2455 produced by Microchip Corporation,and peripheral devices include the Ethernet controller ENC28J60 and temperature and humidity sensor SHT75,which make it an integrated system by design and implement the drivers.Second,the development and realization of network protocols is the keystone of this paper.In order to enhance the performance based on the features of this MCU,the language used for realizing the network protocols is the instructions of MCU.The network protocols applied include 802.3 Ethernet protocol,ARP address resolution protocol,IP protocol and UDP protocol.The innovation of the imitated LRC algorithm to manage the ARP address buffer table.Furthermore it adopts intellectualized measures to process the different data flows of network.Third,the difficulty of the paper is the realization of NAT hole punching technology that is used for the communication between the embedded system and hosts within a local network. This embedded system can realize the network hole punching technology through a server platform with the control software and a fixed IP address.Last but not least,a reasonable,practical and simple protocol used for application layer and PC client software are designed,a sound experiment environment is established elaborately,and a lot of experiments in various network environments are made,which include in a single network segment and cross-gateway.The experiments show that the performance of this embedded system is high stable and outstanding.