Research And Transplant Of LwIP Protocol Based On ARM

As a realization of Internet communications protocol, TCP/IP protocol was paid more and more attention in embedded application field. Embedded equipments, which aim to direct exchange information in Internet, should support the TCP/IP protocol. Embedded system has such features as small kernel, compact, strong specificity, high immediacy, power dissipation and environment strictly demand. Based on these characters, it appears that traditional TCP/IP protocol became not suitable to embedded systems for transplantation. There are two ways to apply the embedded system network access. One is constructing minor communications protocol in accordance with the principle of the TCP/IP protocol. The other is transplant existing minor network protocols, which is proper to the embedded system.Firstly the current status of embedded network protocol research and the contents of this thesis were introduced. The LwIP protocol stack principle, especially the IP protocol, TCP protocol, ICMP protocol and UDP protocol, were analyzed. Because system call and data structure with operating system concerned were not adopted in LwIP, an operating simulation layer between LwIP and operating system, which provide system service, should be affiliated. The protocol held the TCP protocol main function, and reduced the RAM's occupation as well.Secondly, the operating system simulation layer and LwIP interface layer were realized in the transplantation. Without relying on the operating system operation, operating system simulation for the agreement and operating system layer, which need realize the signal, mail-box, thread and critical protection operation, provided an interface between operating system and protocol. LwIP interface layer, which provide various device drivers for different hardware, should inculde such funtion as system initiation, Ethernet initiation, thread receiving, data packet reading and sending.Finally, the testing design architecture was presented in this thesis to test the transplant protocol in ARM development board andμC/OS-II operating system. By the analysis of the experimental result, it shows that the transplanted protocol provided the basic network functions and worked fluently.