Arm + Linux-based Embedded Vpn Development Platform-based Design And Realization

With broad application of Internet, the firms'requirement for safely transfering data through Internet becomes stronger. VPN technology that ensures safely transferring data through Internet appears in such situation and gains success in the market by it's advantage compared with Private Network.During recent years, the arm microprocessor gains broad application in embeded application field because of it's advantages of low cost, high performance. The open source linux OS is famous for it's advantages of steadiness, open source, easy modification.The VPN designing platform being designed in this project is the application of the arm technology and embedded linux technology in VPN field. Through three aspects of overall designing, hardware designing and software designing, this paper introduces the designing process and realization method of this VPN designing platform and give a detail of the software designing that the author is responsible for during designing process. The stage of overall designing: Chose arm & linux as the framework of this system. Divide the function requirement of this system into six modules which are IPSec module, hardware auto-restarting module, ethernet communication module, serial communication module, real-time clock module, linux OS platform module. The stage of hardware designing: Chose sdram and flash as the physical storage of this system; Designing and realizing sdram circuit, flash circuit, watchdog circuit, RTC circuit, Serial communication circuit, networking communication circuit; The stage of software designing: Designing the bootloader program with the function of downloading file with TFTP protocol, flash writing and reading, serial communication, booting linux kernel and so on; Transplanting the linux 2.4 kernel on this hardware system; Designing and realizing linux driver and give a detail of RTC and WDT drivers'designing and realization.