Building Embedded System Based On S3C2410A & Linux 2.6.22

The embedded system is a specia l purpose computer system focused onapplica tions and based on computer technology, and can be cutted out inhardware and software. It is suitable for the applica tion system that is verystrict in request of function, reliability, cost, size, and power consumption etc.In the embeded system field recently, Linux relies on the open sourcecode authoriza tion pattern based on GPL, and the characteristics of being easyto customize,cut out and porting, it applies and popularizes rapid ly to all kindsof different embeded systems and applica tion environments. It's being widelyapplied to telecommunication equipment, switch, router, mobile termina l,smart mobilephone, automobile electron, set-top box, enterta inment equipmentetc. Presently, most of newly-designed embedded systems, especia l rapidmold ing systems based on Soc would be given the software solution based onLinux operation system. Along with the more consumers and developers whichis familiar with Linux, the more be well up on embedded Linux aplica tiondevelopment comparing with VxWorks, LynoOS etc. Currently, embeddedLinux is on the way of high-speed progress, directly cutting out andcustomizing Linux kernel will be more and moe populariza tion. As Linux 2.6kernel released, it has been made great progress in performance and functioncomparing with 2.4 kernel, such as provid ing a preemptive kernel whichenhanced real-time performa nce, using the more effective process schedulingalgorithm, supporting more microcontroller with no MMU, rewritingarchitecture of drivers and programme model for newest wireless networkprotocol such as WLAN, Bluetooth, GPRS, CDMA, WiFi etc. and devices, sothat it can adapt well to variety of those devices. Recieving open and flexible Linux, combining with the widespread applica tion of embedded system,embedded Linux will be more stabiliza tion and more perfect., and It will beeven more extensive applied in all kinds of embedded systems especia lly inhigh-level embedded systems.Therefor, this paper ma inly researched the realization based onS3C2410A with ARM architecture and Linux 2.6 kernel, and particularlystated process of build ing embedded system through startup & load program orbootloader, Linux kernel, file systems etc.In development of embedded system, a sets of cross compile toolcha inmust be absolutely needed. Cross compile is process that codes compiled onsome host system such as PC can be executed on on other kinds of systemssuch as ARM. This paper not use existing cross compile toolcha ins butcrosstool to build newer toolcha ins. This way can give us some benefits ofrapid ly build ing all kinds of cross toolcha in based on all kinds of CPUarchitectures and different cross toolcha in versions based on one CPUarchitecture. The cross compile toolcha in the paper used executed so stably thatit compiled kinds of programs ran well in target board.The startup & load program is the first code collection be executed whensystem is reset, it ma inly to do the initia lize of hardware, boots the embeddedsystem and downloads programs to RAM and copies it to FLASH, and so on. Itis extremely important to embedded system program in module programdesign and firmware updating. This paper then describes the powerful andreliable function of U-Boot and the process of porting U-Boot to S3C2410A.And the porting key lies on understa nding in detail of the U-Boot's startup flowand the S3C2410A's steppingstone which can execute boot code loaded fromFLASH into steppingstone. Besides, some relative registers in S3C2410A mustbe well knowed. In transplating kernel process, the standard Linux kernel is too hugebefore the embedded systems which is limited in resources, so it is necessarythat Linux kernel would be cutted out and configured according targetplatform's hardware resource. When configuring, the majority of options mayuse its default value, only the sma ll part need to be selected in dema nd ofapplica tions , and the principle is to make the function codes which is dista ntfrom kernel and not often used compile into the loadable module so that it mayreduce kernel's size and memory consumption. To make the function codewhich is close to the kernel and often used compile directly into the kernel,ma inly the processor type, board type, device driver and file system should beconfigured.File system include root filesystem and the file system established on theFLASH. In process of build ing root filesystem, we used BusyBox tool in orderto conveniently and rapid ly build the root filesystem of embedded Linux. Thepaper, through configure, compile, insta ll BusyBox and build ima ge file of rootfilesystem, delivers a norma l method of how to use BusyBox to build rootfilesystem. On other side, the embedded file system is always established onsolid-sta te memory such as Nand Flash whitch require specia l file system. Wefirst introduced file system such as Cramfs, Jffs2 and Yaffs, then described theircharacters, compared their advantage, disad vantage and their applica tions ofvarious embedded environment. It is worth while refering Yaffs/Yaffs2filesystem which is specia lly designed for Nand Flash device and it is moreexcellent than other filesystems in I/O effciency. In process of porting Yaffs totarget board, we faced the problem that Yaffs mirror built by mkya ffsima ge toolcould not be correctly read by kernel. The reason is that ECC data structure ofNand device's OOB space in new Linux kernel and Yaffs is different. Theresolvent is to modify the oob data structure in source codes of mkya ffsima ge tool.Porting operating system is the precond ition and foundation of exploitinga embedded system. By porting embedded Linux 2.6.22 to the target board ofS3C2410A, this paper presents theories and methods of build ing embeddedsystem, describes concrete process of how to porting embedded Linux.According the paper's theories and methods, the compiled bootloader such asU-Boot, Linux kernel, some kinds of file systems all runs well and steadily inSBC2410 system, it prove that the above methods of porting embedded systemis viable, and it is helpful to exploit other kinds of embedded systems.