The Android System Based On Arm Transplant And Optimization

Along with the development of the mobile internet, the widespread use ofintelligent terminals, especially the release of the first-generation Apple smart phoneIPHONE2G and the embedded open mobile application platform android in2007,bring new opportunities and challenges to many fields including mobile Internet,software development, industrial control, Cellular Phones Manufacturing and so on.Embedded system has been developing for a long time, but Android is an emergingsystem. All aspects related to this system such as structural analysis, system migration,system development and application development are in the initial stage. The relevantmaterial at home and abroad is so few. And combined with the openness of thisplatform, transplanting, cutting, and customizing of the system become extremelydifficult. On the other hand, the Android system is based on the Linux kernel at thebottom, added the Dalvik virtual machine in the middle, reallized by JAVA in the upperapplication framework. Complex multi-layer structure makes the Android systembooting need to load more than1000classes, and a lot of other resources. Andinitializing the Android runtime and lauching the22local services and40Androidservices also take over a long time.The system startup extremely slowly, bringingterrible experience to users, especially in the field of industrial control and digital TV.To solve these problems, we ported Android system and optimized the boot timeon the basis of the existing ARM platform S5PV210. The main works of system portingare Linux kernel porting, device driver porting and Android file system porting. Amongthe devices we ported, there include FLASH, LCD, Touchscreen, Keyboard and so on.To optimize the boot time of Android system, we developed two methods. One is thekernel-based mode, and the other is based on Uboot. Both techniques have the samebasic principles, such as organizing the system runtime status to system image by acertain fomat, saving the system image to non-volatile external memory and restoringthe system status at startup. The difference between the two kinds of technology is thatthe kernel based Quick Start technology needs to undergo the stage of kernelinitialization other than board-level initialization. The reason for that is the special limitation of image format. We need the stage of kernel initialization to establishthe environment for restoration. While in the other way, due to the design of the newimage format, the phase of kernel initialization before the restoration of the state is notneeded any more. The basic board-level initialization is the only necesseryprocedure. Therefore, the efficiency of the Uboot way is demonstrated to be the moreeffect than kernel-based mode, again from64.12%up to83%, achieving the purpose ofbooting the Android system in less than5seconds.