The Design And Realization Of Touch Screen System Based On Android Platform

Google's Android is an open source software for mobile devices that includes an operating system, middleware and key applications. Android's mobile operating system is based on a modified version of the Linux kernel. There are no proprietary barriers of Android for other mobile industry's innovation.It allows all firms and individuals developing based on Android. Android open platform can not only promote the technology innovation,including the platform itself, and help reduce development costs, but also allow operators to easily develop their own products. At the same time, Google and other members of the Open Handset Alliance collaborated on Android's development and release, making a rapid progress of Android in recent years.Android mobile devices (smart phone, tablet PC, etc.) because of the operation method, are all made of a full touch screen as its main input device, and in order to achieve multi-touch, almost all use capacitive touch screen.It is not a long time since the development of the Android and capacitive touch screen widely used. Although there are a lot of Android handsets in the market, domestic and international basic research in this area is still in the empty stage, in particular, capacitive touch screen hardware system and Android based touch screen driver development. How to ensure the stability of the touch screen system, how to improve system performance, how to enhance the user experience, is the focus research of this paper.During research, I had a internship in Lenovo (Shanghai) R&D Institute, and had the honor to participate in touch screen system development of Lephone project. The main work are as follows.1. Android system architecture and mobile hardware architecture is conscientiously learned.The touch screen hardware system based SPI interface is carefully designed.2. In order to enhance the user experience, the touch screen is designed as A area and B area, A area for the detection of the touch point coordinates, B area for the detection of touch gestures. And parameters of B area is reasonable set.3. Android Linux Kernel is in-depth researched, particularly the input subsystem, SPI subsystem, work queue mechanism, and so on.4. Then the data transmission and protocol of touch screen control IC is designed. Touch screen driver into the system kernel is written, making the data of touch screen control IC rapidly and accurately transfered to the operating system through SPI bus, to achieve interaction between operating system and touch screen hardware.5. When Android version upgraded to 2.2, multi-touch function in the driver layer is completed, making multi-touch data of touch screen IC reported to upper layer. As a result, the users can do two-point even five-point touching operation.6. Finally, a detailed touch screen module test is done, and some problems found during testing are solved, ultimately achieving the stable system, excellent performance, satisfied user experience.