| Since Android smart operating system released in 2008,it has iterated over several versions and has been widely used.With the increasing demand of smartphone function and performance,various integrated sensor IC are being developed.Among them,the air pressure sensor can provide more accurate elevation information,which has broad application prospects and market potential on high-end mobile phone.But on another hand,pressure sensor is rarely used in middle and low end cell phone for high development costs,which restricts its popularity trenmendously.Thus,this paper studies on air pressure sensor worked on Android platform,and proposed a novel development method of layered architecture,which can significantly lower the development costs of pressure sensor system.The driver and application based on Exynos 4412 platform is realizesed at the first time.Firstly,the piezoresistive MEMS pressure sensor chip BM1383 GLV is selected among pressure sensors by evaluating the requirements of pressure sensor module,while the working principle and functional characteristics of the sensor are analyzed at the same time.BM1383 GLV sensor has many advantages like high accuracy,low power consumption,etc.and is suitable for several kinds of mobile devices.Exynos 4412 is the first quad-core processor officially released by Samsung Corp.,while the developing board of Exynos 4412 using Android system is also analyzed and introduced.Secondly,the hardware and software development platform of the pressure sensor module based on Android OS is introduced in detail,while the I2 C driver of BM1383 GLV sensor and the hardware service framework based on Android platform are also analyzed in detail.The calling process of sensor hardware resources on Android system is described at the same time.Based on works mentioned above,various possible integration methods of BM1383 GLV pressure sensor on Android system are analyzed and compared.According to the analysis and design methods above,the general design method and hierarchical design method of pressure sensor integration based on Android intelligent operating system are given.Device identification,data uploading,device controling and other functions are realized in the kerne1 driver layer.Hardware Abstraction Layer(HAL)is the interface between OS and hardware,it connects downward with the kernel driver layer,connects upward with the Java Native Interface(JNI)layer,which realizes the functions of user space node invocation,data forwarding,and the functions of service construction.Java and C++ communication in the JNI layer of the upper layer,realizes the service invocation interface in the Android OS interface,and invokes the interface in APP.Through the use and testing of sensor and corresponding systems in different versions of Android system on Exynos 4412 platform,the results show that the designed system has good display effect under various screens of 3.5 to 5.0 inches.The system can display correct information of pressure and temperature provided by the sensor in real time,and the overall operation is smooth.In addition,the system can control the error of height measurement within 2% through the secondary operation of the barometric raw data,which meets the accuracy requirement of height measurement.The preliminary development of BM1383 GLV sensor on QaulComm SnapDragon 400 platform is carried out by using the developed driver,while the design costs are reduced by more than 60% compared with the first development of Exynos 4412 platform.It shows that the hierarchical design method of driver adopted in this paper can effectively reduce the costs of subsequent research and development. |
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