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Android to do the transplant system, two working

In Electronic Infomation Category: A | on April 14,2011

Android system is to transplant the main purpose of the hardware in a particular run Android. In the transplant process, an important aspect is to grasp the key points to reduce the workload. From the perspective of the work, first of all be familiar with the hardware abstraction layer interface, and EP1S40F780C6 datasheet and secondly to integrate and EP1S40F780C6 price and reuse of existing drivers, the main workload of the hardware abstraction layer implementations. To better understand and EP1S40F780C6 suppliers and debug the system should also be duly informed of the upper layer of hardware abstraction layer calls the situation.

Transplantation has two main parts of the work:

Linux Driver

Android hardware abstraction layer

Linux drivers work in kernel space, Android hardware abstraction layer working in user space, with the combination of these two parts, you can make a huge Android system is running in a specific hardware platform.

Android transplantation main shown in Figure 1.

Figure 1 Android transplants main

With the specific hardware in the system, usually Linux needs to achieve its drivers, these drivers are usually the standard Linux driver, the Android platform and other Linux platforms are basically the same. The realization of the main aspects of Android system Hardware Abstraction Layer (Hardware Abstract Layer), the hardware abstraction layer to the next call to the driver in Linux, and to provide interfaces for the Android rest of the system (usually a local framework for the Android layer) call.

Tip: Android hardware abstraction layer interface is the interface layer of the local transplant, not a standard API, does not have forward or backward compatibility.

Android system needs in the transplant, which mainly consists of the following parts:

Display section (Display)

Including the framebuffer driver + Gralloc module (optional implementation)

User input section (Input)

Including Event-driven + EventHub (Android standard content)

Multimedia codec (Codec)

Including hardware Codec Driver + Codec plug-in (such as OpenMax)

3D accelerator part of the (3D Accelerator)

Including hardware OpenGL drivers + OpenGL plug-in

Audio part (Audio)

Including Audio driver + Audio Hardware Abstraction Layer

Part of the video output (Video Out)

Including video display driver + Overlay hardware abstraction layer

Camera part of the (Camera)

Including the Camera Driver (usually a v4l2) + Camera hardware abstraction layer

Phone parts (Phone)

Modem Driver + RIL library

Part of the global positioning system (GPS)

Include GPS-driven (usually serial) + GPS hardware abstraction layer

Part of wireless LAN (WIFI)

Wlan driver and protocol, including the adaptation layer + WIFI (Android standard content)

Bluetooth part (Blue Tooth)

Including BT + BT drivers and protocol adaptation layer (Android standard content)

Sensor section (Sensor)

Including driver + Sensor Sensor Hardware Abstraction Layer

Vibrator part (Vibrator)

Including Vibrator driver + Vibrator Hardware Abstraction Layer (Android standard content)

Backlight part (Light) Light-driven + Light

including the hardware abstraction layer

Advisor section (Alarm)

Including the driver and RTC Alarm system + user-space call (Android standard content)

Battery parts (Battery)

Including battery part of the driver + hardware abstraction layer cells (Android standard content)

Android has a lot of components, but not every component needs a transplant, for some components of pure soft, there is no need for transplantation. For some components, such as the browser engine, although it requires the underlying network support, but not directly to their portable network interface, but through the wireless LAN data connection or the telephone system to complete the standard network interface.

Android transplantation can be divided into several main types: the basic graphical user interface (GUI) components, including display part and the user input part; and hardware acceleration related parts, including the media codecs and OpenGL; audio and video input and output links, including audio, video output and camera parts; connected components, including wireless LAN, Bluetooth, GPS; phone part; ancillary components: including the sensor, backlight, vibrator and so on.

Transplantation in addition to the above, power management is also very important aspect of it and the various subsystems Android have a relationship.

Android system is mainly part-graft shown in Figure 2.

Figure 2 Android system main graft components

For most subsystems, the hardware abstraction layer and the driver is required to realize the actual situation of the system, such as: sensor parts, audio parts, video parts, camera parts, telephone parts. There are also some subsystems, the hardware abstraction layer is the standard, only need to implement Linux kernel driver can, for example: input part, the vibrator part, some of the wireless LAN, Bluetooth section and so on. For standard hardware abstraction layer of the system, sometimes also usually need to do some configuration work.

Today, with the Android system development, it has been more than just a platform for mobile devices can also be used in consumer electronics and smart appliances, such as: Internet, e-books, digital television, set-top box, fixed telephone. In these platforms, mobile devices often need to implement less than the parts. In general, the basic user interface components (including display and user input) is needed transplant, the other part is optional. For example: telephone system, vibrator, backlight, sensors and other non-mobile devices generally do not need to implement the system; for some fixed location devices usually do not need to implement the GPS system.

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