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Android is the name of open source mobile operating system based on Linux platform Internet giant Google in 2007, November 5 announcement that the platform consists of Linux operating system kernel level, Android framework layer, UI framework layer and numerous Android application composition, It is the first mobile intelligent terminal to create a truly open and complete mobile Internet operating system, tablet PC has been widely used in smart phones and the rise recently.
As an emerging mobile Internet operating system, Android Although originally designed for smart phones, but because of its own mobile Internet properties, powerful scalability and openness, as well as Google has released an uninterrupted upgrade from version assigned to it extremely strong vitality and boundless potential to attract more and more competition terminal electronic device uses an open platform Android as its operating system.
The rapid development of Android has also aroused strong interest in automotive equipment manufacturers, in order to develop more markets and services, more and more powerful car engine manufacturers will use Android as the base operating system on-board equipment. However, as mentioned above, Android so far is mainly designed for mobile phone operating system, does not apply to the car maker. To meet both on-board equipment and operating practices of the user experience, but also compatible with Android features, namely mobile Internet, third-party software extensions, openness and more "flip", more "cool", sleeker user experience, it must be secondary development of the depth, as the basic open source operating system, Android also provides us with such a possibility.
Standing angle vehicle computer industry professionals, in the face of Android brought us market opportunities, our minds still have to be more sober and clear: Android car machine must first be a car machine, we used to develop Android car machine technology, the Android machine to adapt to the car, rather than vice versa will allow the car engine to Android. We only put traditional car machine functions on Android do well to improve, the next Android is an exciting mobile Internet service, which means that Android only function expansion board equipment, and must not drive the machine to literally become a large cell phone or other nondescript things. On-board equipment has matured as a commodity, has its own stringent user experience and product definition, the Android application to the destination machine car is to further improve, improve and expand the user experience and product definition, these "proven" user experience and product definition can not change, as the vehicle computer products "lifeline" products ease but can not regress. It appeared on the market some utilitarian approach, not efforts to develop Android-depth view of the actual needs of the car machine, so that the car will go machine Android, the Android system car made a nondescript large phone; or opportunistic in order to avoid the difficulty of Android car transformation and hard work, the traditional car engine function uses MCU, MPEG or WinCE to achieve, euphemistically called "dual system Android", but the actual user experience is poor, very low, this Although the kinds of acts can be blinded for a time the market, but the market will eventually be seen through, spurned, an industry joke.
We can clearly say: Android is a mobile operating system itself, not Android depth development, it is impossible to make a real car machine! At present, many so-called Car Android development is also limited to the development and application layers, and the "depth" of the word has nothing to do. The above mentioned Android system by the embedded Linux operating system kernel level, Android framework layer, UI framework, and applications layer, and the depth of the development of Android machine is the car for these four major levels, let's briefly introduce Android-based vehicle equipment system to achieve the technical challenges faced:
1. The realization of on-board equipment on Android MPU + MCU + MPEG communication protocol Core smart car machine device architecture is MPU, MCU and MPEG, MPU is responsible for vehicle computer system to display the user interface, handling vehicle systems and user interaction and the need to complete the MPU features such as navigation, Internet and so on; and the MCU on the train system is important to the control unit, MPEG is the process of decoding and playing the disc.
In the Android-based vehicle computer system, MPU (currently commonly used A8 / A9 core chip of ARM, ARM11 running Android will be very reluctant to) operating system is Android, relatively complex, and the MCU and MPEG software is typically small closed system, compared to Android will be much simpler. Since the vehicle system involves three three hardware system kernel, we need to have from hardware to software communication protocols to ensure that these three systems can work together. In a conventional vehicle systems, since the MPU limited functionality (as a lot of it is just to use the navigation board), the operating system of the system is relatively simple to achieve this communication protocol generally without regard to access multiple applications and processes simultaneously the communication protocol.
But implemented on Android communication protocol situation will be different: Android as a powerful mobile operating system, has a complex multi-process and multi-thread mechanism, it is inevitable to achieve this communication protocol on Android to consider a number of application processes even in the case of system services at the same MCU and MPEG communications, coupled with the communication protocol most news will affect the MPU interface display, which determines the mode of the communication protocol on Android Android system must be based on a service implementation, need to use the Android system services MPU side protocol stack, we need to be able via the communication mechanism between the Android Binder process to ensure that multiple processes MPU and MCU and MPU can work together, but also able to register a callback function way to make the system the user operates the service or change the peripheral form of messages reported to the application. So if you want to implement the communication protocol on Android, the first step is to realize the Linux operating system kernel hardware interface drivers, the second step to implement the protocol stack system services in Android framework layer, the third step is to define the system the interface between services and applications, and to use the interface complete with MCU and MPEG-vehicle communication device for custom Android applications.
For the realization of the principle of the communication protocol of the vast majority of Android developers should be able to have a preliminary understanding of the challenges is that although powerful Android as a mobile operating system already contains many common system services (such as power management services, window management service telephone service function, input method services, etc.), but it is after all not specifically designed for on-board equipment, it can not be expected to have a regular vehicle device MPU, MCU and MPEG communication protocol. Common Android developers have the ability to develop cool to the force application interface, is they do not need to understand Android What are the system service because Android SDK has blocked these difficulties to application developers, but for the development of vehicle communication protocol and implementation , Android SDK also can not do anything, only those who have the ability to Android's Linux kernel layer, system framework and UI framework layer depth research and development team in order to achieve this perfect core communications protocol vehicle equipment, and as far as we know currently have the ability to able to do this the team is still rare."Source" Management 2. vehicle equipment
When it comes to on-board equipment, experienced development team will be familiar with a concept that is "Source (Source)", the car machine, the source is not abstract, contrary to its definition is very specific, so-called sources are from the user's actions, such as insert / remove the SD card, plug / unplug the USB device, press the navigation, radio or music player keys, insert / eject CD, turn linked to reverse gear reversing camera and so on. This concept is very good, because the car while driving machine users do not have to focus so much idle operation, they are able to do the most simple operation, plug and play better, so that they drive on the operator interface when several ten applications to find the audio playback application, and then find and select the file you want to play to play, this is something to human life. But Android Is this strategy is not defined, used Android phone friends all know, we are all a bunch of applications to find the music icon in the icon, then click on Run and then select songs to play. Therefore, despite the current Android application functions and interface design is very simple, but the demand for on-board equipment is more to the force of simplicity, requirements and vehicle computer peripherals closely response, such as hanging reverse gear, reversing camera interface to start immediately, insert the CD to immediately start the CD player to play music, play music during and after parking stall to start the car again automatically break before playing the song, etc. all need Android car program be implemented.
Android on-board equipment in order to achieve the perfect response to the user's source is not rigidly adhere to the original design of Android, the need for framework layer, UI framework layer and application layer depth development, this process is very complex, and the need to communicate the above-mentioned interactive systems and services for synchronization protocol to ensure that the handover source of demand in line with the car engine while the vehicle computer applications development must follow the source management strategy MPU, MCU and MPEG state, but also to ensure that the source will not affect the management of the first Android party application uptime. Actually source Android system architecture changes related to far more than that, the limited space of this article does not do much more elaborated.
3. The key response vehicle equipment
Familiar friends all know Android Android requires at least three hard buttons menu, and normal use back home to ensure the systems and applications, in general, the three keys are GPIO mode and MPU connection, Linux system core will three enter keys interrupt reported to the Android framework layer and then forwarded by the system to the application layer framework. This is a practice standard Android mobile devices, but for on-board equipment is not so simple, and the characteristics of the car engine is limited key space, the situation is complex, A model car machine may have 10 keys, B model car machine may only three buttons, sometimes is not the key, the knob (rotary encoder), steering wheel controller or remote control. At the same vehicle computer processing of these input devices and Android also is not the same, these input devices are generally connected to the MCU are unified by the MCU for processing and then through the above-mentioned communication protocol to send to the MPU, which led to the original Android for key input system mode can not be directly applied to the machine in the car, and if a type of vehicle unit can not provide for the Android standard keys even more trouble, in order to deal with the key issues mentioned above, a series of Android on-board equipment, must be in Android system tailored to the needs of the car depth machines.
Obviously, the key-board custom Android system is an extension of the MPU and MCU communication protocols, as also on the Android framework layer is improved, because it involves more levels and modules, with considerable depth and effort, not a general small Android team capable of.
4. Management of the audio source
Car audio source machine management can be described as extremely complex, DISC / SD / USB / AUX / iPod / Bluetooth / Radio / Navigation / games, etc., will design the hardware and software have a huge impact, a long history of traditional car machine, already we have a very mature solution. But to achieve the Android audio switching, have renewed stove, Android itself is divided into audio processing: MUSIC / RING / ALARM / SYSTEM / Phone and other types, these are the types of audio output for MPU, but why have a car machine the audio output is not too MPU, for example, DISC / radio / iPod / Aux / Bluetooth, etc., how to switch the audio source and volume control and audio output by the MPU (such as SD / USB / navigation / game) integrated together ? This is a big problem. For example, adjust the volume when playing a DVD, should prompt the user to the current volume, but this is MPEG output, MPU and no audio output, according to the Android strategy now is not if the MPU audio output, only adjust the ringing tone volume ( you can try to come up with their own mobile phone), which is obviously not true, can only be reconstructed Android audio system service: since logically the current audio source has switched to the MPEG, and we will adjust the volume for heavy audio system configuration service to MCU transmit volume control message, but also to modify the UI framework layer because Android original volume indicating and adjustment for Android interface is also standard audio type, we need the UI layer for each audio frame source type DISC / radio / Bluetooth so provide user-defined volume gain adjustment function, and the need to start the corresponding application after switching matching audio source.
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