Using Android on ARM for feature phones

The Android operating system was previously used mainly for mobile devices such as smartphones and tablets, and now it will enter more markets. ARM processor developers tend to take advantage of Android's flexibility, performance and versatility. The Android system based on the open source Linux kernel still retains many characteristics of open source software. Even after Google acquired Android, it has only transformed into a hybrid model - considering the operating system between open source and commercial. The advantage of Android1 is that there is no licensing fee and it is free from the demands of the open source community. Android is already pre-configured with powerful functions. Google defines the middleware, multimedia framework and key system firmware of the operating system, which is different from other Linux systems that require developers to integrate functions into the open source kernel themselves.

As of October 2011, the number of Android smartphone applications has exceeded 400,000, reflecting its strong growth. The rapid update of Android versions and the future roadmap show the durability of the system. The latest release of Android 4.0 (also known as Ice Cream Sandwich) combines the smartphone and tablet versions of the system into one.

Android's New Frontier

Android has already gained a large market share in mobile phones and is beginning to make inroads into similar markets, including tablets, thin-client PCs, wireless video conferencing systems and televisions using Google TV.

The smooth touchscreen interface of smartphones has become so popular that it has begun to infiltrate everyday home and business products. Thanks to its flexibility, Android has also found its way into rugged PDAs, smart appliances, medical diagnostic user interfaces, and even industrial systems.

From a functionality perspective, most of the apps mentioned above have something in common. All of them emphasize multimedia content and feature a robust, graphics-centric, smooth touch user interface and communication components - all Android strengths!

Designers of these new products should be aware of the differences between Linux and Android when considering integrating existing applications with the Android environment. The two systems have many similar functions, such as multimedia processing, file system responses, cocs, driver patches, and other software modules. But they are not the same, even though Android is built on the Linux kernel. Designers need to recode during the migration stage from Linux to Android.

Optimized for ARM cores

The Android operating system is fully optimized for ARM processor cores, specifically the ARM Cortex-A series cores, including the ARM Cortex-A8. This processor has netbook-level features and low power consumption, making it ideal for mobile embedded systems. ARM Cortex-A8 devices use ARM's advanced SIMD technology called NEON to accelerate encoding or graphics operations, which can significantly improve performance over direct ARM or THUMB encoding. Texas Instruments' ARM devices integrate the NEON advanced SIMD engine. ARM9 cores are widely used in embedded systems, but Android is not optimized for these cores. It can be used on ARM9 devices, but the performance will be severely reduced.

Android systems usually focus on multimedia applications, and developers should pay attention to how the system handles video, audio, and graphics. Android comes pre-installed with many low-resolution multimedia codecs, which is the basis of the ARM Cortex-A8 general-purpose core. However, many processors in the industry, such as Texas Instruments' OMAP, DaVinci video processors, and C6000 DSP + ARM processors, combine the ARM core with the DSP. Doing so can help the DSP share the processing tasks of the ARM core and provide stronger multimedia processing capabilities.

Android Development Tools

Android provides developers with Java and C/C++ development languages. Java uses the Android SDK (Software Development Kit) and the Dalvik virtual machine optimized for mobile devices. Java can run in any environment that supports Java. The Android NDK (Native Development Kit) uses C/C++ coding, which limits the coding to a specific CPU architecture. However, since most Android devices are based on ARM, this is not a serious limitation. It is a big problem for x86 manufacturers who want to use Android. Pure Java applications can run normally, but ARM applications developed using NDK code need to be manually ported to x86 devices.

Developers evaluating Android devices can use a complete virtual environment to build applications before moving to a physical device. The environment can be downloaded at http://developer.android.com/sdk and can run on Apple, Linux or Windows PCs.

Figure 1. Framework application programming interface (API), debugging code, and tools and output for the Android SK. Texas Instruments' Code Composer Studio v.5 IDE supports the Google Android Development Tools (ADT) plug-in.

The Android Development Tools (ADT) plug-in provided by Google supports the popular Eclipse integrated development environment (IDE). Eclipse is bundled with many tools to enable rapid project development, application interface development, adding components and debugging code based on the Android Framework API, tools for Android SK, and output of completed code. Texas Instruments' Code Composer Studio v.5 IDE (Figure 1) is based on Eclipse and has advanced debugging features (such as Linux Aware Debug), hardware debugging, simulation, and other functions. Developers can use Code Composer Studio and ADT plug-ins to debug Android Java and C/C++ code, Linux kernel, DSP code, etc. directly in the same IDE. Developers can also run Android virtual machines through Code Composer Studio and ADT plug-ins.