Incorporating effective power management into a design using the Android distribution of the Linux operating system using either its native power management framework or the widely used Universal Serial Bus hardware specification.
Editorial Note: Excerpted from Unboxing Android: A hands on approach with real world examples, by Rajaram Regupathy, the author takes you through the process incorporating effective power management into a design using the Android distribution of the Linux operating system using either its native power management framework or the widely used Universal Serial Bus hardware specification.
USB technology has evolved over the years as the standard for connecting peripherals like keyboards, printers, and so on, to personal computers, and as a result, USB has replaced serial and parallel ports. Modern devices like smart phones and game controllers have also adopted this technology as a primary transport mechanism. As part of their evolution, USB evolved from a data interface to an important source of power to charge portable devices like a smart phones, or even to power up an external audio speaker. In Battery Charging Specification, the Battery Charging Working Group of the USB Implementers Forum (USB-IF) has standardized how a USB power source has to behave, the different types of USB power sources, and how much power a device can consume when connected to a USB source.
This article explores USB-based charging that you, as an Android developer, need to know to develop applications related to charging in various user contexts: wall charger, personal computer, and charging dock. Because both will be important, this article will discuss battery charging in the context of both the USB.org formal spec as well as the native one included within the Android framework.
USB Battery Specification overview
In a way, the main focus of the USB Battery Charging 1.2 specification is to define the characteristics of different chargers and describe their mechanisms for how to detect the chargers. This section focuses on the different types of charging options (USB ports and chargers) and their characteristics in brief. The specification also details the mechanism that can differentiate the different types, but that is beyond the scope of this book. Before you study the different types of charging ports, you should first understand some key USB terms relevant to this section.
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