Rajaram Regupathy, Cypress Semiconductor
embedded.com (February 04, 2015)
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.
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