为了更好的理解安卓的层次关系，本文在RK3399的安卓系统上增加LED灯的外设，并使用APP打开关闭LED灯。以这样一个最简单的实例，来演示从上层到底层的调用过程。首先从最底层的kernel层开始。 一、驱动开发 Kernel层就是要将LED硬件接入到系统，完成驱动的开发。

Rapid market growth for HB (high-brightness) LEDs is driving what was once a niche industry into full-fledged high-volume production. With the emergence of applications such as display backlighting, ...