一个宽度脉冲调制pwm的模板，因为是学习使用的，增加了数据输入以便在开发板的led灯中观看实验现象，输入数据越大led的亮度越大-A pulse width modulation pwm template, because it is learning to use, increasing the data input for viewing experimental phenomena in the development board led lamp, the greater the gre