单片机采用脉冲宽度调制（PWM）方式控制LED灯亮度;通过软件模拟pwm.在一定的频率的方波中，调整高电平和低电平的占空比，实现LED灯亮度控制。(SCM uses pulse width modulation (PWM) mode to control the brightness of LED lights; through software simulation pwm. in a certain frequency square wave, adjust the duty cycle of high level and low level, realize the LED light brightness control.)