巡线小车里面两个通道的那个代码不懂~求讲解

[zrtd]

pwma = Pin('P7')
pwmb = Pin('P8')
tim = Timer(4, freq=1000)
ch1 = tim.channel(1, Timer.PWM, pin=pwma)
ch2 = tim.channel(2, Timer.PWM, pin=pwmb)
ch1.pulse_width_percent(0)
ch2.pulse_width_percent(0) 

[yuan]

视频教程9-追小球的小车，你看一下视频里面有每一句的讲解。巡线小车的car.py pid.py和追小球的小车完全一样。
https://singtown.com/video/