PWM用户态操作接口/sys/class/pwm

设备树设置了几路PWM，/sys/class/pwm目录下就会生成几路对应的pwmchipN。

调出PWM子目录

echo 0 > /sys/class/pwm/pwmchip2/export

关闭PWM子目录

echo 0 > /sys/class/pwm/pwmchip2/unexport

引脚电平正常或翻转

echo normal> /sys/class/pwm/pwmchip2/pwm0/polarity

频率*周期=1，计算频率。

设置PWM周期，单位ns

echo 50000 > /sys/class/pwm/pwmchip2/pwm0/period

设置PWM占空比，单位ns

echo 10000 > /sys/class/pwm/pwmchip2/pwm0/duty_cycle

使能PWM

echo 1 > /sys/class/pwm/pwmchip2/pwm0/enable

关闭PWM

echo 0 > /sys/class/pwm/pwmchip2/pwm0/enable