According to RK3399 Wiki / PWM you should (as root): acaeronet Export PWM0 to users echo 0 > /sys/class/pwm/pwmchip1/export Control a PWM fan's speed by setting the PWM's period and duty_cycle. echo 0 > /sys/class/pwm/pwmchip1/pwm0/enable echo 50000 > /sys/class/pwm/pwmchip1/pwm0/period echo 1 > /s...