How can I set PWM in PocketBeagle

I want to control PWM but I don’t know how can I set it.

I use Debian 9.3 I try. …

cd /sys/class/pwm/pwmchip0
echo $index > export
cd pwm$index
echo 1 > enable
echo 1000000000 > period
echo 500000000 > duty_cycle

but nothing happened . … and how do I know which PWMchip is PWM0A , PWM0B, PWM1A , PWM1B

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