Is the sysfs pwm interface using hardware pwm?

Question

I followed this answer to enable PWM on my Beaglebone Black, but I wasn't sure if that method is using the PRU to do hardware PWM or if it's toggling the pin in software? I see other references to /sys/class/pwm/ehrpwm (e.g. here) which I'm more confident is hardware PWM, but I'm not sure how to enable that interface.

To summarize how I'm enabling PWM:

echo am33xx_pwm > /sys/devices/bone_capemgr.9/slots
echo cape-universal > /sys/devices/bone_capemgr.9/slots
config-pin P8.13 pwm
echo 6 > /sys/class/pwm/export
echo 1 > /sys/class/pwm/pwm6/run
echo 50000 > /sys/class/pwm/pwm6/period_ns
echo 50000 > /sys/class/pwm/pwm6/duty_ns

Thanks!

Alex Hiam · Accepted Answer · 2015-11-05 13:42:56Z

1

Yup, that's using the hardware PWM modules - the am33xx_pwm overlay enables all the different PWM subsystems (eHRPWM, eCAP), then the PWM kernel driver configures the corresponding PWM module for the pin being configured.

answered Nov 5, 2015 at 13:42

Alex Hiam

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