PWM configuration speed

Robotics & Edge Computing Jetson & Embedded Systems Jetson Xavier NX
1

Hello,

I’m trying to implement a wav player using the PWM output, on pin33 of my xavier nx.
I could test the PWM using SysFS, as well as sample code from jetson-gpio library

The idea is to output a high frequency PWM (~62.5kHz), change the duty cycle for every audio sample, then use a low pass filter to cut off the high frequency component and keep only the audible frequencies.

However, changing the duty cycle through SysFS seems to be taking lots of time.
Each call to the change duty cycle function takes about 196us. (most time is spent on the write() call the duty_cycle file)
Meaning my player can only write ~5100 audio samples/second.
Meanwhile the audio file sample rate is 44.1kHz.

I tried to read the pwm sysfs driver under drivers/pwm/sysfs.c hoping to find something that causes the delay but no luck so far.

Is there any faster way to change the duty cycle of PWM?
Any support would be greatly appreciated.

Thanks.

3

Hi,
From userspace the duty cycle of PWM can be controlled only by sysfs node @ /sys/class/pwm/pwmchipN/ knobs .

sysfs read/write is standard kernel supported apis used by the pwm kernel driver, so not much can be done here.

Are you interested in userspace or trying also to control from kernel drivers directly?.