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Using PWM from a Linux Shell

This mini guide explains how to enable and test a pwm signal using linux command line.

Instructions​

To enable a PWM the steps are as follows (some details might differ depending on the product)

  1. Maneuver to the /sys/class/pwm folder
    In this folder the pwm controllers should be visible as folders pwmchip0, pwmchip1, ...
  2. Enter the chosen pwmchip folder.
$ cd pwmchip0
  1. Export the first pwm (the iMX pwm controllers have one pwm each) by
$ echo 0 > export

This exposes the actual PWM in folder pwm0.

info

If the PWM has been allocated for use by another driver such as a display backlight driver (for control of the backlight brightness), then it might throw an error. If so, check your device tree

  1. Enter the pwm folder
$ cd pwm0

and configure the pwm:

$ echo 10000 > period
$ echo 6000 > duty_cycle
$ echo 1 > enable

This should set the PWM frequency to 100 kHz and set the duty cycle to 60 kHz.