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Title: PWM problems [Print This Page]

Author: Maverick_by_ Time: 5/12/2023 22:32
Title: PWM problems
I have a custom board based on RK3568jq.
I made Linux minimal image using Yocto:
https://wiki.t-firefly.com/en/Fi ... e/manual_yocto.html
I added PWM control and it works fine using next command:echo 100 > /sys/class/backlight/backlight/brightness

but as i can see using oscilloscope , the frequency of PWM signal is about 40 seconds instead of 20 kHz !

my dtsi-file modifications:
rk3568-firefly-roc-pc.dtsi

backlight:backlight {
      status = "okay";
      compatible = "pwm-backlight";
      pwms = <&pwm4 0 50000 0>;
...
}

lvds_panel: lvds-panel {
      compatible = "simple-panel";
      status = "okay";
      backlight = <&backlight>;
.....
}

what im doing wrong about frequency?
The third paramenter 50000 is frequency in nanoseconds ?

pwms = <&pwm4 0 50000 0>;

tchip_askquestions

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Author: 时间的蝴蝶 Time: 5/15/2023 17:45
The 50000 is means 50000ns.
If you need to set the maximum clock frequency, please use 'echo 255 > /sys/class/backlight/backlight/brightness'.

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