How To Use Pwm

VIM3 board use pwm by pwm_f gpio

There is no pwm_f configuration in dts configuration file, You need to add the following configuration in arch/arm/boot/dts/amlogic/kvim3.dts

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&pwm_ef {
status = "okay";
+ pinctrl-names = "default";
+ pinctrl-0 = <&pwm_f_pins2>;
};

Confirm which physical pin corresponds to hardware pwm

PWM_F on VIM3 GPIO-Out

switch to root user

Ordinary users can’t control gpio, so they need to switch to root first

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kvim3:/ $ su

set and open pwm

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root@Khadas:~# echo 1 > /sys/class/pwm/pwmchip4/export
root@Khadas:~# echo 1000000 > /sys/class/pwm/pwmchip4/pwm1/period
root@Khadas:~# echo 500000 > /sys/class/pwm/pwmchip4/pwm1/duty_cycle
root@Khadas:~# echo 1 > /sys/class/pwm/pwmchip4/pwm1/enable

if you successfully turn on the hardware pwm, you can see the waveform through the oscilloscope
pwm-Oscilloscope

note: If you use an oscilloscope to check the waveform, remember that the board and the oscilloscope need to share the same ground

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root@Khadas:~# echo 0 > /sys/class/pwm/pwmchip4/pwm1/enable