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Update backlight.md

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ReFil 2023-10-03 11:54:15 +01:00
parent a164685d5f
commit b89bf69b4f
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docs/docs/features/backlight.md
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@ -82,14 +82,14 @@ Then you have to add the following lines inside the root devicetree node on the
compatible = "pwm-leds"; compatible = "pwm-leds";
label = "Backlight LEDs"; label = "Backlight LEDs";
pwm_led_0 { pwm_led_0 {
pwms = <&pwm0 45 10000 PWM_POLARITY_NORMAL>; pwms = <&pwm0 0 10000 PWM_POLARITY_NORMAL>;
label = "Backlight LED 0"; label = "Backlight LED 0";
}; };
}; };
}; };
``` ```
The value inside `pwm_led_0` must be the same as you used before. The value inside `pwm_led_0` after `&pwm0` must be the channel number. Since (`<ch0-pin>`) is used in the `&pwm0` node the channel in this example is 0.
In this example `10000` is the period of the PWM waveform, some drive circuitry might require different values, it could also be altered in the event the drive frequency is audible. In this example `10000` is the period of the PWM waveform, some drive circuitry might require different values, it could also be altered in the event the drive frequency is audible.
@ -175,6 +175,8 @@ Then you have to add the following lines inside the root devicetree node on the
}; };
``` ```
The value inside `pwm_led_0` after `&pwm0` must be the channel number. Since (`PWM_OUT0`) is defined in the pinctrl node the channel in this example is 0.
In this example `10000` is the period of the PWM waveform, some drive circuitry might require different values, it could also be altered in the event the drive frequency is audible. In this example `10000` is the period of the PWM waveform, some drive circuitry might require different values, it could also be altered in the event the drive frequency is audible.
If your board uses a P-channel MOSFET to control backlight instead of a N-channel MOSFET, you may want to change `PWM_POLARITY_NORMAL` for `PWM_POLARITY_INVERTED`. If your board uses a P-channel MOSFET to control backlight instead of a N-channel MOSFET, you may want to change `PWM_POLARITY_NORMAL` for `PWM_POLARITY_INVERTED`.