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herbingkherbingk
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Merge to official Raspberry Pi repository
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‎README.md‎

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> [!NOTE]
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> This device-tree overlay has been merged to the official Raspberry Pi repository on 01/01/2025 and should be part of Raspberry Pi OS Bookworm with the next firmware release. Below information does still apply, but copying the pwm-gpio-fan.dtbo to /boot/firmware/overlays will not longer be necessary.
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# pwm-gpio-fan overlay
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Raspberry Pi device-tree overlay for a GPIO connected PWM cooling fan controlled by the software-based GPIO PWM kernel module
@@ -47,19 +50,40 @@ This made me write the **pwm-gpio-fan** overlay for my own use and publish it he
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There are several parameters you can specifity in the /boot/firmware/config.txt command line to customize the behaviour of the overlay:
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- "fan_gpio" BCM number of the pin driving the fan, default 18 (GPIO 18)
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- "fan_temp0" CPU temperature at which fan is started with low speed in millicelsius, default 55000 (55 °C)
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- "fan_temp1" CPU temperature at which fan is switched to medium speed in millicelsius, default 60000 (60 °C)
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- "fan_temp2" CPU temperature at which fan is switched to high speed in millicelsius, default 67500 (67.5 °C)
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- "fan_temp3" CPU temperature at which fan is switched to max speed in millicelsius, default 75000 (75 °C)
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- "fan_temp0_hyst" Temperature hysteris at which fan is stopped in millicelsius, default 5000 (resulting in 50 °C)
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- "fan_temp1_hyst" Temperature hysteris at which fan is switched back to low speed in millicelsius, default 5000 (resulting in 55 °C)
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- "fan_temp2_hyst" Temperature hysteris at which fan is switched back to medium speed in millicelsius, default 5000 (resulting in 62.5 °C)
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- "fan_temp3_hyst" Temperature hysteris at which fan is switched back to high speed in millicelsius, default 5000 (resulting in 70 °C)
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- "fan_temp0_speed" Fan speed for low cooling state in range 0 to 255, default 114 (45% PWM duty cycle)
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- "fan_temp1_speed" Fan speed for medium cooling state in range 0 to 255, default 152 (60% PWM duty cycle)
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- "fan_temp2_speed" Fan speed for high cooling state in range 0 to 255, default 204 (80% PWM duty cycle)
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- "fan_temp3_speed" Fan speed for max cooling state in range 0 to 255, default 255 (100% PWM duty cycle)
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fan_gpio BCM number of the pin driving the fan,
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default 18 (GPIO 18)
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fan_temp0 CPU temperature at which fan is started with
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low speed in millicelsius,
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default 55000 (55 °C)
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fan_temp1 CPU temperature at which fan is switched
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to medium speed in millicelsius,
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default 60000 (60 °C)
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fan_temp2 CPU temperature at which fan is switched
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to high speed in millicelsius,
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default 67500 (67.5 °C)
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fan_temp3 CPU temperature at which fan is switched
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to max speed in millicelsius,
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default 75000 (75 °C)
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fan_temp0_hyst Temperature hysteris at which fan is stopped
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in millicelsius,default 5000 (resulting
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in 50 °C)
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fan_temp1_hyst Temperature hysteris at which fan is switched
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back to low speed in millicelsius,
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default 5000 (resulting in 55 °C)
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fan_temp2_hyst Temperature hysteris at which fan is switched
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back to medium speed in millicelsius,
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default 5000 (resulting in 62.5 °C)
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fan_temp3_hyst Temperature hysteris at which fan is switched
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back to high speed in millicelsius,
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default 5000 (resulting in 70 °C)
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fan_temp0_speed Fan speed for low cooling state in range
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0 to 255, default 114 (45% PWM duty cycle)
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fan_temp1_speed Fan speed for medium cooling state in range
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0 to 255, default 152 (60% PWM duty cycle)
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fan_temp2_speed Fan speed for high cooling state in range
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0 to 255, default 204 (80% PWM duty cycle)
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fan_temp3_speed Fan speed for max cooling state in range
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0 to 255, default 255 (100% PWM duty cycle)
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> [!NOTE]
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> Lowest temperature default is set to 55 °C, to keep the fan off when the Pi is idle. PWM duty cycles start from a rather high 45% to ensure the fan is started reliable. Many small fans have difficulties to start reliable at low duty cycle values.

‎pwm-gpio-fan-overlay.dts‎

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*
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* Optional parameters:
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* - "fan_gpio" BCM number of the pin driving the fan, default 18 (GPIO18)
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* - "fan_temp0" CPU temperature at which fan is started with low speed in millicelsius, default 55000 (55 °C)
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* - "fan_temp1" CPU temperature at which fan is switched to medium speed in millicelsius, default 60000 (60 °C)
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* - "fan_temp2" CPU temperature at which fan is switched to high speed in millicelsius, default 67500 (67.5 °C)
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* - "fan_temp3" CPU temperature at which fan is switched to max speed in millicelsius, default 75000 (75 °C)
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* - "fan_temp0_hyst" Temperature hysteris at which fan is stopped in millicelsius, default 5000 (resulting in 50 °C)
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* - "fan_temp1_hyst" Temperature hysteris at which fan is switched back to low speed in millicelsius, default 5000 (resulting in 55 °C)
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* - "fan_temp2_hyst" Temperature hysteris at which fan is switched back to medium speed in millicelsius, default 5000 (resulting in 62.5 °C)
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* - "fan_temp3_hyst" Temperature hysteris at which fan is switched back to high speed in millicelsius, default 5000 (resulting in 70 °C)
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* - "fan_temp0_speed" Fan speed for low cooling state in range 0 to 255, default 114 (45% PWM duty cycle)
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* - "fan_temp1_speed" Fan speed for medium cooling state in range 0 to 255, default 152 (60% PWM duty cycle)
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* - "fan_temp2_speed" Fan speed for high cooling state in range 0 to 255, default 204 (80% PWM duty cycle)
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* - "fan_temp3_speed" Fan speed for max cooling state in range 0 to 255, default 255 (100% PWM duty cycle)
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*
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* - "fan_temp0" CPU temperature at which fan is started with low speed in millicelsius,
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* default 55000 (55 °C)
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* - "fan_temp1" CPU temperature at which fan is switched to medium speed in millicelsius,
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* default 60000 (60 °C)
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* - "fan_temp2" CPU temperature at which fan is switched to high speed in millicelsius,
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* default 67500 (67.5 °C)
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* - "fan_temp3" CPU temperature at which fan is switched to max speed in millicelsius,
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* default 75000 (75 °C)
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* - "fan_temp0_hyst" Temperature hysteris at which fan is stopped in millicelsius,
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* default 5000 (resulting in 50 °C)
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* - "fan_temp1_hyst" Temperature hysteris at which fan is switched back to low speed
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* in millicelsius, default 5000 (resulting in 55 °C)
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* - "fan_temp2_hyst" Temperature hysteris at which fan is switched back to medium speed
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* in millicelsius, default 5000 (resulting in 62.5 °C)
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* - "fan_temp3_hyst" Temperature hysteris at which fan is switched back to high speed
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* in millicelsius, default 5000 (resulting in 70 °C)
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* - "fan_temp0_speed" Fan speed for low cooling state in range 0 to 255,
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* default 114 (45% PWM duty cycle)
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* - "fan_temp1_speed" Fan speed for medium cooling state in range 0 to 255,
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* default 152 (60% PWM duty cycle)
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* - "fan_temp2_speed" Fan speed for high cooling state in range 0 to 255,
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* default 204 (80% PWM duty cycle)
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* - "fan_temp3_speed" Fan speed for max cooling state in range 0 to 255,
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* default 255 (100% PWM duty cycle)
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*
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* N.B.
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* - Uses the software GPIO PWM kernel module instead of the Pis hardware PWMs (PWM0/PWM1).
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cooling-min-state = <0>;
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cooling-max-state = <4>;
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/* PWM duty cycle values in a range from 0 to 255
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which correspond to thermal cooling states 0 to 4 */
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/* PWM duty cycle values in a range from 0 to 255 */
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/* which correspond to thermal cooling states 0 to 4 */
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cooling-levels = <0 114 152 204 255>;
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};
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};
@@ -138,20 +151,20 @@
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};
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__overrides__ {
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fan_gpio = <&pwm_gpio>,"gpios:4",
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fan_gpio = <&pwm_gpio>,"gpios:4",
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<&pwm_gpio_pins>,"brcm,pins:0";
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fan_temp0 = <&trip0>,"temperature:0";
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fan_temp0_hyst = <&trip0>,"hysteresis:0";
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fan_temp0_speed = <&fan0>,"cooling-levels:4";
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fan_temp0_speed = <&fan0>,"cooling-levels:4";
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fan_temp1 = <&trip1>,"temperature:0";
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fan_temp1_hyst = <&trip1>,"hysteresis:0";
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fan_temp1_speed = <&fan0>,"cooling-levels:8";
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fan_temp1_speed = <&fan0>,"cooling-levels:8";
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fan_temp2 = <&trip2>,"temperature:0";
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fan_temp2_hyst = <&trip2>,"hysteresis:0";
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fan_temp2_speed = <&fan0>,"cooling-levels:12";
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fan_temp2_speed = <&fan0>,"cooling-levels:12";
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fan_temp3 = <&trip3>,"temperature:0";
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fan_temp3_hyst = <&trip3>,"hysteresis:0";
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fan_temp3_speed = <&fan0>,"cooling-levels:16";
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fan_temp3_speed = <&fan0>,"cooling-levels:16";
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};
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};

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