weigon
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weigon got a reaction from Oleksii in NanoPI T4 3-pin fan with PWM suggestion needed.
Just for reference, a simplified version that works with both linux 4.4 and the linux 4.20 kernel:
# make the PWM port available to sysfs $ echo 0 | sudo tee /sys/class/pwm/pwmchip1/export 0 # set the PWM-freq to 25kHz (=40000ns) $ echo 40000 | sudo tee /sys/class/pwm/pwmchip1/pwm0/period 40000 # enable the PWM $ echo 1 | sudo tee /sys/class/pwm/pwmchip1/pwm0/enable 1 It starts the fan at fullspeed as by default the polarity of the PWM is inversed: duty_cycle of "0" == "always on".
$ cat /sys/class/pwm/pwmchip1/pwm0/polarity inversed $ cat /sys/class/pwm/pwmchip1/pwm0/duty_cycle 0 To slow the fan down with inversed polarity one needs to bring the duty_cycle close to the "period" set before
$ echo 35000 | sudo tee /sys/class/pwm/pwmchip1/pwm0/duty_cycle 35000
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weigon got a reaction from Oleksii in NanoPI T4 3-pin fan with PWM suggestion needed.
After removing the noise from the input-data, I now got quite reasonable RPM values for the Noctua NF A14:
RPM per duty_cycle [ns] duty_cycle RPM 180 158 200 476 250 637 300 938 400 1111 500 1200 2000 1251
Below 180ns the fan stops, above 500ns it doesn't really increase anymore.
fan.svg
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weigon got a reaction from NicoD in NanoPI T4 3-pin fan with PWM suggestion needed.
After removing the noise from the input-data, I now got quite reasonable RPM values for the Noctua NF A14:
RPM per duty_cycle [ns] duty_cycle RPM 180 158 200 476 250 637 300 938 400 1111 500 1200 2000 1251
Below 180ns the fan stops, above 500ns it doesn't really increase anymore.
fan.svg