Orin NX read Fan speed is Incorrect

Hi, I found that orin nx read fan speed is incorrect.
SDK: 35.2.1-GA
HW: Orin-NX Devkit
when I cmd echo 200 > /sys/devices/pwm-fan/target_pwm , and I can control the fan speed.
So when I try echo 0 > /sys/devices/pwm-fan/target_pwm and the fan stop, I cmd cat /sys/class/hwmon/hwmon0/rpm to read fan speed, the reading is not zero, it reads hundreds. That‘s error.

Your topic was posted in the wrong category. I am moving this to the Jetson Orin NX category for better support.

Hi JackyChen,

Could you try to use the following node to set pwm and read rpm on the devkit respectively?

Set pwm:

$ echo 255 > /sys/devices/platform/pwm-fan/hwmon/hwmon3/pwm1

Read rpm:

$ cat /sys/devices/platform/39c0000.tachometer/hwmon/hwmon0/rpm

@KevinFFF Hi, that still show some number when I echo 0.

Does the fan physically stop spinning at this moment but you still can read the rpm value at this node?

Please also try to stop nvfancontrol service before test

$ systemctl stop nvfancontrol

@KevinFFF Hi, stop nvfancontrol service before test , It worked. When I cmd echo 0 > /sys/devices/platform/pwm-fan/hwmon/hwmon3/pwm1 the fan physically stop spinning at this moment, but cat /sys/devices/platform/39c0000.tachometer/hwmon/hwmon0/rpm it didn’t read 0 right away, it takes a few seconds to read 0

Yes, this behavior is expected because there’s inertia for the fan.

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