How to read fan speed from fan itself (FAN_TACH)

Autonomous Machines Jetson & Embedded Systems Jetson AGX Xavier
1

Hi Sir/Madam,

I can set pwm to change fan speed by “/sys/devices/pwm-fan/target_pwm”

But how to monitor current fan speed that feedback from fan_tach pin.
cur_pwm is also only Xavier pwm output information (even if I don’t connect a fan, it still has value), could we get fan speed that is from fan itself.

I check the fan speed should be monitored by “FAN_TACH” pin, how could I get current fan speed information?

Thank you

2

You could use below node for the fan rpm.

cat /sys/devices/generic_pwm_tachometer/hwmon/hwmon1/rpm

1 Like
3

Hi WayneWWW,

Thank you

4

Hi @WayneWWW,

Thank you so much for pointing out the file (/sys/devices/generic_pwm_tachometer/hwmon/hwmon1/rpm) from where fan speeds could be obtained in a Jetson Xavier NX board.

My question is: Does the file contain the fan speed as RPM or as 10 times the RPM or as 100 times the RPM?

Thanking you in adavnce,
Regards

5

Hi EdmundRay,

Please help to check this issue. Thanks