Read the PWM fan RPM in Jetson NX

Hi,

I am using Jetson NX Stock BSP (L4T 32.5.1)on custom carrier board and want to read the Heat sink fan RPM from the tacho, want to control the fan speed and reset it to auto. can you please help which commands to use?

Hello @vbhm ,

I hope you are doing well.

You can read the fan RPM from the following file:
cat /sys/devices/generic_pwm_tachometer/hwmon/hwmon1/rpm

To control the fan, you can use jetson_clocks utility.
/usr/bin/jetson_clocks --help

With the utility you can set the fan RPM, or reset it to a default.

best regards,
Andres Campos
Embedded Software Engineer

Hi thanks for the reply,

I tried below command, my fan is running with full speed and it reads RPM as zero, I have tried as root user also:
nvidia@nvidia-desktop:~$ cat /sys/devices/pwm-fan/target_pwm
255
nvidia@nvidia-desktop:~$ cat /sys/devices/generic_pwm_tachometer/hwmon/hwmon1/rpm
0
nvidia@nvidia-desktop:~$

hello vbhm,

there’s look-up-table to check the actual fan rotate speed your PWM settings.
for example,
it’s 1000-rpm while pwm settings is 130.

nvidia@nvidia-desktop:/sys/class/hwmon/hwmon2$ cat cur_pwm
130
nvidia@nvidia-desktop:/sys/class/hwmon/hwmon2$ cat pwm_rpm_table
(Index, RPM, PWM, RRU, RRD)
(0, 0, 0, 40, 40)
(1, 1000, 130, 2, 2)
(2, 2000, 160, 1, 1)
(3, 3000, 200, 1, 1)
(4, 4000, 255, 1, 1)
(5, 5000, 255, 1, 1)
(6, 6000, 255, 1, 1)
(7, 7000, 255, 1, 1)
(8, 10000, 255, 1, 1)
(9, 11000, 255, 1, 1)
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