Fan Control and Monitoring on Nvidia Jetson Orin Nano Custom Board

Issue Overview

Users of the Nvidia Jetson Orin Nano custom board are seeking methods to control and monitor the fan status, including connectivity, operation, PWM/RPM, and frequency. The discussion revolves around accessing and manipulating fan-related information using command-line interfaces on a custom board running Jetpack 5.1.1.

Possible Causes

1. Limited Documentation: The specific methods for fan control and monitoring on custom Jetson Orin Nano boards may not be well-documented, leading to user confusion.

2. Hardware Differences: Custom boards may have different fan control implementations compared to the standard devkit, causing inconsistencies in access methods.

3. Software Version Specifics: The Jetpack 5.1.1 version may have particular requirements or limitations for fan control that users are unaware of.

4. File System Structure: The location and permissions of fan control files in the system may not be immediately apparent to users.

Troubleshooting Steps, Solutions & Fixes

Identifying Fan-Related Hardware Monitors

To begin troubleshooting, identify the hardware monitors related to the fan:

ls -l /sys/class/hwmon/

This command reveals several hardware monitors, with hwmon0 likely corresponding to the tachometer and hwmon2 to the PWM fan control.

Monitoring Fan RPM

To check the current fan speed in RPM:

cat /sys/class/hwmon/hwmon0/rpm

This command reads the revolutions per minute of the fan.

Controlling Fan Speed

1. Check current PWM value:

   cat /sys/class/hwmon/hwmon2/pwm1
   

2. Set fan to full speed (requires root privileges):

   sudo su
   echo 255 > /sys/class/hwmon/hwmon2/pwm1
   

The PWM value ranges from 0 to 255, with 255 being the maximum speed.

Alternative Fan Control Method

Some users have reported success with the following method:

sudo su
cd /sys/class/pwm/pwmchip0
echo 0 > export
cd pwm0
echo 200 > period
echo 100 > /sys/devices/platform/pwm-fan/hwmon/hwmon2/pwm1

To verify the changes:

cat /sys/devices/platform/pwm-fan/hwmon/hwmon2/pwm1
cat /sys/devices/platform/39c0000.tachometer/hwmon/hwmon0/rpm

Understanding PWM Values

• PWM: The value (0-255) is a byte representing the duty cycle.
• RPM: Represents actual revolutions per minute.
• Period: Measured in nanoseconds.

Configuring Specific PWM Frequencies

To set a specific PWM frequency and duty cycle:

1. Calculate the period and duty cycle in nanoseconds.
2. Example for 20Hz with 50% duty cycle:

   echo 50000000 > period      # 50M ns = 0.05s = 20Hz
   echo 25000000 > duty_cycle  # 50% of 50M ns
   

This configuration results in a 20Hz PWM signal with a 50% duty cycle.

Best Practices

1. Always use sudo or switch to root when modifying fan control files.
2. Be cautious when setting fan speeds, as inadequate cooling can lead to system instability or damage.
3. Monitor system temperatures when adjusting fan speeds to ensure proper cooling.
4. Create scripts for common fan control operations to simplify management.
5. Refer to the official Nvidia Jetson documentation for any updates or changes in fan control methods for your specific Jetpack version.