Compute Blade PWM Fan Control

Simple fan control and tach read scripts for the Compute Blade fan unit.

Fan Unit Documentation

Install GPIO Zero

apt

GPIO Zero is packaged in the apt repositories of Raspberry Pi OS, Debian and Ubuntu. It is also available on PyPI.

sudo apt update
sudo apt install python3-gpiozero

pip

If you’re using another operating system on your Raspberry Pi, you may need to use pip to install GPIO Zero instead. Install pip using get-pip and then type:

sudo pip3 install gpiozero

Usage

Scripts

• fan_control.py: Drives PWM on GPIO12 and reads CPU temperature to set speed.
  • Profiles: linear, ease_in, ease_out, ease_in_out.
  • Profile file: /etc/fan-control/profile (single word).
  • Must be run as root for GPIO permissions.
• read_fan_speed.py: Reads tach pulses on GPIO13 and prints RPM.

Fan Unit Connections

• J1 is the control node (only J1 can drive PWM). It can also read the tach signal.
• J2 can read tach signals, but cannot control PWM.

Profile File

The fan control script supports some fan easing curves. Create the profile file with a single word inside:

sudo mkdir -p /etc/fan-control
echo ease_out | sudo tee /etc/fan-control/profile

Valid profiles:

Profile	Behavior
linear 🔹	Speed increases linearly with temperature
ease_in	Starts slow, ramps faster at higher temps
ease_out	Ramps quickly, then levels off
ease_in_out	Slow at low temps, faster in the middle, smooth finish

🔹 Default fan profile when not set

Notes

• GPIO13 is reserved for tach reads on the other node; PWM control uses GPIO12.