Strato Pi Fan driver kernel module

Raspberry Pi OS (Debian) Kernel module for Strato Pi Fan - the Raspberry Pi B expansion board for temperature monitoring and regulation.

Compile and Install

For installation on Ubuntu read this.

Make sure your system is updated:

sudo apt update
sudo apt upgrade

If you are using a Raspberry Pi 4 and a 32-bit OS, add to /boot/firmware/config.txt (/boot/config.txt in older versions) the following line: [why?]

arm_64bit=0

Reboot:

sudo reboot

After reboot, install git and the kernel headers:

 sudo apt install git linux-headers-$(uname -r)

Clone this repo:

git clone --depth 1 https://github.com/sfera-labs/strato-pi-fan-kernel-module.git

Make and install:

cd strato-pi-fan-kernel-module
make clean
make
sudo make install

Compile the Device Tree and install it:

dtc -@ -Hepapr -I dts -O dtb -o stratopifan.dtbo stratopifan.dts
sudo cp stratopifan.dtbo /boot/overlays/

Add to /boot/firmware/config.txt (/boot/config.txt in older versions) the following line:

dtoverlay=stratopifan

Optionally, to be able to use the /sys/class/stratopifan/ files not as super user, create a new group "stratopifan" and set it as the module owner group by adding an udev rule:

sudo groupadd stratopifan
sudo cp 99-stratopifan.rules /etc/udev/rules.d/

and add your user to the group, e.g., for user "pi":

sudo usermod -a -G stratopifan pi

Reboot:

sudo reboot

Usage

After installation, you'll find the directory /sys/class/stratopifan/ which gives you access to Strato Pi Fan's functionalities.

To read the temperature measured by the on-board sensor, read the file /sys/class/stratopifan/sys_temp/temp.

To set the temperature thresholds for activating and deactivating the fan write respectively to /sys/class/stratopifan/fan/temp_on and /sys/class/stratopifan/fan/temp_off.

All temperature values are expressed in °C/100, i.e. a value of 4050 corresponds to 40.5°C. Thresholds values range from -128°C to 127.5°C with a 0.5°C resolution.

Examples

Read temperature and thresholds from shell:

$ cat /sys/class/stratopifan/sys_temp/temp
$ cat /sys/class/stratopifan/fan/temp_on
$ cat /sys/class/stratopifan/fan/temp_off

Write thresholds from shell:

$ echo 6000 > /sys/class/stratopifan/fan/temp_on
$ echo 5150 > /sys/class/stratopifan/fan/temp_off

Read temperature and set thresholds using Python:

f = open('/sys/class/stratopifan/sys_temp/temp', 'r')
val = int(f.read().strip())
f.close()
print('Temperature: {} C'.format(val/100.0))

tOn = val + 1000
tOff = val - 1000

f = open('/sys/class/stratopifan/fan/temp_on', 'w')
f.write(str(tOn))
f.close()

f = open('/sys/class/stratopifan/fan/temp_off', 'w')
f.write(str(tOff))
f.close()