Raspberry Pi POE-FAN Hat with ubuntu

Question

Hi im struggling with my POE-FAN Hats for my new raspberry pi 4.

Installed several Pi's with the offical POE-HAT: https://www.raspberrypi.org/products/poe-hat/ POE works just fine, but the fans (on every raspberry) wont turn on.

I saw a lot of possible solutions, but only for raspbian OS. My goal is to have an kubernetes cluster so I installed Ubuntu Server 20.04.2 LTS

Currently my Pis have 70°C and more, so they should be warm enough. Checked with pwmconfig and sensors-detect but both say that there are no sensors/fans available.

Does anybody can explain me how to enable the fans? And what are "healthy" temperatures for Pi 4s?

Answer 1

At the end of file /boot/firmware/usercnf.txt please add dtoverlay=rpi-poe This should activate the default fan settings.

This path is /boot/firmware/config.txt for Ubuntu 21.

Then you can add custom settings like these but I must say that I never get these to work and just use the defaults, it's working for others so worth a try:

dtparam=poe_fan_temp0=50000
dtparam=poe_fan_temp1=58000
dtparam=poe_fan_temp2=64000
dtparam=poe_fan_temp3=68000

When idle my Pi's are around 50C and the room is 25C. These are normal temperatures I think.

Answer 2

Perhaps this post can help: https://raspberrypi.stackexchange.com/questions/98078/poe-hat-fan-activation-on-os-other-than-raspbian

I might also note that linux kernel 5.13 and newer will have a raspberry poe fan kernel module available but some additional customization of an overlay will be needed and documentation is currently sparse.