So I received the 25W PoE hat today and it works! However, the fan placement is not what I was expecting; the fan is not directly over the chip and I should’ve taken a closer look at the placement before ordering but I would’ve ordered anyway.
It took me a bit of searching to find the documentation and instructions on how to setup the fan… (I have not set it up yet)
Too bad this hat does not work with the green fanless case.
I’ve been looking around for a way to solve the heat dissipation issue now that the poe hat makes my metal case useless… and I’ve come upon this forum post:
https://forums.adafruit.com/viewtopic.php?f=19&p=921016
Basically, I’ll use the risers to give myself more space between the PoE hat and the board and then I can install some sort of heatsink and fan solution. Has anyone tried something like this with this board? I assume the risers should just work.
So I’m unable to get the fan working. The only documentation I have is this: https://docs.radxa.com/en/accessories/radxa-25w-poe?model=5b_3b
anyone else have an idea?
I’ll also make a post regarding my new setup with the gpio riser and a heatsink at a later time!
I’d return it for a refund if possible and get the Waveshare. The fan works on those.
Did you enable the overlay as described in the documentation? If everything goes well the fan should only run when CPU temperature is above 60 degrees.
It’s all included in docs: just enable radxa 25W poe overlay:
If You are using armbian - overlay is not yet there included, maybe it will be in future.
Is there a way to change those? 60deg is not that high but I would like to change several things,
I placed heatsink between hat and board, fit’s perfectly, trying now to tweak right rpm to temperatures
Right now the threshold is defined in the device tree, so you would need a custom overlay to override it: https://github.com/radxa/kernel/blob/linux-5.10-gen-rkr4.1/arch/arm64/boot/dts/rockchip/rk3566-rock-3c.dts#L194
If you want to adjust RPM to temperature you can take a look at Armbian device trees about cooling-maps. They define more trip points with each corresponding to a single fan speed. Right now we basically only have on and off state.
Thanks for this tip,
this fan is 15k rpm and its quite loud. With heatsink board board hits 60deg only on high usage, cooling down imidiately, I need to play with those and have some steps in rpm.
Ah that’s what I was missing. I didn’t know the threshold was 60 degrees. Thanks!
60deg or power off 
I’ve adapted a 25W POE hat fan control solution that works on Armbian.
I’ve tested with BSP 6.1 kernel and mainline.
PRs for improvements welcome.
Great, thank for Your effort 
I guess it should work on 5A also?
Gonna be using same pin for PWM so should work just fine.
Great, I’ll take a look at that later, fan control map looks reasonable and it’s still user configurable.
what is needed to make it to work on any board? PWM pin setup, temp sensor readout, anything else?
Except controlling fan is there anything else in this board that is still not supported? Any information about power usage?
There’ some static defines presently for pointing to the pwm interface.
You can see in the diff of my fork the changes I made. The original version was managing pwm to the built in-transistor behind the 5v fan pin on the 5b, vs the hat has an actual PWM fan pin.
Main thing to notice is pwm pin and frequency adjustment
Re: power usage… haven’t looked into it… Does the hat have an i2c sensor of sorts to report?
