PWM fan on Raspberry Pi

Installing and Using OpenWrt
1

Hi,

I am converting and old Raspberry Pi (old because 3B+) to OpenWRT. I used to be able to control the fan speed using PWM, but I could not find the way to do so with OpenWRT.

I have not been able to read the temperature from /sys/class/thermal and I have not been able to find how to install the command line GPIO to configure and invoke PWM.

I have the hardware part running (fan, transistor, cabling) running fine, I used it in an earlier project, that is the software that is causing my problem.

And I know that Raspberry Pi is supposed to run without fan, but in climates where temperature can climb to 40C, a fan is not a bad idea. And I know I could have the fan run permanently, but I like the idea of controlling the speed. it helps preserving the life of the fan.

Thanks in advance,

Olivier

2

Are you intending to run STABLE or SNAPSHOT?

Majority of gpio like stuff is done with C or python, the latter being space intensive but modular for beginners.

How you hook into the GPIO may vary with the version of OpenWrt you are running.

What did you find?

3

I tried installing:
gpioctl-sysfs
gpiod-tools
kmod-gpio-dev
kmod-hwmon-gpiofan
libgpiod
libugpio
kmod-hwmon-pwmfan

And none give me a way to configure GPIO in PWM mode (or I have not understand how to use them because I could not locate the man page).

4

I am looking for the same solution.
This feature would suit raspberry pi stored in the bottom of the box very well.
Has colleague @Olivier2553 found any solutions?

5

Nope, I am running the fan at full speed.

6

i'm not familiar with the rpi3 and it's packages

for the rpi4 os-level pwm(bcm)kmod + config.txt + sysfs do provide the ability to adjust pwm dutycycle...

the actual configuration of the GPIO for os-level pwm is achieved via config.txt... (dtoverlay)

7

Why not just connect a fan and let it run? I think there's not going to be much difference. My pie runs it as I just told you. Since you are running the Raspberry in heaty climates, it is better to just let it run. (Note: by "connect" I mean connect the fan to the pi's 3v3 and gnd pins)

8

This was what I used for the rpi4 case/fan in boot/config.txt as @anon50098793 pointed out, it worked, I'm guessing it would work for other fans, you'd just need to change the PIN number/temp for your needs

dtoverlay=gpio-fan
gpiopin=14
temp=80000
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10

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