FAN PWM smart control

[davepypl]

Hello,
Can you provide some instructions/examples for PWM smart control using Noctua 5V PWM NF-A6x25 4-wire connection with CM5 modules and RPi.GPIO library?

[chibisuke]

I did that for mine already:

1.) Wiring:
Connect:

• 5V to the + terminal of the FAN Header
• the PWM Pin of the Fan (pin 4) to the negative terminal of the fan header
• the GND Pin to the leftmost pin of the uart terminals (marked with a G on the bottom of the board

This is important. It will NOT properly work if you try to use the UART pins, because the CM5 only has 4 GPIOs that are PWM capable. Thats GPIO12, 13, 18 and 19. (UART0 is GPIO14/15, so it cannot do PWM).

Explanation: the negative fan pin is connected to a MOSFET on the board, that is in an open drain configuration. PWM FANs do have an internal PullUp resistor on their PWM PIN, so just pulling them to ground will make it stop. pulling it repeadedly low and then releasing it again will make it go slower than normal.

From there it works pretty similar to the way its describes on the wiki.

Setup PIN 13 to pwm mode in the config.txt:

dtoverlay=pwm-2chan
dtoverlay=pwm,pin=13,func=4

and then setup the PWM using sysctrl:

echo 1 | sudo tee /sys/class/pwm/pwmchip0/export
echo 1000000 | sudo tee /sys/class/pwm/pwmchip0/pwm1/period
echo 500000 | sudo tee /sys/class/pwm/pwmchip0/pwm1/duty_cycle
echo 1 | sudo tee /sys/class/pwm/pwmchip0/pwm1/enable

With the GPIO Python library it should work in a similar manner. Important is just to configure GPIO 13 as PWM.

NOTE: The FAN Control is inversed. 0% PWM = 100% Fanspeed and vice versa.

[davepypl]

Hello @chibisuke

Thanks for the reply!
I did the modification based on your suggestion. But, there's kind of issue with the PWM control using /sys control the FAN speed. Basically it doesn't work on my CM5 modules.

Here's my /boot/firmware/config.txt setup for CM5:

dtparam=audio=off
dtparam=i2c_arm=on
dtoverlay=pca953x,addr=0x18,pca9557
dtoverlay=pwm-2chan
dtoverlay=pwm,pin=13,func=4
dtparam=spi=on

But I did tried the Python gpiozero library and it's working quite well based on below script which detects CPU temperature and align FAN Speed based on few simple funcions:

#!/usr/bin/env python3

from gpiozero import PWMLED
from time import sleep
import os

# Add a delay to give the system time to initialize
sleep(5)

# Set the GPIO pin
FAN_PIN = 13

# Initialize the fan as a PWMLED object
fan = PWMLED(FAN_PIN)

def get_cpu_temp():
    """Reads the CPU temperature from the system using vcgencmd."""
    try:
        res = os.popen('/usr/bin/vcgencmd measure_temp').readline()
        temp = float(res.replace("temp=", "").replace("'C\n", ""))
    except:
        # Fallback to the sysfs method if vcgencmd fails
        with open('/sys/class/thermal/thermal_zone0/temp', 'r') as f:
            temp = float(f.read()) / 1000.0
    return temp

def adjust_fan_speed():
    """Adjusts the fan speed based on CPU temperature thresholds."""
    temp = get_cpu_temp()
    
    # Logic for fan speed based on temperature
    if temp <= 45:
        fan.value = 0.6  # 40% speed
    elif temp <= 50:
        fan.value = 0.5  # 50% speed
    else:  # temp > 50
        fan.value = 0.2  # 80% speed

# Main loop to run the script
try:
    while True:
        adjust_fan_speed()
        sleep(5)  # Check temperature every 5 seconds
except KeyboardInterrupt:
    pass
#finally:
#    fan.on()  # Ensure the fan is on at full speed on script exit

If you see some space for improvements please collaborate.

Also would be great to see in the next versions of the NanoCluster implemented PWM controller with four pinout to support PWM control.

[Mi-Q]

I've tried to recreate the setup and Fan is basically running. But 100% fan size is still so slow that it does not cool down below 55°C. When running Stock Fan at 100% or Noctua 5V NF-A6x25 (non PWM) it's down to 35°C.
Runnign PWM at 100% I can't even hear it running, is that possible?

[davepypl]

I've tried to recreate the setup and Fan is basically running. But 100% fan size is still so slow that it does not cool down below 55°C. When running Stock Fan at 100% or Noctua 5V NF-A6x25 (non PWM) it's down to 35°C. Runnign PWM at 100% I can't even hear it running, is that possible?

Hello,
Be aware that in this setup PWM control is inverted. In my python code 1.0 means FAN is stopped. 0.0 means, it's running at full speed. In my code I didn't push the FAN to 100% because my CM5 never hits 50*C. So I want keep it quiet much as possible.

# Logic for fan speed based on temperature if temp <= 45: fan.value = 0.6 # 40% speed elif temp <= 50: fan.value = 0.5 # 50% speed else: # temp > 50 fan.value = 0.2 # 80% speed

[Mi-Q]

Hello, Be aware that in this setup PWM control is inverted. In my python code 1.0 means FAN is stopped. 0.0 means, it's running at full speed. In my code I didn't push the FAN to 100% because my CM5 never hits 50*C. So I want keep it quiet much as possible.

# Logic for fan speed based on temperature if temp <= 45: fan.value = 0.6 # 40% speed elif temp <= 50: fan.value = 0.5 # 50% speed else: # temp > 50 fan.value = 0.2 # 80% speed

Hi, thank you for the quick answer. I have already applied that. (working with percentages and for inverted pwm I consider 100 - sipeed as value)
I see it's running faster with 100% speed than 80% etc but it actually barely audible even 10cm away from the Fan. Compared to the non pwm 5V from noctua airflow is also close to non-existent.

For cabels I have attached yellow to black + and blue to red -, black from the fan to the gnd pin of the sipeed board.

I don't think the Fan is meant to run that slow even at 100% so I'm wondering what i May miss here

(of course there are two more boards that are installed in slot 1 and 3, just took them out to take a picture)

[chibisuke]

The pinout on the fan header sounds wrong, except there was an error in your package. For mine red is positive and black is negative, so for me it is:

Yellow of the Fan => to red of the cable => to +
Blue of the Fan => to black of the cable => to -
Black of the Fan => to GND.

[davepypl]

Yes,
There's is wrong pin connection. You didn't read the schema correctly. As @chibisuke mentioned,
Yellow goes to +, Blue to -. Black to GND

[Mi-Q]

Thanks for the clarification but for the pin connector cables I got from Temu (yes I know...) black and red are inverted, so red is actually connected to - and black ist connected to + on the board. It's a bit hard to see in the picture 😉

[chibisuke]

I'd try disconnecting the blue pwm wire of the fan. These fans do have internal pull-up resistors, so not connecting the blue wire makes it run at 100% speed. Then you have something to compare against.

[davepypl]

Let check what kind of GPIO module library do you have installed on your system.

For detecting GPIO I use pigpio-tools, but for the script python3-gpiozero.
https://gpiozero.readthedocs.io/en/stable/index.html

root@cloud-kvm-0:~# gpiodetect
gpiochip0 [gpio-brcmstb@107d508500] (32 lines)
gpiochip1 [gpio-brcmstb@107d508520] (4 lines)
gpiochip2 [gpio-brcmstb@107d517c00] (15 lines)
gpiochip3 [gpio-brcmstb@107d517c20] (6 lines)
gpiochip4 [pinctrl-rp1] (54 lines)
gpiochip5 [1-0018] (8 lines)

root@cloud-kvm-0:~# pip3 list installed | grep gpi
gpiozero               2.0.1
lgpio                  0.2.0.0
pigpio                 1.78
rpi-lgpio              0.5

root@cloud-kvm-0:~# apt list --installed | grep gpio
gpiod/noble,now 1.6.3-1.1build1 arm64 [installed]
libgpiod2t64/noble,now 1.6.3-1.1build1 arm64 [installed,automatic]
liblgpio1/noble,now 0.2.0.0-0ubuntu3 arm64 [installed,automatic]
pigpio-tools/noble,now 1.78-1.1build1 arm64 [installed]
python3-gpiozero/noble,now 2.0.1-0ubuntu1 all [installed]
python3-lgpio/noble,now 0.2.0.0-0ubuntu3 arm64 [installed,automatic]
python3-pigpio/noble,now 1.78-1.1build1 all [installed]
python3-rpi-lgpio/noble,now 0.5-0ubuntu1 all [installed]

Also you have to be aware that GPIO control of your FAN is possible from CM5 module located on the First Slot.
Because of that there's more complications comes when your system is been used for heavy workloads and you are using more than one board. Then communication between boards might be needed to send notification to First board that other system need more cooling, or drop it down. For this case I found this great project https://github.com/meteyou/sipeed-nanocluster-server. But unfortunately on my Debian based system can't install, or can't compile with success the pigpio so that's why I switched to compatible and updated Python gpiozero. You can try with this project which looks awesome but author didn't respond on any questions related to CM5 modules.

From this perspective my project is still unfinished for multiple boards on the Cluster. I can manipulate FAN RPM from CM installed on slot 1, but others can't. Had no time to look more deeply on it. Still there's a lot of place for improvement.

[Mi-Q]

Let check what kind of GPIO module library do you have installed on your system.

For detecting GPIO I use pigpio-tools, but for the script python3-gpiozero. https://gpiozero.readthedocs.io/en/stable/index.html

root@cloud-kvm-0:~# gpiodetect
gpiochip0 [gpio-brcmstb@107d508500] (32 lines)
gpiochip1 [gpio-brcmstb@107d508520] (4 lines)
gpiochip2 [gpio-brcmstb@107d517c00] (15 lines)
gpiochip3 [gpio-brcmstb@107d517c20] (6 lines)
gpiochip4 [pinctrl-rp1] (54 lines)
gpiochip5 [1-0018] (8 lines)

root@cloud-kvm-0:~# pip3 list installed | grep gpi
gpiozero               2.0.1
lgpio                  0.2.0.0
pigpio                 1.78
rpi-lgpio              0.5

root@cloud-kvm-0:~# apt list --installed | grep gpio
gpiod/noble,now 1.6.3-1.1build1 arm64 [installed]
libgpiod2t64/noble,now 1.6.3-1.1build1 arm64 [installed,automatic]
liblgpio1/noble,now 0.2.0.0-0ubuntu3 arm64 [installed,automatic]
pigpio-tools/noble,now 1.78-1.1build1 arm64 [installed]
python3-gpiozero/noble,now 2.0.1-0ubuntu1 all [installed]
python3-lgpio/noble,now 0.2.0.0-0ubuntu3 arm64 [installed,automatic]
python3-pigpio/noble,now 1.78-1.1build1 all [installed]
python3-rpi-lgpio/noble,now 0.5-0ubuntu1 all [installed]

Also you have to be aware that GPIO control of your FAN is possible from CM5 module located on the First Slot. Because of that there's more complications comes when your system is been used for heavy workloads and you are using more than one board. Then communication between boards might be needed to send notification to First board that other system need more cooling, or drop it down. For this case I found this great project https://github.com/meteyou/sipeed-nanocluster-server. But unfortunately on my Debian based system can't install, or can't compile with success the pigpio so that's why I switched to compatible and updated Python gpiozero. You can try with this project which looks awesome but author didn't respond on any questions related to CM5 modules.

From this perspective my project is still unfinished for multiple boards on the Cluster. I can manipulate FAN RPM from CM installed on slot 1, but others can't. Had no time to look more deeply on it. Still there's a lot of place for improvement.

I had too much time and Sonnet4.5 went a little bit crazy, so i have seither a systemd Service running on the slots 3,5,7 which expose the temperature via http and in slot 1 a Controller which fetches These and adjusts on the maximum temp of all 4 CM5 modules, or... Since I wanted to run in k3s, i have a deplomyment where on every node in the Cluster runs a temp Exporteur and on the Controller node (which needs to be in slot 1) additionally there runs a Controller pod which collects all temps from these exporters.

Depending on the setup either lgpio or RPI.GPIO is used: https://github.com/Mi-Q/sipeed-cm5-fancontrol/blob/c7316d0b1d15a8b4945c5ffc783753e0ef9cfc2f/deploy-systemd/fan_control.py#L460
Will go ahead with the analysis you have supposed when I get home again.

Update:

pi@nanocluster1:~ $ gpiodetect
gpiochip0 [pinctrl-rp1] (54 lines)
gpiochip10 [gpio-brcmstb@107d508500] (32 lines)
gpiochip11 [gpio-brcmstb@107d517c00] (15 lines)
gpiochip12 [gpio-brcmstb@107d517c20] (6 lines)
gpiochip13 [gpio-brcmstb@107d508520] (4 lines)
gpiochip14 [1-0018] (8 lines)
pi@nanocluster1:~ $ pip list installed | grep gpi
gpiod                        2.2.0
gpiozero                     2.0.1
lgpio                        0.2.2.0
pigpio                       1.78
rpi-lgpio                    0.6
pi@nanocluster1:~ $ apt list --installed | grep gpio

WARNING: apt does not have a stable CLI interface. Use with caution in scripts.

gpiod/stable,now 2.2.1-2 arm64 [installed]
libgpiod3/stable,now 2.2.1-2 arm64 [installed,automatic]
libgpiolib0/testing,now 20251002-1 arm64 [installed,automatic]
liblgpio1/testing,now 0.2.2-1~rpt1+trixie arm64 [installed,automatic]
pigpio-tools/stable,now 1.78-1.1+b1 arm64 [installed]
python3-gpiozero/testing,testing,now 2.0.1-0+rpt1+trixie all [installed]
python3-lgpio/testing,now 0.2.2-1~rpt1+trixie arm64 [installed,automatic]
python3-libgpiod/stable,now 2.2.1-2 arm64 [installed]
python3-pigpio/stable,stable,now 1.78-1.1 all [installed]
python3-rpi-lgpio/testing,testing,now 0.6-0~rpt1+trixie all [installed]