Argon Poly+ fan works in ON mode, but PWM mode never appears on I²C in DietPi 10.5.2

General Discussion
1

I’m trying to get the fan in an Argon Poly+ case for Raspberry Pi 4 working properly under DietPi, and I’m hoping someone here may have seen this before or can suggest a workaround.

Hardware / system

  • Raspberry Pi 4

  • Argon Poly+ case

  • Fan switch is labeled ON / OFF / PWM

  • DietPi version:

    • Core: 10

    • Sub: 5

    • RC: 2

    • Branch: master

  • /dev/i2c-1 exists

  • I²C is enabled in dietpi-config

  • I²C frequency is set to 100 kHz

What I observe

The fan behaves like this:

  • In ON mode, the fan runs normally.

  • In OFF mode, the fan stops.

  • In PWM mode, the fan does not turn on at all.

I expected PWM mode to allow Argon’s fan control daemon to manage fan speed, but it never seems to communicate with the controller.

What I tried

I tried the current Argon install script for the case, and the service appears to install and run normally:

  • argononed.service shows active (running)

  • The daemon process is running from /etc/argon/argononed.py

I also verified that the config file is present and that the service is using the expected daemon config name:

  • /etc/argononed.conf

I then tried the following checks and tests:

I²C scans

bash

sudo i2cdetect -y 1

Result: completely blank grid, no device detected.

This was true even after:

  • confirming I²C is enabled in dietpi-config

  • confirming /dev/i2c-1 exists

  • confirming the i2c_bcm2835, i2c_dev, and i2c_bcm2708 modules are loaded

Temp check

bash

vcgencmd measure_temp

This works and reports a normal temperature, around 55.5°C at idle/light use.

Argon service

bash

systemctl status argononed.service
sudo journalctl -u argononed.service -n 30 --no-pager

The service is running cleanly and doesn’t show an obvious error.

Config file

I checked the fan config and found the expected file is:

bash

/etc/argononed.conf

not /etc/argonone.conf.

What I’ve concluded so far

At this point it seems like:

  • the fan itself is not dead

  • the ON position proves the fan motor and power path work

  • the problem is specific to PWM mode

  • the controller never appears on I²C, so the daemon has nothing to talk to

Because the exact same hardware worked previously under Raspberry Pi OS, I’m wondering whether this is:

  • a DietPi-specific I²C / firmware / device-tree interaction,

  • a board/controller quirk,

  • or a hardware issue with the controller side of the Argon board rather than the fan itself.

Questions

  1. Has anyone gotten the Argon Poly+ PWM fan mode working reliably on DietPi?

  2. Is there a known DietPi-specific fix, overlay, package, or boot setting that helps the Argon controller show up on I²C?

  3. Is there a way to force the Argon controller to enumerate, or a different install path that works better on DietPi?

  4. If PWM mode is unreliable on DietPi, is the best workaround simply to leave the fan in ON mode?

Thank you for any help or suggestions.