An Arduino Nano generates the 25kHz PWM signal, and a companion Windows application reads CPU temp and sends the duty cycle over serial. The Arduino firmware is open source (MIT).

is not true. There is a diagram available for this mobo and U32 (F71889AD) is connected over LPC (modern serial ISA version). Its a full Super IO and it cant be _not connected_ as it also provides keyboard/mouse, serial and printer ports.

The problem must lie elsewhere, most likely bad BIOS.

>Here's what I knew:

> Windows can read CPU temperature directly from the CPU's internal thermal diode, completely bypassing the useless Super IO chip.

why not read temperature directly from Fintek using HwInfo?

https://www.hwinfo.com/forum/threads/faulty-sensor-readings-... and yes it also works on 970 https://forum-en.msi.com/index.php?threads/msi-970-cpu-temps...

not to mention MSI Command Center can read those sensors AND set FAN speeds/curves, and most likely also SpeedFan.

> asked LLMs

LLM failed this person :(

We work in very hot greenhouses, so fans (and peltiers) are essential. And proper thermal sensors. I check 4 different ones. Esp. needed is also a humidity sensor, because we don't want it to cool down below the dew point.

It's PWM, controlled via mraa. mraa_pwm_write()

Using Arduino and serial is a smart way to go here. Still, it’s worth remembering: the Pico W has built-in WiFi, so you don’t have to lean on serial if you don’t want to. You could have your temp-reading app send control signals over HTTP instead. No need to tie up the USB port, and the connection isn’t killed if someone yanks the cable.

And yes, big agreement on the watchdog or failsafe. Any fan controller that doesn’t ramp up to 100% if it loses connection is just waiting for trouble. Fire risk is real.

Would you mind sharing more technical review of what you created?