Xiaomi Smart Tower Fan 2

Preamble

The Xiaomi Smart Tower Fan 2 requires replacing the proprietary Wifi module with an supported ESP module.

You will need a Hot air station, a soldering iron with a fine tip and some soldering skills.

The required ESP module is a ESP32-C3-WROOM-02 or Doit ESPC3-20. I got a Doit ESPC3-20 from Aliexpress.

If you get a module with antenna connector you will need to get a wifi antenna as well.

The Wifi module is mounted in the top of the device.

Open the backcover and remove the rotor.
Remove the visible screws on the backside of the device.
Unclip the two body parts by bending them inwards. You won't be able to unclip the clips in the top. The lower part doesn’t need to be unclipped.
Carefully unclip the clips in the top of the device by reaching in with a flathead screwdriver from the inside.
Remove the top panel and unscrew the circuit board.

A Hot Air station like 858D or similar is required to remove the wifi module. It takes some time to melt the solder under the central ground pad of the module.
Remove the solder from the pads using solder wick.
Solder the new ESP module. Avoid soldering the joint in the top right of the module as that would connect a GPIO pin to ground.
To allow easy removal of the module I kept a distance of 0,5 mm between the PCB and the ESP module and soldered only the required connections (plus one connection for added mechanical strength)
Wire up a USB to UART adaptor to the GND, TX and RX testpoints.
Entering the bootloader mode of the ESP32 C3 requires GPIO9 to be connected to ground. I did that using a thin copper wire.
The board has a 3V3 testpoint that can be used to power the board if your USB to UART adaptor can deliver sufficient current.

Connect the USB to UART adaptor to your PC and try to flash the ESPhome firmware. I had problems connecting to the ESP32 as my USB to UART adaptor didn’t deliver enough current to the board. So I removed the 3V3 connection between the flasher and the board and used the 4 wire connection to the fan to power the board.
When the flashing is done disconnect the wire between GPIO9 and ground to get back to normal flash boot mode.
Connect the PCB to the fan, power it up and check if the device connects to your Wifi. I had to try the installation a few times.
When you are done testing desolder the wires and assemble the fan.

The yaml file contains some controls that are more or less redundant and therefore hidden (internal).
The required Wifi modules are a bit rare. The ESP-WROOM-02 modules are more common but based on the older ESP8266. Using a ESP-WROOM-02 is untested and would require adjusting the configuration. See the Mi Smart Antibacterial Humidifier regarding board type and GPIO pins.

left_side right_side Solderjoints wiring