Xiaomi Smart Air Purifier 4

Disassembly

For this device, getting to the board is straightforward, just 5 screws and 0 force. Read the steps and study the instruction images before starting, and you'll be fine.

1. With the filter and filter cover removed, unscrew the front panel retainer screw.

2. Turn the purifier upside down, and remove the 4 rubber feet. Unscrew the 4 screws hidden under them. Unclip and remove the plastic cover.

Caution

Take extra care not to touch the power supply board with anything. Even when unplugged, capacitors can still pack a punch close to mains voltage for a long time. At best, touching the wrong spot can fry the board; at worst, you will get a very nasty shock. If you don't feel comfortable, ask someone knowledgeable for help.

3. With the bottom cover out of the way, the front panel should easily slide up past the retaining clips. You now have access to the controller board, containing the ESP32. Because the cables are quite short, wiggle the connectors free without moving the front panel too much. The connectors all have different shapes so there should be no confusion plugging them back in. Unscrewing the board is optional, and we're ready for flashing.

Flashing

On the board pictured, all connection points are nicely outlined, just not individually labelled, and soldering is not strictly required in order to flash.

Keep in mind that the electrical connection can be interrupted during download/upload by any slight vibrations if you don't solder, requiring a restart from step 3.

1. Confirm your board looks identically to the pictures.
2. With your flasher unplugged from your computer, connect the wires:
   • Short the two holes labelled "BOOT" in the picture together.
   • Connect the 3.3V supply and GND from your flasher to the holes labelled 3V3 and GND in the pictures.
   • Cross-connect the RX to the TX, and TX to RX on your flasher.
3. Plug your flasher into your computer.
4. Using the tool of your choice (esptool recommended) download the on-board flash and store for safe keeping, in case you want to revert to factory or sell the device.
   • If you didn't solder the cables, but just slotted DuPont cables in the holes, download twice and compare the hashes to make sure no corruption occurred.
5. Using the tool of your choice, flash ESPHome.
6. Unplug the flasher from your computer.
7. Remove or de-solder all cables, and re-assemble device.

If your board doesn't look exactly as pictured, but your device still identifies as zhimi.airp.mb5, use a multimeter on continuity mode and the datasheet of the ESP32 chip and its pins to identify where the connections are broken out.

Once you identified the connections, you can add your findings to this Wiki, in order to help future readers.