Xiaomi Air Purifier 3H Reverse Engineering Part 1: Probing Around

Welcome to the family Xiaomi Air Purifier H3!

If something enters my house I open it as quickly as possible and start probing around.

The following information is for educational Purposes only!
Note, I absolutely love Xiaomi stuff since it is cheap, of decent build quality, and it’s fun to probe around in!

How to disassemble the device:

The device itself is quite easy to disassemble. One of the first things that is noticeable is that a bare minimum of screws that are used. The bottom side has four, and underneath the bottom plate has another four screwed in. Almost the complete assembly is made to click-clack-badabing-badaboom and your done (my way of putting things together). Seldom I see products this well constructed with mass production in mind. The engineers at Xioami absolutely did a great job! For every product engineer on this planet: buy this device, take it apart, and learn from it!

When opening the device we find the following main board:

AC-M6-B01

REV3-BDR

XIaomi Air FIlter H3 Main Board Pinout Pins
Connector _pins:
Function
J1
ESP_PROG_HEADER
-1
3V3
-2
GND
-3
ESP-32-UART0-TX
-4
ESP-32-UART0-RX
J2
STM_SERIAL_DEBUG
-1
STM32-RX
-2
STM32-TX
-3
GND
-4
3V3
J3
ESP_GPIO_0_HEADER
-1
ESP-32-GPIO-0
-2
GND
J4
MOTOR_CONNECTOR
-1
24V
-2
GND
-3
5V
-4
PWM
-5
BRK?
-6
?
-7
FG?
J7
PLANT_POWER_CONNECTOR
-1
?
-2
?
-3
?
-4
RX
-5
TX
-6
SET
-7
GND
-8
5V
J8
POWER_CONNECTOR
-1
24V
-2
GND
J9
STM_PROGRAMMING_HEADER
-1
3V3
-2
GND
-3
SWDIO
-4
CLK
-5
SWO
-6
NC?
J10
NFC_HEADER
-1
SDA
-2
3V3
-3
STATE
-4
GND
-5
SCL
J11
SHT_20+BUTTON_HEADER
-1
SCL
-2
GND
-3
LED_ON
-4
3V3
-5
SDA
-6
? (button?)
J12
DOOR_SWITCH
-1
BOT_DOOR
-2
GND

J6 is the header that is used for the OLED display. I could not be bothered to probe it as I’m not trying to hack the display.

IC’s used:

Designator IC
U3 Fremont   FT24C64A
U4 Espressif ESP-WROOM-32D
U5 ST STM32F412RET6

U3 = an 64K EEPROM datasheet: Click

U4 = an Espressif wifi adapter. This IC/ Package handles all the WIFI/BLE Traffic.

U5= The main Microcontroller.

This is a good start for reverse engineering. No mysterious Chinese crap IC’s. In the following parts of this series of blog posts we will look into the contents of these chips 😀

More info on this project will be added on the project’s GitHub

2 comments

  1. Is it possible to hack the filter lifespan? It is great feature but it doesn’t work perfect. It decreases by hours, not by dust or pollution. So if you run it in perfect space or in very polluted space it will give same lifespan and will ask to change then.

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