[BK7231N / CB3S] TH11 Temperature and humidity sensor (IP65/WiFi)

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21819906 26 Jan 2026 07:37

This is another WiFi temperature sensor that works with the Tuya/Smart Life system as standard. It is an IP65-rated version for outdoor placement. The sensor is powered by two AAA batteries and is based on the CB3S module and the TuyaMCU microcontroller - here, as usual, the sensor was purchased to convert to OpenBK, i.e. to work with Home Assistant bypassing the Tuya cloud.

What we get in the box

Here, without much surprise, a short instruction manual, the sensor itself + pendant and the mounting tape and magnetic tape.

Interior sensor

Here, as expected, there is not much

That is, what was mentioned the module CB3S with BK7231N chip, TuyaMCU that is an unknown microcontroller, transistor Q1 controlled by TuyaMCU chip (U3) whose task is to cut the ground from the CB3S module. As a temperature/humidity sensor, a chip Sensylink CHT8310 communicating with TuyaMCU via I2C bus was used. Plus one button, an LED and some RC passive components....

TuyaMCU connection to CB3S module

TuyaMCU (U3)

TuyaMCU (U3)	CB3S (M1)
GPIO (Pin 7)	RST (Pin 1)
UART TX (Pin 9)	RXD1 (Pin 15)
UART RX (Pin 10)	TXD1 (Pin 16)

In order to upload OpenBK, all I had to do was lift/disconnect the RX and TX legs of the TuyaMCU and power the CB3S module directly....

Image in the Tuya app and data from the Tuya Developer Platform service

Basically, like most temperature/humidity sensors there is not much in the app i.e. data visualisation and simple settings.

Data from the Tuya Developer Platform looks as follows.

Standard Instruction Set


temp_unit_convert	Enum	

{
  "range": [
    "c",
    "f"
  ]
}

Standard Instruction Set


temp_unit_convert	Enum	

{
  "range": [
    "c",
    "f"
  ]
}

Standard Status Set


va_temperature	Integer	

{
  "unit": "℃",
  "min": -200,
  "max": 600,
  "scale": 1,
  "step": 1
}

va_humidity	Integer	

{
  "unit": "%",
  "min": 0,
  "max": 100,
  "scale": 0,
  "step": 1
}

battery_state	Enum	

{
  "range": [
    "low",
    "middle",
    "high"
  ]
}

temp_unit_convert	Enum	

{
  "range": [
    "c",
    "f"
  ]
}

Standard Status Set


va_temperature	Integer	

{
  "unit": "℃",
  "min": -200,
  "max": 600,
  "scale": 1,
  "step": 1
}

va_humidity	Integer	

{
  "unit": "%",
  "min": 0,
  "max": 100,
  "scale": 0,
  "step": 1
}

battery_state	Enum	

{
  "range": [
    "low",
    "middle",
    "high"
  ]
}

temp_unit_convert	Enum	

{
  "range": [
    "c",
    "f"
  ]
}

Additional JSON extracted from original firmware

Logs of TuyaMCU communication with CB3S module

Sensor added to Tuya cloud


Sent by WiFi module:
55 AA	00	01		00 00		00	
HEADER	VER=00	Product		LEN		CHK	

Received by WiFi module:
55 AA	00	01		00 24	7B2270223A226A33666A616A66327830617073716770222C2276223A22312E302E30227D	A3	
HEADER	VER=00	Product		LEN	{"p":"j3fjajf2x0apsqgp","v":"1.0.0"}	CHK	

Received by WiFi module:
55 AA	00	02		00 00		01	
HEADER	VER=00	McuConf		LEN		CHK	

Sent by WiFi module:
55 AA	00	02		00 01	04	06	
HEADER	VER=00	McuConf		LEN	04	CHK	

Received by WiFi module:
55 AA	00	10		00 04	03091718	4E	
HEADER	VER=00	ObtainDPcache		LEN			CHK	

Received by WiFi module:
55 AA	00	0B		00 00		0A	
HEADER	VER=00	Unk		LEN		CHK	

Sent by WiFi module:
55 AA	00	10		00 02	0100	12	
HEADER	VER=00	ObtainDPcache		LEN			CHK	

Sent by WiFi module:
55 AA	00	0B		00 02	013C	49	
HEADER	VER=00	Unk		LEN	013C	CHK	

Received by WiFi module:
55 AA	00	05		00 15	090400010017020004000000001802000400000000	62	
HEADER	VER=00	Unk		LEN	dpId=9 Enum V=0,dpId=23 Val V=0,dpId=24 Val V=0		CHK	

Sent by WiFi module:
55 AA	00	05		00 01	00	05	
HEADER	VER=00	Unk		LEN			CHK	

Received by WiFi module:
55 AA	00	05		00 15	010200040000013402020004000000170304000102	7E	
HEADER	VER=00	Unk		LEN	dpId=1 Val V=308,dpId=2 Val V=23,dpId=3 Enum V=2		CHK	

Sent by WiFi module:
55 AA	00	05		00 01	00	05	
HEADER	VER=00	Unk		LEN			CHK

Sensor not connected to the Tuya cloud


Received by WiFi module:
55 AA	00	01		00 24	7B2270223A226A33666A616A66327830617073716770222C2276223A22312E302E30227D	A3	
HEADER	VER=00	Product		LEN	{"p":"j3fjajf2x0apsqgp","v":"1.0.0"}	CHK	

Sent by WiFi module:
55 AA	00	01		00 00		00	
HEADER	VER=00	Product		LEN		CHK	

Sent by WiFi module:
55 AA	00	02		00 01	03	05	
HEADER	VER=00	McuConf		LEN	03	CHK	

Received by WiFi module:
55 AA	00	02		00 00		01	
HEADER	VER=00	McuConf		LEN		CHK

OpenBK configuration

Here looking in the logs there is not much

Set flags: 2 10 19 37 51

autoexec.bat


startDriver TuyaMCU
startDriver tmSensor

setChannelType 1 temperature_div10
linkTuyaMCUOutputToChannel 1 val 1

setChannelType 2 Humidity
linkTuyaMCUOutputToChannel 2 val 2

setChannelLabel 3 Battery
setChannelType 3 ReadOnlyLowMidHigh
linkTuyaMCUOutputToChannel 3 val 3

Log of TuyaMCU communication with CB3S module with OpenBK firmware


Sent by WiFi module:
55 AA	00	01		00 00		00	
HEADER	VER=00	Product		LEN		CHK	

Received by WiFi module:
55 AA	00	01		00 24	7B2270223A226A33666A616A66327830617073716770222C2276223A22312E302E30227D	A3	
HEADER	VER=00	Product		LEN	{"p":"j3fjajf2x0apsqgp","v":"1.0.0"}	CHK	

Received by WiFi module:
55 AA	00	02		00 00		01	
HEADER	VER=00	McuConf		LEN		CHK	

Sent by WiFi module:
55 AA	00	02		00 01	03	05	
HEADER	VER=00	McuConf		LEN	03	CHK	

Received by WiFi module:
55 AA	00	02		00 00		01	
HEADER	VER=00	McuConf		LEN		CHK	

Sent by WiFi module:
55 AA	00	02		00 01	04	06	
HEADER	VER=00	McuConf		LEN	04	CHK	

Received by WiFi module:
55 AA	00	10		00 04	03091718	4E	
HEADER	VER=00	ObtainDPcache		LEN			CHK	

Sent by WiFi module:
55 AA	00	10		00 02	0100	12	
HEADER	VER=00	ObtainDPcache		LEN			CHK	

Received by WiFi module:
55 AA	00	0B		00 00		0A	
HEADER	VER=00	Unk		LEN		CHK	

Sent by WiFi module:
55 AA	00	0B		00 02	0150	5D	
HEADER	VER=00	Unk		LEN	0150	CHK	

Received by WiFi module:
55 AA	00	05		00 15	090400010017020004000000001802000400000000	62	
HEADER	VER=00	Unk		LEN	dpId=9 Enum V=0,dpId=23 Val V=0,dpId=24 Val V=0		CHK	

Sent by WiFi module:
55 AA	00	05		00 01	00	05	
HEADER	VER=00	Unk		LEN			CHK	

Received by WiFi module:
55 AA	00	05		00 15	010200040000012D02020004000000190304000102	79	
HEADER	VER=00	Unk		LEN	dpId=1 Val V=301,dpId=2 Val V=25,dpId=3 Enum V=2		CHK	

Sent by WiFi module:
55 AA	00	05		00 01	00	05	
HEADER	VER=00	Unk		LEN			CHK

Well, that's pretty much it - you can still future-proof the handling of id 9, 23, 24 - i.e. the sensor settings....

Additional moisture protection

Theoretically the sensor is IP65 rated but after uploading the firmware I decided to additionally protect the electronics with a silicone coating (MG Chemicals 422C)

Here, care must be taken that the preparation does not get into the "window" in the temperature/humidity sensor. Likewise, I do not recommend coating the antenna circuit on the CB3S module with silicone....

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About Author

tplewa tplewa

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tplewa wrote 6667 posts with rating 969, helped 222 times. Live in city Warszawa. Been with us since 2003 year.

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#2 21819998 26 Jan 2026 09:47

p.kaczmarek2 p.kaczmarek2

Moderator Smart Home

» | Helpful post? (0)

Post #2
21819998 26 Jan 2026 09:47

You hit on a slightly better model, not everyone has the settings (ObtainDPcache). From what I remember, we presented with @DeDaMrAz their setting here:
[CB3S/BK7231N] Temperature/humidity sensor with TuyaMCU - Schematic, reverse engineering
You can try if it works for you.

Although I would still prefer to convert to a version without TuyaMCU - there is DeepSleep in the obk.

Does your sensor report every fixed interval or when something changes? CHT has an alert function.

I am creating multiplatform open source firmware (Tasmota replacement), right now supporting BK7231T, BK7231N, XR809, BL602, W800, W600, LN882H and soon supporting RTL and W701:
https://github.com/openshwprojects/OpenBK7231T
If you like my work, support me at: https://paypal.me/openshwprojects

Helpful post? Buy me a coffee.
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[BK7231N / CB3S] TH11 Temperature and humidity sensor (IP65/WiFi)

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