[BK7231N] [CB3S] [AHT20] TH01 Generic Temperature and Humidity Sensor Teardown

I read these articles. I did not have two left hands, but I did not study electric-technic. So I have big problems to understand all of what is written, and I don't know what is really useful if I can't understand everything. I just want it to work.

I now have:
1. Cut the RX and TX traces at the Tuya MCU.
2. Flashed actual BK7231N bin with Windows flasher (had many problems but got it flashed on 2 different devices).
3. Resoldered the cut RX and TX traces at the Tuya MCU.
Did not work: Powered the device (TH01 from this thread). First, I tried to power it with the battery pins, but the access point WLAN goes on and off all the time, so I can't get a stable connection to the access point - I think the reason is the battery saver or Tuya MCU?
4. Then I powered the CB3S platine with 3.3V, and I got a stable connection.
5. I did standard Wi-Fi settings and MQTT and restarted. TH01 is now in my home network. Sometimes it restarts. Is this normal?
6. I copied this line "backlog startDriver tuyaMCU; startDriver tmSensor; linkTuyaMCUOutputToChannel 1 val 1; setChannelType 1 temperature_div10; linkTuyaMCUOutputToChannel 2 val 2; setChannelType 2 Humidity;linkTuyaMCUOutputToChannel 3 val 3; setChannelType 3 ReadOnly;" in the start command.
7. Restarted.
Trying to power it with the battery will not work. Where should I connect the + and -?

grericht wrote:

Ok. Will try this next.

I now have reached 2 different Tuya thermo/hygrometers with Open Beken flashed.
1 I have resoldered the cut traces and on the other I didn't up to now.
When I power the devices there is the Open Beken net, but on both I only get a short connection and can't reach 192.168.4.1. Connection will be lost very shortly.
Is this because of the energy-saving mode of these devices?
Did I have to resolder both?
How can I get the configuration on the devices?

@p.kaczmarek2 this looks to me like the light module, it needs a configuration otherwise the tuyaMCU will shut down - no heartbeat maybe?

My solution for this was to power on the device (WiFi module) externally, configure everything then power it on batteries.

after configuring wlan settings i have some problems with configuration.
i powered directly the cb3s platine

first time i try to search in web app (config/Pick a device from the dropdown) for the correct device an found "Tuya TuyaMCU TH01 ...". -> copy device settings ->
nothing changed but command: "backlog startDriver tuyaMCU; startDriver tmSensor; linkTuyaMCUOutputToChannel 1 val 1; setChannelType 1 temperature_div10; linkTuyaMCUOutputToChannel 2 val 2; setChannelType 2 Humidity;linkTuyaMCUOutputToChannel 3 val 3; setChannelType 3 ReadOnly;" ->
save pins
power off/on -> no change?! why?!

when i use the "normal" interface option "config"/change startup command text it seems to be to long. i can copy and paste. all is pasted.
after saving it is cuted and filed:
original: backlog startDriver tuyaMCU; startDriver tmSensor; linkTuyaMCUOutputToChannel 1 val 1; setChannelType 1 temperature_div10; linkTuyaMCUOutputToChannel 2 val 2; setChannelType 2 Humidity;linkTuyaMCUOutputToChannel 3 val 3; setChannelType 3 ReadOnly;
after saving: backlog startDriver tuyaMCU; startDriver tmSensor; linkTuyaMCUOutputToChannel 1 val 1; setChannelType 1 temperature_div10; linkTuyaMCUOutputToChannel 2 val 2; setChannelType 2 Humidity;linkTuyaMCUOutputToCha<input type='hidden' name='startup_cmd' value='1'><br><input type=
after rebooting i get an error in web app/config/curret device: Error: SyntaxError: JSON.parse: expected ',' or '}' after property value in object at line 1 column 535 of the JSON data

i have to return to factory settings by web app
what is the correct way to get the startup command working

Hi, I'm struggling with the same device...
After flashing and getting the config done, I don't get any useful data on any channel... all are set to 0



Any idea where this effect is coming from?

Hello, it seems that no drivers are running. What is your current GPIO configuration on the panel?

To be honest, I did not change the GPIO configuration since I expected the RX/TX communication with the MCU to be working "out of the box" %-)

Is there a reference pinout I missed while reading the tutorials in the forum?!

I referred to this post: https://www.elektroda.com/rtvforum/topic3947585-30.html#20427369 asking for the pin-setting as well and got the response "Just to get the temperature and humidity, the pin setting is not directly necessary."

If your device is TuyaMCU one, then maybe you need to copy the config from this post?
https://www.elektroda.com/rtvforum/topic3947585-30.html#20383876

With the mentioned Autoexec, it seems to load some drivers, but still no values visible...

It is possible that you are approaching it in an incorrect way.

It seems that you have a TuyaMCU device, a battery-powered one.

Those devices are always controlled by the MCU. MCU only powers on the WiFi module when it wants to report data, WiFi module then initiates the UART conversation and MCU sends data to WiFi module. WiFi module then reports data to cloud and sends an "I'm finished" packet to MCU, which then turns off the WiFi module again.

All that is done in order to preserve the batteries.

If you are powering the WiFi module externally, then you won't get measurement results.

So I will say this, the approach here is as follows:
1. Get dpIDs data (or find existing matching config).
2. Flash OBK.
3. Power externally WiFi module.
4. Setup OBK autoexec with dpIDs and channel types.
5. Pair with Ha, do Home Assistant discovery.
6. Disconnect external power for WiFi module.
7. Put in batteries.
8. Then it should start waking up for itself, for 30 seconds or so, every now and then and report data to your HA.

Here is my topic about such a sensor:
https://www.elektroda.com/rtvforum/topic3975583.html

Hello everyone,

thank you for this post, which was able to give me the basic information I needed in order to setup this sensor (TH01). With the aforementioned discussion about whether or not to sever some pins or desolder the WiFi module, I want to add some comments.
I desoldered it for the reason that I was not able to get the device's created WiFi AP up and running long enough to enter configuration - simply because I was not patient enough. It is not necessary, don't do it, you don't need to. It was taking ages to desolder the battery pins, which was necessary in order not to melt the housing for the later-on desoldering of WiFi module with hot air, it's not worth it, I even damaged the housing while desoldering the battery terminals with my iron - a pain. Now, I would like to quickly give you the steps that worked for me.

I flashed 4 sensors of the same type, and it worked the same for all of them.

1. have a look at the relevant pins:



2. solder 5 indidivual wires to each of those. For TX / RX pins, you can also use the large round test pads on the motherboard, they are easier to access.

3. connect 4 wires (3.3V, GND, TX, RX) to your USB-UART module, mind the 3.3V setting! make sure to connect TX ---> RX and RX ---> TX! If you want to use external 3.3V power source, connect the ground wire (-) of that source to BOTH our sensor AND USB-UART module.

4. prepare Windows tool bk7231flasher: download current firmware (7231N!), I also recommend setting "Change OBK settings for flash write", this way you can already enter your WiFi credentials and mqtt data. Also, here you can already set the flags (I only used flag 10) and enter the startup code that is required for this module

[backlog startDriver tuyaMCU; startDriver tmSensor; linkTuyaMCUOutputToChannel 1 val 1; setChannelType 1 temperature_div10; linkTuyaMCUOutputToChannel 2 val 2; setChannelType 2 Humidity;linkTuyaMCUOutputToChannel 3 val 3; setChannelType 3 ReadOnly;]

so all that's left to do after flashing is to double check all the name settings and start Home Assistant discovery via the web interface.
(--> If the startup command doesn't work later on, you need to enter it again via web interface. If there is no button to submit, it might be necessary to clear OBK config via web app command, after that you can re-enter new startup command)

5. Now connect USB (and then external power if you use it) and wait a moment for it to show up in UART port. Also, give the module few seconds to power on. Don't forget to select "Automatically configure OBK on flash write" if you chose this setting in step 4

6. Now make sure correct firmware is selected and then start process "Do backup and flash new", confirm dialogue and wait for log window to show waiting status. Now shortly (!) connect the end of CEN-wire to one of your GND terminals (just touch it and immediately release again), it will reset the device and reading/writing should start without any error messages. If you get any crucial error message, make sure to repeat step 5 and wait a minute before you start read/flash process. It worked for all my 4 sensors without exception.

7. After successful flash, disconnect the module first. Then the important part in order to make the WiFi-connection work: connect only 3.3V and GND (doesn't matter where from) to the wires that are still attached, to power the device on again. Now, wait patiently! WiFi will pop up few times, after few minutes it will be stable! Either way, as AP if not preconfigured, or already in your router with new IP address. Then open web interface, finish configuration (HA discovery, names, startup command etc), and before you desolder the wires, pop in batteries and test if it still works. After disconnecting wires it will be annoying to acces the web interface - yet it is possible by either keeping the module's button pressed or press it down continuosly in 2 second intervals or so.

Result in HA:



(it was raining a lot here today, we can see it 😅 )

Good luck!

Hi, I also have same device, and load OpenBeken FW (Thanks for it!).
Now, MCU's cycle power on is too short to collect and send data:



After this, MCU disconnect ground from the module. It is possible to make easy modification: bypass ground from the module (pin 9 on CB3S) to BAT- contact, use tuyaMCU driver and try to use FW deep sleep mode.

@dgel27

Go to config, enable WiFi quick connect (flag 37). Also, decrease "Uptime seconds required to mark boot as ok:" from 5 to 3. You can also set up a static IP address for your device, which will help it boot faster and connect to your WiFi faster. This way, the timeout TuyaMCU is imposing will be enough, and your values/states will be reported.

Hope this helps, and sorry for the late response.

I read all the posts and found that I DID NOT need to unsolder anything to do the UART flashing. You can read all about my experience here: https://github.com/rickbronson/Open-Source-So...re-on-a-Tuya-TH01-Temperature-Humidity-Sensor

Cheers,

Rick

Hi,

I don’t get any battery state. Is it not a feature of the device or am I missing something?

Thanks

What is your device configuration? You will not get battery state entry unless you configure it

Hi,

I just added those to startup commands, do i need to add anything for battery?:

backlog startDriver tuyaMCU; startDriver tmSensor; linkTuyaMCUOutputToChannel 1 val 1; setChannelType 1 temperature_div10; linkTuyaMCUOutputToChannel 2 val 2; setChannelType 2 Humidity;linkTuyaMCUOutputToChannel 3 val 3; setChannelType 3 ReadOnly;

Kind regards

So channel 3 is battery level? As in Low-Mid-High?
So change:

To:

See channel type docs at:
https://github.com/openshwprojects/OpenBK7231T_App/blob/main/docs/channelTypes.md

Ok i will. Thank you very much!

Keep in mind that you need to redo HASS discovery after changing the channel type.

I did and also HA discovery. The 3rd channel's value is either 0, 1, or 2. I think it's equal to low-mid-high.

I've just bought two of these and my variants are CBU module and AHT30 sensor.

I see no AHT30 search results yet on elektroda. I am away and cannot flash at the moment, but has anyone played with this type?

My initial searching has found no mention of AHT30 on Aosong site. I've unsuccessfully tried to guess the URL of the datasheet, using a modified file name of the AHT20 pdf and URL.

have you tried SHT30 driver?

Good afternoon. Tell me, data is sent to MQTT 2 times. How to fix it?

Why is it a problem? Which device config?

This config looks ok. My only question would be now why do you think it's a problem? You can try disabling "broadcast self state on MQTT connect" if you really want to, but in my opinion, there is no problem with device broadcasting data twice.

good afternoon. Yes, I did it on your advice, thank you. there is another question in mqtt, the data comes BK7231N_AC4D000A3/1/get 27.000000 how to get rid of zeros and leave 27.00

I tried to flash TH01 with bk7231flasher_1.1.6 like auntlydia and rickbronson did. I use external 3.3V power supply. I connect +3.3V to TH01, GND to TH01 GND and USB-UART ground, TH01 RX2 to USB-UART Tx and TH01 TX2 to Rx USB-UART. (See photo). I powered TH01 on and off or shorted TH01 CEN to ground. All without success. Always got: "Getting bus failed, will try again...". I changed USB-UART (CH340, FTDI). I tried different baud rates. Please help!

Did you cut the connection to MCU? Few posts above user described the procedure well.
https://www.elektroda.com/rtvforum/topic3968377-30.html#20628188

No, I didn't because of Aunt Lydia's post: "I desoldered it for the reason that I was not able to get the device's created WiFi AP up and running long enough to enter configuration - simply because I was not patient enough. It is not necessary, don't do it, you don't need to. It was taking ages to desolder the battery pins, which was necessary in order not to melt the housing..." and Rick Bronson's post: "I read all the posts and found that I DID NOT need to unsolder anything to do the UART flashing...."