logo elektroda
logo elektroda
X
logo elektroda
Advanced Search
logo elektroda

[BK7231N ] Teardown of TH08 LCD Calendar/clock/temperature/humidity, 3xAAA battery, backlight

morgan_flint 42429 254

TL;DR

  • TH08-CBU-ATH20-V2 is a LCD calendar/clock/temperature/humidity unit with a BK7231N CBU module, BL55070 LCD driver, and ATH20 sensor.
  • U3 appears to be the Tuya MCU, while U8 with a 32.768 kHz crystal likely handles RTC and LCD/backlight control, and Q1 switches Wi‑Fi power.
  • It runs from 3xAAA cells at 4.5V and was bought for 4.49€ as a Choice offer.
  • The Tuya app shows a 1 hour update interval, and pairing can fail because the device connects only briefly between updates.
Generated by the language model.
ADVERTISEMENT
Report a violation of the law
Reply Cool? Ranking DIY | New topic
Notify about new articles
📢 Listen (AI):
  • #91 20797516
    p.kaczmarek2
    Moderator Smart Home  
    Posts: 14417
    Help: 650
    Rate: 12374
    @morgan_flint nothing was changed in relation to RSSI, but maybe you need to do HASS discovery again?
    Do you have any non-TuyaMCU devices, can you check if HASS Discovery helps, and if not, check when the problem started?

    Unfortunatelly we don't take in account winter time yet, so you need to change it manually.

    Regarding configuration issue - maybe there is some kind of way to force TuyaMCU to stay on when we want to change config?
    Helpful post? Buy me a coffee.
  • ADVERTISEMENT
  • #92 20797751
    morgan_flint
    Level 14  
    Posts: 251
    Help: 4
    Rate: 59
    p.kaczmarek2 wrote:
    @morgan_flint nothing was changed in relation to RSSI, but maybe you need to do HASS discovery again?

    Bingo! I didi it again and now it shows RSSI:
    A screenshot from Home Assistant showing MQTT device data with icons for humidity, RSSI, and temperature.

    This is what appears under MQTT info in HomeAssistant:
    Screenshot showing MQTT data in HomeAssistant.

    p.kaczmarek2 wrote:
    Unfortunatelly we don't take in account winter time yet, so you need to change it manually

    Ok

    p.kaczmarek2 wrote:
    Regarding configuration issue - maybe there is some kind of way to force TuyaMCU to stay on when we want to change config?

    As I said in my previous post, bypassing Q1 to GND keeps the module on (this device switches on and off the module on the GND side, contrary to others that do it on the Vcc side), and this way the web interface is available and you can do FW updates, change the configuration, etc. I've checked in TuyaMCUAnalyzer that, while doing this, the module keeps sending "55AA0001000000" to the MCU every few seconds with no response from the MCU, it must be because the MCU only listens to the module after powering it on, not as a routine.

    For a "software" solution, if the original FW supports OTA update (probably it does), there must be something in the Tuya protocol for the module to ask the MCU to keep it on during that process, but I don't think is worth working on it, as the "hardware" solution is simple enough
  • #93 20797763
    p.kaczmarek2
    Moderator Smart Home  
    Posts: 14417
    Help: 650
    Rate: 12374
    That "3" on your screenshot, isn't it possible to change it with a setChannelLabel to a more meaningful name?
    Helpful post? Buy me a coffee.
  • ADVERTISEMENT
  • #94 20800273
    morgan_flint
    Level 14  
    Posts: 251
    Help: 4
    Rate: 59
    Done:
    Device status panel with battery level and environmental data.

    Added setChannelLabel 3 Battery level to autoexec.bat and launched Start Home Assistant Discovery afterwards.

    Also updated fw to 305
  • #95 20800307
    p.kaczmarek2
    Moderator Smart Home  
    Posts: 14417
    Help: 650
    Rate: 12374
    Also, isn't there already a "Low Mid High" or something like that channel type, which would display a string instead of a number in HA?
    Helpful post? Buy me a coffee.
  • #96 20800558
    morgan_flint
    Level 14  
    Posts: 251
    Help: 4
    Rate: 59
    These are the possibilities in "Channel types": Dropdown list showing available channel types in a user interface.

    I will try with "LowMidHigh"

    EDIT: Changed "setChannelType 3 ReadOnly" to "setChannelType 3 LowMidHig" in autoexec.bat. The main page changed to this:
    Screenshot of the interface with channel information and MQTT settings.

    But, in Home Assistant, "BatteryLevel" disappears, even after executing "Home Assistant Discovery" several times

    Changed autoexec back to "setChannelType 3 ReadOnly" and the battery level reappeared in Home Assistant.

    Looking at the new "control" in the web interface, I understand "lowMidHig" is intended for something you can control, not a (read only) measurement

    For me it's OK to have 1-2 as BatteryLevel instead of a string; I'm not really sure of the range of this measurement, maybe0-1-2 or 1-2-3 0r even 0-1-2-3, I should use a variable power supply and start lowering voltage from 4.5V to see when it changes, and how does it change
  • #97 20800668
    p.kaczmarek2
    Moderator Smart Home  
    Posts: 14417
    Help: 650
    Rate: 12374
    You are correct, but if you check our docs:
    https://github.com/openshwprojects/OpenBK7231T_App/blob/main/docs/channelTypes.md
    You can see that we also have:
    Code: text Expand Select all Copy to clipboard
    
ReadOnlyLowMidHigh	Like LowMidHigh, but just read only

    Maybe that one can work for you.
    Helpful post? Buy me a coffee.
  • #98 20801203
    morgan_flint
    Level 14  
    Posts: 251
    Help: 4
    Rate: 59
    I've just tried it:
    Screenshot of the OpenBK7231N interface displaying temperature and humidity parameters and connection details. Information panel displaying battery level, humidity, RSSI, and temperature.

    Now we still have to check that 1 is really "Medium". I'm feeding it with a small LiPo which is now 3.9V and the battery low icon isn't showing on the screen, so it could be really "Medium" (the device is designed for 3 * 1.5V batteries)
  • #99 20801209
    p.kaczmarek2
    Moderator Smart Home  
    Posts: 14417
    Help: 650
    Rate: 12374
    Thanks, I can also see that the rounding problem (occasional roundings like 25.02000000000001) is gone?
    Helpful post? Buy me a coffee.
  • #100 20801318
    morgan_flint
    Level 14  
    Posts: 251
    Help: 4
    Rate: 59
    p.kaczmarek2 wrote:
    Thanks, I can also see that the rounding problem (occasional roundings like 25.02000000000001) is gone?

    Yes, at least, I haven't seen it since a long time ago.

    EDIT: I'm now feeding it from 5V, the channel 3 value is 2 and showing "High" in Home Assistant. Now, I'll have to find the low voltage threshold...

    Added after 47 [minutes]:

    morgan_flint wrote:
    As I said in my previous post, bypassing Q1 to GND keeps the module on (this device switches on and off the module on the GND side, contrary to others that do it on the Vcc side), and this way the web interface is available and you can do FW updates, change the configuration, etc. ...

    For a "software" solution, if the original FW supports OTA update (probably it does), there must be something in the Tuya protocol for the module to ask the MCU to keep it on during that process, but I don't think is worth working on it, as the "hardware" solution is simple enough


    I've just found another possibility: With a long press of the button (until the light turns off), the Tuya MCU keeps the module on indefinitely, so it's possible to access the web interface for configuration or OTA FW update. A short press on the button reverts it to its normal state.
  • ADVERTISEMENT
  • #101 20802120
    p.kaczmarek2
    Moderator Smart Home  
    Posts: 14417
    Help: 650
    Rate: 12374
    I have observed something similiar on TuyaMCU door sensonrs, but in their case I had to press button multiple times to keep them awake, it was like each button was keeping it awake, but I may be wrong.

    Okay, what's next, is your TH08 now working better, now that I added the missing packet?
    Helpful post? Buy me a coffee.
  • #102 20802807
    morgan_flint
    Level 14  
    Posts: 251
    Help: 4
    Rate: 59
    p.kaczmarek2 wrote:
    Okay, what's next, is your TH08 now working better, now that I added the missing packet?

    Yes, perfect! The MCU turns off the module as soon as the last packet from the module is received, so now the battery should last the same as with the original FW (I thought I had already reported that). Thank you very much!

    For me, the only thing pending is measuring the thresholds between battery levels (in principle, just for the sake of knowing it, although it might be good to know when using with LiPos, to avoid over-discharging them)..

    Ah! And maybe restructuring the first post, to summarize everything we've found out.
  • #103 20804228
    morgan_flint
    Level 14  
    Posts: 251
    Help: 4
    Rate: 59
    morgan_flint wrote:
    the only thing pending is measuring the thresholds between battery levels

    I did it:
    High-medium: 4V
    Medium-low: 3.1V Under this threshold the low battery icon shows on screen.

    Under 3V the main regulator output starts dropping from 2.8V and the display starts dimming, so it needs 0.2V of minimum voltage drop to work properly. I haven't measured the other regulator, which is only for the backlight.

    Added after 6 [minutes]:

    auntlydia wrote:
    Any voltage between 3.3V and 4.5V should be safe to use, personally I wouldn't want to go higher than that. It may be fine though, but who knows for how long. I prefer to be safe on this one.

    As I said here, I've tried 5V with no issues and no heating on the voltage regulators; I think 5V should be safe (only 0.2V over alkalines, as a fresh alkaline battery is 1.6V so 4.8V in total), although I haven't been able to identify the voltage regulators and find their datasheets.

    In conclusion, the device can be powered also by USB and/or a LiPo battery without problems.
  • #104 20804716
    auntlydia
    Level 10  
    Posts: 70
    Help: 2
    Rate: 14
    Wow guys, I just read the latest posts here and I'm amazed! I will try to flash new firmware right away and set the other parameter to get "low/medium/high" reading for battery level instead of the numbers. If the battery now lasts as long as with original FW (3x1.2V batteries already running almost two months now), I might even consider not to do a USB mod. Also, thanks @morgan_flint for testing it with 5V; in that case we don't even need stepdown converters but can just install a USB-C or Micro socket.

    I can also confirm what @p.kaczmarek2 said about button press with other TuyaMCU devices (TH01 temperature sensor and W06 water leak sensor): as long as the button is pressed, it will keep up the wifi connection and we can make FW adjustments. With the TH08, even one short button press was enough to keep it on long enough to upgrade FW OTA. But not sure if it works with the newer FW, but either a long button press or repeatedly every 2 seconds or so should keep it active as with the other MCU sensors.

    So I'll be testing the new FW now and post an update after a while and see how long the batteries last.

    Thanks a lot @p.kaczmarek2 and @morgan_flint for keeping up the good work and digging into the FW improvement!! It's amazing =)
  • #105 20804880
    p.kaczmarek2
    Moderator Smart Home  
    Posts: 14417
    Help: 650
    Rate: 12374
    Thanks, however, for the record, I will mention that this:
    auntlydia wrote:
    set the other parameter to get "low/medium/high" reading for battery level instead of the numbers

    This actually was in OBK for the very long time already. We have multiple channel types working correctly with HASS Discovery.
    Helpful post? Buy me a coffee.
  • #106 20805344
    auntlydia
    Level 10  
    Posts: 70
    Help: 2
    Rate: 14
    Yea, I haven't read the documentation careful enough I guess. A very nice feature btw, which I applied to my other TH01 sensors as well. By the way, is it possible to set timers for devices in OpenBK? To turn them on/off automatically repeatedly? I found this function in Tasmota but not in OpenBK so far.

    Another note on the RSSI feature that has been added in recent firmware updates (or at least it showed up in my MCU devices after I updated to 1.17.306 and did new HASS discovery): for both my TH08 and TH01 devices, the data is not sent to HASS, but the status remains "Unknown".
    However this changes if I force constant WiFi connection e.g. by long button press until it refreshes, then the status changes to the correct value in HASS. This method worked for my TH01 devices. For TH08 it worked if button is pressed long during HASS discovery. Once HASS or mqtt is restarted, this value is lost again and won't be transfered with normal use of the device. I suppose the WiFi connection that is made by the sensor is too short for this request to be handled and transferred. It is not a problem at all, but I just want to mention it in case other users experience the same issue.
  • #107 20805352
    p.kaczmarek2
    Moderator Smart Home  
    Posts: 14417
    Help: 650
    Rate: 12374
    auntlydia wrote:
    Yea, I haven't read the documentation careful enough I guess. A very nice feature btw, which I applied to my other TH01 sensors as well. By the way, is it possible to set timers for devices in OpenBK? To turn them on/off automatically repeatedly? I found this function in Tasmota but not in OpenBK so far.

    Timers can be created in many ways and they are fully scriptable.
    https://github.com/openshwprojects/OpenBK7231T_App/blob/main/docs/autoexecExamples.md
    For example:
    Screenshot of script code with comments for a timer in the UI.

    auntlydia wrote:

    Another note on the RSSI feature that has been added in recent firmware updates (or at least it showed up in my MCU devices after I updated to 1.17.306 and did new HASS discovery): for both my TH08 and TH01 devices, the data is not sent to HASS, but the status remains "Unknown".
    However this changes if I force constant WiFi connection e.g. by long button press until it refreshes, then the status changes to the correct value in HASS. This method worked for my TH01 devices. For TH08 it worked if button is pressed long during HASS discovery. Once HASS or mqtt is restarted, this value is lost again and won't be transfered with normal use of the device. I suppose the WiFi connection that is made by the sensor is too short for this request to be handled and transferred. It is not a problem at all, but I just want to mention it in case other users experience the same issue.

    can you try adding something like:
    Code: text Expand Select all Copy to clipboard
    
mqtt_broadcastItemsPerSec 10

    or 20, etc, to your autoexec.bat and try again? How much time does it have to broadcast?
    Helpful post? Buy me a coffee.
  • #108 20805366
    auntlydia
    Level 10  
    Posts: 70
    Help: 2
    Rate: 14
    p.kaczmarek2 wrote:
    Timers can be created in many ways and they are fully scriptable.


    Thanks! I will have a look into that. I was just looking in the web interface, but I will try to figure out how the commands for autoexec.bat work for timers.

    p.kaczmarek2 wrote:
    can you try adding something like:
    Code: text Expand Select all Copy to clipboard
    mqtt_broadcastItemsPerSec 10

    or 20, etc, to your autoexec.bat and try again? How much time does it have to broadcast?


    I tried both 10 and 20 but there is no change. The time of active connection is approx. 5 seconds.
  • #109 20805416
    p.kaczmarek2
    Moderator Smart Home  
    Posts: 14417
    Help: 650
    Rate: 12374
    What is your current autoexec.bat @auntlydia ? Maybe we can try to force-publish something. Do you have waitFor MQTT?
    Helpful post? Buy me a coffee.
  • ADVERTISEMENT
  • #110 20805434
    auntlydia
    Level 10  
    Posts: 70
    Help: 2
    Rate: 14
    p.kaczmarek2 wrote:
    What is your current autoexec.bat @auntlydia ? Maybe we can try to force-publish something. Do you have waitFor MQTT?


    Code: text Expand Select all Copy to clipboard
    startDriver NTP
// starts the NTP driver (network time)
startDriver TuyaMCU
// starts the TuyaMCU driver
startDriver tmSensor
//starts the tmSensor driver
ntp_setServer 192.168.86.1
// sets the preferred NTP time server IP adress
ntp_timeZoneOfs 1
// corrects time zone by hour value +/- (time zone offset)
setChannelType 1 temperature_div10
//sets the type of channel 1 (selected freely) to temperature times 10 (i.e. 23.5C written as 235 integer, as this notation is used by Tuya), thanks to which OpenBeken knows how to display its value on the panel
linkTuyaMCUOutputToChannel 1 val 1
// maps dpID from TuyaMCU (variable identifier) 1 to channel 1, value type. In this particular device, dpID 1 is temperature. dpID roles vary by device
setChannelType 2 Humidity
// sets channel 2 type to humidity
linkTuyaMCUOutputToChannel 2 val 2
// as before, here dpID 2 is humidity
linkTuyaMCUOutputToChannel 3 val 3
setChannelType 3 ReadOnlyLowMidHigh
setChannelLabel 3 "Battery Level"
mqtt_broadcastItemsPerSec 20


    that's my current autoexec.bat

    should I include waitFor MQTT?
  • #111 20820474
    duycaf
    Level 3  
    Posts: 3
    Hello Guys,
    I have such a device and is not connecting anymore to app, probably problems with wifi.
    Is there anything I can do?
  • #112 20820485
    auntlydia
    Level 10  
    Posts: 70
    Help: 2
    Rate: 14
    duycaf wrote:
    Hello Guys,
    I have such a device and is not connecting anymore to app, probably problems with wifi.
    Is there anything I can do?


    Hi, are you using it with Tuya App? Or have you flashed OpenBK to the chip?

    I think another user here reported that it occurred that the device didn't connect anymore after flashing at some point. It happened to me as well, so I had to re-flash and it worked again without problems since.

    If you use Tuya only, they only options I see is delete it from the app and configure again, long button press should help to reset it to factory, you might wanna double check the instructions manual. Or maybe try some fresh batteries first?

    Cheers
  • #113 20824256
    morgan_flint
    Level 14  
    Posts: 251
    Help: 4
    Rate: 59
    auntlydia wrote:
    ...I suppose the WiFi connection that is made by the sensor is too short for this request to be handled and transferred. It is not a problem at all, but I just want to mention it in case other users experience the same issue.

    I have already noticed that; the RSSI level gets updated only every long time. I thought it was because it really didn't change so much.

    auntlydia wrote:
    The time of active connection is approx. 5 seconds.

    From what I remember when I did the scans, the MCU turns the module off as soon as it receives the last packet from the module (the one that was added in version 302). As this message is related to RSSI strength, it seems the module doesn't have time to send the corresponding MQTT message before being shut down. A possibility would be to delay a bit this last packet or simply wait to send it until the MQTT message has been sent. Is waitFor MQTT intended for this?

    BTW, have been using the device with OBK uninterruptedly for the last two weeks with fresh alkalines and the battery level remains high (4.3V); the battery consumption issues seem to have gone since version 302. Thanks!
  • #114 20824261
    auntlydia
    Level 10  
    Posts: 70
    Help: 2
    Rate: 14
    I tried with waitFor MQTT - no change unfortunately.

    I just checked the active time by watching the Log window. the message transfer stops after approx. 5 seconds. It should be actually enough to send small data package. but maybe the transfer isn't triggered?
  • #115 20837619
    kuncy7
    Level 9  
    Posts: 33
    Help: 1
    Rate: 2
    Hi,
    Can this device be converted using tuya-cloudcutter?
  • #116 20837627
    p.kaczmarek2
    Moderator Smart Home  
    Posts: 14417
    Help: 650
    Rate: 12374
    It's really hard to tell whether a given device is supported by a Tuya cloudcutter. You can always give it a try and check if any of the existing profiles is matching. What is the Tuya firmware version shown in the Tuya app? Just please do not update Tuya firmware if you want to flash this device remotely.

    You can also search Tuya-cloudcutter profiles on our devices list, select the "cloudcutter profile" from the drop down list:
    https://openbekeniot.github.io/webapp/devicesList.html
    Helpful post? Buy me a coffee.
  • #117 20838882
    kuncy7
    Level 9  
    Posts: 33
    Help: 1
    Rate: 2
    I was hoping it was this device: https://tuya-cloudcutter.github.io/api/device...-temperature-and-humidity-sensor-display.json
    Main module: V2.1.5
    MCU module: V1.0.0

    I'll try using tuya-cloudcutter and let you know how it goes.

    [Edit]
    I tried tuya-cloudcutter and unfortunately it ends like this:
    Code: text Expand Select all Copy to clipboard
    
Scanning for open Tuya SmartLife AP
.........
Found access point name: "SmartLife-18E5", trying to connect...
Device 'wlan0' successfully activated with 'db9376fc-df67-4f25-b1d3-f3018e49cb32'.
Connected to access point.
================================================================================
[!] The profile you selected did not result in a successful exploit.
================================================================================

    Where can I get a valid profile?
  • #118 20892743
    vikicha
    Level 3  
    Posts: 4
    Hello Guys
    I try TH08 with OpenBK but it did not read sensor, it just show zeroes.
    Screenshot of the OpenBK7231N interface showing no sensor readings.
    Also i try to flash it on PCB directly but it did not work, i have to desolder it and then the flash is successful.
    Can you help with the sensor?
  • #119 20892770
    auntlydia
    Level 10  
    Posts: 70
    Help: 2
    Rate: 14
    are you sure it is the same device? also, you may wanna try the current firmware 1.17.391 - I have multiple of those devices and they all work perfectly fine. The problem that a sensor shows zero values happened to me when I forced the device in keeping wifi connection by keeping the button pressed. maybe they have changed the design of the pcbs? it might be worth taking a look at the pcb pictures and compare.
  • #120 20892912
    vikicha
    Level 3  
    Posts: 4
    i think it is the same device or i'm wrong.
    LCD display in a white frame on a gray floral pattern background. Internal view of an electronic device with a visible main board and CBU module.
    and this is the UART i used for flash.
    USB to UART converter module with connected wires. Red circuit board with FTDI chip and connectors.
    i try the latest OBK 1.17.391 firmware but it is the same, no sensor readings only zeroes.

    Config in autoexec.bat is.

    startDriver NTP
    // starts the NTP driver (network time)
    startDriver TuyaMCU
    // starts the TuyaMCU driver
    startDriver tmSensor
    //starts the tmSensor driver
    ntp_setServer 192.168.86.1
    // sets the preferred NTP time server IP adress
    ntp_timeZoneOfs 1
    // corrects time zone by hour value +/- (time zone offset)
    setChannelType 1 temperature_div10
    //sets the type of channel 1 (selected freely) to temperature times 10 (i.e. 23.5C written as 235 integer, as this notation is used by Tuya), thanks to which OpenBeken knows how to display its value on the panel
    linkTuyaMCUOutputToChannel 1 val 1
    // maps dpID from TuyaMCU (variable identifier) 1 to channel 1, value type. In this particular device, dpID 1 is temperature. dpID roles vary by device
    setChannelType 2 Humidity
    // sets channel 2 type to humidity
    linkTuyaMCUOutputToChannel 2 val 2
    // as before, here dpID 2 is humidity
    linkTuyaMCUOutputToChannel 3 val 3
    setChannelType 3 ReadOnlyLowMidHigh
    setChannelLabel 3 "Battery Level"
    mqtt_broadcastItemsPerSec 20

    [Edit]
    Also date and time seems synced from NTP but not pushed to LCD

    The image shows a computer screen displaying information about the OpenBK7231N device and an LCD display with temperature and humidity readings.
Reply Cool? Ranking DIY | New topic
Notify about new articles
📢 Listen (AI):
Report a violation of the law

Topic summary

✨ The discussion centers on the teardown, firmware modification, and protocol analysis of the TH08 LCD calendar/clock/temperature/humidity sensor powered by 3xAAA batteries with backlight, based on the BK7231N chip. The device is identified as a newer version of the TH06 model, featuring a TuyaMCU module communicating via a low-power Tuya serial protocol (version 00). Users successfully flashed OpenBK firmware without desoldering, enabling temperature, humidity, and battery monitoring with MQTT integration and NTP time synchronization. Key challenges included understanding the MCU-module communication, especially time synchronization commands and power management to optimize battery life. The MCU sends commands such as ObtainDPCache and ObtainLocalTime, with the WiFi module responding accordingly. Firmware updates improved battery consumption by ensuring the WiFi module powers down promptly after data transmission. The device’s RTC (U8) communicates with the MCU (U3) over a serial or I2C-like interface, with ongoing efforts to decode this traffic. Users experimented with modifying battery power sources, including LiPo and USB power mods with step-down regulators, confirming device operation at voltages between 3.3V and 4.5V. The Tuya app lacks options to adjust sensor reporting intervals, and attempts to change polling times via Tuya protocol commands were unsuccessful, likely due to firmware limitations. Serial sniffing and analysis tools like TuyaMCU Analyzer and SniffUART were used to decode dpIDs, confirming dpID 1 as temperature, dpID 2 as humidity, dpID 3 as battery state, and dpID 9 as Celsius/Fahrenheit setting. Firmware versions and MCU versions were compared, revealing some early versions had display update issues. The community contributed to improving OpenBK firmware to handle specific Tuya commands, including proper responses to WiFi signal strength queries, enhancing power management. MQTT integration with Home Assistant was refined, including battery level display improvements using LowMidHigh channel types. OTA updates and configuration changes require keeping the WiFi module powered, achievable via long button presses or hardware modifications. Attempts to use Tuya-cloudcutter for remote flashing were unsuccessful due to lack of matching profiles. Some users reported issues with sensor readings showing zero after flashing, possibly due to hardware revisions or firmware mismatches. Overall, the device is well-supported by OpenBK firmware with active community development focusing on power optimization, protocol decoding, and integration with home automation platforms.
Generated by the language model.
Today's popular

FAQ

TL;DR: “Flashing succeeds 100 % when CEN, RX and TX are isolated” and the Wi-Fi module stays powered just 18 s per cycle [Elektroda, spin55, post #20804765] Unit switch is dpID 9; send 55AA001000070101090400010026 to force °C [Elektroda, smoeller95s, post #21550660] Battery life rises from 3 days to 6 weeks after v1.17.302 fix [Elektroda, morgan_flint, post #20796796]

Why it matters: correct pinout, dpIDs and flags avoid soft-brick loops and halve power drain.

Quick Facts

• MCU board rev V3.7 (2023-11-06) uses step-down RT8008-like regulator, 2.3–3.6 V out [Elektroda, bogovik, post #21007162] • Default Tuya baud: 9 600 bps; do not force 115 200 on battery models [Elektroda, bogovik, post #21007162] • Wi-Fi on-time: 10–18 s (after dpCache fix) [Elektroda, p.kaczmarek2, post #20796796] • Battery thresholds: High ≥ 4 V, Medium 4–3.1 V, Low < 3.1 V [Elektroda, morgan_flint, post #20804228] • dpIDs: 1 Temp, 2 RH, 3 Batt-state, 4 Batt-%, 9 Unit, 10–13 limits, 14–15 alarms, 17–20 report/sensitivity [Elektroda, divadiow, post #21357234]

Which pads are Vcc, GND, TX, RX and CEN on TH08/TH08-B?

On CBx/CBU/CB3S modules the corner row is 1 GND, 2 3.3 V, 3 RX2, 4 TX2, 5 CEN (EN). Test pads marked RX1/TX1 belong to the Tuya-MCU and must be cut or unsoldered before flashing [Elektroda, morgan_flint, post #20929625]

How do I flash OpenBeken without desoldering?

  1. Lift (or cut) MCU pins 8 (CEN) and 9/10 (RX/TX) or sever their traces. 2. Power the CBU with 3.3 V (battery V+ bypasses the regulator). 3. Run BK7231Flasher, back up, then write the QIO image at 921 600 bps. 4. Re-join the cuts with thin wire [Elektroda, spin55, post #21003945]

Device reboots endlessly after battery is flat – fix?

Safe-mode reset: toggle power 5 × within 5 s, connect to the OBK-AP, press “Exit safe-mode”, then set a working NTP server and MQTT host [Elektroda, morgan_flint, post #20919613]

Why does NTP show 1970 or 2070 date?

The LAN NTP IP must respond within the 18 s Wi-Fi window. Use e.g. ntp_setServer 217.147.223.78 and keep ntp_timeZoneOfs correct. Each failed packet logs NTP_SendRequest: Unable to send message [Elektroda, spin55, post #21074156]

How to switch the LCD from °F to °C?

Send the unit-convert dpID 9 packet once after boot:
delay_s 2
uartSendHex 55AA001000070101090400010026
Value 00 gives °C; 01 gives °F [Elektroda, smoeller95s, post #21550660]

MQTT values are 10× smaller – why?

Disable flag 33 (apply multiplier before publish). Otherwise temperature_div10 splits the MCU value and HA divides it again, giving 2.2 °C instead of 22 °C [Elektroda, p.kaczmarek2, post #21377733]

Can I map battery percentage to Home Assistant?

Yes.
setChannelType 4 BatteryLevelPercent
linkTuyaMCUOutputToChannel 4 val 4
After OBK 1.17.780 the HA discovery JSON includes this sensor automatically [Elektroda, p.kaczmarek2, post #21378297]

How to keep Wi-Fi on for configuration?

Hold the top button ≥ 3 s; Tuya-MCU holds CBU power high for ~90 s, enough for OTA or web-config [Elektroda, spin55, post #20804765]

What is dpCache and why use it?

Battery devices resend saved limits after every reboot. Mark a channel persistent with SetStartValue <ch> -1 and add 1 at the end of linkTuyaMCUOutputToChannel … to include it in the dpCache reply packet 0x10 [Elektroda, p.kaczmarek2, post #21385904]

Edge case – flashing stops at 70 % every time.

UM8005/UM805 (Tuya-MCU) toggles CEN mid-flash. Isolate CEN first or power the module through 3.3 V and ground while MCU ground is disconnected [Elektroda, spin55, post #21003945]
Generated by the language model.
ADVERTISEMENT