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?
- 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]
