FAQ
TL;DR: “99 % of BK7231N DIN-rail switches flash in <3 min over UART” [Elektroda, silvestro_gatto, post #21173683] “Flashing was quite straightforward” [Elektroda, silvestro_gatto, post #21173683] Use 3.3 V, short CEN to GND, 921 600 baud. Why it matters: fast local firmware = full Home-Assistant control and no Tuya cloud.
Quick Facts
• Chipset: BK7231N Wi-Fi MCU + BL0942 power-meter IC [Elektroda, p.kaczmarek2, post #20663290]
• Recommended UART flashing speed: 921 600 baud [Elektroda, silvestro_gatto, post #21173683]
• Supply for flashing: stable 3.3 V / ≥300 mA (USB-UART alone may reset) [Elektroda, p.kaczmarek2, post #21402384]
• Typical retail cost: US $16-20 on AliExpress [AliExpress listing]
• Relay type: bi-stable 1-pole, driven by pins P24 (FWD) & P26 (REV) [Elektroda, Thread Template, #20663290]
Which pins do I connect to flash the Tongou TO-Q-SY1/2-JWT?
Connect 3.3 V and GND to the CBU module; RX1→USB-TX, TX1→USB-RX, and momentarily short CEN to GND to enter boot. Optional: monitor logs on TX2 [Elektroda, silvestro_gatto, post #21173683]
The flasher keeps showing “Getting bus failed”—what causes this?
Most failures come from weak power or long jumper wires. Use an external 3.3 V supply ≥300 mA, keep leads <10 cm, match baud (921 600 or 1 500 000), and reset with CEN-to-GND pulse [Elektroda, p.kaczmarek2, post #21402384]
How do I restore the relay state after a power loss?
Issue SetStartValue -1 on channel 1 so OpenBeken stores and re-applies the previous state at boot [Elektroda, p.kaczmarek2, post #21402384]
Why does my coil heat to 55 °C after flashing?
Continuous HIGH on BridgeFWD/REV holds current. Use BridgeFWD/BridgeREV pins (pulsed) instead of Rel; set pulse width 100 ms to avoid overheating [Elektroda, dwmw2, post #21265055]
Can I dump original Tuya calibration values?
Yes. Read flash, locate vref/iref/pref/eref words and import them; ESPHome PR #7421 and OBK PowerSet/VoltageSet commands accept these numbers [Elektroda, dwmw2, post #21190960]
Power readings are 5× too high in standby—how to fix?
Enable Flag 25 (allow negative power) and perform a two-point calibration with a known resistive load and real-world inductive load; error falls below 2 % after calibration [Elektroda, casiopeia80, post #21556434]
Does SY2 add hardware over-current/voltage protection?
No discrete link from BL0942 CF1 to driver exists; protection is handled in Tuya software. In OpenBeken you can mimic it with addChangeHandler Voltage > 250 POWER OFF etc. [Elektroda, leśny_ziutek, #21487925].
What screws replace the factory rivets when re-sealing?
M2.5 × 10 mm self-tappers fit the front holes perfectly; ~US $4 for 100 [Elektroda, przemsi_ele, post #21080398]
Is OTA flashing with Tuya-cloudcutter supported?
Only firmware ≤1.0.2 (non-metering) and 1.0.18 (metering) are currently exploitable; newer 1.0.20 requires UART [Elektroda, p.kaczmarek2, post #20974510]
Edge case: relay clicks but no continuity after reverse wiring—what happened?
Back-feeding line/load can weld or misalign the bi-stable contacts; replacement of the relay is required [Elektroda, dwmw2, post #21197592]
3-Step How-To: flash via UART quickly
- Solder or clip to 3.3 V, GND, RX1, TX1, CEN. 2. In BK7231Flasher select BK7231N, 921 600 baud, click “Read+Flash”. 3. Pulse CEN to GND; wait ≤180 s for “Success”. [Elektroda, silvestro_gatto, post #21173683]
Can I log events before random shutdowns?
Create autoexec.bat: startDriver Syslog 192.168.x.x 514 and addChangeHandler Relay 0 addLog; the device then streams last-hours logs to a syslog server [Elektroda, firsoff091, post #21110271]
Where can I buy replacement sealing ferrules?
Uninsulated 1.5 mm² ferrules, 18 mm length, Ø2 mm slide straight into the holes; pack of 200 on Amazon item B08QS2KR49 [Elektroda, onkel11, post #21080758]
Statistic: How long does flashing typically take?
Average full backup plus OpenBeken write is 2 min 47 s (n=12 units) at 921 600 baud [Elektroda, silvestro_gatto, post #21173683]
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Comments
Thank you, just for the clarity, I will add here some screenshot from device seller's page: https://obrazki.elektroda.pl/5593422200_1690005185_thumb.jpg Here is template within post: { "vendor":... [Read more]
użyłem do tego modelu "24": "BridgeFWD;1", "26": "BridgeREV;1" nie tak jak w powyższym template ustawiłem ze po zaniku zasilania przekaźnik ma się wyłączyć SetStartValue 1 0 przekaźnik włączony,... [Read more]
I don't know if the bridge driver author added support for initial state. Maybe we can try to make some kind of work around... Create autoexec.bat with the following script: // turn off... [Read more]
Yes, brigde is setup on channel 1 manualy "save and run as script" working properly, but after disconnect and connect AC, state of switch and LED is off, but bridge doesn't react, and relay remain closed. It's... [Read more]
An interesting module, the price is the same regardless of the current - I wonder if they are identical inside? [Read more]
There is a minimum two hw version, with green paint of solder mask, and the second one with red. I saw pictures with 12V and 5V DC coil [Read more]
new software Build on Aug 20 2023 06:10:59 version 1.17.223 - the same issue i play with commands: SetStartValue 1 0 setchannel 1 1 Info:GEN:CHANNEL_Set channel 1 has changed to 1 (flags... [Read more]
I understand that this device has a relay/contactor inside, a current measurement module and a Bekken circuit in a housing with dimensions that fit the Din rail and looks like an overcurrent switch, but... [Read more]
this is not a circuit breaker that's right, the only thing that can be done is to set an alarm for exceeding the current threshold in Tuya with a resolution of 1A, but I have not checked whether... [Read more]
Setting the limits in A/W in the software works because I just checked it, I have this device. [Read more]
I have erau and tongou models , in one the green plate and in the other the red plate. I import them from Tuya to HA but it does not show me in HA the measurement entity, only the switch, the sockets... [Read more]
I launched this device only to check its correct operation after receiving the shipment from the Chinese. I checked how it worked through the tuya app. I guess it was automatically detected in ha through... [Read more]
Just wondering have anyone successfully flashed it through tuya-cloudcutter OTA? I tried mine (I have the non-metering version btw) but I get an exploit not successful message. [Read more]
Which firmware version is shown by Tuya app? [Read more]
It's 1.0.2 [Read more]
I had the mettering version and yes, I uploaded the dump and could flash it https://github.com/tuya-cloudcutter/tuya-cloudcutter/issues/505 [Read more]
The support for your device has been added to the cloudcutter. Thank your for submitting the flash dump. [Read more]
Hi i tryed to flash the openbeken it worked fine, but now i cant write the configuration on it throws an error. and same thing if i try to read it gives an error. what difference is the rx1 tx1 and rx2... [Read more]
TX2 is a debug log output, it is not used for flashing. Can you configure device via OBK page? [Read more]