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Flashing New Tongou TO-Q-SY1-JWT Device: DIN Rail Switch and Meter, BK7231 template script

VIDPRO 28428 84

TL;DR

  • Tongou TO-Q-SY1-JWT DIN rail switch and meter was flashed with a BK7231 template script.
  • The BK7231N has all pins reachable, so the unit was flashed via serial and a config was attached.
  • All LEDs, the relay, and the meter are fully functional after flashing.
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  • #61 21282254
    luxmcdiver
    Level 3  
    Posts: 5
    Thanks for your quick reply.
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  • #62 21285189
    dwmw2
    Level 6  
    Posts: 19
    Rate: 3
    luxmcdiver wrote:
    Hi, I have a TO-Q-SY2-JWT which has a shunt-resistor instead of the coil. Has anybody flashed such a device?

    Yes, I have flashed a bunch of these, and they're mostly indistinguishable in software from the ones with a coil. Even the calibration parameters are in the same range.
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  • #63 21294869
    leśny_ziutek
    Level 12  
    Posts: 52
    Help: 3
    Rate: 9
    From the manufacturer's information it appears that the SY2 differs from the SY1 not only in the use of a shunt instead of a transformer, but also in the additional function of overcurrent and overvoltage protection (Over and Under Voltage Protection).
  • #64 21294989
    luxmcdiver
    Level 3  
    Posts: 5
    Does anybody know how to configure these additional SY2 protections in openbeken?
  • #65 21297732
    p.kaczmarek2
    Moderator Smart Home  
    Posts: 14416
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    How this device looks like? Which chip is used inside?

    Are the protections you mention handled by WiFi module, or are they implemented outside it? I don't think it's possible to make a reliable, quick protection in the WiFi module code... but if you don't need it to react quickly, then you can just script OBK to turn off relay when current exceeds given value.
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  • #66 21297841
    luxmcdiver
    Level 3  
    Posts: 5
    It looks same as the SY1 and uses the BK7231N & BL0942.
  • #67 21297851
    p.kaczmarek2
    Moderator Smart Home  
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    So Tuya does their protections in the software?
    Pin configuration diagram of the BL0942 chip with a description of each pin function.
    BL0942 just sends data via UART (or SPI) to WiFi module and WiFi module can process it once it's received.
    EDIT: I edited out incorrect information, it seems that BL0942 has actually ability to detect overcurrent/overvoltage via FUNX register and signal it on CF1/CF2/ etc pins.

    If you don't need to react very fast, you can use obk autoexec.bat script:
    Code: text Expand Select all Copy to clipboard
    
addChangeHandler Voltage > 251 POWER OFF

    etc, etc...
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  • #68 21300319
    leśny_ziutek
    Level 12  
    Posts: 52
    Help: 3
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    It seems you can configure the BL0941 V1.06 CF1 output (also CF2, ZX otputs in bigger packages) to signal the over current condition (see OT_ FUNX) register. Is this signal connected anywhere? I can't check this myself for now, but two SY2 are on their way to me so will check when they arrive. The manufacturer clearly distinguishes SY2 from SY1, specifying the protection capability of SY2 as the only difference. But it may actually be poorly and unreliably implemented using the logic executed by the WiFi module as @p.kaczmarek2 said.
  • #69 21300797
    p.kaczmarek2
    Moderator Smart Home  
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    I see, I wasn't aware that CF1 can be configured in that way.
    Logic output configuration register table with options for CF1, CF2, and ZX.
    If CF1 (etc) are connected somewhere, then maybe we indeed just need to configure OT_Funx register and the circuit will do the rest.
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  • #70 21301079
    luxmcdiver
    Level 3  
    Posts: 5
    It would be nice to have the BL0942 Current fast RMS threshold in the Web application /Tools / Power Metering section, as well as a command box to activate the overcurrent protection.
    Is that feasable?
  • #71 21301610
    leśny_ziutek
    Level 12  
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    Only if CF1 is used in the SY2 for this purpose.
  • #72 21305819
    p.kaczmarek2
    Moderator Smart Home  
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    OpenBeken already has mechanism to write to BL0942 registers so it should be possible to enable it if used hardware has CF pin available:
    Code: C / C++
    Log in, to see the code
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  • #73 21390816
    max_mcu
    Level 3  
    Posts: 6
    Hello community, I have the following problem: The relay is a bi stable relay. When the power is lost and then switched back on, the switch + LED is not on if the relay was switched on before the power failure. How can I determine after the power failure whether the relay is still on or off? Can this be fixed in the software?
  • #74 21401656
    Drapol13
    Level 1  
    Posts: 1
    Hi,
    I'm really struggling to load up this firmware. I tried BK7231GUIFlashTool-v5.
    I wanted to read firmware first. I tried disconnecting GND and also connecting CEN to GND for a fraction of a second.
    I keep getting this counter...
    Read parms: start 0x00 (sector 0), len 0x200000 (0 sectors)
    Now is: poniedziałek, 20 stycznia 2025 16:07:49.
    Flasher mode: BK7231T
    Going to open port: COM4.
    Serial port open!
    Getting bus... (now, please do reboot by CEN or by power off/on)
    Getting bus failed, will try again - 0/100!
    Getting bus failed, will try again - 1/100!
    Getting bus failed, will try again - 2/100!
    Getting bus failed, will try again - 3/100!

    I also tried to load up ESPhome but I also can't connect. Tried swapping RX TX nothing helped.
    Connections are good.

    Electronic circuit connected to several PC Bite test probes on a wooden table.
    Close-up of a PCB connected with probes.
  • #75 21402384
    p.kaczmarek2
    Moderator Smart Home  
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    max_mcu wrote:
    Hello community, I have the following problem: The relay is a bi stable relay. When the power is lost and then switched back on, the switch + LED is not on if the relay was switched on before the power failure. How can I determine after the power failure whether the relay is still on or off? Can this be fixed in the software?

    Well, maybe it would be enough to just set startup value of relay channel to -1, so OpenBeken remember it between reboots?

    @Drapol13 There can be multiple issues at play:
    - too long wires, poor contacts
    - BL0942 or something may be blocking UART, I'm not sure, but I remember that it also worked for me several times with BL0942
    - you need to have a good 3.3V power supply, directly from USB to UART won't work
    - maybe you need to try other baud or other USB to UART converter
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  • #76 21487925
    leśny_ziutek
    Level 12  
    Posts: 52
    Help: 3
    Rate: 9
    I've managed to open and flash the SY2 version:

    Opened casing with visible electronics and connected wires.
    Close-up of a yellow PCB with visible electronic components, including an MD7620A integrated circuit.
    Close-up of a circuit board with visible electronic components and the marking 6R3.

    Also checked the connections on the board with a multimeter. The relay is connected to the MD7620A driver. Both inputs of the driver are directly connected to the CBU (P24, P26). The BL0942 CF1 pin seems to be left floating. In case of any autonomous control of the relay by BL0942 it should be some circuity on the board connected to the CF1 and MD7620A but the direct connection between MD7620A and CBU indicates that nothing of this sort is implemented.
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  • #77 21556224
    casiopeia80
    Level 3  
    Posts: 15
    Hello everyone!
    Many thanks for the firmware — great work!
    However, I've encountered one issue. After flashing, the module doesn't seem to take the power factor into account in its calculations.
    I've been using this smart switch with the stock firmware for about a year. It powers three air conditioners, and I’m absolutely sure the original firmware correctly factored in cos(φ) (power factor) when calculating the reactive component of the AC current.
    For example, in standby mode, the three air conditioners consumed around 10 watts on the original firmware. With the new firmware, I’m seeing standby values of around 56 watts, which I believe is because the power factor isn’t being considered.
    Could this be improved in future updates?
    Energy monitoring panel for balcony air conditioners, highlighting apparent power 50.17 VA and reactive power 50.17 var.
  • #78 21556241
    p.kaczmarek2
    Moderator Smart Home  
    Posts: 14416
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    Welcome to forum! Just to confirm, you're using this device from this topic, with BL0942 connected via SPI?

    Added after 41 [seconds]:

    Also, did you calibrate this device after flashing with VoltageSet, PowerSet and CurrentSet commands?
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  • #79 21556434
    casiopeia80
    Level 3  
    Posts: 15
    >>21556241
    Yes, I am using the TO-Q-SY2-JWT device model.
    I realized that I needed to enable Flag 25 – [POWER] Allow negative current/power for power measurement (all chips, BL0937, BL0942, etc) in the device settings.

    I’ve read about the calibration process in the web interface, but I couldn’t understand how the power factor can be properly calibrated using a purely resistive load like an incandescent bulb.

    So, I decided to try a different approach.
    In my apartment, I have three LG air conditioners connected through this TO-Q-SY2-JWT module. Back when the device was running the original firmware, I monitored its readings and noticed that, in standby mode, the total power consumption was shown as around 10 watts. The line voltage was about 235 volts, and the current draw was 400 mA (with cos(φ) close to maximum in this low-power mode).

    At the time, I also measured the current using a True RMS multimeter — the readings matched the module’s output.
    So I tried calibrating your firmware using the same conditions: I set the air conditioners to standby and entered those known values into the calibration fields in the web interface.

    Now, the readings seem quite accurate — both when the air conditioners are in standby mode and when they are running. The measured values closely match the power consumption reported by the air conditioners themselves on their built-in displays.

    I have one more question: is there any way to extract the calibration data from the original firmware?

    Screen showing electric power consumption measurements and StandBy status.

    Screen displaying electrical energy measurement data with a red Power on message.
  • #80 21556477
    przemsi_ele
    Level 12  
    Posts: 62
    Help: 1
    Rate: 14
    >>21556434
    yes u can extract original calibration setup, there is post about that , but i always calibrate using classic bulb, it is olmost true resistance , in my cases it is always satisfy

    https://esphome.io/components/sensor/bl0942.html

    maybe this will be halpfull for you
  • #81 21556582
    sq3evp
    Level 39  
    Posts: 6352
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    Rate: 835
    przemsi_ele wrote:
    >>21556434 .
    yes, you can extract the original calibration configuration, there is a post on this topic, but I always calibrate with a classic bulb, it is almost the true resistance, in my cases it is always satisfactory

    Not really - a cold fibre has a different resistance to a heated one. I guess the heater is a more linear element or high power resistor.
  • #82 21556630
    casiopeia80
    Level 3  
    Posts: 15
    >>21556477 Thanks! I found an old 60W incandescent bulb (with a filament) in storage. I used it for calibration. The readings turned out to be about the same as when I calibrated using the air conditioners. :) At first, I didn’t realize that during this type of calibration, a power factor of 1 is assumed by simply using the measured power value as the product of voltage and current (U × I).
  • #83 21559062
    anatolyshokalo
    Level 1  
    Posts: 1
    >>20663233 Can you please show what pins did you used for flashing? Thanks
  • #84 21617435
    gaengeyachten6h
    Level 1  
    Posts: 1
    Has anyone managed to adjust the AC power direction on this device? The power reading is always negative, and Flag 48 in OpenBeken seems to have no effect.
  • #85 21776554
    pvv4up
    Level 1  
    Posts: 1
    Colleagues, what is the right way to redo it?
    1. We Solder the CBU, Flash the Flaser, And Configure the CBU channels. We sing back and everything is OK?
    2. Right on the board, without soldering the CBU, Flash the Flaserom, Configure the channels and everything is OK? OR WHAT?
    Please make someone a step-by-step instruction. I've flashed a lot of switches, but simple ones. But I still haven't figured out how to deal with it.
    I was typing through a translator.
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Topic summary

✨ The Tongou TO-Q-SY1-JWT is a DIN rail mount smart switch and energy meter based on the BK7231N chip and BL0942 power metering IC. Users successfully flashed the device with OpenBeken firmware via UART after opening the case by drilling rivets, as OTA flashing via Tuya CloudCutter is unreliable or unsupported for some firmware versions (notably metering firmware v1.0.18). The device supports relay control, LEDs, button input, and power metering, with GPIO pins mapped for these functions (e.g., pins 9 and 15 for LEDs, 17 for button, 24 and 26 for relay control). Relay behavior on power loss can be configured using SetStartValue commands or autoexec.bat scripts to restore or force relay state after reboot. Calibration of the BL0942 meter is essential for accurate power measurement, including voltage, current, and power factor; calibration can be done using resistive loads like incandescent bulbs or by extracting original calibration data from Tuya firmware. The device is not a circuit breaker and should not be used as a safety disconnect. Some hardware versions differ in PCB color and coil voltage (5V or 12V). The newer SY2 model uses a shunt resistor instead of a coil and adds overcurrent and overvoltage protection features, which may be software-configurable via BL0942 registers but lack dedicated hardware signaling. ESPHome support is emerging with device pages and calibration improvements. Users report issues such as relay coil heating when driven by pulse commands instead of continuous signals, and occasional unexplained relay power-offs requiring log retention for diagnostics. Flashing challenges include ensuring proper UART connections, stable 3.3V power supply, and correct baud rates (e.g., 921600 or 1500000). Debug logs can be captured via the TX2 pin. Sealing the device after opening can be done using M2.5x10 screws or insulated ferrules. Overall, the community provides detailed pin mappings, flashing instructions, calibration tips, and firmware configuration examples to enable reliable operation and integration with Home Assistant and ESPHome.
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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, post #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]

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, post #21487925]

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

  1. 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]
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