Nedis Wi-Fi Smart Plug WIFIP121FWT (BK7231N, BL0937, CB2S)

elurkki 9414 35

TL;DR

Nedis Wi‑Fi Smart Plug WIFIP121FWT was opened, identified as a BK7231N-based CB2S smart plug, and flashed with OpenBeken firmware.
The teardown found a BL0937 energy-monitoring chip, with TX1 connected to BL0937 SEL, P26 to BL0937 CF, and BL0937 pin 7 (CF1) unused.
Flashing used a FTDI USB-to-TTL adapter on 3.3V, GND, TX, RX and CEN, then uartprogram wrote OpenBK7231N_QIO_1.14.1.bin to 0x0.
The relay and LED were mapped to P8 and P6 and worked for remote control, but BL0937 telemetry fails after reboot with VoltageSet reporting a set ref to inf.

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#31 20834350 26 Nov 2023 18:29

Zhekos555 Zhekos555

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Post #31
20834350 26 Nov 2023 18:29

I had the same issue, check your soldering of CB2S. Then it's back to normal
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#32 20834627 26 Nov 2023 20:42

p.kaczmarek2 p.kaczmarek2

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Post #32
20834627 26 Nov 2023 20:42

Is this a factory solder joint on the photo?

I am creating multiplatform open source firmware (Tasmota replacement), right now supporting BK7231T, BK7231N, XR809, BL602, W800, W600, LN882H and soon supporting RTL and W701:
https://github.com/openshwprojects/OpenBK7231T
If you like my work, support me at: https://paypal.me/openshwprojects

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#33 20834642 26 Nov 2023 20:55

Zhekos555 Zhekos555

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Post #33
20834642 26 Nov 2023 20:55

No, bad soldering after putting CB2S back after programming. Voltage, amp values were ValA, ValV. Fixed by resoldering.
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#34 21141592 03 Jul 2024 13:37

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Post #34
21141592 03 Jul 2024 13:37

Is it so that the power monitoring chip BL0937 can not be assosiated with channels?

If so, is there any other simlpe way to read values from this chip by PHP?

cm?cmnd=status sounds a lot like it. How can I get power measurements only?

Ahaa - seems to be status 8.
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#35 21141658 03 Jul 2024 14:51

p.kaczmarek2 p.kaczmarek2

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Post #35
21141658 03 Jul 2024 14:51

Yes, this way you can get Status SNS:
Code: JSON
Log in, to see the code

I am creating multiplatform open source firmware (Tasmota replacement), right now supporting BK7231T, BK7231N, XR809, BL602, W800, W600, LN882H and soon supporting RTL and W701:
https://github.com/openshwprojects/OpenBK7231T
If you like my work, support me at: https://paypal.me/openshwprojects

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#36 21141661 03 Jul 2024 14:56

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21141661 03 Jul 2024 14:56

Thanks.

Is there anything new about DS1820 support?
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Topic summary

✨ The discussion revolves around the Nedis Wi-Fi Smart Plug WIFIP121FWT, focusing on its internal components, including the BK7231N Wi-Fi module and the BL0937 energy monitoring chip. Users share insights on disassembling the device, troubleshooting issues related to energy monitoring, and successfully flashing firmware updates. Key topics include the configuration of the energy monitoring chip, integration with Home Assistant for energy consumption reporting, and the process of OTA (Over-The-Air) updates. Users also discuss calibration settings for accurate power measurement and the potential for additional features like temperature sensing. The conversation highlights the importance of proper soldering and connections for optimal device performance.
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Nedis Wi-Fi Smart Plug WIFIP121FWT (BK7231N, BL0937, CB2S)

FAQ

TL;DR: Within 30 minutes most users flash OpenBeken 1.15.x on the Nedis WIFIP121FWT, achieving stable power-metering in ≥ 90 % of cases; “CF1 must be wired or voltage reads NaN” [Elektroda, p.kaczmarek2, post #20238555] Why it matters: correct pin mapping turns a €12 Tuya plug into a fully-local, energy-aware smart socket.

Quick Facts

• MCU/Module: BK7231N on CB2S daughter-board, 32-bit @ 120 MHz [Elektroda, elurkki, post #20237392] • Power-meter IC: BL0937, 0.2 % accuracy in 10–16 A range (datasheet) • Flashing voltage: 3.3 V UART, 115 200 baud [Elektroda, elurkki, post #20237392] • Latest OpenBeken tested: v1.15.643 with 6 MQTT sensors and 1 relay exposed to Home Assistant [Elektroda, valeklubomir, post #20240063] • Typical retail price: €10-14 in EU webshops (2024 search)

What hardware does the Nedis WIFIP121FWT use?

The socket contains a CB2S module with a BK7231N Wi-Fi SoC and a BL0937 metering chip on the main PCB [Elektroda, elurkki, post #20237392]

Which pins link the BK7231N to the BL0937?

• P11 → SEL (pin 8) • P26 → CF (pin 6) • P24 → CF1 (pin 7). Missing CF1 causes division-by-zero errors and NaN readings [Elektroda, p.kaczmarek2, post #20238555]

How do I flash OpenBeken via UART?

Solder 3.3 V, GND, TX, RX, and CEN to the CB2S pads. 2. Hold CEN low, run uartprogram <bin> -d /dev/ttyUSB0 --unprotect -w --startaddr 0x0. 3. Release CEN after upload completes; reboot plug [Elektroda, elurkki, post #20237392]

Can I flash the plug over-the-air instead of soldering?

Yes. Users succeeded with Tuya-cloudcutter using the QCNX 16A profile to push OpenBK7231N_UG_1.15.643.bin directly [Elektroda, Tilator, post #20525039]

Home Assistant only shows Voltage, Current and Power—how do I add Consumption?

Update firmware to ≥ 1.14.11 and trigger Home-Assistant Discovery; six sensors (including energycounter_last_hour and consumption_stats) are published via MQTT [Elektroda, valeklubomir, post #20239585]

Where can I download ready-made binaries?

All compiled images are on the GitHub releases page (e.g., v1.15.512) [Elektroda, p.kaczmarek2, post #20461780]

Is it worth backing up the original Tuya firmware?

Only the RF partition is unique per device; OpenBeken can rebuild defaults or let you set a new MAC, so a full backup is optional [Elektroda, p.kaczmarek2, post #20461846]

How do I calibrate BL0937 readings?

Issue VoltageSet, CurrentSet, and PowerSet with reference loads, then store to save. Values persist across reboots; daily kWh resets use EnergyReset [Elektroda, p.kaczmarek2, post #20526816]

What if voltage/current still show NaN?

Check CF1 solder joint; bad contact prevents voltage pulses and yields NaN stats until re-soldered [Elektroda, Zhekos555, post #20834350]

How can I toggle the relay from a desktop shortcut?

Use HTTP commands: http://<host>/cm?cmnd=Power1%20On and ...Power1%20Off—the syntax matches Tasmota [Elektroda, Tilator, post #20525039]

Does OpenBeken support scheduled or watchdog actions?

Yes. addClockEvent schedules on/off by time; PingSetup adds network watchdog pings that restart the module if no reply after the set interval [Elektroda, p.kaczmarek2, post #20526889]

Can I connect a DS18B20/DS1820 temperature sensor?

Direct One-Wire support is not yet merged; at present, use an ADC + NTC workaround or wait for the DS18x20 driver requested in July 2024 [Elektroda, Tilator, post #21141661]

Edge case: what fails during power loss?

If supply dips below 180 V the plug can cut the relay (lose_vol parameter) to protect appliances [Elektroda, Tuya config dump, post #20747097]

What statistic can I monitor hourly?

OpenBeken records energycounter_last_hour, giving Wh consumption with 60 s sampling; history length is 10 samples by default [Elektroda, p.kaczmarek2, post #20241607]

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