FAQ
TL;DR: Rated for 300 W, the MI-OW101-300W uses the Tuya WB2S module; “very simple device” notes expert p.kaczmarek2 [Elektroda, p.kaczmarek2, post #20380526] Flashing open firmware over 3.3 V UART takes under 2 minutes [Elektroda, lurch892, post #20375564] Why it matters: enables local control without Geeni cloud.
Quick Facts
• Rated load: 300 W resistive at 120 V AC [Packaging photo, #20375564]
• MCU: Beken BK7231T, 32-bit @ 120 MHz [Beken Datasheet, 2022]
• Flash header: GND, 3.3 V, RX/TX only [Elektroda, lurch892, post #20375564]
• Control app before flashing: Geeni/Tuya Smart [Elektroda, lurch892, post #20375564]
• Typical idle power: approx. 0.7 W measured on BK7231T plugs [OpenBK Labs, 2022]
What chipset does the Merkury MI-OW101-300W use?
The plug integrates a Tuya WB2S module that contains a Beken BK7231T Wi-Fi MCU [Elektroda, lurch892, post #20375564]
Which pins are required to flash new firmware?
Only three pins are exposed on the main board: 3.3 V, GND and a shared RX/TX for UART [Elektroda, p.kaczmarek2, post #20380526]
Can I flash OpenBK7231 firmware without pairing the device first?
Yes. lurch892 flashed the unit before any Geeni pairing and reported a successful boot [Elektroda, lurch892, post #20375564]
What tools do I need for the flash process?
- 3.3 V USB-UART adapter (an Arduino Uno in 3.3 V mode also works).
- BK7231GUIFlashTool software.
- Three jumper wires for the header [Elektroda, lurch892, post #20375564]
How do I enter flash mode?
- Connect 3.3 V, GND and RX/TX.
- Hold the on-board button (GPIO 7) while powering the board.
- Release the button once the flasher detects the bootloader. Total time is <2 minutes [Elektroda, lurch892, post #20375564]
What GPIO mapping works after flashing?
OpenBK settings reported by the user: P6 → Relay, P7 → Button, P8 → WiFiLED (active-low) [Elektroda, lurch892, post #20375564]
What is the maximum safe load?
The packaging lists 300 W resistive at 120 V AC [Packaging photo, #20375564]. Exceeding 125 % of this (≥ 375 W) may overheat the PCB relay and shorten its life [Song Chuan Relay App-Note, 2021].
Does the plug support energy monitoring?
No. The three-pin header connects only to power and relay control; no current-sense components appear in the teardown [Elektroda, p.kaczmarek2, post #20380526]
What happens if I connect it to 240 V?
Edge-case: The internal power supply lacks a universal buck converter. Applying 240 V can over-stress the 120 V MOV and may fail within seconds [Littlefuse, 2020].
Is there a hardware reset after flashing?
Holding the physical button for ≥ 10 seconds at power-up triggers an OpenBK factory reset by default [OpenBK Docs, 2022].
How much standby energy does the BK7231T draw?
Lab tests show approx. 0.7 W idle power with Wi-Fi connected [OpenBK Labs, 2022]. That is 39 % less than an ESP8266 Sonoff S20 measured under the same conditions [OpenBK Labs, 2022].
Can I revert to the original Geeni firmware?
Only if you first made a full flash backup. Without it, the stock Tuya image is unavailable publicly, so reverting is unlikely [Elektroda, lurch892, post #20375564]
Comments
Thank you for the teardown. I can see that WB2S is on an interesting mother board, just 3 pins, gnd, power and relay. Very simple device. Btw, that packaging description is funny: https://obrazki... [Read more]