WHDZ05 Wi-Fi smart plug: ESPHome over serial

My second WHDZ05 plug turned out to be Wi-Fi, not Zigbee (how I found out). I don’t want it talking to Tuya’s cloud, so it gets ESPHome: Home Assistant talks to it directly, on my own network.

Status, October 2026

Work in progress. I’ve opened the plug and found where each wire goes (steps 1 to 4, with photos). I haven’t flashed it yet: steps 5 to 10 are the plan, checked against the LibreTiny and ESPHome docs but not tried on this plug. The pins in step 6 and the config in step 7 get filled in once I’ve read the factory firmware. This guide gets updated as I go.

No way around the wires

tuya-cloudcutter can flash some Tuya devices over Wi-Fi, without opening them. It only works on Beken BK72xx chips. This plug has a Lightning Semi LN882H, so it’s flashed over its serial port.

The good news: the LN882H’s boot loader is in ROM. A failed flash can’t brick it. You flash again.

What you need

• A USB-serial adapter with 3.3 V logic: CP2102, CH340 or FTDI. If it has a 3.3 V / 5 V jumper, set it to 3.3 V. 5 V on the data pins can kill the chip.
• Thin wire (30 AWG wire-wrap wire is ideal), a soldering iron with a fine tip, flux, and Kapton or masking tape.
• A breadboard and a few jumper wires.
• A multimeter with a continuity beep.
• Maybe a separate 3.3 V supply. A USB-serial adapter’s own 3.3 V pin is often too weak (the LibreTiny docs say most flashing problems are voltage drops or loose wires). A spare ESP32 or ESP8266 dev board’s 3V3 pin works.
• On the laptop: ltchiptool and ESPHome, both installed with pipx.

Danger

The plug’s power supply isn’t isolated: when it’s in the wall, its low-voltage side sits at mains voltage. Never plug it in with the adapter connected. That would put mains on your laptop’s USB port. After unplugging it, give the big capacitors a few minutes to drain, and check them with the multimeter before you touch anything.

Step 1: Open the plug

Open the case. Keep the plug unplugged the whole time.

Step 2: Find the five points

The radio sits on a small blue module, soldered upright into the main board. Its pins are labelled on the back.

The 3.3 V wire goes on U2’s big tab. The other four go on the Wi-Fi module’s back.

Wire	Adapter pin	Where on the plug
3.3 V	3V3	The big tab of U2, the 1117 33 regulator on the main board: that’s its 3.3 V output, and it’s the same as the module’s VCC
Ground	GND	The round GND pad on the module’s back
Plug’s RX	TX	The module’s A3 pin (RX0)
Plug’s TX	RX	The module’s A2 pin (TX0)
Boot	GND on the breadboard	The round A9 pad on the module’s back

A9 decides how the chip starts. Tied to ground at power-up, the chip waits for a flasher instead of running its firmware. It has to stay grounded the whole time you read or write the flash.

The module’s back. GND and A9 are big round pads. A3 and A2 are two of the pins along the bottom edge. They go through the main board and stick out underneath: that’s the easiest place to solder them.

The module’s front, from the other side of the plug. The pins under the board are easy to reach, but on this face they’re other signals: the labels read A10, A6 and A7. The back face has its own row of pins, A3 and A2 among them, sticking out the same way.

Check both power points with the multimeter’s beep before soldering: the U2 tab against the module’s VCC pin, and the GND pad against the module’s GND pin. Both pins are on the bottom edge of the module’s back, labelled.

Step 3: Solder the wires

The trick is never to hold the wire while soldering, so a steady hand isn’t needed.

1. Put flux on the pad and melt a small blob of solder onto it.
2. Strip and tin the end of the wire, then cut the bare end to 1–2 mm.
3. Tape the wire down so its end lies on the pad by itself.
4. Touch the iron to it for a second. The blob melts around the wire.
5. Pull the wire gently. If it holds, tape it to the case so a tug can’t rip the pad off.

Solder paste works too: a dab on the pad, the wire on top, taped, then the iron. Not hot air: it would loosen the module’s own parts.

Step 4: Connect the adapter

Through the breadboard, so nothing needs holding:

The same colours as in the photos above. TX goes to RX, and RX to TX.

• adapter TX → A3, adapter RX → A2
• adapter GND → the GND row, and the plug’s ground wire into that row too
• A9 → the GND row
• adapter 3V3 → the plug’s 3.3 V wire. With a separate supply: its 3.3 V to the plug, and its ground into the GND row

Plug the adapter into the laptop last. It shows up as /dev/ttyUSB0:

ls /dev/ttyUSB*

Step 5: Save the factory firmware

Before anything gets written, save what’s on it. That’s the only copy of Tuya’s firmware and its settings, and it’s where the pins come from in the next step.

ltchiptool flash read -d /dev/ttyUSB0 ln882h whdz05-factory.bin
ltchiptool flash read -d /dev/ttyUSB0 ln882h whdz05-factory-2.bin
cmp whdz05-factory.bin whdz05-factory-2.bin && echo same

It reads all 2 MiB. Reading twice and comparing catches a bad read.

If it can’t connect:

• swap TX and RX
• check A9 is in the GND row, then unplug the adapter and plug it in again: A9 only counts at power-up
• if it stops halfway, the 3.3 V is sagging: use the separate supply

Step 6: Find the pins

The plug needs six GPIOs: the relay, the button, the LED, and three for the BL0937 power meter chip (SEL, CF, CF1). Tuya keeps them in a config block in the flash, so the dump has them.

The relay. One GPIO switches it.

The BL0937 power meter chip. Three of its pins go to the LN882H: SEL, CF and CF1.

Not read yet. This table gets filled in from the dump:

Function	GPIO
Relay	not known yet
Button	not known yet
LED	not known yet
BL0937 SEL	not known yet
BL0937 CF	not known yet
BL0937 CF1	not known yet

Step 7: The ESPHome config

The full config comes once the pins are known. The parts that matter:

ln882x:
  board: generic-ln882h

sensor:
  - platform: hlw8012
    model: BL0937
    sel_pin: # from the dump
    cf_pin: # from the dump
    cf1_pin: # from the dump
    current_resistor: 0.001 ohm  # the shunt on the board is marked R001

Power metering on the LN882H didn’t work in ESPHome until January 2026 (issue 12647): the GPIO interrupts were broken in the LibreTiny version it used. Use a newer ESPHome.

Step 8: Flash ESPHome

esphome compile whdz05-wifi-plug.yaml
ltchiptool flash write -d /dev/ttyUSB0 <path to firmware.uf2>

esphome compile prints where it put firmware.uf2. Writing it also sets the chip’s OTA address, so later updates can go over Wi-Fi.

Step 9: First boot

1. Take A9 out of the GND row.

2. Unplug the adapter and plug it in again. ESPHome starts.

3. Watch it join the Wi-Fi:

   esphome logs whdz05-wifi-plug.yaml --device /dev/ttyUSB0

If it resets when Wi-Fi starts, that’s the 3.3 V again: Wi-Fi draws a lot more than the flasher did.

Step 10: Close it up and add it to Home Assistant

1. Unplug the adapter, then unsolder the wires.
2. Close the case.
3. Plug it into the wall. It joins the Wi-Fi.
4. In Home Assistant: Settings → Devices & services → Add integration → ESPHome, with the plug’s IP address.

Once it’s running, check the power reading against a known load.

Sources

• LibreTiny: Lightning LN882x: firmware.uf2, ltchiptool, and voltage drops as the usual flashing problem
• LibreTiny: Generic LN882HKI: A9 to ground for download mode, the UART0 pins
• ESPHome: LibreTiny platform: cloudcutter is for BK72xx only
• Elektroda: CozyLife B22 bulb with an LN882H: A9 stays grounded while you back up and flash
• ESPHome issue 12647: BL0937 on LN882H, fixed in January 2026

Change history

• 31 Oct 2026: First published.

This guide as plain Markdown, for LLMs and scripts: whdz05-wifi-plug-esphome.md. All posts: API and Markdown.