[LN882HKI] Blow 72-084 WiFi Tuya controller - how to flash to OBK/ESPHome?

Hi,

I'm new here, so please don't shout too much I've been playing around a bit with ESP and ESPHome for Home Assistant integration, but I currently wanted to improve the lighting in the garden a bit, and to that end I acquired a "Tuya Intelligent 16A Blow WiFi Relay Controller". It turned out that not only is it on an LN882HKI, but I can't find any hints about the pin-outs.



After the documentation of the chip and a very similar 16A aubess circuit, I have come to the conclusion that P2 and P3 are TX and RX, while I don't know where to find GND and 3.3V.
I am a rather poor electronics technician, but the soldering iron is no stranger to me and I have some general knowledge.

I'm assuming that in this circuit 220 V is not fully separated, so you would need to connect 3.3 V directly (where?). Alternatively, I don't know if this makes sense, but can I connect 5 V to the BP2525 pin (as that's what I think I found on the board)?
I have a UART to USB converter on the CH340, but from what I understand it won't work as a power supply? Can I connect a separate power supply via a workshop power supply and a step-down converter? This can be completely independent, or do I need to connect e.g. the GND of the converter and the power supply?
AI: Do you perhaps have a schematic of the board or can you upload clear pictures of the PCB (especially around the BP2525 and potential power pins)? This will make it very easy to identify the GND and 3.3V.
I have added a photo
AI: Do you have the ability to measure the voltages on the board (e.g. with a meter) to see where the 3.3V and GND actually appear when the device is running? Have you tried connecting anything yet, or are you just analysing "dry" for now?
I have the possibility (meter), but for now I have only analysed dry

Usually mains are not isolated from low-voltage circuit, so be cautious.
The 3.3 voltage is better from a stable supply, usually the USB converters won't supply enough current.

Often devices will also run with much lower voltage, e.g. if "powering" with an old laptop supply with 19V or (my favorite) an poe supply with 48V.
Still enough to destroy something with this voltage on your equipment, but not life threatening

Problem is, that usually GND of the low power circuit is on one of the mains connectors.

Try finding the 3.3V regulator to provide power or follow the power supply pins from MCU to find a good point to provide VCC.
Pinout e.g. here: https://www.elektroda.com/rtvforum/topic4027545.html

If BP2525 is in 5V mode (Sel is GND) supplying 5V there is also a good choice.