[Solved] LN822H Touch Wall Dimmer: Locating Boot Mode (A9) Pad and Serial Pinout Similarities

Hi !

This is a wall dimmer with touch controls.
I have several on the outside identical older units equipped with TYWE3S (ESP8266).
This one seem to be based on a LN822H module ?
It looks rather similar to the WL2H-U module but partly mirrored.
Anyway, 3.3V and GND are on the same pads (14 and 13).
And possibly RX/TX ? (16 and 15).
But the boot mode pad (A9) ? ("Top side test point" according to the WL2H-U spec).

Anyone have any idea ?



https://www.aliexpress.com/item/32980493334.html
AI: Do you have any clear photos of the LN822H module (both sides) or a datasheet that you could share?
Sorry, no photo from the bottom side (difficult to desolder).
AI: Have you already tried any methods to identify the A9 pad, like continuity testing or comparing PCB traces to the WL2H-U, and if so, what did you find?
Trial and error on the tiny traces visible on the top part would be my next step to find the boot-mode pad. But if anyone have any knowledge of this module that would be great.

What makes you say it's an LN882H? CBU is traditionally BK7231N but some BK7238 have appeared labelled as CBU recently.

https://developer.tuya.com/en/docs/iot/cbu-module?id=Ka8uv3u1q1xxc

>>21804944
Hi!
The LN882 was just a (bad) guess based on some similarities.
So it seems to be the CBU-IPEX module then, BK7231N-based.
As for the boot mode pad, I guess it will be trial-and-error.
Thanks.

no trial and error required. BK7231N flashing process is well known https://www.elektroda.com/rtvforum/topic3951016.html

You're lucky, CBU in light switch makes some cool modifications possible. for example, you can use P16 (SPI output) to control a single or few WS2812 LEDs inserted as new kind of switch background light.

Did you manage to flash it?

Flashed successfully, but there are some more problems.
Continued in https://www.elektroda.com/rtvforum/topic4160885.html.