Zemismart ZMS-206 LCD: display type, MCU and UART protocol reverse engineering

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Hi everyone,

I recently came across the Zemismart ZMS-206, a Zigbee wall switch with a small LCD display. Even though I would rather die than touch something Tuya, this one at least is Zigbee/local. Right now, it only shows a short label (max 10 characters) per gang, sent via Tuya's proprietary Zigbee datapoints.

My goal is to display custom content on that screen: temperature readings, the currently playing song, icons, that kind of thing. Basically, turn it into a small smart home info panel embedded in the wall switch.

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Hardware overview (from this teardown):
https://smarthomescene.com/reviews/zemismart-zigbee-screen-switch-zms-206-review/

The ZT3L handles Zigbee communication and all switch logic. The display sits separately and is almost certainly driven by a dedicated MCU? Between the ZT3L and the LCD?

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1. What type of display is this physically? Is it a segmented LCD (like a calculator) or a pixel LCD?

2. What is the display MCU?

3. Even if the display has a pixel matrix, the MCU firmware might be hard-coded to only accept Tuya's proprietary text protocol?

4. The ZT3L itself is not flashable, so going that route is not an option, but switching this to an ESP would also be a nightmare, right?

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Has anyone opened one of these and looked closely at the display assembly?



Thanks in advance!

It's probably TuyaMCU, but even if you plug your own WiFi module, then MCU won't allow you to display custom content on LCD.

You probably need to disassemble it futher and determine what actually controls the display. Can you try this out and give us futher photos?

Are there any futher chips on the board, how are they marked?

>>21872377

Wish I knew, or had one. I really liked the design and having both screen and buttons. Trying to find a good candidate for this. It seems most are Tuya MCU's.








The Sonoff NSPanel is hackable but I'm not fond of the design being screen oriented, and it is expensive for my customers' target :/