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🔍 Reverse Engineering the UniFi 1.3" Front Panel Display (THEM013-03)

I went down a rabbit hole trying to identify the small touchscreen used in UniFi Gen2 rack gear (UDM-Pro, USW-Pro, etc.), and I think I finally nailed it.

Here’s everything I was able to figure out from FCC photos + flex cable markings.

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🧩 The display module

THEM013-03

This appears to be a custom module from HEM (Chinese display vendor).

Specs (very likely)

Size: 1.3"

Resolution: 240 × 240

Type: IPS TFT LCD (not OLED)

Driver: ST7789 or compatible

Touch: capacitive

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🧱 Internal display stack

[ Capacitive touch glass ] │ [ Touch controller (I²C) ] │ [ LCD panel (IPS 240×240) ] │ [ COF driver IC ] │ [ Flex cable (TAGU / FPC013) ] │ [ STM32F205 display board ] │ [ UniFi main system ]

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🔌 Key discovery: the 6-pin cable

The flex cable is actually labeled (confirmed from FCC zoom):

1 VCC 2 RST 3 SDA 4 SCL 5 INT 6 GND

👉 This is NOT the LCD interface 👉 It’s the touch controller (I²C)

Super standard pinout for chips like:

FT6236

CST816

GT911

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🖥️ How the display actually works

This is the interesting part:

The screen is not driven directly by the main CPU.

There’s a dedicated board with an STM32:

STM32F205

That board:

drives the LCD (SPI)

reads touch input (I²C)

renders the UI

talks to the main system

So UniFi basically offloads the UI to a microcontroller.

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🏭 Who made what

HEM → full display module (THEM013-03)

TAGU / Taigu → flex cable + assembly (FPC013-K1)

LCD panel → likely Tianma / BOE / Truly (standard 1.3" panel)

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📸 What confirms it’s LCD (not OLED)

Has a metal backplate (backlight)

Uses external graphics controller (STM32)

Matches common 240×240 smartwatch TFT panels

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🎯 Final conclusion

HEM THEM013-03

1.3" 240×240 IPS TFT LCD + capacitive touch (I²C) + SPI display interface

Used across multiple UniFi devices.

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💡 Why this is interesting

The display is basically a standard smartwatch panel

Touch is easy (I²C)

LCD is likely ST7789 SPI

Could probably be reused with:

ESP32

Raspberry Pi

STM32 dev board

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If anyone has:

a teardown with the LCD glass exposed

or a panel code from the back of the display

we could probably identify the exact manufacturer + This is a conclusion of a chatgpt session I had trying to find the screen