Originally I had no intention of writing this up, but after nearly two days of head-scratching I realized there’s almost no documentation online for this module. Here’s how to rescue the GM328’s custom ST7735 display and drive it from an ESP8266 (or Arduino).

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1. Identify the Module

The flex-cable is stamped XY18CG958-18B, confirming an ST7735 controller. On the back you’ll find the 8-pin FPC header and an AMS1117 regulator:

Back of GM328 display module (pin labels)

Flipped around, the front side looks like this:

Front of GM328 display module (pin labels)

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2. Pinout & Wiring

This table shows how each LCD header pin maps to a NodeMCUv2 (ESP8266) GPIO:

LCD Pin	ESP8266 Pin
GND	GND
5V	3V3
CS	GPIO5
CLK (SCL)	GPIO14
DIN (MOSI)	GPIO13
DC (A0)	GPIO4
RST	GPIO16
LED (BL)	3V3 (or GPIO + 220 Ω for PWM)

 

Breadboard wiring on a D1 Mini (NodeMCUv2)

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3. ESPHome Example

Add this into your ESPHome YAML to fire up the display and show a test message:

spi:
  clk_pin: GPIO14    # SCL
  mosi_pin: GPIO13   # MOSI
  id: spi_bus

font:
  - file: "gfonts://Roboto:400"
    id: font_big
    size: 28

display:
  - platform: st7735
    model: "INITR_GREENTAB"
    spi_id: spi_bus
    cs_pin: GPIO5
    dc_pin: GPIO4
    reset_pin: GPIO16
    device_width: 128
    device_height: 160
    col_start: -1
    row_start: 1
    invert_colors: false
    eight_bit_color: true
    update_interval: 5s
    rotation: 270°
    lambda: |-
      it.fill(Color::BLACK);
      it.print(it.get_width()/2,
               it.get_height()/2,
               id(font_big),
               TextAlign::CENTER,
               "IanThor.com");

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4. Result

After boot you’ll see your message centered on the screen. From here you can expand to show sensor data, icons, or small graphics:

Final display “IanThor.com” snapshot

 

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This guide exists because at the time of writing (2025), no one else appears to have published this displays unique pinout online. I hope it saves you time—happy hacking!

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