GY-33 Arduino Library

An easy-to-use Arduino library for the GY-33 (TCS34725) Colour Sensor module. This library is a C++ port of the MicroPython GY-33 library by QuirkyCort.
This is for connecting to the GY33's microcontroller (typically STM32), not for direct connection to the TCS34725 color sensor.
This library supports both I2C and UART (Serial) communication modes.

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Credits & Technical Documentation

This library is a C++ port of the original logic developed by QuirkyCort.

Since the GY-33 documentation is often difficult to find in English, please refer to the original repository here: micropython-gy33

Also:
UART Mode overview
UART Mode Protocol Details

I2C Mode overview
I2C Mode Protocol Details

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Hardware Setup

The GY-33 can be powered by 3.3V or 5V via the VCC pin. However, the data pins are 3.3V logic level.

• 3.3V boards (eg. ESP32 / ESP8266) can Connect directly.
• for 5V boards (eg. Arduino Uno / Mega (5V)) please Use a logic level shifter on the I2C (SDA/SCL) or UART (TX/RX) lines to protect the sensor.

Mode Selection (S0 Pin)

The S0 jumper/pin determines the primary communication mode:
Both modes use pins 2 and 3 (CT and DR)

• I2C Mode: S0 = GND (Jumper closed). The module acts as an I2C device. (connect DR to SDA and CT to SCL)
• UART Mode: S0 = High/Floating (Jumper open). The module sends data via Serial. (connect DR to TX and CT to RX)

Note: S1 is used for direct sensor access (TCS34725) via I2C and is left open when using this library. This mode uses pins 7 and 8 (SDA and SCL). Use it with a TCS34725 library such as Adafruit TCS34725 Driver

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Quick Start

1. I2C Mode

Ensure S0 is connected to GND.

#include <GY33.h>

GY33_I2C sensor;

void setup() {
  Serial.begin(115200);
  sensor.begin(); // Uses default SDA/SCL pins
}

void loop() {
  if (sensor.update()) {
    Serial.print("Colour: ");
    Serial.println(sensor.colour());
  }
  delay(500);
}

2. UART Mode

Ensure S0 is Open/High.

#include <GY33.h>

GY33_UART sensor(Serial1);

void setup() {
  Serial.begin(115200);
  Serial1.begin(9600, SERIAL_8N1, 8, 9); // Adjust pins for your board
  sensor.begin();
}

void loop() {
  if (sensor.update()) {
    Serial.print("Colour: ");
    Serial.println(sensor.colour());
  }
  delay(500);
}