The UNIT CO2 from M5Stack is a photoacoustic Carbon Dioxide (CO2) Unit that will tell you the CO2 PPM (parts-per-million) composition of ambient air.
The unit has a built-in Sensirion SCD40 sensor powered by buck converter circuitry and communication handled via I2C. It has a range of 400~2000 ppm with an accuracy of ±(50 ppm + 5% of reading).
It supports temperature and humidity measurements too – perfect for environmental sensing, scientific experiments, air quality and ventilation studies, and more.
Features
- CO2 concentration detection
- Temperature and humidity measurement
- I2C communication (Add: 0x62)
- Integrated 5V -> 3.3V Buck converter
- 2x Brick holes
- HY2.0 4-pin interface
Specifications
| Resources | Parameter |
| CO2 Measurement range | 400 ~ 2000 ppm |
| CO2 Sampling accuracy | ±(50 ppm + 5% of reading) |
| Temperature range | -10 – 60 °C |
| Humidity range | 0 – 95 %RH |
| Communication protocol | I2C: 0x62 |
| Net weight | 7.54g |
| Gross weight | 13.13g |
| Product dimensions | 48mm x 24mm x 16mm |
| Package size | 134mm x 61mm x 16.3mm |
| Housing material | Plastic ( PC ) |
Resources
- Product Documentation
- Schematic
- SCD40 datasheet
- SY8089AAAC datasheet
- Arduino Examples
- M5Unit-CO2 with M5Core
- M5Unit-CO2 with M5Atom
- M5Unit-CO2 with M5StickC
- M5Unit-CO2 with M5StickCPlus
Pinout
| CO2 Unit | SCL | SDA | 5V | GND |
| M5Core (PORT A) | GPIO22 | GPIO21 | 5V | GND |
| M5Core2 (PORT A) | GPIO22 | GPIO21 | 5V | GND |
| M5Atom (PORT A) | GPIO32 | GPIO26 | 5V | GND |
| M5StickC/Plus (PORT A) | GPIO33 | GPIO32 | 5V | GND |
| M5Station (PORT A1,A2) | GPIO33 | GPIO32 | 5V | GND |



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