- VIN - This is the power pin. To power the board, give it the same power as the logic level of your microcontroller - e.g. for a 3V microcontroller like a Feather M4, use 3V, or for a 5V microcontroller like Arduino, use 5V.
- GND - This is common ground for power and logic.
The default I2C address for the SCD-4x is 0x29.
- SCL - I2C clock pin, connect to your microcontroller I2C clock line. There's a 10K pullup on this pin.
- SDA - I2C data pin, connect to your microcontroller I2C data line. There's a 10K pullup on this pin.
- STEMMA QT - These connectors allow you to connect to development boards with STEMMA QT connectors or to other things with various associated accessories.
- GPIO - This is the interrupt output pin, it is 2.8V logic level output - it can be read by 3.3V and most 5V logic microcontrollers
- XSHUT - This is the shutdown pin. It is active low, and is logic-level shifted so you can use 3V or 5V logic.