- Vin - this is the power pin. Since the sensor chip uses 3 VDC, we have included a voltage regulator on board that will take 3-5VDC and safely convert it down. To power the board, give it the same power as the logic level of your microcontroller - e.g. for a 5V micro like Arduino, use 5V
- 3Vo - this is the 3.3V output from the voltage regulator, you can grab up to 100mA from this if you like
- GND - common ground for power and logic
All pins going into the breakout have level shifting circuitry to make them 3-5V logic level safe. Use whatever logic level is on Vin!
- SCK - This is the SPI Clock pin, its an input to the chip
- SDO - this is the Serial Data Out / Master In Slave Out pin, for data sent from the BMP183 to your processor
- SDI - this is the Serial Data In / Master Out Slave In pin, for data sent from your processor to the BME280
- CS - this is the Chip Select pin, drop it low to start an SPI transaction. Its an input to the chip
If you want to connect multiple BME280's to one microcontroller, have them share the SDI, SDO and SCK pins. Then assign each one a unique CS pin.