Hello HelloALL,
Shuttle board was designed to work with application board. Application board introduction, you could refer:
https://www.bosch-sensortec.com/media/boschsensortec/downloads/software_tools/application_boards/bst-dhw-an001-01_app2_0_hardware_description.pdf
In the hardware design of application board and shuttle board, application board can choose to use SPI or I2C to communicate with shuttle board.
If you use shuttle board and application board, HW connection was ready whether you use SPI or I2C.
If you use shuttle board and other host HW board, actually you only need to care the following schematic from BMP280 data sheet. BMP280 8 pins were connected to 28 pins header, you could connect these pins to host HW board and start your SPI or I2C access.
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