There are small and cheap adapters to take a serial/USB line and transform it into a i2c one, but the i2c bus on most motherboards is already accessible and doc

There are small and cheap adapters to take a serial/USB line and transform it into a i2c one, but the i2c bus on most motherboards is already accessible and documented because it's what operating systems use to read various sensors on the board. https://www.kernel.org/doc/html/v4.12/driver-api/i2c.html https://www.kernel.org/doc/html/v4.12/driver-api/i2c.html If the i2c but is used for example to do r/w on gpios, then other products can be used, for example: https://www.hardkernel.com/shop/usb-io-board/ https://www.hardkernel.com/shop/usb-io-board/