The lamp’s color temperature and brightness are set with a rotary encoder / push button combo switch, and the LEDs themselves are controlled via PWM.

Adafruit has made an I2C interface for four rotary encoders. It comes in the form of a PCB with four footprints that accept one of the most common rotary encoder forms (Bournes PEC11 horizontal style) ...

Elma's E18 rotary encoder comes in through-hole and surface-mount versions in the 14.4 x 11.4 x 6.5mm body size.