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) ...

A new class of position sensing devices is manufactured with proven technologies such as pc-board assembly and injection molding techniques. Called the Sine/Cosine Rotary Electric Encoder(TM), from ...