RT & Arduino experiment was successfully conducted at my own lab using the ALPS-EC11E RT and Arduino UNO-R3, ported with a sketch borrowed from the web. You may ask why I did not prepare my own sketch ...

I needed a rotary encoder — I pulled a cheap one out of one of those “49 boards for Arduino” kits you see around. Not the finest encoder in the land, I’m sure, but it should do the job.

It is amazing how many Arduino programmes for decoding rotary encoders start with something like: "I looked at all the available rotary encoder sketches ...

This lovely input has an Arduino Pro Micro for a brain, and Gateron browns for brawn. That knob there is a rotary encoder, not a potentiometer, because endless volume knob twiddling is just so ...

Absolute encoders contain multiple detectors and up to 20 tracks of segment patterns. For each encoder position, there is a different binary output -- shaft position is absolutely determined.

Absolute rotary optical encoders use a disc to intercept light beams to create a pattern decoded by circuitry. Rotary encoders are specified for form factor, level of ruggedness, and resolution.