I will not go into greater detail of the code behind the rotary encoder + arduino experiment, as featured articles and great tutorials are available all over the web.

I have to thank one author of a rotary encoder decoder (Ben Buxton). While his code seemed overly complex to my untutored eye, for example creating a new data type, it did show Arduino-novice me two ...

Rotary encoders ... Arduino daughter boards and have additional pins for ST morpho boards (whatever those are). The mbed system is the ARM’s answer to Arduino. A web-based IDE lets you write C++ ...

that means that a lot of libraries and examples you can find don’t work with the newer system. I needed a rotary encoder — I pulled a cheap one out of one of those “49 boards for Arduino ...