STM32 Rotary Encoder

Rotary encoder on de-bouncing breakout board

Rotary Encoders are devices which will generate pulses when they are turned.

Typically they will have two outputs with the pulses out of phase. By checking which pulse "comes first" the direction of the turn can be determined. It is not overly complicated to handle this manually, for example by hooking the signals up to an external GPIO Interrupt.

Rotary encoder signals

A rotary encoder will output 2 signals 90 degrees out of phase with each other.

By analysing the order of the transitions the steps can be counted and the direction can be detected.

Rotary encoder de-bouncing

Rotary encoders are build with mechanical contacts and they are prone to "bouncing" (one press generate more than one interrupt". The "signals" can be cleaned up by implementing a low-pass filter like this:

I just happened to have a few of those rotary encoder breakout boards lying around.

Miscellaneous Links

• Rotary Encoder Breakout w. de-bouncing circuit