Incremental QUADRATURE ENCODER

Electrical schema

The ideal form of a quadrature signal

Slow rotation with a contacts noise (bounce)

These screenshots are obtained using the Logic analyzer on Processing.
See DIY Logic Analyzer. Thanks, Vincenzo G.

The contact noise present

LDmicro QUADRATURE ENCODER instruction.

quad_mega.zip

Rotation reversing when changing RV1.

quad_877.zip

See also:
Rotary Encoder: H/W, S/W or No Debounce?
Bounce-Free Rotary Encoder