Quadrature Encoder Interface(QEI) module provides the interface to incremental encoders for obtaining mechanical position data. The quadrature encoder detect position and speed of rotating motion systems. And it has three output channels, channel A, channel B and index I, provides information on the movement of the motor shaft, including distance and direction. Channel A and B are coded ninety electrical degrees out of phase, and the controller can determine direction of movement based on the phase relationship between Channels A and B.