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UM10503
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© NXP B.V. 2012. All rights reserved.
User manual
Rev. 1.3 — 6 July 2012
894 of 1269
NXP Semiconductors
UM10503
Chapter 31: LPC43xx Quadrature Encoder Interface (QEI)
31.4 Introduction
A quadrature encoder, also known as a 2-channel incremental encoder, converts angular
displacement into two pulse signals. By monitoring both the number of pulses and the
relative phase of the two signals, you can track the position, direction of rotation, and
velocity. In addition, a third channel, or index signal, can be used to reset the position
counter. This quadrature encoder interface module decodes the digital pulses from a
quadrature encoder wheel to integrate position over time and determine direction of
rotation. In addition, it can capture the velocity of the encoder wheel.