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UM10316_0
© NXP B.V. 2008. All rights reserved.
User manual
Rev. 00.06 — 17 December 2008
459 of 571
1.
How to read this chapter
The contents of this chapter apply to all LPC29xx parts.
2.
Introduction
The MSCSS includes a quadrature encoder interface (QEI) with the following features:
•
Tracks encoder position.
•
Increments/ decrements depending on direction.
•
Programmable for 2X or 4X position counting.
•
Velocity capture using built-in timer.
•
Velocity compare function with less than interrupt.
•
Uses 32-bit registers for position and velocity.
•
Three position compare registers with interrupts.
•
Index counter for revolution counting.
•
Index compare register with interrupts.
•
Can combine index and position interrupts to produce an interrupt for whole and
partial revolution displacement.
•
Digital filter with programmable delays for encoder input signals.
•
Can accept decoded signal inputs (clk and direction).
•
Connected to APB.
3.
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.
UM10316
Chapter 27: LPC29xx Quadrature Encoder Interface (QEI)
Rev. 00.06 — 17 December 2008
User manual