LM3S2965_0711 Datasheet, PDF (500/574 Pages) List of Unclassifed Manufacturers – Microcontroller

Quadrature Encoder Interface (QEI)
19
19.1
Quadrature Encoder Interface (QEI)
A quadrature encoder, also known as a 2-channel incremental encoder, converts linear displacement
into a pulse signal. By monitoring both the number of pulses and the relative phase of the two signals,
you can track the position, direction of rotation, and speed. In addition, a third channel, or index
signal, can be used to reset the position counter.
The LM3S2965 microcontroller includes two quadrature encoder interface (QEI) modules. Each
QEI module interprets the code produced by a quadrature encoder wheel to integrate position over
time and determine direction of rotation. In addition, it can capture a running estimate of the velocity
of the encoder wheel.
Each Stellaris^® quadrature encoder has the following features:
■ Position integrator that tracks the encoder position
■ Velocity capture using built-in timer
■ Interrupt generation on:
– Index pulse
– Velocity-timer expiration
– Direction change
– Quadrature error detection
Block Diagram
Figure 19-1 on page 501 provides a block diagram of a Stellaris^® QEI module.
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November 30, 2007
Preliminary