LM3S2965 Luminary Micro, Inc, LM3S2965 Datasheet - Page 508

• Manufacturer Part Number: LM3S2965
• Description: Lm3s2965 Arm Microcontroller
• Manufacturer: Luminary Micro, Inc

Quadrature Encoder Interface (QEI)
19
19.1
508
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
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■
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Block Diagram
Figure 19-1 on page 509 provides a block diagram of a Stellaris
Position integrator that tracks the encoder position
Velocity capture using built-in timer
Interrupt generation on:
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–
–
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Index pulse
Velocity-timer expiration
Direction change
Quadrature error detection
®
quadrature encoder has the following features:
Preliminary
®
QEI module.
July 25, 2008