LM3S3768 Luminary Micro, Inc, LM3S3768 Datasheet - Page 659

• Manufacturer Part Number: LM3S3768
• Description: Lm3s3768 Arm Microcontroller
• Manufacturer: Luminary Micro, Inc

20
20.1
June 02, 2008
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 Stellaris
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.
The Stellaris
■
■
■
Block Diagram
Figure 20-1 on page 659 provides a block diagram of a Stellaris
Figure 20-1. QEI Block Diagram
PhA
IDX
PhB
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
Quadrature
®
®
Encoder
quadrature encoder interface (QEI) module interprets the code produced by a
quadrature encoder has the following features:
Control & Status
QEISTAT
dir
QEICTL
clk
Predivider
Velocity
Preliminary
Velocity Accumulator
Position Integrator
Interrupt Control
Velocity Timer
QEIMAXPOS
QEICOUNT
QEISPEED
QEIINTEN
QEILOAD
QEITIME
QEIPOS
QEIRIS
QEIISC
®
QEI module.
LM3S3768 Microcontroller
Interrupt
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