Texas Instruments TMS320F2837 D Series

eQEP
TMS320F2837xD Microcontroller Workshop - Control Peripherals 7 - 47
eQEP
What is an Incremental Quadrature
Encoder?
A digital (angular) position sensor
slots spaced θ deg. apart
photo sensors spaced
θ/4 deg. apart
light source (LED)
shaft rotation
Ch. A
Ch. B
Quadrature Output from Photo Sensors
θ
θ/4
Incremental Optical Encoder
The eQEP module interfaces with a linear or rotary incremental encoder for determining position,
direction, and speed information from a rotating machine that is typically found in high-
performance motion and position-control systems.
How is Position Determined from
Quadrature Signals?
Ch. A
Ch. B
(00)
(11)
(10) (01)
(A,B) =
00
01
11
10
Quadrature Decoder
State Machine
increment
counter
decrement
counter
Position resolution is θ/4 degrees
Illegal
Transitions;
generate
phase error
interrupt