The eQEP inputs include two pins for
quadrature-clock mode or direction-count mode, an index (or 0 marker), and a strobe
input. The eQEP module requires that the QEPA, QEPB, and QEPI inputs are
synchronized to SYSCLK prior to entering the module. The application code can enable
the synchronous GPIO input feature on any eQEP-enabled GPIO pins (see the General-Purpose Input/Output (GPIO) chapter for more details).
- QEPA/XCLK and QEPB/XDIR: These two pins can be used in
quadrature-clock mode or direction-count mode.
- Quadrature-clock Mode:
The eQEP encoders provide two square wave signals (A and B) 90
electrical degrees out of phase. This phase relationship is used to
determine the direction of rotation of the input shaft and number of
eQEP pulses from the index position to derive the relative position
information. For forward or clockwise rotation, QEPA signal leads QEPB
signal and conversely. The quadrature decoder uses these two inputs to
generate quadrature-clock and direction signals.
- Direction-count Mode: In
direction-count mode, direction and clock signals are provided directly
from the external source. Some position encoders have this type of
output instead of quadrature output. The QEPA pin provides the clock
input and the QEPB pin provides the direction input.
- QEPI: Index or Zero Marker:
The eQEP encoder uses an index signal to assign an absolute start position
from which position information is incrementally encoded using quadrature
pulses. This pin is connected to the index output of the eQEP encoder to
optionally reset the position counter for each revolution. This signal can be
used to initialize or latch the position counter on the occurrence of a desired
event on the index pin.
- QEPS: Strobe Input: This
general-purpose strobe signal can initialize or latch the position counter on
the occurrence of a desired event on the strobe pin. This signal is typically
connected to a sensor or limit switch to notify that the motor has reached a
defined position.