Kei Ohta
enc
Fork of
QEI
by 
Aaron Berk
Diff: QEI.cpp
- Revision:
- 1:7e60713aefc2
- Parent:
- 0:5c2ad81551aa
--- a/QEI.cpp Thu Sep 02 16:48:55 2010 +0000
+++ b/QEI.cpp Mon Dec 09 23:57:01 2013 +0000
@@ -1,131 +1,4 @@
-/**
- * @author Aaron Berk
- *
- * @section LICENSE
- *
- * Copyright (c) 2010 ARM Limited
- *
- * Permission is hereby granted, free of charge, to any person obtaining a copy
- * of this software and associated documentation files (the "Software"), to deal
- * in the Software without restriction, including without limitation the rights
- * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
- * copies of the Software, and to permit persons to whom the Software is
- * furnished to do so, subject to the following conditions:
- *
- * The above copyright notice and this permission notice shall be included in
- * all copies or substantial portions of the Software.
- *
- * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
- * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
- * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
- * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
- * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
- * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
- * THE SOFTWARE.
- *
- * @section DESCRIPTION
- *
- * Quadrature Encoder Interface.
- *
- * A quadrature encoder consists of two code tracks on a disc which are 90
- * degrees out of phase. It can be used to determine how far a wheel has
- * rotated, relative to a known starting position.
- *
- * Only one code track changes at a time leading to a more robust system than
- * a single track, because any jitter around any edge won't cause a state
- * change as the other track will remain constant.
- *
- * Encoders can be a homebrew affair, consisting of infrared emitters/receivers
- * and paper code tracks consisting of alternating black and white sections;
- * alternatively, complete disk and PCB emitter/receiver encoder systems can
- * be bought, but the interface, regardless of implementation is the same.
- *
- * +-----+ +-----+ +-----+
- * Channel A | ^ | | | | |
- * ---+ ^ +-----+ +-----+ +-----
- * ^ ^
- * ^ +-----+ +-----+ +-----+
- * Channel B ^ | | | | | |
- * ------+ +-----+ +-----+ +-----
- * ^ ^
- * ^ ^
- * 90deg
- *
- * The interface uses X2 encoding by default which calculates the pulse count
- * based on reading the current state after each rising and falling edge of
- * channel A.
- *
- * +-----+ +-----+ +-----+
- * Channel A | | | | | |
- * ---+ +-----+ +-----+ +-----
- * ^ ^ ^ ^ ^
- * ^ +-----+ ^ +-----+ ^ +-----+
- * Channel B ^ | ^ | ^ | ^ | ^ | |
- * ------+ ^ +-----+ ^ +-----+ +--
- * ^ ^ ^ ^ ^
- * ^ ^ ^ ^ ^
- * Pulse count 0 1 2 3 4 5 ...
- *
- * This interface can also use X4 encoding which calculates the pulse count
- * based on reading the current state after each rising and falling edge of
- * either channel.
- *
- * +-----+ +-----+ +-----+
- * Channel A | | | | | |
- * ---+ +-----+ +-----+ +-----
- * ^ ^ ^ ^ ^
- * ^ +-----+ ^ +-----+ ^ +-----+
- * Channel B ^ | ^ | ^ | ^ | ^ | |
- * ------+ ^ +-----+ ^ +-----+ +--
- * ^ ^ ^ ^ ^ ^ ^ ^ ^ ^
- * ^ ^ ^ ^ ^ ^ ^ ^ ^ ^
- * Pulse count 0 1 2 3 4 5 6 7 8 9 ...
- *
- * It defaults
- *
- * An optional index channel can be used which determines when a full
- * revolution has occured.
- *
- * If a 4 pules per revolution encoder was used, with X4 encoding,
- * the following would be observed.
- *
- * +-----+ +-----+ +-----+
- * Channel A | | | | | |
- * ---+ +-----+ +-----+ +-----
- * ^ ^ ^ ^ ^
- * ^ +-----+ ^ +-----+ ^ +-----+
- * Channel B ^ | ^ | ^ | ^ | ^ | |
- * ------+ ^ +-----+ ^ +-----+ +--
- * ^ ^ ^ ^ ^ ^ ^ ^ ^ ^
- * ^ ^ ^ ^ ^ ^ ^ ^ ^ ^
- * ^ ^ ^ +--+ ^ ^ +--+ ^
- * ^ ^ ^ | | ^ ^ | | ^
- * Index ------------+ +--------+ +-----------
- * ^ ^ ^ ^ ^ ^ ^ ^ ^ ^
- * Pulse count 0 1 2 3 4 5 6 7 8 9 ...
- * Rev. count 0 1 2
- *
- * Rotational position in degrees can be calculated by:
- *
- * (pulse count / X * N) * 360
- *
- * Where X is the encoding type [e.g. X4 encoding => X=4], and N is the number
- * of pulses per revolution.
- *
- * Linear position can be calculated by:
- *
- * (pulse count / X * N) * (1 / PPI)
- *
- * Where X is encoding type [e.g. X4 encoding => X=44], N is the number of
- * pulses per revolution, and PPI is pulses per inch, or the equivalent for
- * any other unit of displacement. PPI can be calculated by taking the
- * circumference of the wheel or encoder disk and dividing it by the number
- * of pulses per revolution.
- */
-/**
- * Includes
- */
#include "QEI.h"
QEI::QEI(PinName channelA,
@@ -163,127 +36,64 @@
if (index != NC) {
index_.rise(this, &QEI::index);
}
-
}
void QEI::reset(void) {
-
pulses_ = 0;
revolutions_ = 0;
-
}
int QEI::getCurrentState(void) {
-
return currState_;
-
}
int QEI::getPulses(void) {
-
return pulses_;
-
}
int QEI::getRevolutions(void) {
-
return revolutions_;
-
}
-// +-------------+
-// | X2 Encoding |
-// +-------------+
-//
-// When observing states two patterns will appear:
-//
-// Counter clockwise rotation:
-//
-// 10 -> 01 -> 10 -> 01 -> ...
-//
-// Clockwise rotation:
-//
-// 11 -> 00 -> 11 -> 00 -> ...
-//
-// We consider counter clockwise rotation to be "forward" and
-// counter clockwise to be "backward". Therefore pulse count will increase
-// during counter clockwise rotation and decrease during clockwise rotation.
-//
-// +-------------+
-// | X4 Encoding |
-// +-------------+
-//
-// There are four possible states for a quadrature encoder which correspond to
-// 2-bit gray code.
-//
-// A state change is only valid if of only one bit has changed.
-// A state change is invalid if both bits have changed.
-//
-// Clockwise Rotation ->
-//
-// 00 01 11 10 00
-//
-// <- Counter Clockwise Rotation
-//
-// If we observe any valid state changes going from left to right, we have
-// moved one pulse clockwise [we will consider this "backward" or "negative"].
-//
-// If we observe any valid state changes going from right to left we have
-// moved one pulse counter clockwise [we will consider this "forward" or
-// "positive"].
-//
-// We might enter an invalid state for a number of reasons which are hard to
-// predict - if this is the case, it is generally safe to ignore it, update
-// the state and carry on, with the error correcting itself shortly after.
void QEI::encode(void) {
-
int change = 0;
int chanA = channelA_.read();
int chanB = channelB_.read();
-
//2-bit state.
currState_ = (chanA << 1) | (chanB);
if (encoding_ == X2_ENCODING) {
-
//11->00->11->00 is counter clockwise rotation or "forward".
if ((prevState_ == 0x3 && currState_ == 0x0) ||
(prevState_ == 0x0 && currState_ == 0x3)) {
-
pulses_++;
-
}
//10->01->10->01 is clockwise rotation or "backward".
else if ((prevState_ == 0x2 && currState_ == 0x1) ||
(prevState_ == 0x1 && currState_ == 0x2)) {
-
pulses_--;
-
}
-
} else if (encoding_ == X4_ENCODING) {
-
//Entered a new valid state.
if (((currState_ ^ prevState_) != INVALID) && (currState_ != prevState_)) {
//2 bit state. Right hand bit of prev XOR left hand bit of current
//gives 0 if clockwise rotation and 1 if counter clockwise rotation.
change = (prevState_ & PREV_MASK) ^ ((currState_ & CURR_MASK) >> 1);
-
if (change == 0) {
change = -1;
}
-
pulses_ -= change;
}
-
}
-
prevState_ = currState_;
-
}
void QEI::index(void) {
-
revolutions_++;
-
}
+/*
+void QEI::move(float theta_z) {
+ float tmp = theta_z.getPulses();
+ return tmp;
+}
+*/
\ No newline at end of file