amin omar
Quadrature encoder interface by Aaron Berk
Fork of
QEI
by 
Aaron Berk
Revision 1:5f28ceec8280, committed 2016-05-04
- Comitter:
- aminomar
- Date:
- Wed May 04 18:47:39 2016 +0000
- Parent:
- 0:5c2ad81551aa
- Commit message:
- test encoder;
Changed in this revision
| QEI.cpp | Show annotated file Show diff for this revision Revisions of this file |
| QEI.h | Show annotated file Show diff for this revision Revisions of this file |
diff -r 5c2ad81551aa -r 5f28ceec8280 QEI.cpp
--- a/QEI.cpp Thu Sep 02 16:48:55 2010 +0000
+++ b/QEI.cpp Wed May 04 18:47:39 2016 +0000
@@ -1,139 +1,9 @@
-/**
- * @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,
- PinName channelB,
- PinName index,
- int pulsesPerRev,
- Encoding encoding) : channelA_(channelA), channelB_(channelB),
- index_(index) {
+QEI::QEI(PinName channelA, PinName channelB, PinName index, int pulsesPerRev, Encoding encoding) :
+ channelA_(channelA), channelB_(channelB), index_(index)
+ {
pulses_ = 0;
revolutions_ = 0;
@@ -246,9 +116,9 @@
if (encoding_ == X2_ENCODING) {
- //11->00->11->00 is counter clockwise rotation or "forward".
+ //11->00->11->00 is counter clockwise rotation or "forward". If it follows the sequence, then pulses ++
if ((prevState_ == 0x3 && currState_ == 0x0) ||
- (prevState_ == 0x0 && currState_ == 0x3)) {
+ (prevState_ == 0x0 && currState_ == 0x3)) {
pulses_++;
diff -r 5c2ad81551aa -r 5f28ceec8280 QEI.h
--- a/QEI.h Thu Sep 02 16:48:55 2010 +0000
+++ b/QEI.h Wed May 04 18:47:39 2016 +0000
@@ -1,158 +1,24 @@
-/**
- * @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.
- */
#ifndef QEI_H
#define QEI_H
-/**
- * Includes
- */
#include "mbed.h"
-/**
- * Defines
- */
-#define PREV_MASK 0x1 //Mask for the previous state in determining direction
-//of rotation.
-#define CURR_MASK 0x2 //Mask for the current state in determining direction
-//of rotation.
+#define PREV_MASK 0x1 //Mask for the previous state in determining direction of rotation.
+#define CURR_MASK 0x2 //Mask for the current state in determining direction of rotation.
#define INVALID 0x3 //XORing two states where both bits have changed.
-/**
- * Quadrature Encoder Interface.
- */
+
class QEI {
public:
- typedef enum Encoding {
-
- X2_ENCODING,
+ typedef enum Encoding
+ {
+ X2_ENCODING,
X4_ENCODING
-
- } Encoding;
+ }
+ Encoding;
/**
* Constructor.