Feike van Veen
QEI2
Revision 1:2d418d07997d, committed 2019-10-21
- Comitter:
- Feike
- Date:
- Mon Oct 21 11:01:02 2019 +0000
- Parent:
- 0:5c2ad81551aa
- Commit message:
- nieuwe lib
Changed in this revision
diff -r 5c2ad81551aa -r 2d418d07997d QEI.cpp
--- a/QEI.cpp Thu Sep 02 16:48:55 2010 +0000
+++ /dev/null Thu Jan 01 00:00:00 1970 +0000
@@ -1,289 +0,0 @@
-/**
- * @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) {
-
- pulses_ = 0;
- revolutions_ = 0;
- pulsesPerRev_ = pulsesPerRev;
- encoding_ = encoding;
-
- //Workout what the current state is.
- int chanA = channelA_.read();
- int chanB = channelB_.read();
-
- //2-bit state.
- currState_ = (chanA << 1) | (chanB);
- prevState_ = currState_;
-
- //X2 encoding uses interrupts on only channel A.
- //X4 encoding uses interrupts on channel A,
- //and on channel B.
- channelA_.rise(this, &QEI::encode);
- channelA_.fall(this, &QEI::encode);
-
- //If we're using X4 encoding, then attach interrupts to channel B too.
- if (encoding == X4_ENCODING) {
- channelB_.rise(this, &QEI::encode);
- channelB_.fall(this, &QEI::encode);
- }
- //Index is optional.
- 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_++;
-
-}
diff -r 5c2ad81551aa -r 2d418d07997d QEI.h
--- a/QEI.h Thu Sep 02 16:48:55 2010 +0000
+++ /dev/null Thu Jan 01 00:00:00 1970 +0000
@@ -1,244 +0,0 @@
-/**
- * @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 INVALID 0x3 //XORing two states where both bits have changed.
-
-/**
- * Quadrature Encoder Interface.
- */
-class QEI {
-
-public:
-
- typedef enum Encoding {
-
- X2_ENCODING,
- X4_ENCODING
-
- } Encoding;
-
- /**
- * Constructor.
- *
- * Reads the current values on channel A and channel B to determine the
- * initial state.
- *
- * Attaches the encode function to the rise/fall interrupt edges of
- * channels A and B to perform X4 encoding.
- *
- * Attaches the index function to the rise interrupt edge of channel index
- * (if it is used) to count revolutions.
- *
- * @param channelA mbed pin for channel A input.
- * @param channelB mbed pin for channel B input.
- * @param index mbed pin for optional index channel input,
- * (pass NC if not needed).
- * @param pulsesPerRev Number of pulses in one revolution.
- * @param encoding The encoding to use. Uses X2 encoding by default. X2
- * encoding uses interrupts on the rising and falling edges
- * of only channel A where as X4 uses them on both
- * channels.
- */
- QEI(PinName channelA, PinName channelB, PinName index, int pulsesPerRev, Encoding encoding = X2_ENCODING);
-
- /**
- * Reset the encoder.
- *
- * Sets the pulses and revolutions count to zero.
- */
- void reset(void);
-
- /**
- * Read the state of the encoder.
- *
- * @return The current state of the encoder as a 2-bit number, where:
- * bit 1 = The reading from channel B
- * bit 2 = The reading from channel A
- */
- int getCurrentState(void);
-
- /**
- * Read the number of pulses recorded by the encoder.
- *
- * @return Number of pulses which have occured.
- */
- int getPulses(void);
-
- /**
- * Read the number of revolutions recorded by the encoder on the index channel.
- *
- * @return Number of revolutions which have occured on the index channel.
- */
- int getRevolutions(void);
-
-private:
-
- /**
- * Update the pulse count.
- *
- * Called on every rising/falling edge of channels A/B.
- *
- * Reads the state of the channels and determines whether a pulse forward
- * or backward has occured, updating the count appropriately.
- */
- void encode(void);
-
- /**
- * Called on every rising edge of channel index to update revolution
- * count by one.
- */
- void index(void);
-
- Encoding encoding_;
-
- InterruptIn channelA_;
- InterruptIn channelB_;
- InterruptIn index_;
-
- int pulsesPerRev_;
- int prevState_;
- int currState_;
-
- volatile int pulses_;
- volatile int revolutions_;
-
-};
-
-#endif /* QEI_H */
diff -r 5c2ad81551aa -r 2d418d07997d QEI2.cpp
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/QEI2.cpp Mon Oct 21 11:01:02 2019 +0000
@@ -0,0 +1,289 @@
+/**
+ * @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 "QEI2.h"
+
+QEI2::QEI2(PinName channelA,
+ PinName channelB,
+ PinName index,
+ int pulsesPerRev,
+ Encoding encoding) : channelA_(channelA), channelB_(channelB),
+ index_(index) {
+
+ pulses_ = 0;
+ revolutions_ = 0;
+ pulsesPerRev_ = pulsesPerRev;
+ encoding_ = encoding;
+
+ //Workout what the current state is.
+ int chanA = channelA_.read();
+ int chanB = channelB_.read();
+
+ //2-bit state.
+ currState_ = (chanA << 1) | (chanB);
+ prevState_ = currState_;
+
+ //X2 encoding uses interrupts on only channel A.
+ //X4 encoding uses interrupts on channel A,
+ //and on channel B.
+ channelA_.rise(this, &QEI2::encode);
+ channelA_.fall(this, &QEI2::encode);
+
+ //If we're using X4 encoding, then attach interrupts to channel B too.
+ if (encoding == X4_ENCODING) {
+ channelB_.rise(this, &QEI2::encode);
+ channelB_.fall(this, &QEI2::encode);
+ }
+ //Index is optional.
+ if (index != NC) {
+ index_.rise(this, &QEI2::index);
+ }
+
+}
+
+void QEI2::reset(void) {
+
+ pulses_ = 0;
+ revolutions_ = 0;
+
+}
+
+int QEI2::getCurrentState(void) {
+
+ return currState_;
+
+}
+
+int QEI2::getPulses(void) {
+
+ return pulses_;
+
+}
+
+int QEI2::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 QEI2::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 QEI2::index(void) {
+
+ revolutions_++;
+
+}
diff -r 5c2ad81551aa -r 2d418d07997d QEI2.h
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/QEI2.h Mon Oct 21 11:01:02 2019 +0000
@@ -0,0 +1,244 @@
+/**
+ * @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 QEI2_H
+#define QEI2_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 INVALID 0x3 //XORing two states where both bits have changed.
+
+/**
+ * Quadrature Encoder Interface.
+ */
+class QEI2 {
+
+public:
+
+ typedef enum Encoding {
+
+ X2_ENCODING,
+ X4_ENCODING
+
+ } Encoding;
+
+ /**
+ * Constructor.
+ *
+ * Reads the current values on channel A and channel B to determine the
+ * initial state.
+ *
+ * Attaches the encode function to the rise/fall interrupt edges of
+ * channels A and B to perform X4 encoding.
+ *
+ * Attaches the index function to the rise interrupt edge of channel index
+ * (if it is used) to count revolutions.
+ *
+ * @param channelA mbed pin for channel A input.
+ * @param channelB mbed pin for channel B input.
+ * @param index mbed pin for optional index channel input,
+ * (pass NC if not needed).
+ * @param pulsesPerRev Number of pulses in one revolution.
+ * @param encoding The encoding to use. Uses X2 encoding by default. X2
+ * encoding uses interrupts on the rising and falling edges
+ * of only channel A where as X4 uses them on both
+ * channels.
+ */
+ QEI2(PinName channelA, PinName channelB, PinName index, int pulsesPerRev, Encoding encoding = X2_ENCODING);
+
+ /**
+ * Reset the encoder.
+ *
+ * Sets the pulses and revolutions count to zero.
+ */
+ void reset(void);
+
+ /**
+ * Read the state of the encoder.
+ *
+ * @return The current state of the encoder as a 2-bit number, where:
+ * bit 1 = The reading from channel B
+ * bit 2 = The reading from channel A
+ */
+ int getCurrentState(void);
+
+ /**
+ * Read the number of pulses recorded by the encoder.
+ *
+ * @return Number of pulses which have occured.
+ */
+ int getPulses(void);
+
+ /**
+ * Read the number of revolutions recorded by the encoder on the index channel.
+ *
+ * @return Number of revolutions which have occured on the index channel.
+ */
+ int getRevolutions(void);
+
+private:
+
+ /**
+ * Update the pulse count.
+ *
+ * Called on every rising/falling edge of channels A/B.
+ *
+ * Reads the state of the channels and determines whether a pulse forward
+ * or backward has occured, updating the count appropriately.
+ */
+ void encode(void);
+
+ /**
+ * Called on every rising edge of channel index to update revolution
+ * count by one.
+ */
+ void index(void);
+
+ Encoding encoding_;
+
+ InterruptIn channelA_;
+ InterruptIn channelB_;
+ InterruptIn index_;
+
+ int pulsesPerRev_;
+ int prevState_;
+ int currState_;
+
+ volatile int pulses_;
+ volatile int revolutions_;
+
+};
+
+#endif /* QEI2_H */