Feike van Veen / QEI1

Minor test serial map

QEI1.cpp@1:e567b2f1aebf, 2019-10-21 (annotated)

Committer:
Feike
Date:
Mon Oct 21 11:00:54 2019 +0000
Revision:
1:e567b2f1aebf
Nieuwe lib

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Feike 1:e567b2f1aebf 1 /**
Feike 1:e567b2f1aebf 2 * @author Aaron Berk
Feike 1:e567b2f1aebf 3 *
Feike 1:e567b2f1aebf 4 * @section LICENSE
Feike 1:e567b2f1aebf 5 *
Feike 1:e567b2f1aebf 6 * Copyright (c) 2010 ARM Limited
Feike 1:e567b2f1aebf 7 *
Feike 1:e567b2f1aebf 8 * Permission is hereby granted, free of charge, to any person obtaining a copy
Feike 1:e567b2f1aebf 9 * of this software and associated documentation files (the "Software"), to deal
Feike 1:e567b2f1aebf 10 * in the Software without restriction, including without limitation the rights
Feike 1:e567b2f1aebf 11 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
Feike 1:e567b2f1aebf 12 * copies of the Software, and to permit persons to whom the Software is
Feike 1:e567b2f1aebf 13 * furnished to do so, subject to the following conditions:
Feike 1:e567b2f1aebf 14 *
Feike 1:e567b2f1aebf 15 * The above copyright notice and this permission notice shall be included in
Feike 1:e567b2f1aebf 16 * all copies or substantial portions of the Software.
Feike 1:e567b2f1aebf 17 *
Feike 1:e567b2f1aebf 18 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
Feike 1:e567b2f1aebf 19 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
Feike 1:e567b2f1aebf 20 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
Feike 1:e567b2f1aebf 21 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
Feike 1:e567b2f1aebf 22 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
Feike 1:e567b2f1aebf 23 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
Feike 1:e567b2f1aebf 24 * THE SOFTWARE.
Feike 1:e567b2f1aebf 25 *
Feike 1:e567b2f1aebf 26 * @section DESCRIPTION
Feike 1:e567b2f1aebf 27 *
Feike 1:e567b2f1aebf 28 * Quadrature Encoder Interface.
Feike 1:e567b2f1aebf 29 *
Feike 1:e567b2f1aebf 30 * A quadrature encoder consists of two code tracks on a disc which are 90
Feike 1:e567b2f1aebf 31 * degrees out of phase. It can be used to determine how far a wheel has
Feike 1:e567b2f1aebf 32 * rotated, relative to a known starting position.
Feike 1:e567b2f1aebf 33 *
Feike 1:e567b2f1aebf 34 * Only one code track changes at a time leading to a more robust system than
Feike 1:e567b2f1aebf 35 * a single track, because any jitter around any edge won't cause a state
Feike 1:e567b2f1aebf 36 * change as the other track will remain constant.
Feike 1:e567b2f1aebf 37 *
Feike 1:e567b2f1aebf 38 * Encoders can be a homebrew affair, consisting of infrared emitters/receivers
Feike 1:e567b2f1aebf 39 * and paper code tracks consisting of alternating black and white sections;
Feike 1:e567b2f1aebf 40 * alternatively, complete disk and PCB emitter/receiver encoder systems can
Feike 1:e567b2f1aebf 41 * be bought, but the interface, regardless of implementation is the same.
Feike 1:e567b2f1aebf 42 *
Feike 1:e567b2f1aebf 43 * +-----+ +-----+ +-----+
Feike 1:e567b2f1aebf 44 * Channel A | ^ | | | | |
Feike 1:e567b2f1aebf 45 * ---+ ^ +-----+ +-----+ +-----
Feike 1:e567b2f1aebf 46 * ^ ^
Feike 1:e567b2f1aebf 47 * ^ +-----+ +-----+ +-----+
Feike 1:e567b2f1aebf 48 * Channel B ^ | | | | | |
Feike 1:e567b2f1aebf 49 * ------+ +-----+ +-----+ +-----
Feike 1:e567b2f1aebf 50 * ^ ^
Feike 1:e567b2f1aebf 51 * ^ ^
Feike 1:e567b2f1aebf 52 * 90deg
Feike 1:e567b2f1aebf 53 *
Feike 1:e567b2f1aebf 54 * The interface uses X2 encoding by default which calculates the pulse count
Feike 1:e567b2f1aebf 55 * based on reading the current state after each rising and falling edge of
Feike 1:e567b2f1aebf 56 * channel A.
Feike 1:e567b2f1aebf 57 *
Feike 1:e567b2f1aebf 58 * +-----+ +-----+ +-----+
Feike 1:e567b2f1aebf 59 * Channel A | | | | | |
Feike 1:e567b2f1aebf 60 * ---+ +-----+ +-----+ +-----
Feike 1:e567b2f1aebf 61 * ^ ^ ^ ^ ^
Feike 1:e567b2f1aebf 62 * ^ +-----+ ^ +-----+ ^ +-----+
Feike 1:e567b2f1aebf 63 * Channel B ^ | ^ | ^ | ^ | ^ | |
Feike 1:e567b2f1aebf 64 * ------+ ^ +-----+ ^ +-----+ +--
Feike 1:e567b2f1aebf 65 * ^ ^ ^ ^ ^
Feike 1:e567b2f1aebf 66 * ^ ^ ^ ^ ^
Feike 1:e567b2f1aebf 67 * Pulse count 0 1 2 3 4 5 ...
Feike 1:e567b2f1aebf 68 *
Feike 1:e567b2f1aebf 69 * This interface can also use X4 encoding which calculates the pulse count
Feike 1:e567b2f1aebf 70 * based on reading the current state after each rising and falling edge of
Feike 1:e567b2f1aebf 71 * either channel.
Feike 1:e567b2f1aebf 72 *
Feike 1:e567b2f1aebf 73 * +-----+ +-----+ +-----+
Feike 1:e567b2f1aebf 74 * Channel A | | | | | |
Feike 1:e567b2f1aebf 75 * ---+ +-----+ +-----+ +-----
Feike 1:e567b2f1aebf 76 * ^ ^ ^ ^ ^
Feike 1:e567b2f1aebf 77 * ^ +-----+ ^ +-----+ ^ +-----+
Feike 1:e567b2f1aebf 78 * Channel B ^ | ^ | ^ | ^ | ^ | |
Feike 1:e567b2f1aebf 79 * ------+ ^ +-----+ ^ +-----+ +--
Feike 1:e567b2f1aebf 80 * ^ ^ ^ ^ ^ ^ ^ ^ ^ ^
Feike 1:e567b2f1aebf 81 * ^ ^ ^ ^ ^ ^ ^ ^ ^ ^
Feike 1:e567b2f1aebf 82 * Pulse count 0 1 2 3 4 5 6 7 8 9 ...
Feike 1:e567b2f1aebf 83 *
Feike 1:e567b2f1aebf 84 * It defaults
Feike 1:e567b2f1aebf 85 *
Feike 1:e567b2f1aebf 86 * An optional index channel can be used which determines when a full
Feike 1:e567b2f1aebf 87 * revolution has occured.
Feike 1:e567b2f1aebf 88 *
Feike 1:e567b2f1aebf 89 * If a 4 pules per revolution encoder was used, with X4 encoding,
Feike 1:e567b2f1aebf 90 * the following would be observed.
Feike 1:e567b2f1aebf 91 *
Feike 1:e567b2f1aebf 92 * +-----+ +-----+ +-----+
Feike 1:e567b2f1aebf 93 * Channel A | | | | | |
Feike 1:e567b2f1aebf 94 * ---+ +-----+ +-----+ +-----
Feike 1:e567b2f1aebf 95 * ^ ^ ^ ^ ^
Feike 1:e567b2f1aebf 96 * ^ +-----+ ^ +-----+ ^ +-----+
Feike 1:e567b2f1aebf 97 * Channel B ^ | ^ | ^ | ^ | ^ | |
Feike 1:e567b2f1aebf 98 * ------+ ^ +-----+ ^ +-----+ +--
Feike 1:e567b2f1aebf 99 * ^ ^ ^ ^ ^ ^ ^ ^ ^ ^
Feike 1:e567b2f1aebf 100 * ^ ^ ^ ^ ^ ^ ^ ^ ^ ^
Feike 1:e567b2f1aebf 101 * ^ ^ ^ +--+ ^ ^ +--+ ^
Feike 1:e567b2f1aebf 102 * ^ ^ ^ | | ^ ^ | | ^
Feike 1:e567b2f1aebf 103 * Index ------------+ +--------+ +-----------
Feike 1:e567b2f1aebf 104 * ^ ^ ^ ^ ^ ^ ^ ^ ^ ^
Feike 1:e567b2f1aebf 105 * Pulse count 0 1 2 3 4 5 6 7 8 9 ...
Feike 1:e567b2f1aebf 106 * Rev. count 0 1 2
Feike 1:e567b2f1aebf 107 *
Feike 1:e567b2f1aebf 108 * Rotational position in degrees can be calculated by:
Feike 1:e567b2f1aebf 109 *
Feike 1:e567b2f1aebf 110 * (pulse count / X * N) * 360
Feike 1:e567b2f1aebf 111 *
Feike 1:e567b2f1aebf 112 * Where X is the encoding type [e.g. X4 encoding => X=4], and N is the number
Feike 1:e567b2f1aebf 113 * of pulses per revolution.
Feike 1:e567b2f1aebf 114 *
Feike 1:e567b2f1aebf 115 * Linear position can be calculated by:
Feike 1:e567b2f1aebf 116 *
Feike 1:e567b2f1aebf 117 * (pulse count / X * N) * (1 / PPI)
Feike 1:e567b2f1aebf 118 *
Feike 1:e567b2f1aebf 119 * Where X is encoding type [e.g. X4 encoding => X=44], N is the number of
Feike 1:e567b2f1aebf 120 * pulses per revolution, and PPI is pulses per inch, or the equivalent for
Feike 1:e567b2f1aebf 121 * any other unit of displacement. PPI can be calculated by taking the
Feike 1:e567b2f1aebf 122 * circumference of the wheel or encoder disk and dividing it by the number
Feike 1:e567b2f1aebf 123 * of pulses per revolution.
Feike 1:e567b2f1aebf 124 */
Feike 1:e567b2f1aebf 125
Feike 1:e567b2f1aebf 126 /**
Feike 1:e567b2f1aebf 127 * Includes
Feike 1:e567b2f1aebf 128 */
Feike 1:e567b2f1aebf 129 #include "QEI1.h"
Feike 1:e567b2f1aebf 130
Feike 1:e567b2f1aebf 131 QEI1::QEI1(PinName channelA,
Feike 1:e567b2f1aebf 132 PinName channelB,
Feike 1:e567b2f1aebf 133 PinName index,
Feike 1:e567b2f1aebf 134 int pulsesPerRev,
Feike 1:e567b2f1aebf 135 Encoding encoding) : channelA_(channelA), channelB_(channelB),
Feike 1:e567b2f1aebf 136 index_(index) {
Feike 1:e567b2f1aebf 137
Feike 1:e567b2f1aebf 138 pulses_ = 0;
Feike 1:e567b2f1aebf 139 revolutions_ = 0;
Feike 1:e567b2f1aebf 140 pulsesPerRev_ = pulsesPerRev;
Feike 1:e567b2f1aebf 141 encoding_ = encoding;
Feike 1:e567b2f1aebf 142
Feike 1:e567b2f1aebf 143 //Workout what the current state is.
Feike 1:e567b2f1aebf 144 int chanA = channelA_.read();
Feike 1:e567b2f1aebf 145 int chanB = channelB_.read();
Feike 1:e567b2f1aebf 146
Feike 1:e567b2f1aebf 147 //2-bit state.
Feike 1:e567b2f1aebf 148 currState_ = (chanA << 1) | (chanB);
Feike 1:e567b2f1aebf 149 prevState_ = currState_;
Feike 1:e567b2f1aebf 150
Feike 1:e567b2f1aebf 151 //X2 encoding uses interrupts on only channel A.
Feike 1:e567b2f1aebf 152 //X4 encoding uses interrupts on channel A,
Feike 1:e567b2f1aebf 153 //and on channel B.
Feike 1:e567b2f1aebf 154 channelA_.rise(this, &QEI1::encode);
Feike 1:e567b2f1aebf 155 channelA_.fall(this, &QEI1::encode);
Feike 1:e567b2f1aebf 156
Feike 1:e567b2f1aebf 157 //If we're using X4 encoding, then attach interrupts to channel B too.
Feike 1:e567b2f1aebf 158 if (encoding == X4_ENCODING) {
Feike 1:e567b2f1aebf 159 channelB_.rise(this, &QEI1::encode);
Feike 1:e567b2f1aebf 160 channelB_.fall(this, &QEI1::encode);
Feike 1:e567b2f1aebf 161 }
Feike 1:e567b2f1aebf 162 //Index is optional.
Feike 1:e567b2f1aebf 163 if (index != NC) {
Feike 1:e567b2f1aebf 164 index_.rise(this, &QEI1::index);
Feike 1:e567b2f1aebf 165 }
Feike 1:e567b2f1aebf 166
Feike 1:e567b2f1aebf 167 }
Feike 1:e567b2f1aebf 168
Feike 1:e567b2f1aebf 169 void QEI1::reset(void) {
Feike 1:e567b2f1aebf 170
Feike 1:e567b2f1aebf 171 pulses_ = 0;
Feike 1:e567b2f1aebf 172 revolutions_ = 0;
Feike 1:e567b2f1aebf 173
Feike 1:e567b2f1aebf 174 }
Feike 1:e567b2f1aebf 175
Feike 1:e567b2f1aebf 176 int QEI1::getCurrentState(void) {
Feike 1:e567b2f1aebf 177
Feike 1:e567b2f1aebf 178 return currState_;
Feike 1:e567b2f1aebf 179
Feike 1:e567b2f1aebf 180 }
Feike 1:e567b2f1aebf 181
Feike 1:e567b2f1aebf 182 int QEI1::getPulses(void) {
Feike 1:e567b2f1aebf 183
Feike 1:e567b2f1aebf 184 return pulses_;
Feike 1:e567b2f1aebf 185
Feike 1:e567b2f1aebf 186 }
Feike 1:e567b2f1aebf 187
Feike 1:e567b2f1aebf 188 int QEI1::getRevolutions(void) {
Feike 1:e567b2f1aebf 189
Feike 1:e567b2f1aebf 190 return revolutions_;
Feike 1:e567b2f1aebf 191
Feike 1:e567b2f1aebf 192 }
Feike 1:e567b2f1aebf 193
Feike 1:e567b2f1aebf 194 // +-------------+
Feike 1:e567b2f1aebf 195 // | X2 Encoding |
Feike 1:e567b2f1aebf 196 // +-------------+
Feike 1:e567b2f1aebf 197 //
Feike 1:e567b2f1aebf 198 // When observing states two patterns will appear:
Feike 1:e567b2f1aebf 199 //
Feike 1:e567b2f1aebf 200 // Counter clockwise rotation:
Feike 1:e567b2f1aebf 201 //
Feike 1:e567b2f1aebf 202 // 10 -> 01 -> 10 -> 01 -> ...
Feike 1:e567b2f1aebf 203 //
Feike 1:e567b2f1aebf 204 // Clockwise rotation:
Feike 1:e567b2f1aebf 205 //
Feike 1:e567b2f1aebf 206 // 11 -> 00 -> 11 -> 00 -> ...
Feike 1:e567b2f1aebf 207 //
Feike 1:e567b2f1aebf 208 // We consider counter clockwise rotation to be "forward" and
Feike 1:e567b2f1aebf 209 // counter clockwise to be "backward". Therefore pulse count will increase
Feike 1:e567b2f1aebf 210 // during counter clockwise rotation and decrease during clockwise rotation.
Feike 1:e567b2f1aebf 211 //
Feike 1:e567b2f1aebf 212 // +-------------+
Feike 1:e567b2f1aebf 213 // | X4 Encoding |
Feike 1:e567b2f1aebf 214 // +-------------+
Feike 1:e567b2f1aebf 215 //
Feike 1:e567b2f1aebf 216 // There are four possible states for a quadrature encoder which correspond to
Feike 1:e567b2f1aebf 217 // 2-bit gray code.
Feike 1:e567b2f1aebf 218 //
Feike 1:e567b2f1aebf 219 // A state change is only valid if of only one bit has changed.
Feike 1:e567b2f1aebf 220 // A state change is invalid if both bits have changed.
Feike 1:e567b2f1aebf 221 //
Feike 1:e567b2f1aebf 222 // Clockwise Rotation ->
Feike 1:e567b2f1aebf 223 //
Feike 1:e567b2f1aebf 224 // 00 01 11 10 00
Feike 1:e567b2f1aebf 225 //
Feike 1:e567b2f1aebf 226 // <- Counter Clockwise Rotation
Feike 1:e567b2f1aebf 227 //
Feike 1:e567b2f1aebf 228 // If we observe any valid state changes going from left to right, we have
Feike 1:e567b2f1aebf 229 // moved one pulse clockwise [we will consider this "backward" or "negative"].
Feike 1:e567b2f1aebf 230 //
Feike 1:e567b2f1aebf 231 // If we observe any valid state changes going from right to left we have
Feike 1:e567b2f1aebf 232 // moved one pulse counter clockwise [we will consider this "forward" or
Feike 1:e567b2f1aebf 233 // "positive"].
Feike 1:e567b2f1aebf 234 //
Feike 1:e567b2f1aebf 235 // We might enter an invalid state for a number of reasons which are hard to
Feike 1:e567b2f1aebf 236 // predict - if this is the case, it is generally safe to ignore it, update
Feike 1:e567b2f1aebf 237 // the state and carry on, with the error correcting itself shortly after.
Feike 1:e567b2f1aebf 238 void QEI1::encode(void) {
Feike 1:e567b2f1aebf 239
Feike 1:e567b2f1aebf 240 int change = 0;
Feike 1:e567b2f1aebf 241 int chanA = channelA_.read();
Feike 1:e567b2f1aebf 242 int chanB = channelB_.read();
Feike 1:e567b2f1aebf 243
Feike 1:e567b2f1aebf 244 //2-bit state.
Feike 1:e567b2f1aebf 245 currState_ = (chanA << 1) | (chanB);
Feike 1:e567b2f1aebf 246
Feike 1:e567b2f1aebf 247 if (encoding_ == X2_ENCODING) {
Feike 1:e567b2f1aebf 248
Feike 1:e567b2f1aebf 249 //11->00->11->00 is counter clockwise rotation or "forward".
Feike 1:e567b2f1aebf 250 if ((prevState_ == 0x3 && currState_ == 0x0) ||
Feike 1:e567b2f1aebf 251 (prevState_ == 0x0 && currState_ == 0x3)) {
Feike 1:e567b2f1aebf 252
Feike 1:e567b2f1aebf 253 pulses_++;
Feike 1:e567b2f1aebf 254
Feike 1:e567b2f1aebf 255 }
Feike 1:e567b2f1aebf 256 //10->01->10->01 is clockwise rotation or "backward".
Feike 1:e567b2f1aebf 257 else if ((prevState_ == 0x2 && currState_ == 0x1) ||
Feike 1:e567b2f1aebf 258 (prevState_ == 0x1 && currState_ == 0x2)) {
Feike 1:e567b2f1aebf 259
Feike 1:e567b2f1aebf 260 pulses_--;
Feike 1:e567b2f1aebf 261
Feike 1:e567b2f1aebf 262 }
Feike 1:e567b2f1aebf 263
Feike 1:e567b2f1aebf 264 } else if (encoding_ == X4_ENCODING) {
Feike 1:e567b2f1aebf 265
Feike 1:e567b2f1aebf 266 //Entered a new valid state.
Feike 1:e567b2f1aebf 267 if (((currState_ ^ prevState_) != INVALID) && (currState_ != prevState_)) {
Feike 1:e567b2f1aebf 268 //2 bit state. Right hand bit of prev XOR left hand bit of current
Feike 1:e567b2f1aebf 269 //gives 0 if clockwise rotation and 1 if counter clockwise rotation.
Feike 1:e567b2f1aebf 270 change = (prevState_ & PREV_MASK) ^ ((currState_ & CURR_MASK) >> 1);
Feike 1:e567b2f1aebf 271
Feike 1:e567b2f1aebf 272 if (change == 0) {
Feike 1:e567b2f1aebf 273 change = -1;
Feike 1:e567b2f1aebf 274 }
Feike 1:e567b2f1aebf 275
Feike 1:e567b2f1aebf 276 pulses_ -= change;
Feike 1:e567b2f1aebf 277 }
Feike 1:e567b2f1aebf 278
Feike 1:e567b2f1aebf 279 }
Feike 1:e567b2f1aebf 280
Feike 1:e567b2f1aebf 281 prevState_ = currState_;
Feike 1:e567b2f1aebf 282
Feike 1:e567b2f1aebf 283 }
Feike 1:e567b2f1aebf 284
Feike 1:e567b2f1aebf 285 void QEI1::index(void) {
Feike 1:e567b2f1aebf 286
Feike 1:e567b2f1aebf 287 revolutions_++;
Feike 1:e567b2f1aebf 288
Feike 1:e567b2f1aebf 289 }