Geo Electronics "Show2Me" / Mbed 2 deprecated GEO_SHOW2ME_F411RE

Show2Me control FW, initial shared version

Dependencies:   SDFileSystem_HelloWorld mbed FATFileSystem

Fork of 000_GEO_SHOW2ME_OK_F411RE by Walter Trovo

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QEI/QEI.cpp@2:bbc3e860fa3d, 2018-02-13 (annotated)

Committer:
walter76
Date:
Tue Feb 13 08:22:23 2018 +0000
Revision:
2:bbc3e860fa3d
Preliminary version used to test all HW sections

Who changed what in which revision?

UserRevisionLine numberNew contents of line
walter76 2:bbc3e860fa3d 1 /**
walter76 2:bbc3e860fa3d 2 * @author Aaron Berk
walter76 2:bbc3e860fa3d 3 *
walter76 2:bbc3e860fa3d 4 * @section LICENSE
walter76 2:bbc3e860fa3d 5 *
walter76 2:bbc3e860fa3d 6 * Copyright (c) 2010 ARM Limited
walter76 2:bbc3e860fa3d 7 *
walter76 2:bbc3e860fa3d 8 * Permission is hereby granted, free of charge, to any person obtaining a copy
walter76 2:bbc3e860fa3d 9 * of this software and associated documentation files (the "Software"), to deal
walter76 2:bbc3e860fa3d 10 * in the Software without restriction, including without limitation the rights
walter76 2:bbc3e860fa3d 11 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
walter76 2:bbc3e860fa3d 12 * copies of the Software, and to permit persons to whom the Software is
walter76 2:bbc3e860fa3d 13 * furnished to do so, subject to the following conditions:
walter76 2:bbc3e860fa3d 14 *
walter76 2:bbc3e860fa3d 15 * The above copyright notice and this permission notice shall be included in
walter76 2:bbc3e860fa3d 16 * all copies or substantial portions of the Software.
walter76 2:bbc3e860fa3d 17 *
walter76 2:bbc3e860fa3d 18 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
walter76 2:bbc3e860fa3d 19 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
walter76 2:bbc3e860fa3d 20 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
walter76 2:bbc3e860fa3d 21 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
walter76 2:bbc3e860fa3d 22 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
walter76 2:bbc3e860fa3d 23 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
walter76 2:bbc3e860fa3d 24 * THE SOFTWARE.
walter76 2:bbc3e860fa3d 25 *
walter76 2:bbc3e860fa3d 26 * @section DESCRIPTION
walter76 2:bbc3e860fa3d 27 *
walter76 2:bbc3e860fa3d 28 * Quadrature Encoder Interface.
walter76 2:bbc3e860fa3d 29 *
walter76 2:bbc3e860fa3d 30 * A quadrature encoder consists of two code tracks on a disc which are 90
walter76 2:bbc3e860fa3d 31 * degrees out of phase. It can be used to determine how far a wheel has
walter76 2:bbc3e860fa3d 32 * rotated, relative to a known starting position.
walter76 2:bbc3e860fa3d 33 *
walter76 2:bbc3e860fa3d 34 * Only one code track changes at a time leading to a more robust system than
walter76 2:bbc3e860fa3d 35 * a single track, because any jitter around any edge won't cause a state
walter76 2:bbc3e860fa3d 36 * change as the other track will remain constant.
walter76 2:bbc3e860fa3d 37 *
walter76 2:bbc3e860fa3d 38 * Encoders can be a homebrew affair, consisting of infrared emitters/receivers
walter76 2:bbc3e860fa3d 39 * and paper code tracks consisting of alternating black and white sections;
walter76 2:bbc3e860fa3d 40 * alternatively, complete disk and PCB emitter/receiver encoder systems can
walter76 2:bbc3e860fa3d 41 * be bought, but the interface, regardless of implementation is the same.
walter76 2:bbc3e860fa3d 42 *
walter76 2:bbc3e860fa3d 43 * +-----+ +-----+ +-----+
walter76 2:bbc3e860fa3d 44 * Channel A | ^ | | | | |
walter76 2:bbc3e860fa3d 45 * ---+ ^ +-----+ +-----+ +-----
walter76 2:bbc3e860fa3d 46 * ^ ^
walter76 2:bbc3e860fa3d 47 * ^ +-----+ +-----+ +-----+
walter76 2:bbc3e860fa3d 48 * Channel B ^ | | | | | |
walter76 2:bbc3e860fa3d 49 * ------+ +-----+ +-----+ +-----
walter76 2:bbc3e860fa3d 50 * ^ ^
walter76 2:bbc3e860fa3d 51 * ^ ^
walter76 2:bbc3e860fa3d 52 * 90deg
walter76 2:bbc3e860fa3d 53 *
walter76 2:bbc3e860fa3d 54 * The interface uses X2 encoding by default which calculates the pulse count
walter76 2:bbc3e860fa3d 55 * based on reading the current state after each rising and falling edge of
walter76 2:bbc3e860fa3d 56 * channel A.
walter76 2:bbc3e860fa3d 57 *
walter76 2:bbc3e860fa3d 58 * +-----+ +-----+ +-----+
walter76 2:bbc3e860fa3d 59 * Channel A | | | | | |
walter76 2:bbc3e860fa3d 60 * ---+ +-----+ +-----+ +-----
walter76 2:bbc3e860fa3d 61 * ^ ^ ^ ^ ^
walter76 2:bbc3e860fa3d 62 * ^ +-----+ ^ +-----+ ^ +-----+
walter76 2:bbc3e860fa3d 63 * Channel B ^ | ^ | ^ | ^ | ^ | |
walter76 2:bbc3e860fa3d 64 * ------+ ^ +-----+ ^ +-----+ +--
walter76 2:bbc3e860fa3d 65 * ^ ^ ^ ^ ^
walter76 2:bbc3e860fa3d 66 * ^ ^ ^ ^ ^
walter76 2:bbc3e860fa3d 67 * Pulse count 0 1 2 3 4 5 ...
walter76 2:bbc3e860fa3d 68 *
walter76 2:bbc3e860fa3d 69 * This interface can also use X4 encoding which calculates the pulse count
walter76 2:bbc3e860fa3d 70 * based on reading the current state after each rising and falling edge of
walter76 2:bbc3e860fa3d 71 * either channel.
walter76 2:bbc3e860fa3d 72 *
walter76 2:bbc3e860fa3d 73 * +-----+ +-----+ +-----+
walter76 2:bbc3e860fa3d 74 * Channel A | | | | | |
walter76 2:bbc3e860fa3d 75 * ---+ +-----+ +-----+ +-----
walter76 2:bbc3e860fa3d 76 * ^ ^ ^ ^ ^
walter76 2:bbc3e860fa3d 77 * ^ +-----+ ^ +-----+ ^ +-----+
walter76 2:bbc3e860fa3d 78 * Channel B ^ | ^ | ^ | ^ | ^ | |
walter76 2:bbc3e860fa3d 79 * ------+ ^ +-----+ ^ +-----+ +--
walter76 2:bbc3e860fa3d 80 * ^ ^ ^ ^ ^ ^ ^ ^ ^ ^
walter76 2:bbc3e860fa3d 81 * ^ ^ ^ ^ ^ ^ ^ ^ ^ ^
walter76 2:bbc3e860fa3d 82 * Pulse count 0 1 2 3 4 5 6 7 8 9 ...
walter76 2:bbc3e860fa3d 83 *
walter76 2:bbc3e860fa3d 84 * It defaults
walter76 2:bbc3e860fa3d 85 *
walter76 2:bbc3e860fa3d 86 * An optional index channel can be used which determines when a full
walter76 2:bbc3e860fa3d 87 * revolution has occured.
walter76 2:bbc3e860fa3d 88 *
walter76 2:bbc3e860fa3d 89 * If a 4 pules per revolution encoder was used, with X4 encoding,
walter76 2:bbc3e860fa3d 90 * the following would be observed.
walter76 2:bbc3e860fa3d 91 *
walter76 2:bbc3e860fa3d 92 * +-----+ +-----+ +-----+
walter76 2:bbc3e860fa3d 93 * Channel A | | | | | |
walter76 2:bbc3e860fa3d 94 * ---+ +-----+ +-----+ +-----
walter76 2:bbc3e860fa3d 95 * ^ ^ ^ ^ ^
walter76 2:bbc3e860fa3d 96 * ^ +-----+ ^ +-----+ ^ +-----+
walter76 2:bbc3e860fa3d 97 * Channel B ^ | ^ | ^ | ^ | ^ | |
walter76 2:bbc3e860fa3d 98 * ------+ ^ +-----+ ^ +-----+ +--
walter76 2:bbc3e860fa3d 99 * ^ ^ ^ ^ ^ ^ ^ ^ ^ ^
walter76 2:bbc3e860fa3d 100 * ^ ^ ^ ^ ^ ^ ^ ^ ^ ^
walter76 2:bbc3e860fa3d 101 * ^ ^ ^ +--+ ^ ^ +--+ ^
walter76 2:bbc3e860fa3d 102 * ^ ^ ^ | | ^ ^ | | ^
walter76 2:bbc3e860fa3d 103 * Index ------------+ +--------+ +-----------
walter76 2:bbc3e860fa3d 104 * ^ ^ ^ ^ ^ ^ ^ ^ ^ ^
walter76 2:bbc3e860fa3d 105 * Pulse count 0 1 2 3 4 5 6 7 8 9 ...
walter76 2:bbc3e860fa3d 106 * Rev. count 0 1 2
walter76 2:bbc3e860fa3d 107 *
walter76 2:bbc3e860fa3d 108 * Rotational position in degrees can be calculated by:
walter76 2:bbc3e860fa3d 109 *
walter76 2:bbc3e860fa3d 110 * (pulse count / X * N) * 360
walter76 2:bbc3e860fa3d 111 *
walter76 2:bbc3e860fa3d 112 * Where X is the encoding type [e.g. X4 encoding => X=4], and N is the number
walter76 2:bbc3e860fa3d 113 * of pulses per revolution.
walter76 2:bbc3e860fa3d 114 *
walter76 2:bbc3e860fa3d 115 * Linear position can be calculated by:
walter76 2:bbc3e860fa3d 116 *
walter76 2:bbc3e860fa3d 117 * (pulse count / X * N) * (1 / PPI)
walter76 2:bbc3e860fa3d 118 *
walter76 2:bbc3e860fa3d 119 * Where X is encoding type [e.g. X4 encoding => X=44], N is the number of
walter76 2:bbc3e860fa3d 120 * pulses per revolution, and PPI is pulses per inch, or the equivalent for
walter76 2:bbc3e860fa3d 121 * any other unit of displacement. PPI can be calculated by taking the
walter76 2:bbc3e860fa3d 122 * circumference of the wheel or encoder disk and dividing it by the number
walter76 2:bbc3e860fa3d 123 * of pulses per revolution.
walter76 2:bbc3e860fa3d 124 */
walter76 2:bbc3e860fa3d 125
walter76 2:bbc3e860fa3d 126 /**
walter76 2:bbc3e860fa3d 127 * Includes
walter76 2:bbc3e860fa3d 128 */
walter76 2:bbc3e860fa3d 129 #include "QEI.h"
walter76 2:bbc3e860fa3d 130
walter76 2:bbc3e860fa3d 131 QEI::QEI(PinName channelA,
walter76 2:bbc3e860fa3d 132 PinName channelB,
walter76 2:bbc3e860fa3d 133 PinName index,
walter76 2:bbc3e860fa3d 134 int pulsesPerRev,
walter76 2:bbc3e860fa3d 135 Encoding encoding) : channelA_(channelA), channelB_(channelB),
walter76 2:bbc3e860fa3d 136 index_(index) {
walter76 2:bbc3e860fa3d 137
walter76 2:bbc3e860fa3d 138 pulses_ = 0;
walter76 2:bbc3e860fa3d 139 revolutions_ = 0;
walter76 2:bbc3e860fa3d 140 pulsesPerRev_ = pulsesPerRev;
walter76 2:bbc3e860fa3d 141 encoding_ = encoding;
walter76 2:bbc3e860fa3d 142
walter76 2:bbc3e860fa3d 143 //Workout what the current state is.
walter76 2:bbc3e860fa3d 144 int chanA = channelA_.read();
walter76 2:bbc3e860fa3d 145 int chanB = channelB_.read();
walter76 2:bbc3e860fa3d 146
walter76 2:bbc3e860fa3d 147 //2-bit state.
walter76 2:bbc3e860fa3d 148 currState_ = (chanA << 1) | (chanB);
walter76 2:bbc3e860fa3d 149 prevState_ = currState_;
walter76 2:bbc3e860fa3d 150
walter76 2:bbc3e860fa3d 151 //X2 encoding uses interrupts on only channel A.
walter76 2:bbc3e860fa3d 152 //X4 encoding uses interrupts on channel A,
walter76 2:bbc3e860fa3d 153 //and on channel B.
walter76 2:bbc3e860fa3d 154 channelA_.rise(this, &QEI::encode);
walter76 2:bbc3e860fa3d 155 channelA_.fall(this, &QEI::encode);
walter76 2:bbc3e860fa3d 156
walter76 2:bbc3e860fa3d 157 //If we're using X4 encoding, then attach interrupts to channel B too.
walter76 2:bbc3e860fa3d 158 if (encoding == X4_ENCODING) {
walter76 2:bbc3e860fa3d 159 channelB_.rise(this, &QEI::encode);
walter76 2:bbc3e860fa3d 160 channelB_.fall(this, &QEI::encode);
walter76 2:bbc3e860fa3d 161 }
walter76 2:bbc3e860fa3d 162 //Index is optional.
walter76 2:bbc3e860fa3d 163 if (index != NC) {
walter76 2:bbc3e860fa3d 164 index_.rise(this, &QEI::index);
walter76 2:bbc3e860fa3d 165 }
walter76 2:bbc3e860fa3d 166
walter76 2:bbc3e860fa3d 167 }
walter76 2:bbc3e860fa3d 168
walter76 2:bbc3e860fa3d 169 void QEI::reset(void) {
walter76 2:bbc3e860fa3d 170
walter76 2:bbc3e860fa3d 171 pulses_ = 0;
walter76 2:bbc3e860fa3d 172 revolutions_ = 0;
walter76 2:bbc3e860fa3d 173
walter76 2:bbc3e860fa3d 174 }
walter76 2:bbc3e860fa3d 175
walter76 2:bbc3e860fa3d 176 int QEI::getCurrentState(void) {
walter76 2:bbc3e860fa3d 177
walter76 2:bbc3e860fa3d 178 return currState_;
walter76 2:bbc3e860fa3d 179
walter76 2:bbc3e860fa3d 180 }
walter76 2:bbc3e860fa3d 181
walter76 2:bbc3e860fa3d 182 int QEI::getPulses(void) {
walter76 2:bbc3e860fa3d 183
walter76 2:bbc3e860fa3d 184 return pulses_;
walter76 2:bbc3e860fa3d 185
walter76 2:bbc3e860fa3d 186 }
walter76 2:bbc3e860fa3d 187
walter76 2:bbc3e860fa3d 188 int QEI::getRevolutions(void) {
walter76 2:bbc3e860fa3d 189
walter76 2:bbc3e860fa3d 190 return revolutions_;
walter76 2:bbc3e860fa3d 191
walter76 2:bbc3e860fa3d 192 }
walter76 2:bbc3e860fa3d 193
walter76 2:bbc3e860fa3d 194 // +-------------+
walter76 2:bbc3e860fa3d 195 // | X2 Encoding |
walter76 2:bbc3e860fa3d 196 // +-------------+
walter76 2:bbc3e860fa3d 197 //
walter76 2:bbc3e860fa3d 198 // When observing states two patterns will appear:
walter76 2:bbc3e860fa3d 199 //
walter76 2:bbc3e860fa3d 200 // Counter clockwise rotation:
walter76 2:bbc3e860fa3d 201 //
walter76 2:bbc3e860fa3d 202 // 10 -> 01 -> 10 -> 01 -> ...
walter76 2:bbc3e860fa3d 203 //
walter76 2:bbc3e860fa3d 204 // Clockwise rotation:
walter76 2:bbc3e860fa3d 205 //
walter76 2:bbc3e860fa3d 206 // 11 -> 00 -> 11 -> 00 -> ...
walter76 2:bbc3e860fa3d 207 //
walter76 2:bbc3e860fa3d 208 // We consider counter clockwise rotation to be "forward" and
walter76 2:bbc3e860fa3d 209 // counter clockwise to be "backward". Therefore pulse count will increase
walter76 2:bbc3e860fa3d 210 // during counter clockwise rotation and decrease during clockwise rotation.
walter76 2:bbc3e860fa3d 211 //
walter76 2:bbc3e860fa3d 212 // +-------------+
walter76 2:bbc3e860fa3d 213 // | X4 Encoding |
walter76 2:bbc3e860fa3d 214 // +-------------+
walter76 2:bbc3e860fa3d 215 //
walter76 2:bbc3e860fa3d 216 // There are four possible states for a quadrature encoder which correspond to
walter76 2:bbc3e860fa3d 217 // 2-bit gray code.
walter76 2:bbc3e860fa3d 218 //
walter76 2:bbc3e860fa3d 219 // A state change is only valid if of only one bit has changed.
walter76 2:bbc3e860fa3d 220 // A state change is invalid if both bits have changed.
walter76 2:bbc3e860fa3d 221 //
walter76 2:bbc3e860fa3d 222 // Clockwise Rotation ->
walter76 2:bbc3e860fa3d 223 //
walter76 2:bbc3e860fa3d 224 // 00 01 11 10 00
walter76 2:bbc3e860fa3d 225 //
walter76 2:bbc3e860fa3d 226 // <- Counter Clockwise Rotation
walter76 2:bbc3e860fa3d 227 //
walter76 2:bbc3e860fa3d 228 // If we observe any valid state changes going from left to right, we have
walter76 2:bbc3e860fa3d 229 // moved one pulse clockwise [we will consider this "backward" or "negative"].
walter76 2:bbc3e860fa3d 230 //
walter76 2:bbc3e860fa3d 231 // If we observe any valid state changes going from right to left we have
walter76 2:bbc3e860fa3d 232 // moved one pulse counter clockwise [we will consider this "forward" or
walter76 2:bbc3e860fa3d 233 // "positive"].
walter76 2:bbc3e860fa3d 234 //
walter76 2:bbc3e860fa3d 235 // We might enter an invalid state for a number of reasons which are hard to
walter76 2:bbc3e860fa3d 236 // predict - if this is the case, it is generally safe to ignore it, update
walter76 2:bbc3e860fa3d 237 // the state and carry on, with the error correcting itself shortly after.
walter76 2:bbc3e860fa3d 238 void QEI::encode(void) {
walter76 2:bbc3e860fa3d 239
walter76 2:bbc3e860fa3d 240 int change = 0;
walter76 2:bbc3e860fa3d 241 int chanA = channelA_.read();
walter76 2:bbc3e860fa3d 242 int chanB = channelB_.read();
walter76 2:bbc3e860fa3d 243
walter76 2:bbc3e860fa3d 244 //2-bit state.
walter76 2:bbc3e860fa3d 245 currState_ = (chanA << 1) | (chanB);
walter76 2:bbc3e860fa3d 246
walter76 2:bbc3e860fa3d 247 if (encoding_ == X2_ENCODING) {
walter76 2:bbc3e860fa3d 248
walter76 2:bbc3e860fa3d 249 //11->00->11->00 is counter clockwise rotation or "forward".
walter76 2:bbc3e860fa3d 250 if ((prevState_ == 0x3 && currState_ == 0x0) ||
walter76 2:bbc3e860fa3d 251 (prevState_ == 0x0 && currState_ == 0x3)) {
walter76 2:bbc3e860fa3d 252
walter76 2:bbc3e860fa3d 253 pulses_++;
walter76 2:bbc3e860fa3d 254
walter76 2:bbc3e860fa3d 255 }
walter76 2:bbc3e860fa3d 256 //10->01->10->01 is clockwise rotation or "backward".
walter76 2:bbc3e860fa3d 257 else if ((prevState_ == 0x2 && currState_ == 0x1) ||
walter76 2:bbc3e860fa3d 258 (prevState_ == 0x1 && currState_ == 0x2)) {
walter76 2:bbc3e860fa3d 259
walter76 2:bbc3e860fa3d 260 pulses_--;
walter76 2:bbc3e860fa3d 261
walter76 2:bbc3e860fa3d 262 }
walter76 2:bbc3e860fa3d 263
walter76 2:bbc3e860fa3d 264 } else if (encoding_ == X4_ENCODING) {
walter76 2:bbc3e860fa3d 265
walter76 2:bbc3e860fa3d 266 //Entered a new valid state.
walter76 2:bbc3e860fa3d 267 if (((currState_ ^ prevState_) != INVALID) && (currState_ != prevState_)) {
walter76 2:bbc3e860fa3d 268 //2 bit state. Right hand bit of prev XOR left hand bit of current
walter76 2:bbc3e860fa3d 269 //gives 0 if clockwise rotation and 1 if counter clockwise rotation.
walter76 2:bbc3e860fa3d 270 change = (prevState_ & PREV_MASK) ^ ((currState_ & CURR_MASK) >> 1);
walter76 2:bbc3e860fa3d 271
walter76 2:bbc3e860fa3d 272 if (change == 0) {
walter76 2:bbc3e860fa3d 273 change = -1;
walter76 2:bbc3e860fa3d 274 }
walter76 2:bbc3e860fa3d 275
walter76 2:bbc3e860fa3d 276 pulses_ -= change;
walter76 2:bbc3e860fa3d 277 }
walter76 2:bbc3e860fa3d 278
walter76 2:bbc3e860fa3d 279 }
walter76 2:bbc3e860fa3d 280
walter76 2:bbc3e860fa3d 281 prevState_ = currState_;
walter76 2:bbc3e860fa3d 282
walter76 2:bbc3e860fa3d 283 }
walter76 2:bbc3e860fa3d 284
walter76 2:bbc3e860fa3d 285 void QEI::index(void) {
walter76 2:bbc3e860fa3d 286
walter76 2:bbc3e860fa3d 287 revolutions_++;
walter76 2:bbc3e860fa3d 288
walter76 2:bbc3e860fa3d 289 }