quadcopter cufe / Mbed 2 deprecated FollowWall2

Go to goal robot with follow wall algo

Dependencies:   mbed

QEI/QEI.cpp@0:efef62b55c86, 2014-04-08 (annotated)

Committer:
khaledelmadawi
Date:
Tue Apr 08 13:21:17 2014 +0000
Revision:
0:efef62b55c86
Follow wall

Who changed what in which revision?

UserRevisionLine numberNew contents of line
khaledelmadawi 0:efef62b55c86 1 /**
khaledelmadawi 0:efef62b55c86 2 * @author Aaron Berk
khaledelmadawi 0:efef62b55c86 3 *
khaledelmadawi 0:efef62b55c86 4 * @section LICENSE
khaledelmadawi 0:efef62b55c86 5 *
khaledelmadawi 0:efef62b55c86 6 * Copyright (c) 2010 ARM Limited
khaledelmadawi 0:efef62b55c86 7 *
khaledelmadawi 0:efef62b55c86 8 * Permission is hereby granted, free of charge, to any person obtaining a copy
khaledelmadawi 0:efef62b55c86 9 * of this software and associated documentation files (the "Software"), to deal
khaledelmadawi 0:efef62b55c86 10 * in the Software without restriction, including without limitation the rights
khaledelmadawi 0:efef62b55c86 11 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
khaledelmadawi 0:efef62b55c86 12 * copies of the Software, and to permit persons to whom the Software is
khaledelmadawi 0:efef62b55c86 13 * furnished to do so, subject to the following conditions:
khaledelmadawi 0:efef62b55c86 14 *
khaledelmadawi 0:efef62b55c86 15 * The above copyright notice and this permission notice shall be included in
khaledelmadawi 0:efef62b55c86 16 * all copies or substantial portions of the Software.
khaledelmadawi 0:efef62b55c86 17 *
khaledelmadawi 0:efef62b55c86 18 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
khaledelmadawi 0:efef62b55c86 19 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
khaledelmadawi 0:efef62b55c86 20 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
khaledelmadawi 0:efef62b55c86 21 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
khaledelmadawi 0:efef62b55c86 22 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
khaledelmadawi 0:efef62b55c86 23 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
khaledelmadawi 0:efef62b55c86 24 * THE SOFTWARE.
khaledelmadawi 0:efef62b55c86 25 *
khaledelmadawi 0:efef62b55c86 26 * @section DESCRIPTION
khaledelmadawi 0:efef62b55c86 27 *
khaledelmadawi 0:efef62b55c86 28 * Quadrature Encoder Interface.
khaledelmadawi 0:efef62b55c86 29 *
khaledelmadawi 0:efef62b55c86 30 * A quadrature encoder consists of two code tracks on a disc which are 90
khaledelmadawi 0:efef62b55c86 31 * degrees out of phase. It can be used to determine how far a wheel has
khaledelmadawi 0:efef62b55c86 32 * rotated, relative to a known starting position.
khaledelmadawi 0:efef62b55c86 33 *
khaledelmadawi 0:efef62b55c86 34 * Only one code track changes at a time leading to a more robust system than
khaledelmadawi 0:efef62b55c86 35 * a single track, because any jitter around any edge won't cause a state
khaledelmadawi 0:efef62b55c86 36 * change as the other track will remain constant.
khaledelmadawi 0:efef62b55c86 37 *
khaledelmadawi 0:efef62b55c86 38 * Encoders can be a homebrew affair, consisting of infrared emitters/receivers
khaledelmadawi 0:efef62b55c86 39 * and paper code tracks consisting of alternating black and white sections;
khaledelmadawi 0:efef62b55c86 40 * alternatively, complete disk and PCB emitter/receiver encoder systems can
khaledelmadawi 0:efef62b55c86 41 * be bought, but the interface, regardless of implementation is the same.
khaledelmadawi 0:efef62b55c86 42 *
khaledelmadawi 0:efef62b55c86 43 * +-----+ +-----+ +-----+
khaledelmadawi 0:efef62b55c86 44 * Channel A | ^ | | | | |
khaledelmadawi 0:efef62b55c86 45 * ---+ ^ +-----+ +-----+ +-----
khaledelmadawi 0:efef62b55c86 46 * ^ ^
khaledelmadawi 0:efef62b55c86 47 * ^ +-----+ +-----+ +-----+
khaledelmadawi 0:efef62b55c86 48 * Channel B ^ | | | | | |
khaledelmadawi 0:efef62b55c86 49 * ------+ +-----+ +-----+ +-----
khaledelmadawi 0:efef62b55c86 50 * ^ ^
khaledelmadawi 0:efef62b55c86 51 * ^ ^
khaledelmadawi 0:efef62b55c86 52 * 90deg
khaledelmadawi 0:efef62b55c86 53 *
khaledelmadawi 0:efef62b55c86 54 * The interface uses X2 encoding by default which calculates the pulse count
khaledelmadawi 0:efef62b55c86 55 * based on reading the current state after each rising and falling edge of
khaledelmadawi 0:efef62b55c86 56 * channel A.
khaledelmadawi 0:efef62b55c86 57 *
khaledelmadawi 0:efef62b55c86 58 * +-----+ +-----+ +-----+
khaledelmadawi 0:efef62b55c86 59 * Channel A | | | | | |
khaledelmadawi 0:efef62b55c86 60 * ---+ +-----+ +-----+ +-----
khaledelmadawi 0:efef62b55c86 61 * ^ ^ ^ ^ ^
khaledelmadawi 0:efef62b55c86 62 * ^ +-----+ ^ +-----+ ^ +-----+
khaledelmadawi 0:efef62b55c86 63 * Channel B ^ | ^ | ^ | ^ | ^ | |
khaledelmadawi 0:efef62b55c86 64 * ------+ ^ +-----+ ^ +-----+ +--
khaledelmadawi 0:efef62b55c86 65 * ^ ^ ^ ^ ^
khaledelmadawi 0:efef62b55c86 66 * ^ ^ ^ ^ ^
khaledelmadawi 0:efef62b55c86 67 * Pulse count 0 1 2 3 4 5 ...
khaledelmadawi 0:efef62b55c86 68 *
khaledelmadawi 0:efef62b55c86 69 * This interface can also use X4 encoding which calculates the pulse count
khaledelmadawi 0:efef62b55c86 70 * based on reading the current state after each rising and falling edge of
khaledelmadawi 0:efef62b55c86 71 * either channel.
khaledelmadawi 0:efef62b55c86 72 *
khaledelmadawi 0:efef62b55c86 73 * +-----+ +-----+ +-----+
khaledelmadawi 0:efef62b55c86 74 * Channel A | | | | | |
khaledelmadawi 0:efef62b55c86 75 * ---+ +-----+ +-----+ +-----
khaledelmadawi 0:efef62b55c86 76 * ^ ^ ^ ^ ^
khaledelmadawi 0:efef62b55c86 77 * ^ +-----+ ^ +-----+ ^ +-----+
khaledelmadawi 0:efef62b55c86 78 * Channel B ^ | ^ | ^ | ^ | ^ | |
khaledelmadawi 0:efef62b55c86 79 * ------+ ^ +-----+ ^ +-----+ +--
khaledelmadawi 0:efef62b55c86 80 * ^ ^ ^ ^ ^ ^ ^ ^ ^ ^
khaledelmadawi 0:efef62b55c86 81 * ^ ^ ^ ^ ^ ^ ^ ^ ^ ^
khaledelmadawi 0:efef62b55c86 82 * Pulse count 0 1 2 3 4 5 6 7 8 9 ...
khaledelmadawi 0:efef62b55c86 83 *
khaledelmadawi 0:efef62b55c86 84 * It defaults
khaledelmadawi 0:efef62b55c86 85 *
khaledelmadawi 0:efef62b55c86 86 * An optional index channel can be used which determines when a full
khaledelmadawi 0:efef62b55c86 87 * revolution has occured.
khaledelmadawi 0:efef62b55c86 88 *
khaledelmadawi 0:efef62b55c86 89 * If a 4 pules per revolution encoder was used, with X4 encoding,
khaledelmadawi 0:efef62b55c86 90 * the following would be observed.
khaledelmadawi 0:efef62b55c86 91 *
khaledelmadawi 0:efef62b55c86 92 * +-----+ +-----+ +-----+
khaledelmadawi 0:efef62b55c86 93 * Channel A | | | | | |
khaledelmadawi 0:efef62b55c86 94 * ---+ +-----+ +-----+ +-----
khaledelmadawi 0:efef62b55c86 95 * ^ ^ ^ ^ ^
khaledelmadawi 0:efef62b55c86 96 * ^ +-----+ ^ +-----+ ^ +-----+
khaledelmadawi 0:efef62b55c86 97 * Channel B ^ | ^ | ^ | ^ | ^ | |
khaledelmadawi 0:efef62b55c86 98 * ------+ ^ +-----+ ^ +-----+ +--
khaledelmadawi 0:efef62b55c86 99 * ^ ^ ^ ^ ^ ^ ^ ^ ^ ^
khaledelmadawi 0:efef62b55c86 100 * ^ ^ ^ ^ ^ ^ ^ ^ ^ ^
khaledelmadawi 0:efef62b55c86 101 * ^ ^ ^ +--+ ^ ^ +--+ ^
khaledelmadawi 0:efef62b55c86 102 * ^ ^ ^ | | ^ ^ | | ^
khaledelmadawi 0:efef62b55c86 103 * Index ------------+ +--------+ +-----------
khaledelmadawi 0:efef62b55c86 104 * ^ ^ ^ ^ ^ ^ ^ ^ ^ ^
khaledelmadawi 0:efef62b55c86 105 * Pulse count 0 1 2 3 4 5 6 7 8 9 ...
khaledelmadawi 0:efef62b55c86 106 * Rev. count 0 1 2
khaledelmadawi 0:efef62b55c86 107 *
khaledelmadawi 0:efef62b55c86 108 * Rotational position in degrees can be calculated by:
khaledelmadawi 0:efef62b55c86 109 *
khaledelmadawi 0:efef62b55c86 110 * (pulse count / X * N) * 360
khaledelmadawi 0:efef62b55c86 111 *
khaledelmadawi 0:efef62b55c86 112 * Where X is the encoding type [e.g. X4 encoding => X=4], and N is the number
khaledelmadawi 0:efef62b55c86 113 * of pulses per revolution.
khaledelmadawi 0:efef62b55c86 114 *
khaledelmadawi 0:efef62b55c86 115 * Linear position can be calculated by:
khaledelmadawi 0:efef62b55c86 116 *
khaledelmadawi 0:efef62b55c86 117 * (pulse count / X * N) * (1 / PPI)
khaledelmadawi 0:efef62b55c86 118 *
khaledelmadawi 0:efef62b55c86 119 * Where X is encoding type [e.g. X4 encoding => X=44], N is the number of
khaledelmadawi 0:efef62b55c86 120 * pulses per revolution, and PPI is pulses per inch, or the equivalent for
khaledelmadawi 0:efef62b55c86 121 * any other unit of displacement. PPI can be calculated by taking the
khaledelmadawi 0:efef62b55c86 122 * circumference of the wheel or encoder disk and dividing it by the number
khaledelmadawi 0:efef62b55c86 123 * of pulses per revolution.
khaledelmadawi 0:efef62b55c86 124 */
khaledelmadawi 0:efef62b55c86 125
khaledelmadawi 0:efef62b55c86 126 /**
khaledelmadawi 0:efef62b55c86 127 * Includes
khaledelmadawi 0:efef62b55c86 128 */
khaledelmadawi 0:efef62b55c86 129 #include "QEI.h"
khaledelmadawi 0:efef62b55c86 130
khaledelmadawi 0:efef62b55c86 131 QEI::QEI(PinName channelA,
khaledelmadawi 0:efef62b55c86 132 PinName channelB,
khaledelmadawi 0:efef62b55c86 133 PinName index,
khaledelmadawi 0:efef62b55c86 134 int pulsesPerRev,
khaledelmadawi 0:efef62b55c86 135 Encoding encoding) : channelA_(channelA), channelB_(channelB),
khaledelmadawi 0:efef62b55c86 136 index_(index) {
khaledelmadawi 0:efef62b55c86 137
khaledelmadawi 0:efef62b55c86 138 pulses_ = 0;
khaledelmadawi 0:efef62b55c86 139 revolutions_ = 0;
khaledelmadawi 0:efef62b55c86 140 pulsesPerRev_ = pulsesPerRev;
khaledelmadawi 0:efef62b55c86 141 encoding_ = encoding;
khaledelmadawi 0:efef62b55c86 142
khaledelmadawi 0:efef62b55c86 143 //Workout what the current state is.
khaledelmadawi 0:efef62b55c86 144 int chanA = channelA_.read();
khaledelmadawi 0:efef62b55c86 145 int chanB = channelB_.read();
khaledelmadawi 0:efef62b55c86 146
khaledelmadawi 0:efef62b55c86 147 //2-bit state.
khaledelmadawi 0:efef62b55c86 148 currState_ = (chanA << 1) | (chanB);
khaledelmadawi 0:efef62b55c86 149 prevState_ = currState_;
khaledelmadawi 0:efef62b55c86 150
khaledelmadawi 0:efef62b55c86 151 //X2 encoding uses interrupts on only channel A.
khaledelmadawi 0:efef62b55c86 152 //X4 encoding uses interrupts on channel A,
khaledelmadawi 0:efef62b55c86 153 //and on channel B.
khaledelmadawi 0:efef62b55c86 154 channelA_.rise(this, &QEI::encode);
khaledelmadawi 0:efef62b55c86 155 channelA_.fall(this, &QEI::encode);
khaledelmadawi 0:efef62b55c86 156
khaledelmadawi 0:efef62b55c86 157 //If we're using X4 encoding, then attach interrupts to channel B too.
khaledelmadawi 0:efef62b55c86 158 if (encoding == X4_ENCODING) {
khaledelmadawi 0:efef62b55c86 159 channelB_.rise(this, &QEI::encode);
khaledelmadawi 0:efef62b55c86 160 channelB_.fall(this, &QEI::encode);
khaledelmadawi 0:efef62b55c86 161 }
khaledelmadawi 0:efef62b55c86 162 //Index is optional.
khaledelmadawi 0:efef62b55c86 163 if (index != NC) {
khaledelmadawi 0:efef62b55c86 164 index_.rise(this, &QEI::index);
khaledelmadawi 0:efef62b55c86 165 }
khaledelmadawi 0:efef62b55c86 166
khaledelmadawi 0:efef62b55c86 167 }
khaledelmadawi 0:efef62b55c86 168
khaledelmadawi 0:efef62b55c86 169 void QEI::reset(void) {
khaledelmadawi 0:efef62b55c86 170
khaledelmadawi 0:efef62b55c86 171 pulses_ = 0;
khaledelmadawi 0:efef62b55c86 172 revolutions_ = 0;
khaledelmadawi 0:efef62b55c86 173
khaledelmadawi 0:efef62b55c86 174 }
khaledelmadawi 0:efef62b55c86 175
khaledelmadawi 0:efef62b55c86 176 int QEI::getCurrentState(void) {
khaledelmadawi 0:efef62b55c86 177
khaledelmadawi 0:efef62b55c86 178 return currState_;
khaledelmadawi 0:efef62b55c86 179
khaledelmadawi 0:efef62b55c86 180 }
khaledelmadawi 0:efef62b55c86 181
khaledelmadawi 0:efef62b55c86 182 int QEI::getPulses(void) {
khaledelmadawi 0:efef62b55c86 183
khaledelmadawi 0:efef62b55c86 184 return pulses_;
khaledelmadawi 0:efef62b55c86 185
khaledelmadawi 0:efef62b55c86 186 }
khaledelmadawi 0:efef62b55c86 187
khaledelmadawi 0:efef62b55c86 188 int QEI::getRevolutions(void) {
khaledelmadawi 0:efef62b55c86 189
khaledelmadawi 0:efef62b55c86 190 return revolutions_;
khaledelmadawi 0:efef62b55c86 191
khaledelmadawi 0:efef62b55c86 192 }
khaledelmadawi 0:efef62b55c86 193
khaledelmadawi 0:efef62b55c86 194 // +-------------+
khaledelmadawi 0:efef62b55c86 195 // | X2 Encoding |
khaledelmadawi 0:efef62b55c86 196 // +-------------+
khaledelmadawi 0:efef62b55c86 197 //
khaledelmadawi 0:efef62b55c86 198 // When observing states two patterns will appear:
khaledelmadawi 0:efef62b55c86 199 //
khaledelmadawi 0:efef62b55c86 200 // Counter clockwise rotation:
khaledelmadawi 0:efef62b55c86 201 //
khaledelmadawi 0:efef62b55c86 202 // 10 -> 01 -> 10 -> 01 -> ...
khaledelmadawi 0:efef62b55c86 203 //
khaledelmadawi 0:efef62b55c86 204 // Clockwise rotation:
khaledelmadawi 0:efef62b55c86 205 //
khaledelmadawi 0:efef62b55c86 206 // 11 -> 00 -> 11 -> 00 -> ...
khaledelmadawi 0:efef62b55c86 207 //
khaledelmadawi 0:efef62b55c86 208 // We consider counter clockwise rotation to be "forward" and
khaledelmadawi 0:efef62b55c86 209 // counter clockwise to be "backward". Therefore pulse count will increase
khaledelmadawi 0:efef62b55c86 210 // during counter clockwise rotation and decrease during clockwise rotation.
khaledelmadawi 0:efef62b55c86 211 //
khaledelmadawi 0:efef62b55c86 212 // +-------------+
khaledelmadawi 0:efef62b55c86 213 // | X4 Encoding |
khaledelmadawi 0:efef62b55c86 214 // +-------------+
khaledelmadawi 0:efef62b55c86 215 //
khaledelmadawi 0:efef62b55c86 216 // There are four possible states for a quadrature encoder which correspond to
khaledelmadawi 0:efef62b55c86 217 // 2-bit gray code.
khaledelmadawi 0:efef62b55c86 218 //
khaledelmadawi 0:efef62b55c86 219 // A state change is only valid if of only one bit has changed.
khaledelmadawi 0:efef62b55c86 220 // A state change is invalid if both bits have changed.
khaledelmadawi 0:efef62b55c86 221 //
khaledelmadawi 0:efef62b55c86 222 // Clockwise Rotation ->
khaledelmadawi 0:efef62b55c86 223 //
khaledelmadawi 0:efef62b55c86 224 // 00 01 11 10 00
khaledelmadawi 0:efef62b55c86 225 //
khaledelmadawi 0:efef62b55c86 226 // <- Counter Clockwise Rotation
khaledelmadawi 0:efef62b55c86 227 //
khaledelmadawi 0:efef62b55c86 228 // If we observe any valid state changes going from left to right, we have
khaledelmadawi 0:efef62b55c86 229 // moved one pulse clockwise [we will consider this "backward" or "negative"].
khaledelmadawi 0:efef62b55c86 230 //
khaledelmadawi 0:efef62b55c86 231 // If we observe any valid state changes going from right to left we have
khaledelmadawi 0:efef62b55c86 232 // moved one pulse counter clockwise [we will consider this "forward" or
khaledelmadawi 0:efef62b55c86 233 // "positive"].
khaledelmadawi 0:efef62b55c86 234 //
khaledelmadawi 0:efef62b55c86 235 // We might enter an invalid state for a number of reasons which are hard to
khaledelmadawi 0:efef62b55c86 236 // predict - if this is the case, it is generally safe to ignore it, update
khaledelmadawi 0:efef62b55c86 237 // the state and carry on, with the error correcting itself shortly after.
khaledelmadawi 0:efef62b55c86 238 void QEI::encode(void) {
khaledelmadawi 0:efef62b55c86 239
khaledelmadawi 0:efef62b55c86 240 int change = 0;
khaledelmadawi 0:efef62b55c86 241 int chanA = channelA_.read();
khaledelmadawi 0:efef62b55c86 242 int chanB = channelB_.read();
khaledelmadawi 0:efef62b55c86 243
khaledelmadawi 0:efef62b55c86 244 //2-bit state.
khaledelmadawi 0:efef62b55c86 245 currState_ = (chanA << 1) | (chanB);
khaledelmadawi 0:efef62b55c86 246
khaledelmadawi 0:efef62b55c86 247 if (encoding_ == X2_ENCODING) {
khaledelmadawi 0:efef62b55c86 248
khaledelmadawi 0:efef62b55c86 249 //11->00->11->00 is counter clockwise rotation or "forward".
khaledelmadawi 0:efef62b55c86 250 if ((prevState_ == 0x3 && currState_ == 0x0) ||
khaledelmadawi 0:efef62b55c86 251 (prevState_ == 0x0 && currState_ == 0x3)) {
khaledelmadawi 0:efef62b55c86 252
khaledelmadawi 0:efef62b55c86 253 pulses_++;
khaledelmadawi 0:efef62b55c86 254
khaledelmadawi 0:efef62b55c86 255 }
khaledelmadawi 0:efef62b55c86 256 //10->01->10->01 is clockwise rotation or "backward".
khaledelmadawi 0:efef62b55c86 257 else if ((prevState_ == 0x2 && currState_ == 0x1) ||
khaledelmadawi 0:efef62b55c86 258 (prevState_ == 0x1 && currState_ == 0x2)) {
khaledelmadawi 0:efef62b55c86 259
khaledelmadawi 0:efef62b55c86 260 pulses_--;
khaledelmadawi 0:efef62b55c86 261
khaledelmadawi 0:efef62b55c86 262 }
khaledelmadawi 0:efef62b55c86 263
khaledelmadawi 0:efef62b55c86 264 } else if (encoding_ == X4_ENCODING) {
khaledelmadawi 0:efef62b55c86 265
khaledelmadawi 0:efef62b55c86 266 //Entered a new valid state.
khaledelmadawi 0:efef62b55c86 267 if (((currState_ ^ prevState_) != INVALID) && (currState_ != prevState_)) {
khaledelmadawi 0:efef62b55c86 268 //2 bit state. Right hand bit of prev XOR left hand bit of current
khaledelmadawi 0:efef62b55c86 269 //gives 0 if clockwise rotation and 1 if counter clockwise rotation.
khaledelmadawi 0:efef62b55c86 270 change = (prevState_ & PREV_MASK) ^ ((currState_ & CURR_MASK) >> 1);
khaledelmadawi 0:efef62b55c86 271
khaledelmadawi 0:efef62b55c86 272 if (change == 0) {
khaledelmadawi 0:efef62b55c86 273 change = -1;
khaledelmadawi 0:efef62b55c86 274 }
khaledelmadawi 0:efef62b55c86 275
khaledelmadawi 0:efef62b55c86 276 pulses_ -= change;
khaledelmadawi 0:efef62b55c86 277 }
khaledelmadawi 0:efef62b55c86 278
khaledelmadawi 0:efef62b55c86 279 }
khaledelmadawi 0:efef62b55c86 280
khaledelmadawi 0:efef62b55c86 281 prevState_ = currState_;
khaledelmadawi 0:efef62b55c86 282
khaledelmadawi 0:efef62b55c86 283 }
khaledelmadawi 0:efef62b55c86 284
khaledelmadawi 0:efef62b55c86 285 void QEI::index(void) {
khaledelmadawi 0:efef62b55c86 286
khaledelmadawi 0:efef62b55c86 287 revolutions_++;
khaledelmadawi 0:efef62b55c86 288
khaledelmadawi 0:efef62b55c86 289 }