Sik Chiu Chow / Mbed 2 deprecated encoder

encoder

Dependencies:   mbed

QEI.h@1:36b9ba5a34ff, 2021-10-31 (annotated)

Committer:
ea78anana
Date:
Sun Oct 31 09:43:58 2021 +0000
Revision:
1:36b9ba5a34ff
Parent:
0:4d7336a951bd 
for 1 encoder

Who changed what in which revision?

UserRevisionLine numberNew contents of line
ea78anana 1:36b9ba5a34ff 1 /**
ea78anana 1:36b9ba5a34ff 2 * @author Aaron Berk
ea78anana 1:36b9ba5a34ff 3 *
ea78anana 1:36b9ba5a34ff 4 * @section LICENSE
ea78anana 1:36b9ba5a34ff 5 *
ea78anana 1:36b9ba5a34ff 6 * Copyright (c) 2010 ARM Limited
ea78anana 1:36b9ba5a34ff 7 *
ea78anana 1:36b9ba5a34ff 8 * Permission is hereby granted, free of charge, to any person obtaining a copy
ea78anana 1:36b9ba5a34ff 9 * of this software and associated documentation files (the "Software"), to deal
ea78anana 1:36b9ba5a34ff 10 * in the Software without restriction, including without limitation the rights
ea78anana 1:36b9ba5a34ff 11 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
ea78anana 1:36b9ba5a34ff 12 * copies of the Software, and to permit persons to whom the Software is
ea78anana 1:36b9ba5a34ff 13 * furnished to do so, subject to the following conditions:
ea78anana 1:36b9ba5a34ff 14 *
ea78anana 1:36b9ba5a34ff 15 * The above copyright notice and this permission notice shall be included in
ea78anana 1:36b9ba5a34ff 16 * all copies or substantial portions of the Software.
ea78anana 1:36b9ba5a34ff 17 *
ea78anana 1:36b9ba5a34ff 18 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
ea78anana 1:36b9ba5a34ff 19 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
ea78anana 1:36b9ba5a34ff 20 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
ea78anana 1:36b9ba5a34ff 21 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
ea78anana 1:36b9ba5a34ff 22 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
ea78anana 1:36b9ba5a34ff 23 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
ea78anana 1:36b9ba5a34ff 24 * THE SOFTWARE.
ea78anana 1:36b9ba5a34ff 25 *
ea78anana 1:36b9ba5a34ff 26 * @section DESCRIPTION
ea78anana 1:36b9ba5a34ff 27 *
ea78anana 1:36b9ba5a34ff 28 * Quadrature Encoder Interface.
ea78anana 1:36b9ba5a34ff 29 *
ea78anana 1:36b9ba5a34ff 30 * A quadrature encoder consists of two code tracks on a disc which are 90
ea78anana 1:36b9ba5a34ff 31 * degrees out of phase. It can be used to determine how far a wheel has
ea78anana 1:36b9ba5a34ff 32 * rotated, relative to a known starting position.
ea78anana 1:36b9ba5a34ff 33 *
ea78anana 1:36b9ba5a34ff 34 * Only one code track changes at a time leading to a more robust system than
ea78anana 1:36b9ba5a34ff 35 * a single track, because any jitter around any edge won't cause a state
ea78anana 1:36b9ba5a34ff 36 * change as the other track will remain constant.
ea78anana 1:36b9ba5a34ff 37 *
ea78anana 1:36b9ba5a34ff 38 * Encoders can be a homebrew affair, consisting of infrared emitters/receivers
ea78anana 1:36b9ba5a34ff 39 * and paper code tracks consisting of alternating black and white sections;
ea78anana 1:36b9ba5a34ff 40 * alternatively, complete disk and PCB emitter/receiver encoder systems can
ea78anana 1:36b9ba5a34ff 41 * be bought, but the interface, regardless of implementation is the same.
ea78anana 1:36b9ba5a34ff 42 *
ea78anana 1:36b9ba5a34ff 43 * +-----+ +-----+ +-----+
ea78anana 1:36b9ba5a34ff 44 * Channel A | ^ | | | | |
ea78anana 1:36b9ba5a34ff 45 * ---+ ^ +-----+ +-----+ +-----
ea78anana 1:36b9ba5a34ff 46 * ^ ^
ea78anana 1:36b9ba5a34ff 47 * ^ +-----+ +-----+ +-----+
ea78anana 1:36b9ba5a34ff 48 * Channel B ^ | | | | | |
ea78anana 1:36b9ba5a34ff 49 * ------+ +-----+ +-----+ +-----
ea78anana 1:36b9ba5a34ff 50 * ^ ^
ea78anana 1:36b9ba5a34ff 51 * ^ ^
ea78anana 1:36b9ba5a34ff 52 * 90deg
ea78anana 1:36b9ba5a34ff 53 *
ea78anana 1:36b9ba5a34ff 54 * The interface uses X2 encoding by default which calculates the pulse count
ea78anana 1:36b9ba5a34ff 55 * based on reading the current state after each rising and falling edge of
ea78anana 1:36b9ba5a34ff 56 * channel A.
ea78anana 1:36b9ba5a34ff 57 *
ea78anana 1:36b9ba5a34ff 58 * +-----+ +-----+ +-----+
ea78anana 1:36b9ba5a34ff 59 * Channel A | | | | | |
ea78anana 1:36b9ba5a34ff 60 * ---+ +-----+ +-----+ +-----
ea78anana 1:36b9ba5a34ff 61 * ^ ^ ^ ^ ^
ea78anana 1:36b9ba5a34ff 62 * ^ +-----+ ^ +-----+ ^ +-----+
ea78anana 1:36b9ba5a34ff 63 * Channel B ^ | ^ | ^ | ^ | ^ | |
ea78anana 1:36b9ba5a34ff 64 * ------+ ^ +-----+ ^ +-----+ +--
ea78anana 1:36b9ba5a34ff 65 * ^ ^ ^ ^ ^
ea78anana 1:36b9ba5a34ff 66 * ^ ^ ^ ^ ^
ea78anana 1:36b9ba5a34ff 67 * Pulse count 0 1 2 3 4 5 ...
ea78anana 1:36b9ba5a34ff 68 *
ea78anana 1:36b9ba5a34ff 69 * This interface can also use X4 encoding which calculates the pulse count
ea78anana 1:36b9ba5a34ff 70 * based on reading the current state after each rising and falling edge of
ea78anana 1:36b9ba5a34ff 71 * either channel.
ea78anana 1:36b9ba5a34ff 72 *
ea78anana 1:36b9ba5a34ff 73 * +-----+ +-----+ +-----+
ea78anana 1:36b9ba5a34ff 74 * Channel A | | | | | |
ea78anana 1:36b9ba5a34ff 75 * ---+ +-----+ +-----+ +-----
ea78anana 1:36b9ba5a34ff 76 * ^ ^ ^ ^ ^
ea78anana 1:36b9ba5a34ff 77 * ^ +-----+ ^ +-----+ ^ +-----+
ea78anana 1:36b9ba5a34ff 78 * Channel B ^ | ^ | ^ | ^ | ^ | |
ea78anana 1:36b9ba5a34ff 79 * ------+ ^ +-----+ ^ +-----+ +--
ea78anana 1:36b9ba5a34ff 80 * ^ ^ ^ ^ ^ ^ ^ ^ ^ ^
ea78anana 1:36b9ba5a34ff 81 * ^ ^ ^ ^ ^ ^ ^ ^ ^ ^
ea78anana 1:36b9ba5a34ff 82 * Pulse count 0 1 2 3 4 5 6 7 8 9 ...
ea78anana 1:36b9ba5a34ff 83 *
ea78anana 1:36b9ba5a34ff 84 * It defaults
ea78anana 1:36b9ba5a34ff 85 *
ea78anana 1:36b9ba5a34ff 86 * An optional index channel can be used which determines when a full
ea78anana 1:36b9ba5a34ff 87 * revolution has occured.
ea78anana 1:36b9ba5a34ff 88 *
ea78anana 1:36b9ba5a34ff 89 * If a 4 pules per revolution encoder was used, with X4 encoding,
ea78anana 1:36b9ba5a34ff 90 * the following would be observed.
ea78anana 1:36b9ba5a34ff 91 *
ea78anana 1:36b9ba5a34ff 92 * +-----+ +-----+ +-----+
ea78anana 1:36b9ba5a34ff 93 * Channel A | | | | | |
ea78anana 1:36b9ba5a34ff 94 * ---+ +-----+ +-----+ +-----
ea78anana 1:36b9ba5a34ff 95 * ^ ^ ^ ^ ^
ea78anana 1:36b9ba5a34ff 96 * ^ +-----+ ^ +-----+ ^ +-----+
ea78anana 1:36b9ba5a34ff 97 * Channel B ^ | ^ | ^ | ^ | ^ | |
ea78anana 1:36b9ba5a34ff 98 * ------+ ^ +-----+ ^ +-----+ +--
ea78anana 1:36b9ba5a34ff 99 * ^ ^ ^ ^ ^ ^ ^ ^ ^ ^
ea78anana 1:36b9ba5a34ff 100 * ^ ^ ^ ^ ^ ^ ^ ^ ^ ^
ea78anana 1:36b9ba5a34ff 101 * ^ ^ ^ +--+ ^ ^ +--+ ^
ea78anana 1:36b9ba5a34ff 102 * ^ ^ ^ | | ^ ^ | | ^
ea78anana 1:36b9ba5a34ff 103 * Index ------------+ +--------+ +-----------
ea78anana 1:36b9ba5a34ff 104 * ^ ^ ^ ^ ^ ^ ^ ^ ^ ^
ea78anana 1:36b9ba5a34ff 105 * Pulse count 0 1 2 3 4 5 6 7 8 9 ...
ea78anana 1:36b9ba5a34ff 106 * Rev. count 0 1 2
ea78anana 1:36b9ba5a34ff 107 *
ea78anana 1:36b9ba5a34ff 108 * Rotational position in degrees can be calculated by:
ea78anana 1:36b9ba5a34ff 109 *
ea78anana 1:36b9ba5a34ff 110 * (pulse count / X * N) * 360
ea78anana 1:36b9ba5a34ff 111 *
ea78anana 1:36b9ba5a34ff 112 * Where X is the encoding type [e.g. X4 encoding => X=4], and N is the number
ea78anana 1:36b9ba5a34ff 113 * of pulses per revolution.
ea78anana 1:36b9ba5a34ff 114 *
ea78anana 1:36b9ba5a34ff 115 * Linear position can be calculated by:
ea78anana 1:36b9ba5a34ff 116 *
ea78anana 1:36b9ba5a34ff 117 * (pulse count / X * N) * (1 / PPI)
ea78anana 1:36b9ba5a34ff 118 *
ea78anana 1:36b9ba5a34ff 119 * Where X is encoding type [e.g. X4 encoding => X=44], N is the number of
ea78anana 1:36b9ba5a34ff 120 * pulses per revolution, and PPI is pulses per inch, or the equivalent for
ea78anana 1:36b9ba5a34ff 121 * any other unit of displacement. PPI can be calculated by taking the
ea78anana 1:36b9ba5a34ff 122 * circumference of the wheel or encoder disk and dividing it by the number
ea78anana 1:36b9ba5a34ff 123 * of pulses per revolution.
ea78anana 1:36b9ba5a34ff 124 */
ea78anana 0:4d7336a951bd 125
ea78anana 1:36b9ba5a34ff 126 #ifndef QEI_H
ea78anana 1:36b9ba5a34ff 127 #define QEI_H
ea78anana 1:36b9ba5a34ff 128
ea78anana 1:36b9ba5a34ff 129 /**
ea78anana 1:36b9ba5a34ff 130 * Includes
ea78anana 1:36b9ba5a34ff 131 */
ea78anana 1:36b9ba5a34ff 132 #include "mbed.h"
ea78anana 1:36b9ba5a34ff 133
ea78anana 1:36b9ba5a34ff 134 /**
ea78anana 1:36b9ba5a34ff 135 * Defines
ea78anana 1:36b9ba5a34ff 136 */
ea78anana 1:36b9ba5a34ff 137 #define PREV_MASK 0x1 //Mask for the previous state in determining direction
ea78anana 1:36b9ba5a34ff 138 //of rotation.
ea78anana 1:36b9ba5a34ff 139 #define CURR_MASK 0x2 //Mask for the current state in determining direction
ea78anana 1:36b9ba5a34ff 140 //of rotation.
ea78anana 1:36b9ba5a34ff 141 #define INVALID 0x3 //XORing two states where both bits have changed.
ea78anana 1:36b9ba5a34ff 142
ea78anana 1:36b9ba5a34ff 143 /**
ea78anana 1:36b9ba5a34ff 144 * Quadrature Encoder Interface.
ea78anana 1:36b9ba5a34ff 145 */
ea78anana 1:36b9ba5a34ff 146 class QEI {
ea78anana 1:36b9ba5a34ff 147
ea78anana 1:36b9ba5a34ff 148 public:
ea78anana 1:36b9ba5a34ff 149
ea78anana 1:36b9ba5a34ff 150 typedef enum Encoding {
ea78anana 1:36b9ba5a34ff 151
ea78anana 1:36b9ba5a34ff 152 X2_ENCODING,
ea78anana 1:36b9ba5a34ff 153 X4_ENCODING
ea78anana 1:36b9ba5a34ff 154
ea78anana 1:36b9ba5a34ff 155 } Encoding;
ea78anana 1:36b9ba5a34ff 156
ea78anana 1:36b9ba5a34ff 157 /**
ea78anana 1:36b9ba5a34ff 158 * Constructor.
ea78anana 1:36b9ba5a34ff 159 *
ea78anana 1:36b9ba5a34ff 160 * Reads the current values on channel A and channel B to determine the
ea78anana 1:36b9ba5a34ff 161 * initial state.
ea78anana 1:36b9ba5a34ff 162 *
ea78anana 1:36b9ba5a34ff 163 * Attaches the encode function to the rise/fall interrupt edges of
ea78anana 1:36b9ba5a34ff 164 * channels A and B to perform X4 encoding.
ea78anana 1:36b9ba5a34ff 165 *
ea78anana 1:36b9ba5a34ff 166 * Attaches the index function to the rise interrupt edge of channel index
ea78anana 1:36b9ba5a34ff 167 * (if it is used) to count revolutions.
ea78anana 1:36b9ba5a34ff 168 *
ea78anana 1:36b9ba5a34ff 169 * @param channelA mbed pin for channel A input.
ea78anana 1:36b9ba5a34ff 170 * @param channelB mbed pin for channel B input.
ea78anana 1:36b9ba5a34ff 171 * @param index mbed pin for optional index channel input,
ea78anana 1:36b9ba5a34ff 172 * (pass NC if not needed).
ea78anana 1:36b9ba5a34ff 173 * @param pulsesPerRev Number of pulses in one revolution.
ea78anana 1:36b9ba5a34ff 174 * @param encoding The encoding to use. Uses X2 encoding by default. X2
ea78anana 1:36b9ba5a34ff 175 * encoding uses interrupts on the rising and falling edges
ea78anana 1:36b9ba5a34ff 176 * of only channel A where as X4 uses them on both
ea78anana 1:36b9ba5a34ff 177 * channels.
ea78anana 1:36b9ba5a34ff 178 */
ea78anana 1:36b9ba5a34ff 179 QEI(PinName channelA, PinName channelB, PinName index, int pulsesPerRev, Encoding encoding = X2_ENCODING);
ea78anana 1:36b9ba5a34ff 180
ea78anana 1:36b9ba5a34ff 181 /**
ea78anana 1:36b9ba5a34ff 182 * Reset the encoder.
ea78anana 1:36b9ba5a34ff 183 *
ea78anana 1:36b9ba5a34ff 184 * Sets the pulses and revolutions count to zero.
ea78anana 1:36b9ba5a34ff 185 */
ea78anana 1:36b9ba5a34ff 186 void reset(void);
ea78anana 1:36b9ba5a34ff 187
ea78anana 1:36b9ba5a34ff 188 /**
ea78anana 1:36b9ba5a34ff 189 * Read the state of the encoder.
ea78anana 1:36b9ba5a34ff 190 *
ea78anana 1:36b9ba5a34ff 191 * @return The current state of the encoder as a 2-bit number, where:
ea78anana 1:36b9ba5a34ff 192 * bit 1 = The reading from channel B
ea78anana 1:36b9ba5a34ff 193 * bit 2 = The reading from channel A
ea78anana 1:36b9ba5a34ff 194 */
ea78anana 1:36b9ba5a34ff 195 int getCurrentState(void);
ea78anana 1:36b9ba5a34ff 196
ea78anana 1:36b9ba5a34ff 197 /**
ea78anana 1:36b9ba5a34ff 198 * Read the number of pulses recorded by the encoder.
ea78anana 1:36b9ba5a34ff 199 *
ea78anana 1:36b9ba5a34ff 200 * @return Number of pulses which have occured.
ea78anana 1:36b9ba5a34ff 201 */
ea78anana 1:36b9ba5a34ff 202 int getPulses(void);
ea78anana 1:36b9ba5a34ff 203
ea78anana 1:36b9ba5a34ff 204 /**
ea78anana 1:36b9ba5a34ff 205 * Read the number of revolutions recorded by the encoder on the index channel.
ea78anana 1:36b9ba5a34ff 206 *
ea78anana 1:36b9ba5a34ff 207 * @return Number of revolutions which have occured on the index channel.
ea78anana 1:36b9ba5a34ff 208 */
ea78anana 1:36b9ba5a34ff 209 int getRevolutions(void);
ea78anana 1:36b9ba5a34ff 210
ea78anana 1:36b9ba5a34ff 211 private:
ea78anana 1:36b9ba5a34ff 212
ea78anana 1:36b9ba5a34ff 213 /**
ea78anana 1:36b9ba5a34ff 214 * Update the pulse count.
ea78anana 1:36b9ba5a34ff 215 *
ea78anana 1:36b9ba5a34ff 216 * Called on every rising/falling edge of channels A/B.
ea78anana 1:36b9ba5a34ff 217 *
ea78anana 1:36b9ba5a34ff 218 * Reads the state of the channels and determines whether a pulse forward
ea78anana 1:36b9ba5a34ff 219 * or backward has occured, updating the count appropriately.
ea78anana 1:36b9ba5a34ff 220 */
ea78anana 1:36b9ba5a34ff 221 void encode(void);
ea78anana 1:36b9ba5a34ff 222
ea78anana 1:36b9ba5a34ff 223 /**
ea78anana 1:36b9ba5a34ff 224 * Called on every rising edge of channel index to update revolution
ea78anana 1:36b9ba5a34ff 225 * count by one.
ea78anana 1:36b9ba5a34ff 226 */
ea78anana 1:36b9ba5a34ff 227 void index(void);
ea78anana 1:36b9ba5a34ff 228
ea78anana 1:36b9ba5a34ff 229 Encoding encoding_;
ea78anana 1:36b9ba5a34ff 230
ea78anana 1:36b9ba5a34ff 231 InterruptIn channelA_;
ea78anana 1:36b9ba5a34ff 232 InterruptIn channelB_;
ea78anana 1:36b9ba5a34ff 233 InterruptIn index_;
ea78anana 1:36b9ba5a34ff 234
ea78anana 1:36b9ba5a34ff 235 int pulsesPerRev_;
ea78anana 1:36b9ba5a34ff 236 int prevState_;
ea78anana 1:36b9ba5a34ff 237 int currState_;
ea78anana 1:36b9ba5a34ff 238
ea78anana 1:36b9ba5a34ff 239 volatile int pulses_;
ea78anana 1:36b9ba5a34ff 240 volatile int revolutions_;
ea78anana 1:36b9ba5a34ff 241
ea78anana 1:36b9ba5a34ff 242 };
ea78anana 1:36b9ba5a34ff 243
ea78anana 1:36b9ba5a34ff 244 #endif /* QEI_H */
ea78anana 1:36b9ba5a34ff 245