Sik Chiu Chow / Mbed 2 deprecated encoder

encoder

Dependencies:   mbed

QEI.h@2:92fd61600fa8, 2021-10-31 (annotated)

Committer:
ea78anana
Date:
Sun Oct 31 09:45:26 2021 +0000
Revision:
2:92fd61600fa8
Parent:
0:4d7336a951bd
Child:
1:36b9ba5a34ff
for 3 encoders

Who changed what in which revision?

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