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for 3 encoders
QEI.h@0:4d7336a951bd, 2021-10-27 (annotated)
- Committer:
- ea78anana
- Date:
- Wed Oct 27 05:18:30 2021 +0000
- Revision:
- 0:4d7336a951bd
- Child:
- 2:36b9ba5a34ff
encoder
Who changed what in which revision?
User | Revision | Line number | New contents of line |
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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 |