Simon Ford
Simple PID example for LabVIEW
QEI.h@1:ddfe18427154, 2010-08-03 (annotated)
- Committer:
- simon
- Date:
- Tue Aug 03 15:32:30 2010 +0000
- Revision:
- 1:ddfe18427154
- Parent:
- 0:e3b759ab4b5c
Who changed what in which revision?
| User | Revision | Line number | New contents of line |
|---|---|---|---|
| simon | 0:e3b759ab4b5c | 1 | //****************************************************************************/ |
| simon | 0:e3b759ab4b5c | 2 | //@section LICENSE |
| simon | 0:e3b759ab4b5c | 3 | // |
| simon | 0:e3b759ab4b5c | 4 | //Copyright (c) 2010 ARM Limited |
| simon | 0:e3b759ab4b5c | 5 | // |
| simon | 0:e3b759ab4b5c | 6 | //Permission is hereby granted, free of charge, to any person obtaining a copy |
| simon | 0:e3b759ab4b5c | 7 | //of this software and associated documentation files (the "Software"), to deal |
| simon | 0:e3b759ab4b5c | 8 | //in the Software without restriction, including without limitation the rights |
| simon | 0:e3b759ab4b5c | 9 | //to use, copy, modify, merge, publish, distribute, sublicense, and/or sell |
| simon | 0:e3b759ab4b5c | 10 | //copies of the Software, and to permit persons to whom the Software is |
| simon | 0:e3b759ab4b5c | 11 | //furnished to do so, subject to the following conditions: |
| simon | 0:e3b759ab4b5c | 12 | // |
| simon | 0:e3b759ab4b5c | 13 | //The above copyright notice and this permission notice shall be included in |
| simon | 0:e3b759ab4b5c | 14 | //all copies or substantial portions of the Software. |
| simon | 0:e3b759ab4b5c | 15 | // |
| simon | 0:e3b759ab4b5c | 16 | //THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR |
| simon | 0:e3b759ab4b5c | 17 | //IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, |
| simon | 0:e3b759ab4b5c | 18 | //FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE |
| simon | 0:e3b759ab4b5c | 19 | //AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER |
| simon | 0:e3b759ab4b5c | 20 | //LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, |
| simon | 0:e3b759ab4b5c | 21 | //OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN |
| simon | 0:e3b759ab4b5c | 22 | //THE SOFTWARE. |
| simon | 0:e3b759ab4b5c | 23 | //****************************************************************************/ |
| simon | 0:e3b759ab4b5c | 24 | //@section DESCRIPTION |
| simon | 0:e3b759ab4b5c | 25 | // |
| simon | 0:e3b759ab4b5c | 26 | // Quadrature Encoder Interface. |
| simon | 0:e3b759ab4b5c | 27 | // |
| simon | 0:e3b759ab4b5c | 28 | // A quadrature encoder consists of two code tracks on a disk which are 90 |
| simon | 0:e3b759ab4b5c | 29 | // degrees out of phase. It can be used to determine how far a wheel has |
| simon | 0:e3b759ab4b5c | 30 | // rotated, relative to a known starting position. |
| simon | 0:e3b759ab4b5c | 31 | // |
| simon | 0:e3b759ab4b5c | 32 | // Only one code track changes at a time leading to a more robust system than |
| simon | 0:e3b759ab4b5c | 33 | // a single track, because any jitter around any edge won't cause a state |
| simon | 0:e3b759ab4b5c | 34 | // change as the other track will remain constant. |
| simon | 0:e3b759ab4b5c | 35 | // |
| simon | 0:e3b759ab4b5c | 36 | // Encoders can be a homebrew affair, consisting of infrared emitters/receivers |
| simon | 0:e3b759ab4b5c | 37 | // and paper code tracks consisting of alternating black and white sections; |
| simon | 0:e3b759ab4b5c | 38 | // alternatively, complete disk and PCB emitter/receiver encoder systems can |
| simon | 0:e3b759ab4b5c | 39 | // be bought, but the interface, regardless of implementation is the same. |
| simon | 0:e3b759ab4b5c | 40 | // |
| simon | 0:e3b759ab4b5c | 41 | // +-----+ +-----+ +-----+ |
| simon | 0:e3b759ab4b5c | 42 | // Channel A | ^ | | | | | |
| simon | 0:e3b759ab4b5c | 43 | // ---+ ^ +-----+ +-----+ +----- |
| simon | 0:e3b759ab4b5c | 44 | // ^ ^ |
| simon | 0:e3b759ab4b5c | 45 | // ^ +-----+ +-----+ +-----+ |
| simon | 0:e3b759ab4b5c | 46 | // Channel B ^ | | | | | | |
| simon | 0:e3b759ab4b5c | 47 | // ------+ +-----+ +-----+ +----- |
| simon | 0:e3b759ab4b5c | 48 | // ^ ^ |
| simon | 0:e3b759ab4b5c | 49 | // ^ ^ |
| simon | 0:e3b759ab4b5c | 50 | // 90deg |
| simon | 0:e3b759ab4b5c | 51 | // |
| simon | 0:e3b759ab4b5c | 52 | // This interface uses X4 encoding which calculates the pulse count based on |
| simon | 0:e3b759ab4b5c | 53 | // reading the current state after each rising and falling edge of either |
| simon | 0:e3b759ab4b5c | 54 | // channel. |
| simon | 0:e3b759ab4b5c | 55 | // |
| simon | 0:e3b759ab4b5c | 56 | // +-----+ +-----+ +-----+ |
| simon | 0:e3b759ab4b5c | 57 | // Channel A | | | | | | |
| simon | 0:e3b759ab4b5c | 58 | // ---+ +-----+ +-----+ +----- |
| simon | 0:e3b759ab4b5c | 59 | // ^ ^ ^ ^ ^ |
| simon | 0:e3b759ab4b5c | 60 | // ^ +-----+ ^ +-----+ ^ +-----+ |
| simon | 0:e3b759ab4b5c | 61 | // Channel B ^ | ^ | ^ | ^ | ^ | | |
| simon | 0:e3b759ab4b5c | 62 | // ------+ ^ +-----+ ^ +-----+ +-- |
| simon | 0:e3b759ab4b5c | 63 | // ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ |
| simon | 0:e3b759ab4b5c | 64 | // ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ |
| simon | 0:e3b759ab4b5c | 65 | // Pulse count 0 1 2 3 4 5 6 7 8 9 ... |
| simon | 0:e3b759ab4b5c | 66 | // |
| simon | 0:e3b759ab4b5c | 67 | // An optional index channel can be used which determines when a full |
| simon | 0:e3b759ab4b5c | 68 | // revolution has occured. |
| simon | 0:e3b759ab4b5c | 69 | // |
| simon | 0:e3b759ab4b5c | 70 | // If a 4 pules per revolution encoder was used, the following would be |
| simon | 0:e3b759ab4b5c | 71 | // observed. |
| simon | 0:e3b759ab4b5c | 72 | // |
| simon | 0:e3b759ab4b5c | 73 | // +-----+ +-----+ +-----+ |
| simon | 0:e3b759ab4b5c | 74 | // Channel A | | | | | | |
| simon | 0:e3b759ab4b5c | 75 | // ---+ +-----+ +-----+ +----- |
| simon | 0:e3b759ab4b5c | 76 | // ^ ^ ^ ^ ^ |
| simon | 0:e3b759ab4b5c | 77 | // ^ +-----+ ^ +-----+ ^ +-----+ |
| simon | 0:e3b759ab4b5c | 78 | // Channel B ^ | ^ | ^ | ^ | ^ | | |
| simon | 0:e3b759ab4b5c | 79 | // ------+ ^ +-----+ ^ +-----+ +-- |
| simon | 0:e3b759ab4b5c | 80 | // ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ |
| simon | 0:e3b759ab4b5c | 81 | // ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ |
| simon | 0:e3b759ab4b5c | 82 | // ^ ^ ^ +--+ ^ ^ +--+ ^ |
| simon | 0:e3b759ab4b5c | 83 | // ^ ^ ^ | | ^ ^ | | ^ |
| simon | 0:e3b759ab4b5c | 84 | // Index ------------+ +--------+ +----------- |
| simon | 0:e3b759ab4b5c | 85 | // ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ |
| simon | 0:e3b759ab4b5c | 86 | // Pulse count 0 1 2 3 4 5 6 7 8 9 ... |
| simon | 0:e3b759ab4b5c | 87 | // Rev. count 0 1 2 |
| simon | 0:e3b759ab4b5c | 88 | // |
| simon | 0:e3b759ab4b5c | 89 | // Rotational position in degrees can be calculated by: |
| simon | 0:e3b759ab4b5c | 90 | // |
| simon | 0:e3b759ab4b5c | 91 | // (pulse count / X * N) * 360 |
| simon | 0:e3b759ab4b5c | 92 | // |
| simon | 0:e3b759ab4b5c | 93 | // Where X is the encoding type [in our case X=4], and N is the number of |
| simon | 0:e3b759ab4b5c | 94 | // pulses per revolution. |
| simon | 0:e3b759ab4b5c | 95 | // |
| simon | 0:e3b759ab4b5c | 96 | // Linear position can be calculated by: |
| simon | 0:e3b759ab4b5c | 97 | // |
| simon | 0:e3b759ab4b5c | 98 | // (pulse count / X * N) * (1 / PPI) |
| simon | 0:e3b759ab4b5c | 99 | // |
| simon | 0:e3b759ab4b5c | 100 | // Where X is encoding type [in our case X=4], N is the number of pulses per |
| simon | 0:e3b759ab4b5c | 101 | // revolution, and PPI is pulses per inch, or the equivalent for any other |
| simon | 0:e3b759ab4b5c | 102 | // unit of displacement. PPI can be calculated by taking the circumference |
| simon | 0:e3b759ab4b5c | 103 | // of the wheel or encoder disk and dividing it by the number of pulses per |
| simon | 0:e3b759ab4b5c | 104 | // revolution. |
| simon | 0:e3b759ab4b5c | 105 | //****************************************************************************/ |
| simon | 0:e3b759ab4b5c | 106 | |
| simon | 0:e3b759ab4b5c | 107 | #ifndef QEI_H |
| simon | 0:e3b759ab4b5c | 108 | #define QEI_H |
| simon | 0:e3b759ab4b5c | 109 | |
| simon | 0:e3b759ab4b5c | 110 | //****************************************************************************/ |
| simon | 0:e3b759ab4b5c | 111 | // Includes |
| simon | 0:e3b759ab4b5c | 112 | //****************************************************************************/ |
| simon | 0:e3b759ab4b5c | 113 | #include "mbed.h" |
| simon | 0:e3b759ab4b5c | 114 | |
| simon | 0:e3b759ab4b5c | 115 | //****************************************************************************/ |
| simon | 0:e3b759ab4b5c | 116 | // Defines |
| simon | 0:e3b759ab4b5c | 117 | //****************************************************************************/ |
| simon | 0:e3b759ab4b5c | 118 | #define PREV_MASK 0x1 //Mask for the previous state in determining direction |
| simon | 0:e3b759ab4b5c | 119 | //of rotation. |
| simon | 0:e3b759ab4b5c | 120 | #define CURR_MASK 0x2 //Mask for the current state in determining direction |
| simon | 0:e3b759ab4b5c | 121 | //of rotation. |
| simon | 0:e3b759ab4b5c | 122 | #define INVALID 0x3 //XORing two states where both bits have changed. |
| simon | 0:e3b759ab4b5c | 123 | |
| simon | 0:e3b759ab4b5c | 124 | /** |
| simon | 0:e3b759ab4b5c | 125 | * Quadrature Encoder Interface. |
| simon | 0:e3b759ab4b5c | 126 | */ |
| simon | 0:e3b759ab4b5c | 127 | class QEI { |
| simon | 0:e3b759ab4b5c | 128 | |
| simon | 0:e3b759ab4b5c | 129 | public: |
| simon | 0:e3b759ab4b5c | 130 | |
| simon | 0:e3b759ab4b5c | 131 | /** |
| simon | 0:e3b759ab4b5c | 132 | * Constructor. |
| simon | 0:e3b759ab4b5c | 133 | * |
| simon | 0:e3b759ab4b5c | 134 | * Reads the current values on channel A and channel B to determine the |
| simon | 0:e3b759ab4b5c | 135 | * initial state. |
| simon | 0:e3b759ab4b5c | 136 | * |
| simon | 0:e3b759ab4b5c | 137 | * Attaches the encode function to the rise/fall interrupt edges of |
| simon | 0:e3b759ab4b5c | 138 | * channels A and B to perform X4 encoding. |
| simon | 0:e3b759ab4b5c | 139 | * |
| simon | 0:e3b759ab4b5c | 140 | * Attaches the index function to the rise interrupt edge of channel index |
| simon | 0:e3b759ab4b5c | 141 | * (if it is used) to count revolutions. |
| simon | 0:e3b759ab4b5c | 142 | * |
| simon | 0:e3b759ab4b5c | 143 | * @param channelA mbed pin for channel A input. |
| simon | 0:e3b759ab4b5c | 144 | * @param channelB mbed pin for channel B input. |
| simon | 0:e3b759ab4b5c | 145 | * @param index mbed pin for optional index channel input, |
| simon | 0:e3b759ab4b5c | 146 | * (pass NC if not needed). |
| simon | 0:e3b759ab4b5c | 147 | * @param pulsesPerRev Number of pulses in one revolution. |
| simon | 0:e3b759ab4b5c | 148 | */ |
| simon | 0:e3b759ab4b5c | 149 | QEI(PinName channelA, PinName channelB, PinName index, int pulsesPerRev); |
| simon | 0:e3b759ab4b5c | 150 | |
| simon | 0:e3b759ab4b5c | 151 | /** |
| simon | 0:e3b759ab4b5c | 152 | * Reset the encoder. |
| simon | 0:e3b759ab4b5c | 153 | * |
| simon | 0:e3b759ab4b5c | 154 | * Sets the pulses and revolutions count to zero. |
| simon | 0:e3b759ab4b5c | 155 | */ |
| simon | 0:e3b759ab4b5c | 156 | void reset(void); |
| simon | 0:e3b759ab4b5c | 157 | |
| simon | 0:e3b759ab4b5c | 158 | /** |
| simon | 0:e3b759ab4b5c | 159 | * Read the state of the encoder. |
| simon | 0:e3b759ab4b5c | 160 | * |
| simon | 0:e3b759ab4b5c | 161 | * @return The current state of the encoder as a 2-bit number, where: |
| simon | 0:e3b759ab4b5c | 162 | * bit 1 = The reading from channel B |
| simon | 0:e3b759ab4b5c | 163 | * bit 2 = The reading from channel A |
| simon | 0:e3b759ab4b5c | 164 | */ |
| simon | 0:e3b759ab4b5c | 165 | int getCurrentState(void); |
| simon | 0:e3b759ab4b5c | 166 | |
| simon | 0:e3b759ab4b5c | 167 | /** |
| simon | 0:e3b759ab4b5c | 168 | * Read the number of pulses recorded by the encoder. |
| simon | 0:e3b759ab4b5c | 169 | * |
| simon | 0:e3b759ab4b5c | 170 | * @return Number of pulses which have occured. |
| simon | 0:e3b759ab4b5c | 171 | */ |
| simon | 0:e3b759ab4b5c | 172 | int getPulses(void); |
| simon | 0:e3b759ab4b5c | 173 | |
| simon | 0:e3b759ab4b5c | 174 | private: |
| simon | 0:e3b759ab4b5c | 175 | |
| simon | 0:e3b759ab4b5c | 176 | /** |
| simon | 0:e3b759ab4b5c | 177 | * Update the pulse count. |
| simon | 0:e3b759ab4b5c | 178 | * |
| simon | 0:e3b759ab4b5c | 179 | * Called on every rising/falling edge of channels A/B. |
| simon | 0:e3b759ab4b5c | 180 | * |
| simon | 0:e3b759ab4b5c | 181 | * Reads the state of the channels and determines whether a pulse forward |
| simon | 0:e3b759ab4b5c | 182 | * or backward has occured, updating the count appropriately. |
| simon | 0:e3b759ab4b5c | 183 | */ |
| simon | 0:e3b759ab4b5c | 184 | void encode(void); |
| simon | 0:e3b759ab4b5c | 185 | |
| simon | 0:e3b759ab4b5c | 186 | /** |
| simon | 0:e3b759ab4b5c | 187 | * Called on every rising edge of channel index to update revolution |
| simon | 0:e3b759ab4b5c | 188 | * count by one. |
| simon | 0:e3b759ab4b5c | 189 | */ |
| simon | 0:e3b759ab4b5c | 190 | void index(void); |
| simon | 0:e3b759ab4b5c | 191 | |
| simon | 0:e3b759ab4b5c | 192 | InterruptIn* channelA_; |
| simon | 0:e3b759ab4b5c | 193 | InterruptIn* channelB_; |
| simon | 0:e3b759ab4b5c | 194 | InterruptIn* index_; |
| simon | 0:e3b759ab4b5c | 195 | |
| simon | 0:e3b759ab4b5c | 196 | int pulsesPerRev_; |
| simon | 0:e3b759ab4b5c | 197 | int revolutions_; |
| simon | 0:e3b759ab4b5c | 198 | int prevState_; |
| simon | 0:e3b759ab4b5c | 199 | int currState_; |
| simon | 0:e3b759ab4b5c | 200 | |
| simon | 0:e3b759ab4b5c | 201 | volatile int pulses_; |
| simon | 0:e3b759ab4b5c | 202 | |
| simon | 0:e3b759ab4b5c | 203 | }; |
| simon | 0:e3b759ab4b5c | 204 | |
| simon | 0:e3b759ab4b5c | 205 | #endif /* QEI_H */ |