OpenMoCo
Quadrature Encoder Interface for motion control with resistance to jitter and chatter on AB signals and motor vibrations
Dependents: QEIx4_Example realtimeMM_V3 realtimeMM_V3
Quadrature Encoder Interface for Motion Control.
A class to decode pulses on a rotary encoder with AB signals (quadrature encoder). It uses all 4 edges of the AB signals to increase the counter resolution 4 times of cycles per rotation/revolution (CPR) (e.g. an encoder with 500 CPR get 2000 counts per rotation)
In opposite to most common QEI implementation this is resistant to jitter and chatter on AB signals and motor vibrations. When using interrupts (IRQ_NO_JAMMING-mode) only the needed edge and pin is activated to prevent jamming CPU time with unnecessary interrupts. Whes reaching the next position the edge that triggerd this position (state) is ignored to aboid oscillating up/down counts.
It can also be used in polling mode i.g. in idle routines if interrupts are not desired. At this mode be sure that the sampling frequency is heigher than the maximum rotation speed (expeced counts per second)
The internal state machine is based on a look up table (LUT) to minimize interrupt retention time and get all necessary flags at once.
Additional the rotation speed of the encoder can be measured. The algorithm is based on the measuring time between the edges to get a very precise speed at very slow rotation.
The library is designed to support closed loop speed- and motion-controller for also slow and smooth motions like movie camera motion control.
Quadrature Encoder Signals:
(+) Count UP; (-) Count DOWN
FPointer_vi.h@1:ac6b7b1bf6c5, 2014-09-30 (annotated)
- Committer:
- jocis
- Date:
- Tue Sep 30 12:34:07 2014 +0000
- Revision:
- 1:ac6b7b1bf6c5
- Child:
- 2:c0b87b11b9cd
Added speed measurement; improved state machine and irq handling
Who changed what in which revision?
| User | Revision | Line number | New contents of line |
|---|---|---|---|
| jocis | 1:ac6b7b1bf6c5 | 1 | /* |
| jocis | 1:ac6b7b1bf6c5 | 2 | Copyright (c) 2011 Andy Kirkham |
| jocis | 1:ac6b7b1bf6c5 | 3 | modified by Jochen Krapf |
| jocis | 1:ac6b7b1bf6c5 | 4 | |
| jocis | 1:ac6b7b1bf6c5 | 5 | Permission is hereby granted, free of charge, to any person obtaining a copy |
| jocis | 1:ac6b7b1bf6c5 | 6 | of this software and associated documentation files (the "Software"), to deal |
| jocis | 1:ac6b7b1bf6c5 | 7 | in the Software without restriction, including without limitation the rights |
| jocis | 1:ac6b7b1bf6c5 | 8 | to use, copy, modify, merge, publish, distribute, sublicense, and/or sell |
| jocis | 1:ac6b7b1bf6c5 | 9 | copies of the Software, and to permit persons to whom the Software is |
| jocis | 1:ac6b7b1bf6c5 | 10 | furnished to do so, subject to the following conditions: |
| jocis | 1:ac6b7b1bf6c5 | 11 | |
| jocis | 1:ac6b7b1bf6c5 | 12 | The above copyright notice and this permission notice shall be included in |
| jocis | 1:ac6b7b1bf6c5 | 13 | all copies or substantial portions of the Software. |
| jocis | 1:ac6b7b1bf6c5 | 14 | |
| jocis | 1:ac6b7b1bf6c5 | 15 | THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR |
| jocis | 1:ac6b7b1bf6c5 | 16 | IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, |
| jocis | 1:ac6b7b1bf6c5 | 17 | FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE |
| jocis | 1:ac6b7b1bf6c5 | 18 | AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER |
| jocis | 1:ac6b7b1bf6c5 | 19 | LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, |
| jocis | 1:ac6b7b1bf6c5 | 20 | OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN |
| jocis | 1:ac6b7b1bf6c5 | 21 | THE SOFTWARE. |
| jocis | 1:ac6b7b1bf6c5 | 22 | */ |
| jocis | 1:ac6b7b1bf6c5 | 23 | |
| jocis | 1:ac6b7b1bf6c5 | 24 | #ifndef AJK_FPOINTER_H |
| jocis | 1:ac6b7b1bf6c5 | 25 | #define AJK_FPOINTER_H |
| jocis | 1:ac6b7b1bf6c5 | 26 | |
| jocis | 1:ac6b7b1bf6c5 | 27 | namespace AjK { |
| jocis | 1:ac6b7b1bf6c5 | 28 | |
| jocis | 1:ac6b7b1bf6c5 | 29 | class FPointerDummy; |
| jocis | 1:ac6b7b1bf6c5 | 30 | |
| jocis | 1:ac6b7b1bf6c5 | 31 | /** FPointer - Adds callbacks that take and return a 32bit uint32_t data type. |
| jocis | 1:ac6b7b1bf6c5 | 32 | * |
| jocis | 1:ac6b7b1bf6c5 | 33 | * The Mbed library supplies a callback using the FunctionPointer object as |
| jocis | 1:ac6b7b1bf6c5 | 34 | * defined in FunctionPointer.h However, this callback system does not allow |
| jocis | 1:ac6b7b1bf6c5 | 35 | * the caller to pass a value to the callback. Likewise, the callback itself |
| jocis | 1:ac6b7b1bf6c5 | 36 | * cannot return a value. |
| jocis | 1:ac6b7b1bf6c5 | 37 | * |
| jocis | 1:ac6b7b1bf6c5 | 38 | * FPointer operates in the same way but allows the callback function to be |
| jocis | 1:ac6b7b1bf6c5 | 39 | * passed one arg, a uint32_t value. Additionally, the callback can return |
| jocis | 1:ac6b7b1bf6c5 | 40 | * a single uint32_t value. The reason for using uint32_t is that the Mbed |
| jocis | 1:ac6b7b1bf6c5 | 41 | * and the microcontroller (LPC1768) have a natural data size of 32bits and |
| jocis | 1:ac6b7b1bf6c5 | 42 | * this means we can use the uint32_t as a pointer. See example1.h for more |
| jocis | 1:ac6b7b1bf6c5 | 43 | * information. This example passes an "int" by passing a pointer to that |
| jocis | 1:ac6b7b1bf6c5 | 44 | * int as a 32bit value. Using this technique you can pass any value you like. |
| jocis | 1:ac6b7b1bf6c5 | 45 | * All you have to do is pass a pointer to your value cast to (uint32_t). Your |
| jocis | 1:ac6b7b1bf6c5 | 46 | * callback can the deference it to get the original value. |
| jocis | 1:ac6b7b1bf6c5 | 47 | * |
| jocis | 1:ac6b7b1bf6c5 | 48 | * example2.h shows how to do the same thing but demostrates how to specify |
| jocis | 1:ac6b7b1bf6c5 | 49 | * the callback into a class object/method. |
| jocis | 1:ac6b7b1bf6c5 | 50 | * |
| jocis | 1:ac6b7b1bf6c5 | 51 | * Finally, example3.h shows how to pass multiple values. In this example we |
| jocis | 1:ac6b7b1bf6c5 | 52 | * define a data structure and in the callback we pass a pointer to that |
| jocis | 1:ac6b7b1bf6c5 | 53 | * data structure thus allowing the callback to again get the values. |
| jocis | 1:ac6b7b1bf6c5 | 54 | * |
| jocis | 1:ac6b7b1bf6c5 | 55 | * Note, when passing pointers to variables to the callback, if the callback |
| jocis | 1:ac6b7b1bf6c5 | 56 | * function/method changes that variable's value then it will also change the |
| jocis | 1:ac6b7b1bf6c5 | 57 | * value the caller sees. If C pointers are new to you, you are strongly |
| jocis | 1:ac6b7b1bf6c5 | 58 | * advised to read up on the subject. It's pointers that often get beginners |
| jocis | 1:ac6b7b1bf6c5 | 59 | * into trouble when mis-used. |
| jocis | 1:ac6b7b1bf6c5 | 60 | * |
| jocis | 1:ac6b7b1bf6c5 | 61 | * @see example1.h |
| jocis | 1:ac6b7b1bf6c5 | 62 | * @see example2.h |
| jocis | 1:ac6b7b1bf6c5 | 63 | * @see example3.h |
| jocis | 1:ac6b7b1bf6c5 | 64 | * @see http://mbed.org/handbook/C-Data-Types |
| jocis | 1:ac6b7b1bf6c5 | 65 | * @see http://mbed.org/projects/libraries/svn/mbed/trunk/FunctionPointer.h |
| jocis | 1:ac6b7b1bf6c5 | 66 | */ |
| jocis | 1:ac6b7b1bf6c5 | 67 | class FPointer_vi { |
| jocis | 1:ac6b7b1bf6c5 | 68 | |
| jocis | 1:ac6b7b1bf6c5 | 69 | protected: |
| jocis | 1:ac6b7b1bf6c5 | 70 | |
| jocis | 1:ac6b7b1bf6c5 | 71 | //! C callback function pointer. |
| jocis | 1:ac6b7b1bf6c5 | 72 | void (*c_callback)(int); |
| jocis | 1:ac6b7b1bf6c5 | 73 | |
| jocis | 1:ac6b7b1bf6c5 | 74 | //! C++ callback object/method pointer (the object part). |
| jocis | 1:ac6b7b1bf6c5 | 75 | FPointerDummy *obj_callback; |
| jocis | 1:ac6b7b1bf6c5 | 76 | |
| jocis | 1:ac6b7b1bf6c5 | 77 | //! C++ callback object/method pointer (the method part). |
| jocis | 1:ac6b7b1bf6c5 | 78 | void (FPointerDummy::*method_callback)(int); |
| jocis | 1:ac6b7b1bf6c5 | 79 | |
| jocis | 1:ac6b7b1bf6c5 | 80 | public: |
| jocis | 1:ac6b7b1bf6c5 | 81 | |
| jocis | 1:ac6b7b1bf6c5 | 82 | /** Constructor |
| jocis | 1:ac6b7b1bf6c5 | 83 | */ |
| jocis | 1:ac6b7b1bf6c5 | 84 | FPointer_vi() { |
| jocis | 1:ac6b7b1bf6c5 | 85 | c_callback = NULL; |
| jocis | 1:ac6b7b1bf6c5 | 86 | obj_callback = NULL; |
| jocis | 1:ac6b7b1bf6c5 | 87 | method_callback = NULL; |
| jocis | 1:ac6b7b1bf6c5 | 88 | } |
| jocis | 1:ac6b7b1bf6c5 | 89 | |
| jocis | 1:ac6b7b1bf6c5 | 90 | /** attach - Overloaded attachment function. |
| jocis | 1:ac6b7b1bf6c5 | 91 | * |
| jocis | 1:ac6b7b1bf6c5 | 92 | * Attach a C type function pointer as the callback. |
| jocis | 1:ac6b7b1bf6c5 | 93 | * |
| jocis | 1:ac6b7b1bf6c5 | 94 | * Note, the callback function prototype must be:- |
| jocis | 1:ac6b7b1bf6c5 | 95 | * @code |
| jocis | 1:ac6b7b1bf6c5 | 96 | * void myCallbackFunction(int); |
| jocis | 1:ac6b7b1bf6c5 | 97 | * @endcode |
| jocis | 1:ac6b7b1bf6c5 | 98 | * @param A C function pointer to call. |
| jocis | 1:ac6b7b1bf6c5 | 99 | */ |
| jocis | 1:ac6b7b1bf6c5 | 100 | void attach(void (*function)(int) = 0) { c_callback = function; } |
| jocis | 1:ac6b7b1bf6c5 | 101 | |
| jocis | 1:ac6b7b1bf6c5 | 102 | /** attach - Overloaded attachment function. |
| jocis | 1:ac6b7b1bf6c5 | 103 | * |
| jocis | 1:ac6b7b1bf6c5 | 104 | * Attach a C++ type object/method pointer as the callback. |
| jocis | 1:ac6b7b1bf6c5 | 105 | * |
| jocis | 1:ac6b7b1bf6c5 | 106 | * Note, the callback method prototype must be:- |
| jocis | 1:ac6b7b1bf6c5 | 107 | * @code |
| jocis | 1:ac6b7b1bf6c5 | 108 | * public: |
| jocis | 1:ac6b7b1bf6c5 | 109 | * void myCallbackFunction(int); |
| jocis | 1:ac6b7b1bf6c5 | 110 | * @endcode |
| jocis | 1:ac6b7b1bf6c5 | 111 | * @param A C++ object pointer. |
| jocis | 1:ac6b7b1bf6c5 | 112 | * @param A C++ method within the object to call. |
| jocis | 1:ac6b7b1bf6c5 | 113 | */ |
| jocis | 1:ac6b7b1bf6c5 | 114 | template<class T> |
| jocis | 1:ac6b7b1bf6c5 | 115 | void attach(T* item, void (T::*method)(int)) { |
| jocis | 1:ac6b7b1bf6c5 | 116 | obj_callback = (FPointerDummy *)item; |
| jocis | 1:ac6b7b1bf6c5 | 117 | method_callback = (void (FPointerDummy::*)(int))method; |
| jocis | 1:ac6b7b1bf6c5 | 118 | } |
| jocis | 1:ac6b7b1bf6c5 | 119 | |
| jocis | 1:ac6b7b1bf6c5 | 120 | /** call - Overloaded callback initiator. |
| jocis | 1:ac6b7b1bf6c5 | 121 | * |
| jocis | 1:ac6b7b1bf6c5 | 122 | * call the callback function. |
| jocis | 1:ac6b7b1bf6c5 | 123 | * |
| jocis | 1:ac6b7b1bf6c5 | 124 | * @param int The value to pass to the callback. |
| jocis | 1:ac6b7b1bf6c5 | 125 | */ |
| jocis | 1:ac6b7b1bf6c5 | 126 | void call(int arg) { |
| jocis | 1:ac6b7b1bf6c5 | 127 | if (c_callback != NULL) { |
| jocis | 1:ac6b7b1bf6c5 | 128 | (*c_callback)(arg); |
| jocis | 1:ac6b7b1bf6c5 | 129 | } |
| jocis | 1:ac6b7b1bf6c5 | 130 | else { |
| jocis | 1:ac6b7b1bf6c5 | 131 | if (obj_callback != NULL && method_callback != NULL) { |
| jocis | 1:ac6b7b1bf6c5 | 132 | (obj_callback->*method_callback)(arg); |
| jocis | 1:ac6b7b1bf6c5 | 133 | } |
| jocis | 1:ac6b7b1bf6c5 | 134 | } |
| jocis | 1:ac6b7b1bf6c5 | 135 | } |
| jocis | 1:ac6b7b1bf6c5 | 136 | |
| jocis | 1:ac6b7b1bf6c5 | 137 | }; |
| jocis | 1:ac6b7b1bf6c5 | 138 | |
| jocis | 1:ac6b7b1bf6c5 | 139 | }; // namespace AjK ends |
| jocis | 1:ac6b7b1bf6c5 | 140 | |
| jocis | 1:ac6b7b1bf6c5 | 141 | using namespace AjK; |
| jocis | 1:ac6b7b1bf6c5 | 142 | |
| jocis | 1:ac6b7b1bf6c5 | 143 | #endif |