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
QEIx4 Class Reference
Quadrature Encoder Interface for Motion Control. More...
#include <QEIx4.h>
Public Member Functions | |
| QEIx4 (PinName pinA, PinName pinB, PinName pinI=NC, EMODE eMode=IRQ) | |
| constructor of QEIx4 object | |
| ~QEIx4 () | |
| destructor of QEIx4 object | |
| int | read () |
| Gets the actual counter value. | |
| operator int () | |
| Gets the actual counter value as int operator. | |
| void | write (int counter) |
| Sets the counter value at actual encoder position to given value. | |
| int | operator= (int counter) |
| Sets the counter value at actual encoder position to given value as assign operator. | |
| void | poll () |
| Polls the state machine manually and updates the counter value. | |
| void | setIndexTrigger (bool bIndexTrigger) |
| Sets the flag for zeroing on next high on index pin while AB lines triggers next counting. | |
| void | attachCounterChange (void(*function)(int)=0) |
| attach - Overloaded attachment function. | |
| template<class T > | |
| void | attachCounterChange (T *item, void(T::*method)(int)) |
| attachCounterChange - Overloaded attachment function. | |
| void | attachDirectionChange (void(*function)(int)=0) |
| attachDirectionChange - Overloaded attachment function. | |
| template<class T > | |
| void | attachDirectionChange (T *item, void(T::*method)(int)) |
| attachDirectionChange - Overloaded attachment function. | |
| void | attachIndexTrigger (void(*function)(int)=0) |
| attachIndexTrigger - Overloaded attachment function. | |
| template<class T > | |
| void | attachIndexTrigger (T *item, void(T::*method)(int)) |
| attachIndexTrigger - Overloaded attachment function. | |
| void | setSpeedFactor (float fSpeedFactor) |
| Sets the factor for the getter-functions to convert in another unit (1.0=Hz, 1/(4*CPR)=rps, 1/(60*4*CPR)=rpm, 360/(4*CPR)=°/s, ...) | |
| float | getSpeed () |
| Gets the actual speed as float value. | |
| void | setPositionFactor (float fPositionFactor) |
| Sets the factor for the getter-functions to convert in another unit (e.g. | |
| float | getPosition () |
| Gets the actual counter value as float value. | |
Detailed Description
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.
Example:
#include "mbed.h" #include "QEIx4.h" DigitalOut LEDalive(LED1); DigitalOut LEDzero(LED2); DigitalOut LEDup(LED4); DigitalOut LEDdown(LED3); Timer t; // timer for polling // ports for nxp LPC 1768 QEIx4 qei1(p30, p29, p28, (QEIx4::EMODE)(QEIx4::IRQ | QEIx4::SPEED)); // QEI with index signal for zeroing QEIx4 qei2(p21, p22, NC, QEIx4::IRQ_NO_JAMMING); // QEI with AB signals only QEIx4 qei3(p25, p24, NC, QEIx4::POLLING); // QEI without interrups in polling mode // The callback functions void myCounterChangeCallback(int value) { static int valueLast=-1; if ( value > valueLast ) { LEDup = !LEDup; LEDdown = 0; } else { LEDdown = !LEDdown; LEDup = 0; } valueLast = value; } void myIndexTriggerCallback(int value) { qei1 = 0; // reset counter LEDzero = 1; } int main() { t.start(); qei1.setIndexTrigger(true); // set the flag to zero counter on next index signal rises qei1.setSpeedFactor(1.0f); // factor to scale from Hz (edges pe second = 4 * CPS) to user units (1.0=Hz, 1/(4*CPR)=rps, 1/(60*4*CPR)=rpm, 360/(4*CPR)=°/s, ...) qei3.attachIndexTrigger(myIndexTriggerCallback); qei3.attachCounterChange(myCounterChangeCallback); while(1) { qei3.poll(); // poll manually without interrupt - sampling in this loop with about 2kHz if ( t.read_ms() > 250 ) { // every quater second (4 Hz) t.reset(); t.start(); LEDalive = !LEDalive; printf ( "\r\n%6d %6d %6d %10.3f", (int)qei1, (int)qei2, (int)qei3, (float)qei1.getSpeed() ); // print counter values } wait_us(20); // for about 50kHz polling } }
Definition at line 119 of file QEIx4.h.
Constructor & Destructor Documentation
| QEIx4 | ( | PinName | pinA, |
| PinName | pinB, | ||
| PinName | pinI = NC, |
||
| EMODE | eMode = IRQ |
||
| ) |
constructor of QEIx4 object
- Parameters:
-
pinA Pin number of input/interrupt pin for encoder line A. All port pins are possible except p19 and p20 pinB Pin number of input/interrupt pin for encoder line B. All port pins are possible except p19 and p20 pinI Pin number of input pin for optional encoder index or reference switch. eMode Flag to use interrups to detect changes on line A and B. For none interrupt use mode POLLING and call the function poll() frequently. For optional speed calculation the mode SPEED can be ored
Member Function Documentation
| void attachCounterChange | ( | void(*)(int) | function = 0 ) |
| void attachCounterChange | ( | T * | item, |
| void(T::*)(int) | method | ||
| ) |
attachCounterChange - Overloaded attachment function.
Attach a C++ type object/method pointer as the callback.
Note, the callback method prototype must be:-
public: static void myCallbackFunction(int);
- Parameters:
-
A C++ object pointer. A C++ method within the object to call.
| void attachDirectionChange | ( | void(*)(int) | function = 0 ) |
| void attachDirectionChange | ( | T * | item, |
| void(T::*)(int) | method | ||
| ) |
attachDirectionChange - Overloaded attachment function.
Attach a C++ type object/method pointer as the callback.
Note, the callback method prototype must be:-
public: static void myCallbackFunction(int);
- Parameters:
-
A C++ object pointer. A C++ method within the object to call.
| void attachIndexTrigger | ( | void(*)(int) | function = 0 ) |
| void attachIndexTrigger | ( | T * | item, |
| void(T::*)(int) | method | ||
| ) |
attachIndexTrigger - Overloaded attachment function.
Attach a C++ type object/method pointer as the callback.
Note, the callback method prototype must be:-
public: static void myCallbackFunction(int);
- Parameters:
-
A C++ object pointer. A C++ method within the object to call.
| float getPosition | ( | ) |
Gets the actual counter value as float value.
The value is scales by the facor set by setSpeedFactor()
- Returns:
- Actual encoder position as float
| float getSpeed | ( | ) |
Gets the actual speed as float value.
The value is scales by the facor set by setPositionFactor()
- Returns:
- Actual encoder speed as float
| operator int | ( | ) |
| int operator= | ( | int | counter ) |
| void poll | ( | ) |
| int read | ( | ) |
| void setIndexTrigger | ( | bool | bIndexTrigger ) |
Sets the flag for zeroing on next high on index pin while AB lines triggers next counting.
The trigger calls tha callback function in which the counter can be set to zero or the actual counter can be latched in for later offset calculation
- Parameters:
-
Flag for triggering. Set to 1 for call the attached callback. It is reseted after this call
| void setPositionFactor | ( | float | fPositionFactor ) |
| void setSpeedFactor | ( | float | fSpeedFactor ) |
Generated on Fri Jul 15 2022 02:24:32 by
1.7.2