QEI2
Diff: QEI.h
- Revision:
- 1:2d418d07997d
- Parent:
- 0:5c2ad81551aa
diff -r 5c2ad81551aa -r 2d418d07997d QEI.h --- a/QEI.h Thu Sep 02 16:48:55 2010 +0000 +++ /dev/null Thu Jan 01 00:00:00 1970 +0000 @@ -1,244 +0,0 @@ -/** - * @author Aaron Berk - * - * @section LICENSE - * - * Copyright (c) 2010 ARM Limited - * - * Permission is hereby granted, free of charge, to any person obtaining a copy - * of this software and associated documentation files (the "Software"), to deal - * in the Software without restriction, including without limitation the rights - * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell - * copies of the Software, and to permit persons to whom the Software is - * furnished to do so, subject to the following conditions: - * - * The above copyright notice and this permission notice shall be included in - * all copies or substantial portions of the Software. - * - * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR - * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, - * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE - * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER - * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, - * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN - * THE SOFTWARE. - * - * @section DESCRIPTION - * - * Quadrature Encoder Interface. - * - * A quadrature encoder consists of two code tracks on a disc which are 90 - * degrees out of phase. It can be used to determine how far a wheel has - * rotated, relative to a known starting position. - * - * Only one code track changes at a time leading to a more robust system than - * a single track, because any jitter around any edge won't cause a state - * change as the other track will remain constant. - * - * Encoders can be a homebrew affair, consisting of infrared emitters/receivers - * and paper code tracks consisting of alternating black and white sections; - * alternatively, complete disk and PCB emitter/receiver encoder systems can - * be bought, but the interface, regardless of implementation is the same. - * - * +-----+ +-----+ +-----+ - * Channel A | ^ | | | | | - * ---+ ^ +-----+ +-----+ +----- - * ^ ^ - * ^ +-----+ +-----+ +-----+ - * Channel B ^ | | | | | | - * ------+ +-----+ +-----+ +----- - * ^ ^ - * ^ ^ - * 90deg - * - * The interface uses X2 encoding by default which calculates the pulse count - * based on reading the current state after each rising and falling edge of - * channel A. - * - * +-----+ +-----+ +-----+ - * Channel A | | | | | | - * ---+ +-----+ +-----+ +----- - * ^ ^ ^ ^ ^ - * ^ +-----+ ^ +-----+ ^ +-----+ - * Channel B ^ | ^ | ^ | ^ | ^ | | - * ------+ ^ +-----+ ^ +-----+ +-- - * ^ ^ ^ ^ ^ - * ^ ^ ^ ^ ^ - * Pulse count 0 1 2 3 4 5 ... - * - * This interface can also use X4 encoding which calculates the pulse count - * based on reading the current state after each rising and falling edge of - * either channel. - * - * +-----+ +-----+ +-----+ - * Channel A | | | | | | - * ---+ +-----+ +-----+ +----- - * ^ ^ ^ ^ ^ - * ^ +-----+ ^ +-----+ ^ +-----+ - * Channel B ^ | ^ | ^ | ^ | ^ | | - * ------+ ^ +-----+ ^ +-----+ +-- - * ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ - * ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ - * Pulse count 0 1 2 3 4 5 6 7 8 9 ... - * - * It defaults - * - * An optional index channel can be used which determines when a full - * revolution has occured. - * - * If a 4 pules per revolution encoder was used, with X4 encoding, - * the following would be observed. - * - * +-----+ +-----+ +-----+ - * Channel A | | | | | | - * ---+ +-----+ +-----+ +----- - * ^ ^ ^ ^ ^ - * ^ +-----+ ^ +-----+ ^ +-----+ - * Channel B ^ | ^ | ^ | ^ | ^ | | - * ------+ ^ +-----+ ^ +-----+ +-- - * ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ - * ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ - * ^ ^ ^ +--+ ^ ^ +--+ ^ - * ^ ^ ^ | | ^ ^ | | ^ - * Index ------------+ +--------+ +----------- - * ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ - * Pulse count 0 1 2 3 4 5 6 7 8 9 ... - * Rev. count 0 1 2 - * - * Rotational position in degrees can be calculated by: - * - * (pulse count / X * N) * 360 - * - * Where X is the encoding type [e.g. X4 encoding => X=4], and N is the number - * of pulses per revolution. - * - * Linear position can be calculated by: - * - * (pulse count / X * N) * (1 / PPI) - * - * Where X is encoding type [e.g. X4 encoding => X=44], N is the number of - * pulses per revolution, and PPI is pulses per inch, or the equivalent for - * any other unit of displacement. PPI can be calculated by taking the - * circumference of the wheel or encoder disk and dividing it by the number - * of pulses per revolution. - */ - -#ifndef QEI_H -#define QEI_H - -/** - * Includes - */ -#include "mbed.h" - -/** - * Defines - */ -#define PREV_MASK 0x1 //Mask for the previous state in determining direction -//of rotation. -#define CURR_MASK 0x2 //Mask for the current state in determining direction -//of rotation. -#define INVALID 0x3 //XORing two states where both bits have changed. - -/** - * Quadrature Encoder Interface. - */ -class QEI { - -public: - - typedef enum Encoding { - - X2_ENCODING, - X4_ENCODING - - } Encoding; - - /** - * Constructor. - * - * Reads the current values on channel A and channel B to determine the - * initial state. - * - * Attaches the encode function to the rise/fall interrupt edges of - * channels A and B to perform X4 encoding. - * - * Attaches the index function to the rise interrupt edge of channel index - * (if it is used) to count revolutions. - * - * @param channelA mbed pin for channel A input. - * @param channelB mbed pin for channel B input. - * @param index mbed pin for optional index channel input, - * (pass NC if not needed). - * @param pulsesPerRev Number of pulses in one revolution. - * @param encoding The encoding to use. Uses X2 encoding by default. X2 - * encoding uses interrupts on the rising and falling edges - * of only channel A where as X4 uses them on both - * channels. - */ - QEI(PinName channelA, PinName channelB, PinName index, int pulsesPerRev, Encoding encoding = X2_ENCODING); - - /** - * Reset the encoder. - * - * Sets the pulses and revolutions count to zero. - */ - void reset(void); - - /** - * Read the state of the encoder. - * - * @return The current state of the encoder as a 2-bit number, where: - * bit 1 = The reading from channel B - * bit 2 = The reading from channel A - */ - int getCurrentState(void); - - /** - * Read the number of pulses recorded by the encoder. - * - * @return Number of pulses which have occured. - */ - int getPulses(void); - - /** - * Read the number of revolutions recorded by the encoder on the index channel. - * - * @return Number of revolutions which have occured on the index channel. - */ - int getRevolutions(void); - -private: - - /** - * Update the pulse count. - * - * Called on every rising/falling edge of channels A/B. - * - * Reads the state of the channels and determines whether a pulse forward - * or backward has occured, updating the count appropriately. - */ - void encode(void); - - /** - * Called on every rising edge of channel index to update revolution - * count by one. - */ - void index(void); - - Encoding encoding_; - - InterruptIn channelA_; - InterruptIn channelB_; - InterruptIn index_; - - int pulsesPerRev_; - int prevState_; - int currState_; - - volatile int pulses_; - volatile int revolutions_; - -}; - -#endif /* QEI_H */