Initial Arduino IDE based on Processing.

build/shared/lib/avrlib/encoder.h

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+/*! \file encoder.h \brief Quadrature Encoder reader/driver. */
+//*****************************************************************************
+//
+// File Name	: 'encoder.h'
+// Title		: Quadrature Encoder reader/driver
+// Author		: Pascal Stang - Copyright (C) 2003-2004
+// Created		: 2003.01.26
+// Revised		: 2004.06.25
+// Version		: 0.3
+// Target MCU	: Atmel AVR Series
+// Editor Tabs	: 4
+//
+// Description	: This library allows easy interfacing of quadrature encoders
+//		to the Atmel AVR-series processors.
+//
+//		Quadrature encoders have two digital outputs usually called PhaseA and
+//	PhaseB.  When the encoder rotates, PhaseA and PhaseB produce square wave
+//	pulses where each pulse represents a fraction of a turn of the encoder
+//	shaft.  Encoders are rated for a certain number of pulses (or counts) per
+//	complete revolution of the shaft.  Common counts/revolution specs are 50,
+//	100,128,200,250,256,500,etc.  By counting the number of pulses output on
+//	one of the phases starting from time0, you can calculate the total
+//	rotational distance the encoder has traveled.
+//	
+//  Often, however, we want current position not just total distance traveled.
+//	For this it is necessary to know not only how far the encoder has traveled,
+//	but also which direction it was going at each step of the way.  To do this
+//	we need to use both outputs (or phases) of the quadrature encoder.
+//
+//  The pulses from PhaseA and PhaseB on quadrature encoders are always aligned
+//	90 degrees out-of-phase (otherwise said: 1/4 wavelength apart).  This
+//	special phase relationship lets us extract both the distance and direction
+//	the encoder has rotated from the outputs.
+//
+//  To do this, consider Phase A to be the distance counter.  On each rising
+//	edge of PhaseA we will count 1 "tic" of distance, but we need to know the
+//	direction.  Look at the quadrature waveform plot below.  Notice that when
+//	we travel forward in time (left->right), PhaseB is always low (logic 0) at
+//	the rising edge of PhaseA.  When we travel backwards in time (right->left),
+//	PhaseB is always high (logic 1) at the rising edge of PhaseA.  Note that
+//	traveling forward or backwards in time is the same thing as rotating
+//	forwards or bardwards. Thus, if PhaseA is our counter, PhaseB indicates
+//	direction.
+//
+//	Here is an example waveform from a quadrature encoder:
+/*
+//                /---\   /---\   /---\   /---\   /---\   /---\
+//  Phase A:      |   |   |   |   |   |   |   |   |   |   |   |
+//             ---/   \---/   \---/   \---/   \---/   \---/   \-
+//             -\   /---\   /---\   /---\   /---\   /---\   /---
+//  Phase B:    |   |   |   |   |   |   |   |   |   |   |   |
+//              \---/   \---/   \---/   \---/   \---/   \---/
+//  Time:    <--------------------------------------------------->
+//  Rotate FWD: >----------------------------------------------> 
+//  Rotate REV: <----------------------------------------------<
+*/
+//	To keep track of the encoder position in software, we connect PhaseA to an
+//	external processor interrupt line, and PhaseB to any I/O pin.  We set up
+//	the external interrupt to trigger whenever PhaseA produces a rising edge.
+//	When a rising edge is detected, our interrupt handler function is executed.
+//	Inside the handler function, we quickly check the PhaseB line to see if it
+//	is high or low.  If it is high, we increment the encoder's position
+//	counter, otherwise we decrement it.  The encoder position counter can be
+//	read at any time to find out the current position.
+//
+//
+// NOTE: This code is currently below version 1.0, and therefore is considered
+// to be lacking in some functionality or documentation, or may not be fully
+// tested.  Nonetheless, you can expect most functions to work.
+//
+// This code is distributed under the GNU Public License
+//		which can be found at http://www.gnu.org/licenses/gpl.txt
+//
+//*****************************************************************************
+
+#ifndef ENCODER_H
+#define ENCODER_H
+
+#include "global.h"
+
+// include encoder configuration file
+#include "encoderconf.h"
+
+// constants/macros/typdefs
+
+// defines for processor compatibility
+// chose proper Interrupt Mask (IMSK)
+#ifdef EIMSK
+	#define IMSK	EIMSK	// for processors mega128, mega64
+#else
+	#define IMSK	GIMSK	// for other processors 90s8515, mega163, etc
+#endif
+
+
+//! Encoder state structure
+//   stores the position and other information from each encoder
+typedef struct struct_EncoderState
+{	
+	s32 position;		///< position
+//	s32 velocity;		///< velocity
+} EncoderStateType;
+
+
+// functions
+
+//! encoderInit() initializes hardware and encoder position readings
+//		Run this init routine once before using any other encoder function.
+void encoderInit(void);
+
+//! encoderOff() disables hardware and stops encoder position updates
+void encoderOff(void);
+
+//! encoderGetPosition() reads the current position of the encoder 
+s32 encoderGetPosition(u08 encoderNum);
+
+//! encoderSetPosition() sets the current position of the encoder
+void encoderSetPosition(u08 encoderNum, s32 position);
+
+#endif