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encoder.c

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/*! \file encoder.c \brief Quadrature Encoder reader/driver. */
//*****************************************************************************
//
// File Name    : 'encoder.c'
// Title        : Quadrature Encoder reader/driver
// Author       : Pascal Stang - Copyright (C) 2003
// Created      : 2003.01.26
// Revised      : 2003.01.26
// Version      : 0.1
// Target MCU   : Atmel AVR Series
// Editor Tabs  : 4
//
// 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 WIN32
    #include <avr/io.h>
    #include <avr/signal.h>
    #include <avr/interrupt.h>
#endif

#include "global.h"
#include "encoder.h"

// Program ROM constants

// Global variables
EncoderStateType EncoderState[NUM_ENCODERS];

// Functions

// encoderInit() initializes hardware and encoder position readings
//      Run this init routine once before using any other encoder functions.
void encoderInit(void)
{
    u08 i;

    // configure encoder direction pins for input
    cbi(ENC0_DIR_PORT, ENC0_DIR_PIN);
    cbi(ENC1_DIR_PORT, ENC1_DIR_PIN);

    // configure interrupt I/O pins for input
    // INT0 and INT1 are pins PD2 and PD3 on processors
    // 90s8515, mega161, mega163, mega323, mega16, mega32
    cbi(DDRD, PD2);
    cbi(DDRD, PD3);
    
    // INT0 and INT1 are pins PD0 and PD1 on processors
    // mega103, mega128, mega64
    //cbi(DDRD, PD2);
    //cbi(DDRD, PD3);

    // configure interrupts for rising-edge triggering
    // for processors 90s8515, mega161, mega163, mega323, mega16, mega32
    sbi(MCUCR, ISC11);
    sbi(MCUCR, ISC10);
    sbi(MCUCR, ISC01);
    sbi(MCUCR, ISC00);
    // for processors mega103, mega128, mega64
    //sbi(EICRA, ISC11);
    //sbi(EICRA, ISC10);
    //sbi(EICRA, ISC01);
    //sbi(EICRA, ISC00);

    // initialize/clear encoder data
    for(i=0; i<NUM_ENCODERS; i++)
    {
        EncoderState[i].position = 0;
        EncoderState[i].velocity = 0;
    }
    // start tracking encoders
    // enable interrupts
    // for processors 90s8515, mega161, mega163, mega323, mega16, mega32
    sbi(GIMSK, INT0);
    sbi(GIMSK, INT1);
    // for processors mega103, mega128, mega64
    //sbi(EIMSK, INT0);
    //sbi(EIMSK, INT1);
    
    // enable global interrupts
    sei();
}

// encoderOff() disables hardware and stops encoder position updates
void encoderOff(void)
{
    // disable interrutps
    cbi(GIMSK, INT0);
    cbi(GIMSK, INT1);
}

// encoderGetPosition() reads the current position of the encoder 
s32 encoderGetPosition(u08 encoderNum)
{
    // sanity check
    if(encoderNum < NUM_ENCODERS)
        return EncoderState[encoderNum].position;
    else
        return 0;
}

// encoderSetPosition() sets the current position of the encoder
void encoderSetPosition(u08 encoderNum, s32 position)
{
    // sanity check
    if(encoderNum < NUM_ENCODERS)
        EncoderState[encoderNum].position = position;
    // else do nothing
}

SIGNAL(ENC0_INTERRUPT)
{
    // encoder has generated a pulse
    // check the direction line and update position accordingly
    if( inb(ENC0_DIR_PORT) & ENC0_DIR_PIN )
        EncoderState[0].position++;
    else
        EncoderState[0].position--;
}

SIGNAL(ENC1_INTERRUPT)
{
    // encoder has generated a pulse
    // check the direction line and update position accordingly
    if( inb(ENC1_DIR_PORT) & ENC1_DIR_PIN )
        EncoderState[1].position++;
    else
        EncoderState[1].position--;
}

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