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/* counter_ext.avr.c - External counter support. */
/* asserv - Position & speed motor control on AVR. {{{
 *
 * Copyright (C) 2008 Nicolas Schodet
 *
 * APBTeam:
 *        Web: http://apbteam.org/
 *      Email: team AT apbteam DOT org
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 *
 * }}} */
#include "common.h"
#include "counter.h"

#include "modules/utils/utils.h"
#include "modules/math/fixed/fixed.h"
#include "io.h"

/**
 * This file add support for an external counter like the hdlcounter or
 * avrcounter project.  This can be better in order not to loose steps and
 * support more counters.
 *
 * There is additionnal support for error correction on the right counter.
 */

/** Define the left counter address. */
#define COUNTER_LEFT 0
/** Define the right counter address. */
#define COUNTER_RIGHT 1

/** Define to 1 to reverse the left counter. */
#define COUNTER_LEFT_REVERSE 0
/** Define to 1 to reverse the right counter. */
#define COUNTER_RIGHT_REVERSE 0

/** Left counter shift. */
#define COUNTER_LEFT_SHIFT 0
/** Right counter shift. */
#define COUNTER_RIGHT_SHIFT 0

/** Define to 1 to use the AVR External Memory system, or 0 to use hand made
 * signals. */
#define COUNTER_USE_XMEM 0

/** Last values. */
static uint16_t counter_left_old, counter_right_old;
/** New values, being updated by step update. */
static int16_t counter_left_new_step, counter_right_new_step;
/** Last raw step values */
static uint8_t counter_left_old_step, counter_right_old_step;
/** Overall counter values. */
uint16_t counter_left, counter_right;
/** Overall uncorrected counter values. */
static int32_t counter_right_raw;
/** Correction factor (f8.24). */
uint32_t counter_right_correction = 1L << 24;
/** Counter differences since last update.
 * Maximum of 9 significant bits, sign included. */
int16_t counter_left_diff, counter_right_diff;

#if !COUNTER_USE_XMEM
# define COUNTER_ALE_IO B, 4
# define COUNTER_RD_IO D, 6
#endif

/** Read an external counter. */
static inline uint8_t
counter_read (uint8_t n)
{
#if COUNTER_USE_XMEM
    uint8_t * const ext = (void *) 0x1100;
    return ext[n];
#else
    uint8_t v;
    PORTA = (PORTA & 0xf0) | (n & 0x0f);
    IO_CLR (COUNTER_ALE_IO);
    PORTA &= 0xf0;
    DDRA &= 0xf0;
    DDRB &= 0xf0;
    IO_CLR (COUNTER_RD_IO);
    utils_nop ();
    utils_nop ();
    v = (PINA & 0x0f) | (PINB & 0x0f) << 4;
    IO_SET (COUNTER_RD_IO);
    IO_SET (COUNTER_ALE_IO);
    DDRA |= 0x0f;
    DDRB |= 0x0f;
    return v;
#endif
}

/** Initialize the counters. */
void
counter_init (void)
{
#if COUNTER_USE_XMEM
    /* Long wait-states. */
    XMCRA = _BV (SRW11);
    /* Do not use port C for address. */
    XMCRB = _BV (XMM2) | _BV (XMM1) | _BV (XMM0);
    /* Long wait-states and enable. */
    MCUCR |= _BV (SRE) | _BV (SRW10);
#else
    IO_SET (COUNTER_ALE_IO);
    IO_SET (COUNTER_RD_IO);
    IO_OUTPUT (COUNTER_ALE_IO);
    IO_OUTPUT (COUNTER_RD_IO);
    PORTA &= 0xf0;
    PORTB &= 0xf0;
    DDRA |= 0x0f;
    DDRB |= 0x0f;
#endif
    /* Begin with safe values. */
    counter_left_old_step = counter_read (COUNTER_LEFT);
    counter_right_old_step = counter_read (COUNTER_RIGHT);
}

/** Update one step.  If counters are not read fast enough, they could
 * overflow, call this function often to update step counters. */
void
counter_update_step (void)
{
    uint8_t left, right;
    int8_t diff;
    /* Sample counters. */
    left = counter_read (COUNTER_LEFT);
    right = counter_read (COUNTER_RIGHT);
    /* Update step counters. */
    diff = (int8_t) (left - counter_left_old_step);
    counter_left_old_step = left;
    counter_left_new_step += diff;
    diff = (int8_t) (right - counter_right_old_step);
    counter_right_old_step = right;
    counter_right_new_step += diff;
}

/** Update overall counter values and compute diffs. */
void
counter_update (void)
{
    /* Wants fresh data. */
    counter_update_step ();
    /* Left counter. */
    uint16_t left = counter_left_new_step;
    left &= 0xffff << COUNTER_LEFT_SHIFT; /* Reset unused bits. */
#if !COUNTER_LEFT_REVERSE
    counter_left_diff = (int16_t) (left - counter_left_old);
#else
    counter_left_diff = (int16_t) (counter_left_old - left);
#endif
    counter_left_diff >>= COUNTER_LEFT_SHIFT;
    counter_left_old = left;
    counter_left += counter_left_diff;
    /* Right counter. */
    uint16_t right = counter_right_new_step;
    right &= 0xffff << COUNTER_RIGHT_SHIFT; /* Reset unused bits. */
#if !COUNTER_RIGHT_REVERSE
    counter_right_diff = (int16_t) (right - counter_right_old);
#else
    counter_right_diff = (int16_t) (counter_right_old - right);
#endif
    counter_right_diff >>= COUNTER_RIGHT_SHIFT;
    counter_right_old = right;
    /* Fix right counter. */
    counter_right_raw += counter_right_diff;
    uint16_t right_new = fixed_mul_f824 (counter_right_raw,
					 counter_right_correction);
    counter_right_diff = (int16_t) (right_new - counter_right);
    counter_right = right_new;
}