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/* speed.c - PI speed control. */
/* asserv - Position & speed motor control on a ATmega128. {{{
 *
 * Copyright (C) 2004 Nicolas Schodet
 *
 * Robot APB Team/Efrei 2005.
 *        Web: http://assos.efrei.fr/robot/
 *      Email: robot AT efrei DOT fr
 *
 * 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.
 *
 * }}} */

/** Actual speed. */
int8_t speed_left, speed_right;
/** Wanted speed. */
int8_t speed_left_aim, speed_right_aim;
/** Max speed. */
int8_t speed_max = 0x20;
/** Acceleration value. */
uint8_t speed_acc = 8;
/** Acceleration counter, speed gets updated when it reachs 0. */
uint8_t speed_acc_cpt;
/** Integral term. */
int16_t speed_left_int, speed_right_int;
/** Integral max value. */
int16_t speed_int_max = 1024;
/** Last error value. */
int16_t speed_left_e_old, speed_right_e_old;
/** P coeficients. 5.8 fixed point format. */
uint16_t speed_kp = 5 * 255;
/** I coeficients. 4.8 fixed point format. */
uint16_t speed_ki = 1 * 255;

/* +AutoDec */

/** Initialise speed parameters. */
static inline void
speed_init (void);

/** Update speeds according to the wanted speeds and the acceleration. */
static inline void
speed_update (void);

/** Compute new pwm value for left motor. */
static inline void
speed_compute_left_pwm (void);

/** Compute new pwm value for right motor. */
static inline void
speed_compute_right_pwm (void);

/** Forget past event, usefull when the speed control is disabled for some
 * time. */
static inline void
speed_restart (void);

/* -AutoDec */

/** Initialise speed parameters. */
static inline void
speed_init (void)
{
    speed_acc = 8;
    speed_int_max = 1024;
    speed_kp = 2 * 255;
    speed_ki = 1 * 255;
}

/** Update speeds according to the wanted speeds and the acceleration. */
static inline void
speed_update (void)
{
    if (speed_acc)
      {
	speed_acc_cpt--;
	if (speed_acc_cpt == 0)
	  {
	    speed_acc_cpt = speed_acc;
	    /* Update speeds. */
	    if (speed_left > speed_left_aim)
		speed_left--;
	    else if (speed_left < speed_left_aim)
		speed_left++;
	    if (speed_right > speed_right_aim)
		speed_right--;
	    else if (speed_right < speed_right_aim)
		speed_right++;
	  }
      }
    else
      {
	speed_left = speed_left_aim;
	speed_right = speed_right_aim;
      }
}

/** Compute new pwm value for left motor. */
static inline void
speed_compute_left_pwm (void)
{
    int16_t e;
    int16_t pwm;
    e = speed_left - counter_left_diff;			/* 10b = 8b + 9b */
    /* Integral update. */
    speed_left_int += e;				/* 12b = 11b + 10b */
    if (speed_left_int > speed_int_max)			/* 11b */
	speed_left_int = speed_int_max;
    else if (speed_left_int < -speed_int_max)
	speed_left_int = -speed_int_max;
    /* Compute PI. */					/* 16b = 15b + 15b */
    pwm = dsp_mul_i16f88 (e, speed_kp)			/* 15b = 10b * 5.8b */
	+ dsp_mul_i16f88 (speed_left_int, speed_ki);	/* 15b = 11b * 4.8b */
    /* Save result. */
    speed_left_e_old = e;
    pwm_left = pwm;
}

/** Compute new pwm value for right motor. */
static inline void
speed_compute_right_pwm (void)
{
    int16_t e;
    int16_t pwm;
    e = speed_right - counter_right_diff;
    /* Integral update. */
    speed_right_int += e;
    if (speed_right_int > speed_int_max)
	speed_right_int = speed_int_max;
    else if (speed_right_int < -speed_int_max)
	speed_right_int = -speed_int_max;
    /* Compute PI. */
    pwm = dsp_mul_i16f88 (e, speed_kp)
	+ dsp_mul_i16f88 (speed_right_int, speed_ki);
    /* Save result. */
    speed_right_e_old = e;
    pwm_right = pwm;
}

/** Forget past event, usefull when the speed control is disabled for some
 * time. */
static inline void
speed_restart (void)
{
    speed_left_int = 0;
    speed_right_int = 0;
    speed_left = 0;
    speed_right = 0;
}

/** Set maximum speed in order to be able to break before a distance and
 * angle, inputs are f24.8 */
static inline void
speed_distance (int32_t dist, int32_t arc)
{
    /* XXX: There are some buggy assertions there if dist and arc are both
     * big. */
    uint8_t vls, vas;
    uint32_t vl248, va248;
    int8_t vl, va;
    /* Drop sign. */
    vls = dist < 0;
    if (vls) dist = -dist;
    vas = arc < 0;
    if (vas) arc = -arc;
    /* Compute speed.
     * v = sqrt (2 * a * d), a = 1/speed_acc */
    vl248 = dsp_sqrt (dist * 2 / speed_acc);
    vl = (vl248 >> 8) & 0xff;
    va248 = dsp_sqrt (arc * 2 / speed_acc);
    va = (va248 >> 8) & 0xff;
    /* Saturate. */
    if (vl248 & 0xffff0000 || vl > speed_max)
	vl = speed_max;
    if (va248 & 0xffff0000 || va > speed_max)
	va = speed_max;
    /* Get sign back. */
    if (vls) vl = -vl;
    if (vas) va = -va;
    speed_left_aim = vl - va;
    speed_right_aim = vl + va;
}