/* timer.avr.c */ /* asserv - Position & speed motor control on AVR. {{{ * * Copyright (C) 2005 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 "modules/utils/utils.h" #include "modules/motor/encoder/encoder.h" #include "io.h" /** Top timer value. */ #define TIMER_TOP 255 /** Number of steps during wait. */ #define TIMER_STEPS 4 /** Size of step. */ #define TIMER_STEP ((TIMER_TOP + 1) / TIMER_STEPS) /** Initialise the timer. */ void timer_init (void) { TCCR0 = regv (FOC0, WGM00, COM01, COM00, WGM01, CS02, CS01, CS00, 0, 0, 0, 0, 0, 1, 0, 0); /* Fov = F_io / (prescaler * (TOP + 1)) * TOP = 0xff * prescaler = 256 * Tov = 1 / Fov = 4.444 ms */ } /** Wait for timer overflow. */ void timer_wait (void) { uint8_t i; /* Make small steps with counter updates. */ for (i = 1; i < TIMER_STEPS; i++) { while (TCNT0 < i * TIMER_STEP) ; encoder_update_step (); } /* Wait overflow. */ while (!(TIFR & _BV (TOV0))) ; /* Write 1 to clear. */ TIFR = _BV (TOV0); }