/* pwm.avr.c */ /* asserv - Position & speed motor control on AVR. {{{ * * Copyright (C) 2005 Nicolas Schodet * * Robot APB Team/Efrei 2006. * 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. * * }}} */ /** Define the PWM output used for left motor. */ #define PWM_LEFT_OCR OCR1C /** Define the PWM output used for right motor. */ #define PWM_RIGHT_OCR OCR1B /** Define the direction output for left motor. */ #define PWM_LEFT_DIR 3 /** Define the direction output for right motor. */ #define PWM_RIGHT_DIR 2 /** Define the absolute maximum PWM value. */ #define PWM_MAX 0x3ff /** PWM values, this is an error if absolute value is greater than the * maximum. */ int16_t pwm_left, pwm_right; /** PWM reverse direction, only set pwm dir bits or you will get weird results * on port B. */ uint8_t pwm_dir = _BV (PWM_LEFT_DIR); /* +AutoDec */ /** Initialise PWM generator. */ static inline void pwm_init (void); /** Update the hardware PWM values. */ static inline void pwm_update (void); /* -AutoDec */ /** Initialise PWM generator. */ static inline void pwm_init (void) { /* Fast PWM, TOP = 0x3ff, OC1B & OC1C with positive logic. f_IO without prescaler. Fpwm = f_IO / (prescaler * (1 + TOP)) = 14400 Hz. */ TCCR1A = regv (COM1A1, COM1A0, COM1B1, COM1B0, COM1C1, COM1C0, WGM11, WGM10, 0, 0, 1, 0, 1, 0, 1, 1); TCCR1B = regv (ICNC1, ICES1, 5, WGM13, WGM12, CS12, CS11, CS10, 0, 0, 0, 0, 1, 0, 0, 1); /* Enable pwm and direction outputs in DDRB. */ DDRB |= _BV (7) | _BV (6) | _BV (PWM_LEFT_DIR) | _BV (PWM_RIGHT_DIR); } /** Update the hardware PWM values. */ static inline void pwm_update (void) { uint16_t left, right; uint8_t dir; /* Some assumption checks. */ assert (pwm_left >= -PWM_MAX && pwm_left <= PWM_MAX); assert (pwm_right >= -PWM_MAX && pwm_right <= PWM_MAX); assert ((pwm_dir & ~(_BV (PWM_LEFT_DIR) | _BV (PWM_RIGHT_DIR))) == 0); /* Sample port B. */ dir = PORTB & ~(_BV (PWM_LEFT_DIR) | _BV (PWM_RIGHT_DIR)); /* Set left PWM. */ if (pwm_left == 0) { left = 0; } else if (pwm_left < 0) { left = -pwm_left; } else { dir |= _BV (PWM_LEFT_DIR); left = pwm_left; } /* Set right PWM. */ if (pwm_right == 0) { right = 0; } else if (pwm_right < 0) { right = -pwm_right; } else { dir |= _BV (PWM_RIGHT_DIR); right = pwm_right; } /* Setup registers. */ /* Here, there could be a problem because OCRx are double buffered, not * PORTB! */ /* Another problem arise if the OCR sampling is done between left and * right OCR: the right PWM is one cycle late. */ /* A solution could be to use interrupts to update PWM or to synchronise * general timer with PWM. */ dir ^= pwm_dir; PORTB = dir; PWM_LEFT_OCR = left; PWM_RIGHT_OCR = right; }