summaryrefslogtreecommitdiffhomepage
path: root/digital/io/src/servo.avr.c
diff options
context:
space:
mode:
Diffstat (limited to 'digital/io/src/servo.avr.c')
-rw-r--r--digital/io/src/servo.avr.c201
1 files changed, 201 insertions, 0 deletions
diff --git a/digital/io/src/servo.avr.c b/digital/io/src/servo.avr.c
new file mode 100644
index 00000000..c2603c6e
--- /dev/null
+++ b/digital/io/src/servo.avr.c
@@ -0,0 +1,201 @@
+/* servo.avr.c */
+/* io - Input & Output with Artificial Intelligence (ai) support on AVR. {{{
+ *
+ * Copyright (C) 2008 Dufour Jérémy
+ *
+ * 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 "servo.h"
+
+#include "modules/utils/utils.h" /* regv, set_bit */
+#include "modules/utils/byte.h" /* v16_to_v8 */
+#include "io.h" /* General defines of registers */
+
+/**
+ * @defgroup ServoConfig Servo module configuration variables and defines.
+ * @{
+ */
+
+/**
+ * All servos are connected to the PORTA.
+ */
+#define SERVO_PORT PORTA
+#define SERVO_DDR DDRA
+
+/**
+ * TOP of the timer/counter.
+ */
+#define SERVO_TCNT_TOP 0xFF
+
+/**
+ * Number of TIC the timer/counter need to do to make a whole cycle of servo
+ * update.
+ * It does not depend on the servo motors we manage but on the time we want a
+ * whole cycle to last.
+ * The formula used is:
+ * time_of_a_cycle * AVR_frequency / timer_counter_prescaler
+ * We want a time of 20ms (20/1000).
+ * See @a servo_init to know the prescaler value of the timer/counter.
+ */
+static const uint16_t servo_tic_cyle_ = ((20/1000) * AC_FREQ / 256);
+
+/** @} */
+
+/**
+ * @defgroup ServoPrivate Servo module private variables and functions
+ * declarations
+ * @{
+ */
+
+/**
+ * Identifier of the servo we are currently updating.
+ * Note: -1 is a special value used by the servo module system to update the
+ * low state of all the servos.
+ */
+volatile int8_t servo_updating_id_;
+
+/**
+ * A table for the time spent by each servo in high state.
+ */
+volatile uint8_t servo_high_time_[SERVO_NUMBER];
+
+/**
+ * Overflow of timer/counter 2 handler.
+ */
+SIGNAL (SIG_OVERFLOW2);
+
+/** @} */
+
+/* Initialize servo module. */
+void
+servo_init (void)
+{
+ /* Set-up all the pins of the servo to out direction */
+ set_bit (SERVO_DDR, 0);
+ set_bit (SERVO_DDR, 1);
+ set_bit (SERVO_DDR, 2);
+ set_bit (SERVO_DDR, 3);
+ set_bit (SERVO_DDR, 4);
+ /* All pins are at low state by default */
+
+ /* Set-up the timer/counter 2:
+ - prescaler 256 => 4.44 ms TOP */
+ TCCR2 = regv (FOC2, WGM20, COM21, COM20, WGM21, CS22, CS21, CS20,
+ 0, 0, 0, 0, 0, 1, 0, 0);
+
+ /* The state machine start with the first servo */
+ servo_updating_id_ = 0;
+
+ /* Enable overflow interrupt */
+ set_bit (TIMSK, TOIE2);
+}
+
+/* Set the high time of the input signal of a servo (and its position). */
+void
+servo_set_high_time (uint8_t servo, uint8_t high_time)
+{
+ /* Sanity check */
+ if (servo < SERVO_NUMBER)
+ /* Set new desired position (high value time) */
+ servo_high_time_[servo] = high_time;
+}
+
+/* Get the high time of the servo. */
+uint8_t
+servo_get_high_time (uint8_t servo)
+{
+ /* Sanity check */
+ if (servo < SERVO_NUMBER)
+ return servo_high_time_[servo];
+ return 0;
+}
+
+/* Overflow of timer/counter 2 handler. */
+SIGNAL (SIG_OVERFLOW2)
+{
+ /* Overflow count (used when we wait in the lower state).
+ -1 is used for the first count where we wait less than a complete
+ overflow */
+ static int8_t servo_overflow_count = -1;
+ /* Time spent by each servo motor at high state during a whole cycle */
+ static uint16_t servo_high_time_cycle = servo_tic_cyle_;
+
+ /* State machine actions */
+ switch (servo_updating_id_)
+ {
+ case 0:
+ case 1:
+ case 2:
+ case 3:
+ case 4:
+ /* Servos motor high state mode */
+
+ /* Set to low state the previous servo motor pin if needed (not for
+ * the first one) */
+ if (servo_updating_id_ != 0)
+ SERVO_PORT &= ~_BV (servo_updating_id_ - 1);
+ /* Set to high state the current servo motor pin */
+ set_bit (SERVO_PORT, servo_updating_id_);
+ /* Plan next timer overflow to the TOP minus the current configuration
+ * of the servo motor */
+ TCNT2 = SERVO_TCNT_TOP - servo_high_time_[servo_updating_id_];
+ /* Update the time spent at high state by all servo motors for this
+ * cycle */
+ servo_high_time_cycle += servo_high_time_[servo_updating_id_];
+ /* Update the identifier of the current servo motor (and manage when
+ * we are at the last one) */
+ if (++servo_updating_id_ == SERVO_NUMBER)
+ servo_updating_id_ = -1;
+ break;
+
+ case -1:
+ /* Sleeping time mode */
+
+ /* Is it the first we are in this mode? */
+ if (servo_overflow_count == -1)
+ {
+ /* Set to low state the previous servo motor pin */
+ SERVO_PORT &= ~_BV (SERVO_NUMBER - 1);
+ /* Number of full overflow (from 0 to SERVO_TCNT_TOP) we need to
+ * wait (division by SERVO_TCNT_TOP or >> 8) */
+ servo_overflow_count = servo_high_time_cycle >> 8;
+ /* Restart the counter from remaining TIC that are left and can
+ * not be used to make a full overflow */
+ TCNT2 = SERVO_TCNT_TOP - v16_to_v8 (servo_high_time_cycle, 0);
+ }
+ else
+ {
+ /* We just have an overflow, are we at the last one needed? The -1
+ * is normal: we do not count the first overflow of the sleeping
+ * mode because it is not a full one */
+ if (--servo_overflow_count == -1)
+ {
+ /* Restart with first servo motor */
+ servo_updating_id_ = 0;
+ /* Re-initialize the counter of time spent by each servo motor
+ * at high state */
+ servo_high_time_cycle = servo_tic_cyle_;
+ }
+ }
+ break;
+ }
+}