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-rw-r--r--digital/asserv/src/asserv/counter_ext.avr.c95
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diff --git a/digital/asserv/src/asserv/counter_ext.avr.c b/digital/asserv/src/asserv/counter_ext.avr.c
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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.
+ *
+ * }}} */
+
+/**
+ * This file add support for an external counter like the hdlcounter or
+ * avrcounter project. This can be better in order not to loose steps.
+ */
+
+/** Last values. */
+static uint8_t counter_left_old, counter_right_old;
+/** Overall counter values. */
+static uint16_t counter_left, counter_right;
+/** Counter differences since last update.
+ * Maximum of 7 significant bits, sign included. */
+static int16_t counter_left_diff, counter_right_diff;
+
+#define COUNTER_ALE _BV (2)
+#define COUNTER_RD _BV (1)
+#define COUNTER_WR _BV (0)
+
+static inline void
+counter_restart (void);
+
+/** Initialize the counters. */
+static inline void
+counter_init (void)
+{
+ PORTG |= COUNTER_ALE | COUNTER_RD | COUNTER_WR;
+ DDRG |= COUNTER_ALE | COUNTER_RD | COUNTER_WR;
+ PORTA = 0;
+ DDRA = 0xff;
+ /* Begin with safe values. */
+ counter_restart ();
+}
+
+/** Read an external counter. */
+static inline uint8_t
+counter_read (uint8_t n)
+{
+ uint8_t v;
+ PORTA = n;
+ PORTG &= ~COUNTER_ALE;
+ PORTA = 0;
+ DDRA = 0;
+ PORTG &= ~COUNTER_RD;
+ v = PINA;
+ PORTG |= COUNTER_RD;
+ PORTG |= COUNTER_ALE;
+ DDRA = 0xff;
+ return v;
+}
+
+/** Update overall counter values and compute diffs. */
+static inline void
+counter_update (void)
+{
+ uint8_t left, right;
+ left = counter_read (0);
+ counter_left_diff = (int8_t) (left - counter_left_old);
+ counter_left += counter_left_diff;
+ right = counter_read (1);
+ counter_right_diff = (int8_t) (right - counter_right_old);
+ counter_right += counter_right_diff;
+}
+
+/** Restart counting. */
+static inline void
+counter_restart (void)
+{
+ counter_left_old = counter_read (0);
+ counter_right_old = counter_read (1);
+}
+