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-rw-r--r--digital/avr/modules/motor/encoder/encoder_corrector.c55
1 files changed, 55 insertions, 0 deletions
diff --git a/digital/avr/modules/motor/encoder/encoder_corrector.c b/digital/avr/modules/motor/encoder/encoder_corrector.c
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+/* encoder_corrector.c */
+/* motor - Motor control module. {{{
+ *
+ * Copyright (C) 2011 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 "encoder_corrector.h"
+
+#include "modules/math/fixed/fixed.h"
+
+/*
+ * The encoder corrector apply a correction factor to an encoder output to
+ * take into account a difference in wheel size. This should be used on the
+ * right encoder for example for a two wheeled robot.
+ */
+
+void
+encoder_corrector_init (encoder_corrector_t *corrector)
+{
+ /* Default value: no correction. */
+ corrector->correction = 1L << 24;
+}
+
+void
+encoder_corrector_update (encoder_corrector_t *corrector, encoder_t *encoder)
+{
+ /* First cancel encoder update work. */
+ encoder->cur -= encoder->diff;
+ /* Update our own raw encoder position and apply factor. */
+ corrector->cur_raw += encoder->diff;
+ uint16_t new = fixed_mul_f824 (corrector->cur_raw, corrector->correction);
+ /* Now patch encoder state. */
+ encoder->diff = (int16_t) (new - encoder->cur);
+ encoder->cur = new;
+}
+