altos: Rename 'core' to 'kernel'

[fw/altos] / src / kernel / ao_microkalman.c

diff --git a/src/kernel/ao_microkalman.c b/src/kernel/ao_microkalman.c
new file mode 100644 (file)
index 0000000..0684ea2
--- /dev/null
+++ b/src/kernel/ao_microkalman.c
@@ -0,0 +1,74 @@
+/*
+ * Copyright © 2013 Keith Packard <keithp@keithp.com>
+ *
+ * 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; version 2 of the License.
+ *
+ * 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.
+ */
+
+#ifndef AO_FLIGHT_TEST
+#include <ao.h>
+#endif
+#include <ao_micropeak.h>
+
+#define FIX_BITS       16
+
+#define to_fix16(x) ((int16_t) ((x) * 65536.0 + 0.5))
+#define to_fix32(x) ((int32_t) ((x) * 65536.0 + 0.5))
+#define from_fix8(x)   ((x) >> 8)
+#define from_fix(x)    ((x) >> 16)
+#define fix8_to_fix16(x)       ((x) << 8)
+#define fix16_to_fix8(x)       ((x) >> 8)
+
+#include <ao_kalman.h>
+
+/* Basic time step (96ms) */
+#define AO_MK_STEP     to_fix16(0.096)
+/* step ** 2 / 2 */
+#define AO_MK_STEP_2_2 to_fix16(0.004608)
+
+uint32_t       ao_k_pa;                /* 24.8 fixed point */
+int32_t                ao_k_pa_speed;          /* 16.16 fixed point */
+int32_t                ao_k_pa_accel;          /* 16.16 fixed point */
+
+uint32_t       ao_pa;                  /* integer portion */
+int16_t                ao_pa_speed;            /* integer portion */
+int16_t                ao_pa_accel;            /* integer portion */
+
+void
+ao_microkalman_init(void)
+{
+       ao_pa = pa;
+       ao_k_pa = pa << 8;
+}      
+
+void
+ao_microkalman_predict(void)
+{
+       ao_k_pa       += fix16_to_fix8((int32_t) ao_pa_speed * AO_MK_STEP + (int32_t) ao_pa_accel * AO_MK_STEP_2_2);
+       ao_k_pa_speed += (int32_t) ao_pa_accel * AO_MK_STEP;
+}
+
+void
+ao_microkalman_correct(void)
+{
+       int16_t e;      /* Height error in Pa */
+
+       e = pa - from_fix8(ao_k_pa);
+
+       ao_k_pa       += fix16_to_fix8((int32_t) e * AO_MK_BARO_K0_10);
+       ao_k_pa_speed += (int32_t) e * AO_MK_BARO_K1_10;
+       ao_k_pa_accel += (int32_t) e * AO_MK_BARO_K2_10;
+       ao_pa = from_fix8(ao_k_pa);
+       ao_pa_speed = from_fix(ao_k_pa_speed);
+       ao_pa_accel = from_fix(ao_k_pa_accel);
+}