X-Git-Url: https://git.gag.com/?a=blobdiff_plain;f=src%2Fcore%2Fao_convert.c;fp=src%2Fcore%2Fao_convert.c;h=0969f107928272e18f04990a428cebc3ba2dcc63;hb=9513be7f9d3d0b0ec29f6487fa9dc8f1ac24d0de;hp=0000000000000000000000000000000000000000;hpb=3bfe8df44b575ca430ffaa051e20faa955a06c03;p=fw%2Faltos

diff --git a/src/core/ao_convert.c b/src/core/ao_convert.c
new file mode 100644
index 00000000..0969f107
--- /dev/null
+++ b/src/core/ao_convert.c
@@ -0,0 +1,85 @@
+/*
+ * Copyright © 2009 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.
+ */
+
+#if !defined(AO_CONVERT_TEST) && !defined(AO_FLIGHT_TEST)
+#include "ao.h"
+#endif
+
+static const int16_t altitude_table[] = {
+#include "altitude.h"
+};
+
+#define ALT_FRAC_SCALE	(1 << ALT_FRAC_BITS)
+#define ALT_FRAC_MASK	(ALT_FRAC_SCALE - 1)
+
+int16_t
+ao_pres_to_altitude(int16_t pres) __reentrant
+{
+	uint8_t	o;
+	int16_t	part;
+
+	if (pres < 0)
+		pres = 0;
+	o = pres >> ALT_FRAC_BITS;
+	part = pres & ALT_FRAC_MASK;
+
+	return ((int32_t) altitude_table[o] * (ALT_FRAC_SCALE - part) +
+		(int32_t) altitude_table[o+1] * part + (ALT_FRAC_SCALE >> 1)) >> ALT_FRAC_BITS;
+}
+
+int16_t
+ao_altitude_to_pres(int16_t alt) __reentrant
+{
+	int16_t span, sub_span;
+	uint8_t	l, h, m;
+	int32_t pres;
+
+	l = 0;
+	h = NALT - 1;
+	while ((h - l) != 1) {
+		m = (l + h) >> 1;
+		if (altitude_table[m] < alt)
+			h = m;
+		else
+			l = m;
+	}
+	span = altitude_table[l] - altitude_table[h];
+	sub_span = altitude_table[l] - alt;
+	pres = ((((int32_t) l * (span - sub_span) + (int32_t) h * sub_span) << ALT_FRAC_BITS) + (span >> 1)) / span;
+	if (pres > 32767)
+		pres = 32767;
+	if (pres < 0)
+		pres = 0;
+	return (int16_t) pres;
+}
+
+int16_t
+ao_temp_to_dC(int16_t temp) __reentrant
+{
+	int16_t	ret;
+
+	/* Output voltage at 0°C = 0.755V
+	 * Coefficient = 0.00247V/°C
+	 * Reference voltage = 1.25V
+	 *
+	 * temp = ((value / 32767) * 1.25 - 0.755) / 0.00247
+	 *      = (value - 19791.268) / 32768 * 1.25 / 0.00247
+	 *	≃ (value - 19791) * 1012 / 65536
+	 */
+	ret = ((temp - 19791) * 1012L) >> 16;
+	return ret;
+}