/* * Copyright © 2009 Keith Packard * * 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 #include static const ao_v_t altitude_table[] = { #include "altitude.h" }; #define ALT_FRAC_SCALE (1 << ALT_FRAC_BITS) #define ALT_FRAC_MASK (ALT_FRAC_SCALE - 1) ao_v_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; } #if AO_NEED_ALTITUDE_TO_PRES int16_t ao_altitude_to_pres(ao_v_t alt) __reentrant { ao_v_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; } #endif #if 0 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; } #endif