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/*
* 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.
*/
#include "ao.h"
static const int16_t altitude_table[2048] = {
#include "altitude.h"
};
int16_t
ao_pres_to_altitude(int16_t pres) __reentrant
{
pres = pres >> 4;
if (pres < 0) pres = 0;
if (pres > 2047) pres = 2047;
return altitude_table[pres];
}
int16_t
ao_altitude_to_pres(int16_t alt) __reentrant
{
int16_t pres;
for (pres = 0; pres < 2047; pres++)
if (altitude_table[pres] <= alt)
break;
return pres << 4;
}
static __xdata uint8_t ao_temp_mutex;
int16_t
ao_temp_to_dC(int16_t temp) __reentrant
{
int16_t ret;
ao_mutex_get(&ao_temp_mutex);
/* 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;
ao_mutex_put(&ao_temp_mutex);
return ret;
}
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