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/*
* Copyright © 2012 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; 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 <ao.h>
/*
* The provided 'calibration' value is
* that needed to tune the radio to precisely 434550kHz.
* Use that to 'walk' to the target frequency by following
* a 'bresenham' line from 434550kHz to the target
* frequency, and updating the radio setting along the way
*/
int32_t ao_freq_to_set(int32_t freq, int32_t cal) __reentrant
{
static __pdata int32_t set;
static __pdata uint8_t neg;
static __pdata int32_t error;
set = 0;
neg = 0;
error = -434550 / 2;
if ((freq -= 434550) < 0) {
neg = 1;
freq = -freq;
}
for (;;) {
if (error > 0) {
error -= 434550;
set++;
} else {
error += cal;
if (--freq < 0)
break;
}
}
if (neg)
set = -set;
return cal + set;
}
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