68 lines
1.9 KiB
C
68 lines
1.9 KiB
C
/* AFC (Automatic Gain Control) Implementation */
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/* (C) 2010 by Harald Welte <laforge@gnumonks.org>
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*
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* All Rights Reserved
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with this program; if not, write to the Free Software Foundation, Inc.,
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* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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*/
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#include <stdint.h>
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#include <stdio.h>
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#include <osmocore/gsm_utils.h>
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#include <debug.h>
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#include <rffe.h>
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#include <layer1/agc.h>
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#include <calypso/dsp.h>
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/* This is a value that has been measured on the C123 by Harald: 71dBm,
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it is the difference between the input level at the antenna and what
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the DSP reports, subtracted by the total gain of the TRF6151 */
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#define SYSTEM_INHERENT_GAIN 71
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/* compute the input level present at the antenna based on a baseband
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* power measurement of the DSP at baseband */
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int16_t agc_inp_dbm8_by_pm(int16_t pm)
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{
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/* pm is in 1/8 dBm at baseband */
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int16_t total_gain_dbm8;
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/* compute total current gain */
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total_gain_dbm8 = (SYSTEM_INHERENT_GAIN + rffe_get_gain()) * 8;
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/* subtract gain from power measurement at baseband level */
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return pm - total_gain_dbm8;
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}
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uint8_t agc_il_by_dbm8(int16_t dbm8)
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{
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uint16_t il;
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/* convert from 1/8 dBm to l1c format: [220..0] in -1/2dBm unit */
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if (dbm8 >= 0)
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il = 0;
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else
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il = -dbm8;
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/* saturate */
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if (il > 4 * 255)
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il = 4 * 255;
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return (uint8_t)(il >> 2);
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}
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