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Diffstat (limited to 'src/target/firmware/layer1/agc.c')
-rw-r--r-- | src/target/firmware/layer1/agc.c | 67 |
1 files changed, 67 insertions, 0 deletions
diff --git a/src/target/firmware/layer1/agc.c b/src/target/firmware/layer1/agc.c new file mode 100644 index 00000000..aa4af5e1 --- /dev/null +++ b/src/target/firmware/layer1/agc.c @@ -0,0 +1,67 @@ +/* AFC (Automatic Gain Control) Implementation */ + +/* (C) 2010 by Harald Welte <laforge@gnumonks.org> + * + * All Rights Reserved + * + * 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., + * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. + * + */ + +#include <stdint.h> +#include <stdio.h> + +#include <debug.h> +#include <gsm.h> +#include <rffe.h> + +#include <layer1/agc.h> +#include <calypso/dsp.h> + +/* This is a value that has been measured on the C123 by Harald: 71dBm, + it is the difference between the input level at the antenna and what + the DSP reports, subtracted by the total gain of the TRF6151 */ +#define SYSTEM_INHERENT_GAIN 71 + +/* compute the input level present at the antenna based on a baseband + * power measurement of the DSP at baseband */ +int16_t agc_inp_dbm8_by_pm(int16_t pm) +{ + /* pm is in 1/8 dBm at baseband */ + int16_t total_gain_dbm8; + + /* compute total current gain */ + total_gain_dbm8 = (SYSTEM_INHERENT_GAIN + rffe_get_gain()) * 8; + + /* subtract gain from power measurement at baseband level */ + return pm - total_gain_dbm8; +} + +uint8_t agc_il_by_dbm8(int16_t dbm8) +{ + uint16_t il; + + /* convert from 1/8 dBm to l1c format: [220..0] in -1/2dBm unit */ + if (dbm8 >= 0) + il = 0; + else + il = -dbm8; + + /* saturate */ + if (il > 4 * 255) + il = 4 * 255; + + return (uint8_t)(il >> 2); +} |