src/target/firmware/layer1/toa.c

   1 /* AFC (Automatic Frequency Correction) Implementation */
   2
   3 /* (C) 2010 by Harald Welte <laforge@gnumonks.org>
   4  * (C) 2011 by Andreas Eversberg <jolly@eversberg.eu>
   5  *
   6  * All Rights Reserved
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License as published by
  10  * the Free Software Foundation; either version 2 of the License, or
  11  * (at your option) any later version.
  12  *
  13  * This program is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16  * GNU General Public License for more details.
  17  *
  18  */
  19
  20 #include <stdint.h>
  21 #include <stdio.h>
  22
  23 #include <debug.h>
  24 #include <osmocom/gsm/gsm_utils.h>
  25
  26 #include <layer1/toa.h>
  27 #include <layer1/avg.h>
  28 #include <layer1/sync.h>
  29
  30 /* Over how many TDMA frames do we want to average? */
  31 #define TOA_PERIOD              250
  32 /* How many of our measurements have to be valid? */
  33 #define TOA_MIN_MUN_VALID       125
  34
  35 // FIXME:
  36 #define TOA_SNR_THRESHOLD       2560    /* 2.5 dB in fx6.10 */
  37
  38 struct toa_state {
  39         struct running_avg ravg;                /* running average */
  40 };
  41
  42
  43 static void toa_ravg_output(struct running_avg *ravg, int32_t avg);
  44
  45 static struct toa_state toa_state = {
  46         .ravg = {
  47                 .outfn = &toa_ravg_output,
  48                 .period = TOA_PERIOD,
  49                 .min_valid = TOA_MIN_MUN_VALID,
  50         },
  51 };
  52
  53 void toa_input(int32_t offset, uint32_t snr)
  54 {
  55         int valid = 1;
  56
  57         if (snr < TOA_SNR_THRESHOLD || offset < 0 || offset >31)
  58                 valid = 0;
  59         runavg_input(&toa_state.ravg, offset, valid);
  60         runavg_check_output(&toa_state.ravg);
  61 }
  62
  63 void toa_reset(void)
  64 {
  65         toa_state.ravg.num_samples = toa_state.ravg.num_samples_valid = 0;
  66         toa_state.ravg.acc_val = 0;
  67 }
  68
  69 /* callback function for runavg */
  70 static void toa_ravg_output(struct running_avg *ravg, int32_t avg)
  71 {
  72         if (avg != 16) {
  73                 printf("TOA AVG is not 16 qbits, correcting (got %ld)\n", avg);
  74                 l1s.tpu_offset_correction = avg - 16;
  75         }
  76 }