67 lines
1.7 KiB
C++
67 lines
1.7 KiB
C++
// P25 TDMA Decoder (C) Copyright 2013, 2014 Max H. Parke KA1RBI
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//
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// This file is part of OP25
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//
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// OP25 is free software; you can redistribute it and/or modify it
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// under the terms of the GNU General Public License as published by
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// the Free Software Foundation; either version 3, or (at your option)
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// any later version.
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//
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// OP25 is distributed in the hope that it will be useful, but WITHOUT
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// ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
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// or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public
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// License for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with OP25; see the file COPYING. If not, write to the Free
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// Software Foundation, Inc., 51 Franklin Street, Boston, MA
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// 02110-1301, USA.
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#include <stdio.h>
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#include <stdint.h>
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#include <map>
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#include <string.h>
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#include <string>
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#include <iostream>
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#include "p25p2_sync.h"
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p25p2_sync::p25p2_sync(void) : // constructor
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sync_confidence(0),
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_tdma_slotid(0),
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packets(0)
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{
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}
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bool p25p2_sync::in_sync(void)
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{
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return (sync_confidence != 0);
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}
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void p25p2_sync::check_confidence (const uint8_t dibits[])
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{
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static const int expected_sync[] = {0, 1, -2, -2, 4, 5, -2, -2, 8, 9, -2, -2};
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_tdma_slotid ++;
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packets++;
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if (_tdma_slotid >= 12)
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_tdma_slotid = 0;
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int rc, cnt, fr, loc, chn, checkval;
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rc = isch.isch_lookup(dibits);
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checkval = cnt = fr = loc = chn = rc;
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if (rc >= 0) {
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cnt = rc & 3;
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rc = rc >> 2;
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fr = rc & 1;
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rc = rc >> 1;
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loc = rc & 3;
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rc = rc >> 2;
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chn = rc & 3;
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checkval = loc*4 + chn;
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}
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if (expected_sync[_tdma_slotid] != checkval && checkval != -1)
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sync_confidence = 0;
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if (chn >= 0) {
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sync_confidence = 1;
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_tdma_slotid = checkval;
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}
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}
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