You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
166 lines
3.1 KiB
166 lines
3.1 KiB
/*
|
|
* Copyright 2007 Free Software Foundation, Inc.
|
|
*
|
|
* This file is part of GNU Radio
|
|
*
|
|
* GNU Radio 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, or (at your option)
|
|
* any later version.
|
|
*
|
|
* GNU Radio 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 GNU Radio; see the file COPYING. If not, write to
|
|
* the Free Software Foundation, Inc., 51 Franklin Street,
|
|
* Boston, MA 02110-1301, USA.
|
|
*/
|
|
|
|
//this is copied almost verbatim from Eric Cottrell's gr-air platform.
|
|
|
|
#ifdef HAVE_CONFIG_H
|
|
#include "config.h"
|
|
#endif
|
|
|
|
#include <stdio.h>
|
|
#include <gr_air_modes/types.h>
|
|
#include <gr_air_modes/modes_crc.h>
|
|
#include <math.h>
|
|
#include <stdlib.h>
|
|
|
|
/* Mode S Parity Table
|
|
* Index is bit position with bit 0 being the first bit after preamble
|
|
* On short frames an offset of 56 is used.
|
|
*/
|
|
const unsigned int modes_crc_table[112] =
|
|
{
|
|
0x3935ea, // Start of Long Frame CRC
|
|
0x1c9af5,
|
|
0xf1b77e,
|
|
0x78dbbf,
|
|
0xc397db,
|
|
0x9e31e9,
|
|
0xb0e2f0,
|
|
0x587178,
|
|
0x2c38bc,
|
|
0x161c5e,
|
|
0x0b0e2f,
|
|
0xfa7d13,
|
|
0x82c48d,
|
|
0xbe9842,
|
|
0x5f4c21,
|
|
0xd05c14,
|
|
0x682e0a,
|
|
0x341705,
|
|
0xe5f186,
|
|
0x72f8c3,
|
|
0xc68665,
|
|
0x9cb936,
|
|
0x4e5c9b,
|
|
0xd8d449,
|
|
0x939020,
|
|
0x49c810,
|
|
0x24e408,
|
|
0x127204,
|
|
0x093902,
|
|
0x049c81,
|
|
0xfdb444,
|
|
0x7eda22,
|
|
0x3f6d11, // Extended 56 bit field
|
|
0xe04c8c,
|
|
0x702646,
|
|
0x381323,
|
|
0xe3f395,
|
|
0x8e03ce,
|
|
0x4701e7,
|
|
0xdc7af7,
|
|
0x91c77f,
|
|
0xb719bb,
|
|
0xa476d9,
|
|
0xadc168,
|
|
0x56e0b4,
|
|
0x2b705a,
|
|
0x15b82d,
|
|
0xf52612,
|
|
0x7a9309,
|
|
0xc2b380,
|
|
0x6159c0,
|
|
0x30ace0,
|
|
0x185670,
|
|
0x0c2b38,
|
|
0x06159c,
|
|
0x030ace,
|
|
0x018567,
|
|
0xff38b7, // Start of Short Frame CRC
|
|
0x80665f,
|
|
0xbfc92b,
|
|
0xa01e91,
|
|
0xaff54c,
|
|
0x57faa6,
|
|
0x2bfd53,
|
|
0xea04ad,
|
|
0x8af852,
|
|
0x457c29,
|
|
0xdd4410,
|
|
0x6ea208,
|
|
0x375104,
|
|
0x1ba882,
|
|
0x0dd441,
|
|
0xf91024,
|
|
0x7c8812,
|
|
0x3e4409,
|
|
0xe0d800,
|
|
0x706c00,
|
|
0x383600,
|
|
0x1c1b00,
|
|
0x0e0d80,
|
|
0x0706c0,
|
|
0x038360,
|
|
0x01c1b0,
|
|
0x00e0d8,
|
|
0x00706c,
|
|
0x003836,
|
|
0x001c1b,
|
|
0xfff409,
|
|
0x800000, // 24 PI or PA bits
|
|
0x400000,
|
|
0x200000,
|
|
0x100000,
|
|
0x080000,
|
|
0x040000,
|
|
0x020000,
|
|
0x010000,
|
|
0x008000,
|
|
0x004000,
|
|
0x002000,
|
|
0x001000,
|
|
0x000800,
|
|
0x000400,
|
|
0x000200,
|
|
0x000100,
|
|
0x000080,
|
|
0x000040,
|
|
0x000020,
|
|
0x000010,
|
|
0x000008,
|
|
0x000004,
|
|
0x000002,
|
|
0x000001,
|
|
};
|
|
|
|
int modes_check_crc(unsigned char data[], int length)
|
|
{
|
|
int crc=0, i;
|
|
for(i = 0; i < length; i++)
|
|
{
|
|
if(data[i/8] & (1 << (7-(i%8))))
|
|
{
|
|
crc ^= modes_crc_table[i+(112-length)];
|
|
}
|
|
}
|
|
return crc;
|
|
}
|