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Moved helper functions for M17 Golay to a dedicated source file

This commit is contained in:
Silvano Seva 2022-05-26 21:49:54 +02:00
parent 1620889640
commit 63f4c787c0
3 changed files with 122 additions and 85 deletions
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1
meson.build
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@ -42,6 +42,7 @@ openrtx_src = ['openrtx/src/core/state.c',
'openrtx/src/rtx/OpMode_FM.cpp',
'openrtx/src/rtx/OpMode_M17.cpp',
'openrtx/src/protocols/M17/M17DSP.cpp',
'openrtx/src/protocols/M17/M17Golay.cpp',
'openrtx/src/protocols/M17/M17Callsign.cpp',
'openrtx/src/protocols/M17/M17Modulator.cpp',
'openrtx/src/protocols/M17/M17Demodulator.cpp',

87
openrtx/include/protocols/M17/M17Golay.h
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@ -35,47 +35,13 @@ namespace M17
namespace Golay24
{
/**
* Data encoding matrix for Golay(24,12) code with generator polynomial 0xC75;
*/
static const uint16_t encode_matrix[12] =
{
0x8eb, 0x93e, 0xa97, 0xdc6, 0x367, 0x6cd,
0xd99, 0x3da, 0x7b4, 0xf68, 0x63b, 0xc75
};
/**
* Data decoding matrix for Golay(24,12) code with generator polynomial 0xC75;
*/
static const uint16_t decode_matrix[12] =
{
0xc75, 0x49f, 0x93e, 0x6e3, 0xdc6, 0xf13,
0xab9, 0x1ed, 0x3da, 0x7b4, 0xf68, 0xa4f
};
/**
* Function computing the Golay(24,12) checksum of a given 12-bit data block.
*
* @param value: input data.
* @return Golay(24,12) checksum.
*/
static uint16_t calcChecksum(const uint16_t& value)
{
uint16_t checksum = 0;
for(uint8_t i = 0; i < 12; i++)
{
if(value & (1 << i))
{
checksum ^= encode_matrix[i];
}
}
return checksum;
}
uint16_t calcChecksum(const uint16_t& value);
/**
* Detect and correct errors in a Golay(24,12) codeword.
@ -84,56 +50,7 @@ static uint16_t calcChecksum(const uint16_t& value)
* @return bitmask corresponding to detected bit errors in the codeword, or
* 0xFFFFFFFF if bit errors are unrecoverable.
*/
static uint32_t detectErrors(const uint32_t& codeword)
{
uint16_t data = codeword >> 12;
uint16_t parity = codeword & 0xFFF;
uint16_t syndrome = parity ^ calcChecksum(data);
if(__builtin_popcount(syndrome) <= 3)
{
return syndrome;
}
for(uint8_t i = 0; i<12; i++)
{
uint16_t e = 1 << i;
uint16_t coded_error = encode_matrix[i];
if(__builtin_popcount(syndrome^coded_error) <= 2)
{
return (e << 12) | (syndrome ^ coded_error);
}
}
uint16_t inv_syndrome = 0;
for(uint8_t i = 0; i < 12; i++)
{
if(syndrome & (1 << i))
{
inv_syndrome ^= decode_matrix[i];
}
}
if(__builtin_popcount(inv_syndrome) <= 3)
{
return inv_syndrome << 12;
}
for(uint8_t i = 0; i < 12; i++ )
{
uint16_t e = 1 << i;
uint16_t coding_error = decode_matrix[i];
if(__builtin_popcount(inv_syndrome ^ coding_error) <= 2 )
{
return ((inv_syndrome ^ coding_error) << 12) | e;
}
}
return 0xFFFFFFFF;
}
uint32_t detectErrors(const uint32_t& codeword);
} // namespace Golay24

119
openrtx/src/protocols/M17/M17Golay.cpp Normal file
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@ -0,0 +1,119 @@
/***************************************************************************
* Copyright (C) 2021 - 2022 by Federico Amedeo Izzo IU2NUO, *
* Niccolò Izzo IU2KIN *
* Wojciech Kaczmarski SP5WWP *
* Frederik Saraci IU2NRO *
* Silvano Seva IU2KWO *
* *
* *
* 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 3 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, see <http://www.gnu.org/licenses/> *
***************************************************************************/
#include <M17/M17Golay.h>
using namespace M17;
/*
* Data encoding matrix for Golay(24,12) code with generator polynomial 0xC75
*/
static constexpr uint16_t encode_matrix[12] =
{
0x8eb, 0x93e, 0xa97, 0xdc6, 0x367, 0x6cd,
0xd99, 0x3da, 0x7b4, 0xf68, 0x63b, 0xc75
};
/*
* Data decoding matrix for Golay(24,12) code with generator polynomial 0xC75
*/
static constexpr uint16_t decode_matrix[12] =
{
0xc75, 0x49f, 0x93e, 0x6e3, 0xdc6, 0xf13,
0xab9, 0x1ed, 0x3da, 0x7b4, 0xf68, 0xa4f
};
uint16_t Golay24::calcChecksum(const uint16_t& value)
{
uint16_t checksum = 0;
for(uint8_t i = 0; i < 12; i++)
{
if(value & (1 << i))
{
checksum ^= encode_matrix[i];
}
}
return checksum;
}
/**
* Detect and correct errors in a Golay(24,12) codeword.
*
* @param codeword: input codeword.
* @return bitmask corresponding to detected bit errors in the codeword, or
* 0xFFFFFFFF if bit errors are unrecoverable.
*/
uint32_t Golay24::detectErrors(const uint32_t& codeword)
{
uint16_t data = codeword >> 12;
uint16_t parity = codeword & 0xFFF;
uint16_t syndrome = parity ^ calcChecksum(data);
if(__builtin_popcount(syndrome) <= 3)
{
return syndrome;
}
for(uint8_t i = 0; i<12; i++)
{
uint16_t e = 1 << i;
uint16_t coded_error = encode_matrix[i];
if(__builtin_popcount(syndrome^coded_error) <= 2)
{
return (e << 12) | (syndrome ^ coded_error);
}
}
uint16_t inv_syndrome = 0;
for(uint8_t i = 0; i < 12; i++)
{
if(syndrome & (1 << i))
{
inv_syndrome ^= decode_matrix[i];
}
}
if(__builtin_popcount(inv_syndrome) <= 3)
{
return inv_syndrome << 12;
}
for(uint8_t i = 0; i < 12; i++ )
{
uint16_t e = 1 << i;
uint16_t coding_error = decode_matrix[i];
if(__builtin_popcount(inv_syndrome ^ coding_error) <= 2 )
{
return ((inv_syndrome ^ coding_error) << 12) | e;
}
}
return 0xFFFFFFFF;
}