mirror of
https://github.com/f4exb/sdrangel.git
synced 2024-11-14 12:22:00 -05:00
91 lines
3.4 KiB
C++
91 lines
3.4 KiB
C++
///////////////////////////////////////////////////////////////////////////////////////
|
|
// Copyright (C) 2018-2019, 2021 Edouard Griffiths, F4EXB <f4exb06@gmail.com> //
|
|
// //
|
|
// This file is part of LeanSDR Copyright (C) 2016-2019 <pabr@pabr.org>. //
|
|
// //
|
|
// 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 as 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 V3 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/>. //
|
|
///////////////////////////////////////////////////////////////////////////////////////
|
|
|
|
#ifndef LEANSDR_IESS_H
|
|
#define LEANSDR_IESS_H
|
|
|
|
#include "leansdr/framework.h"
|
|
|
|
namespace leansdr
|
|
{
|
|
|
|
// SELF-SYNCHRONIZING DESCRAMBLER
|
|
// Per ETSI TR 192 figure 8 (except Q20/ not connected to CLOCK).
|
|
// This implementation operates on packed bits, MSB first.
|
|
|
|
struct etr192_descrambler : runnable
|
|
{
|
|
etr192_descrambler(
|
|
scheduler *sch,
|
|
pipebuf<u8> &_in, // Packed scrambled bits
|
|
pipebuf<u8> &_out // Packed bits
|
|
) :
|
|
runnable(sch, "etr192_dec"),
|
|
in(_in),
|
|
out(_out),
|
|
shiftreg(0),
|
|
counter(0)
|
|
{
|
|
}
|
|
|
|
void run()
|
|
{
|
|
int count = min(in.readable(), out.writable());
|
|
|
|
for (u8 *pin = in.rd(), *pend = pin + count, *pout = out.wr();
|
|
pin < pend; ++pin, ++pout)
|
|
{
|
|
u8 byte_in = *pin, byte_out = 0;
|
|
|
|
for (int b = 8; b--; byte_in <<= 1)
|
|
{
|
|
// Levels before clock transition
|
|
int bit_in = (byte_in & 128) ? 1 : 0;
|
|
int reset_counter = (shiftreg ^ (shiftreg >> 8)) & 1;
|
|
int counter_overflow = (counter == 31) ? 1 : 0;
|
|
int taps = (shiftreg >> 2) ^ (shiftreg >> 19);
|
|
int bit_out = (taps ^ counter_overflow ^ bit_in ^ 1) & 1;
|
|
// Execute clock transition
|
|
#if 1 // Descramble
|
|
shiftreg = (shiftreg << 1) | bit_in;
|
|
#else // Scramble
|
|
shiftreg = (shiftreg << 1) | bit_out;
|
|
#endif
|
|
counter = reset_counter ? 0 : (counter + 1) & 31;
|
|
byte_out = (byte_out << 1) | bit_out;
|
|
}
|
|
|
|
*pout = byte_out;
|
|
}
|
|
|
|
in.read(count);
|
|
out.written(count);
|
|
}
|
|
|
|
private:
|
|
pipereader<u8> in;
|
|
pipewriter<u8> out;
|
|
u32 shiftreg; // 20 bits
|
|
u8 counter; // 5 bits
|
|
}; // etr192_descrambler
|
|
|
|
} // namespace leansdr
|
|
|
|
#endif // LEANSDR_IESS_H
|