mirror of
https://github.com/f4exb/sdrangel.git
synced 2024-11-04 16:01:14 -05:00
80 lines
2.6 KiB
C++
80 lines
2.6 KiB
C++
// This file is part of LeanSDR Copyright (C) 2016-2018 <pabr@pabr.org>.
|
|
// See the toplevel README for more information.
|
|
//
|
|
// 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/>.
|
|
|
|
#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
|