HackRF-Treasure-Chest/Software/portapack-mayhem/firmware/baseband/phase_detector.hpp

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2022-09-22 18:26:57 +02:00
/*
* Copyright (C) 2016 Jared Boone, ShareBrained Technology, Inc.
*
* This file is part of PortaPack.
*
* 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 2, 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; see the file COPYING. If not, write to
* the Free Software Foundation, Inc., 51 Franklin Street,
* Boston, MA 02110-1301, USA.
*/
#ifndef __PHASE_DETECTOR_HPP__
#define __PHASE_DETECTOR_HPP__
#include <cstdint>
#include <cstddef>
#include <cmath>
class PhaseDetectorEarlyLateGate {
public:
using history_t = uint32_t;
using symbol_t = bool;
using error_t = int;
struct result_t {
symbol_t symbol;
error_t error;
};
constexpr PhaseDetectorEarlyLateGate(
const size_t samples_per_symbol
) : sample_threshold { samples_per_symbol / 2 },
late_mask { (1UL << sample_threshold) - 1UL },
early_mask { late_mask << sample_threshold }
{
}
result_t operator()(const history_t symbol_history) const {
static_assert(sizeof(history_t) == sizeof(unsigned long), "popcountl size mismatch");
// history = ...0111, early
// history = ...1110, late
const size_t late_side = __builtin_popcountl(symbol_history & late_mask);
const size_t early_side = __builtin_popcountl(symbol_history & early_mask);
const size_t total_count = late_side + early_side;
const auto lateness = static_cast<int>(late_side) - static_cast<int>(early_side);
const symbol_t symbol = (total_count >= sample_threshold);
const error_t error = symbol ? -lateness : lateness;
return { symbol, error };
}
private:
const size_t sample_threshold;
const history_t late_mask;
const history_t early_mask;
};
#endif/*__PHASE_DETECTOR_HPP__*/