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M17: reworked ClockRecovery

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This commit is contained in:
f4exb 2022-07-27 14:58:33 +02:00
parent 414e695121
commit 1601fa43ca
4 changed files with 38 additions and 21 deletions
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1
modemm17/CMakeLists.txt
View File

@ -1,6 +1,7 @@
project(modemm17)
set(modemm17_SOURCES
ClockRecovery.cpp
Correlator.cpp
FreqDevEstimator.cpp
Golay24.cpp

7
modemm17/ClockRecovery.cpp Normal file
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@ -0,0 +1,7 @@
#include "ClockRecovery.h"
namespace modemm17
{
const float ClockRecovery::MAX_CLOCK = 1.0005;
const float ClockRecovery::MIN_CLOCK = 0.9995;
}

48
modemm17/ClockRecovery.h
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@ -2,7 +2,7 @@
#pragma once
#include <array>
#include <vector>
#include <cstddef>
#include <cstdint>
#include <numeric>
@ -37,16 +37,9 @@ namespace modemm17
* @inv sample_index_ is in the interval [0, SAMPLES_PER_SYMBOL).
* @inv clock_ is in the interval [0.9995, 1.0005]
*/
template <size_t SampleRate, size_t SymbolRate>
class ClockRecovery
{
static constexpr size_t SAMPLES_PER_SYMBOL = SampleRate / SymbolRate;
static constexpr int8_t MAX_OFFSET = SAMPLES_PER_SYMBOL / 2;
static constexpr float dx = 1.0 / SAMPLES_PER_SYMBOL;
static constexpr float MAX_CLOCK = 1.0005;
static constexpr float MIN_CLOCK = 0.9995;
std::array<float, SAMPLES_PER_SYMBOL> estimates_;
std::vector<float> estimates_;
size_t sample_count_ = 0;
uint16_t frame_count_ = 0;
uint8_t sample_index_ = 0;
@ -76,7 +69,7 @@ class ClockRecovery
// Find falling edge.
bool is_positive = false;
for (size_t i = 0; i != SAMPLES_PER_SYMBOL; ++i)
for (size_t i = 0; i != samples_per_symbol_; ++i)
{
float phase = estimates_[i];
@ -91,7 +84,7 @@ class ClockRecovery
}
}
sample_index_ = index == 0 ? SAMPLES_PER_SYMBOL - 1 : index - 1;
sample_index_ = index == 0 ? samples_per_symbol_ - 1 : index - 1;
}
/**
@ -104,13 +97,13 @@ class ClockRecovery
int8_t offset = sample_index_ - prev_sample_index_;
// When in spec, the clock should drift by less than 1 sample per frame.
if (offset >= MAX_OFFSET)
if (offset >= max_offset_)
{
offset -= SAMPLES_PER_SYMBOL;
offset -= samples_per_symbol_;
}
else if (offset <= -MAX_OFFSET)
else if (offset <= -max_offset_)
{
offset += SAMPLES_PER_SYMBOL;
offset += samples_per_symbol_;
}
return offset;
@ -135,9 +128,15 @@ class ClockRecovery
}
public:
ClockRecovery()
ClockRecovery(size_t sampleRate, size_t symbolRate) :
sampleRate_(sampleRate),
symbolRate_(symbolRate)
{
estimates_.fill(0);
samples_per_symbol_ = sampleRate_ / symbolRate_;
max_offset_ = samples_per_symbol_ / 2;
dx_ = 1.0 / samples_per_symbol_;
estimates_.resize(samples_per_symbol_);
std::fill(estimates_.begin(), estimates_.end(), 0);
}
/**
@ -158,7 +157,7 @@ public:
estimates_[index_] += dy;
index_ += 1;
if (index_ == SAMPLES_PER_SYMBOL)
if (index_ == samples_per_symbol_)
{
index_ = 0;
}
@ -175,7 +174,7 @@ public:
frame_count_ = 0;
index_ = 0;
sample_index_ = 0;
estimates_.fill(0);
std::fill(estimates_.begin(), estimates_.end(), 0);
}
/**
@ -234,9 +233,18 @@ public:
frame_count_ = std::min(0x1000, 1 + frame_count_);
sample_count_ = 0;
estimates_.fill(0);
std::fill(estimates_.begin(), estimates_.end(), 0);
return true;
}
private:
size_t sampleRate_;
size_t symbolRate_;
size_t samples_per_symbol_;
int8_t max_offset_;
float dx_;
static const float MAX_CLOCK;
static const float MIN_CLOCK;
};
} // modemm17

3
modemm17/M17Demodulator.h
View File

@ -48,7 +48,7 @@ struct MODEMM17_API M17Demodulator
};
DataCarrierDetect<SAMPLE_RATE, 500> dcd{2500, 4000, 1.0, 4.0};
ClockRecovery<SAMPLE_RATE, SYMBOL_RATE> clock_recovery;
ClockRecovery clock_recovery;
sync_word_t preamble_sync{{+3, -3, +3, -3, +3, -3, +3, -3}, 29.f};
sync_word_t lsf_sync{ {+3, +3, +3, +3, -3, -3, +3, -3}, 32.f, -31.f}; // LSF or STREAM (inverted)
@ -77,6 +77,7 @@ struct MODEMM17_API M17Demodulator
diagnostic_callback_t diagnostic_callback;
M17Demodulator(callback_t callback) :
clock_recovery(SAMPLE_RATE, SYMBOL_RATE),
decoder(callback),
initializing_count_(1920)
{