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68 lines
2.1 KiB
C++
68 lines
2.1 KiB
C++
//
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// DigitalPhaseLockedLoop.cpp
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// Clock Signal
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//
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// Created by Thomas Harte on 11/07/2016.
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// Copyright © 2016 Thomas Harte. All rights reserved.
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//
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#include "DigitalPhaseLockedLoop.hpp"
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#include <algorithm>
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#include <cstdlib>
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using namespace Storage;
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DigitalPhaseLockedLoop::DigitalPhaseLockedLoop(int clocks_per_bit, int tolerance, size_t length_of_history) :
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clocks_per_bit_(clocks_per_bit),
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tolerance_(tolerance),
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phase_(0),
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window_length_(clocks_per_bit),
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phase_error_pointer_(0) {
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phase_error_history_.reset(new std::vector<int>(length_of_history, 0));
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}
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void DigitalPhaseLockedLoop::run_for_cycles(int number_of_cycles) {
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phase_ += number_of_cycles;
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if(phase_ >= window_length_) {
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int windows_crossed = phase_ / window_length_;
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// check whether this triggers any 0s, if anybody cares
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if(delegate_) {
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if(window_was_filled_) windows_crossed--;
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for(int c = 0; c < windows_crossed; c++)
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delegate_->digital_phase_locked_loop_output_bit(0);
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}
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window_was_filled_ = false;
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phase_ %= window_length_;
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}
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}
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void DigitalPhaseLockedLoop::add_pulse() {
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if(!window_was_filled_) {
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if(delegate_) delegate_->digital_phase_locked_loop_output_bit(1);
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window_was_filled_ = true;
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post_phase_error(phase_ - (window_length_ >> 1));
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}
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}
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void DigitalPhaseLockedLoop::post_phase_error(int error) {
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// use a simple spring mechanism as a lowpass filter for phase
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phase_ -= (error + 1) >> 1;
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// use the average of the last few errors to affect frequency
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std::vector<int> *phase_error_history = phase_error_history_.get();
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size_t phase_error_history_size = phase_error_history->size();
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(*phase_error_history)[phase_error_pointer_] = error;
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phase_error_pointer_ = (phase_error_pointer_ + 1)%phase_error_history_size;
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int total_error = 0;
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for(size_t c = 0; c < phase_error_history_size; c++) {
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total_error += (*phase_error_history)[c];
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}
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int denominator = (int)(phase_error_history_size * 4);
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window_length_ += (total_error + (denominator >> 1)) / denominator;
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window_length_ = std::max(std::min(window_length_, clocks_per_bit_ + tolerance_), clocks_per_bit_ - tolerance_);
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}
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