mirror of
https://github.com/TomHarte/CLK.git
synced 2024-11-11 14:05:21 +00:00
78 lines
2.1 KiB
C++
78 lines
2.1 KiB
C++
//
|
|
// DigitalPhaseLockedLoop.cpp
|
|
// Clock Signal
|
|
//
|
|
// Created by Thomas Harte on 11/07/2016.
|
|
// Copyright © 2016 Thomas Harte. All rights reserved.
|
|
//
|
|
|
|
#include "DigitalPhaseLockedLoop.hpp"
|
|
#include <algorithm>
|
|
#include <cstdlib>
|
|
|
|
using namespace Storage;
|
|
|
|
DigitalPhaseLockedLoop::DigitalPhaseLockedLoop(int clocks_per_bit, int tolerance, size_t length_of_history) :
|
|
clocks_per_bit_(clocks_per_bit),
|
|
tolerance_(tolerance),
|
|
|
|
phase_(0),
|
|
window_length_(clocks_per_bit),
|
|
|
|
phase_error_pointer_(0)
|
|
{
|
|
phase_error_history_.reset(new std::vector<int>(length_of_history, 0));
|
|
}
|
|
|
|
void DigitalPhaseLockedLoop::run_for_cycles(int number_of_cycles)
|
|
{
|
|
phase_ += number_of_cycles;
|
|
if(phase_ >= window_length_)
|
|
{
|
|
int windows_crossed = phase_ / window_length_;
|
|
|
|
// check whether this triggers any 0s, if anybody cares
|
|
if(delegate_)
|
|
{
|
|
if(window_was_filled_) windows_crossed--;
|
|
for(int c = 0; c < windows_crossed; c++)
|
|
delegate_->digital_phase_locked_loop_output_bit(0);
|
|
}
|
|
|
|
window_was_filled_ = false;
|
|
phase_ %= window_length_;
|
|
}
|
|
}
|
|
|
|
void DigitalPhaseLockedLoop::add_pulse()
|
|
{
|
|
if(!window_was_filled_)
|
|
{
|
|
if(delegate_) delegate_->digital_phase_locked_loop_output_bit(1);
|
|
window_was_filled_ = true;
|
|
post_phase_error(phase_ - (window_length_ >> 1));
|
|
}
|
|
}
|
|
|
|
void DigitalPhaseLockedLoop::post_phase_error(int error)
|
|
{
|
|
// use a simple spring mechanism as a lowpass filter for phase
|
|
phase_ -= (error + 1) >> 1;
|
|
|
|
// use the average of the last few errors to affect frequency
|
|
std::vector<int> *phase_error_history = phase_error_history_.get();
|
|
size_t phase_error_history_size = phase_error_history->size();
|
|
|
|
(*phase_error_history)[phase_error_pointer_] = error;
|
|
phase_error_pointer_ = (phase_error_pointer_ + 1)%phase_error_history_size;
|
|
|
|
int total_error = 0;
|
|
for(size_t c = 0; c < phase_error_history_size; c++)
|
|
{
|
|
total_error += (*phase_error_history)[c];
|
|
}
|
|
int denominator = (int)(phase_error_history_size * 4);
|
|
window_length_ += (total_error + (denominator >> 1)) / denominator;
|
|
window_length_ = std::max(std::min(window_length_, clocks_per_bit_ + tolerance_), clocks_per_bit_ - tolerance_);
|
|
}
|