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Switched to a full-on linear regression. Which causes the current tests to pass.

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This commit is contained in:
Thomas Harte 2016-07-14 19:42:01 -04:00
parent 6d6b26b99f
commit 481475a0f4
2 changed files with 47 additions and 23 deletions
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45
Storage/Disk/DigitalPhaseLockedLoop.cpp
View File

@ -10,17 +10,18 @@
using namespace Storage; using namespace Storage;
DigitalPhaseLockedLoop::DigitalPhaseLockedLoop(unsigned int clocks_per_bit, unsigned int tolerance, unsigned int length_of_history) : DigitalPhaseLockedLoop::DigitalPhaseLockedLoop(int clocks_per_bit, int tolerance, int length_of_history) :
_clocks_per_bit(clocks_per_bit), _clocks_per_bit(clocks_per_bit),
_tolerance(tolerance), _tolerance(tolerance),
_length_of_history(length_of_history), _length_of_history(length_of_history),
_pulse_history(new unsigned int[length_of_history]), _pulse_history(new int[length_of_history]),
_current_window_length(clocks_per_bit), _current_window_length(clocks_per_bit),
_next_pulse_time(0), _next_pulse_time(0),
_window_was_filled(false), _window_was_filled(false),
_window_offset(0) {} _window_offset(0),
_samples_collected(0) {}
void DigitalPhaseLockedLoop::run_for_cycles(unsigned int number_of_cycles) void DigitalPhaseLockedLoop::run_for_cycles(int number_of_cycles)
{ {
// check whether this triggers any 0s // check whether this triggers any 0s
_window_offset += number_of_cycles; _window_offset += number_of_cycles;
@ -44,18 +45,40 @@ void DigitalPhaseLockedLoop::run_for_cycles(unsigned int number_of_cycles)
void DigitalPhaseLockedLoop::add_pulse() void DigitalPhaseLockedLoop::add_pulse()
{ {
unsigned int *const _pulse_history_array = _pulse_history.get(); int *const _pulse_history_array = (int *)_pulse_history.get();
// attempt a phase correction by means of adjusting the window length if(_samples_collected < _length_of_history)
int total_offset = 0; {
_samples_collected++;
}
else
{
// perform a linear regression
float sum_xy = 0;
float sum_x = 0;
float sum_y = 0;
float sum_x_squared = 0;
for(size_t pulse = 0; pulse < _length_of_history; pulse++) for(size_t pulse = 0; pulse < _length_of_history; pulse++)
{ {
total_offset += _pulse_history_array[pulse] % _current_window_length; int x = _pulse_history_array[pulse] / (int)_current_window_length;
int y = _pulse_history_array[pulse] % (int)_current_window_length;
sum_xy += (float)(x*y);
sum_x += (float)x;
sum_y += (float)y;
sum_x_squared += (float)x*x;
} }
_current_window_length += (unsigned int)(((total_offset - (int)(_length_of_history*_current_window_length >> 1)) >> 2) / (int)_length_of_history);
sum_xy /= (float)_length_of_history;
sum_x /= (float)_length_of_history;
sum_y /= (float)_length_of_history;
sum_x_squared /= (float)_length_of_history;
float gradient = (sum_xy - sum_x*sum_y) / (sum_x_squared - sum_x*sum_x);
_current_window_length += (unsigned int)(gradient / 2.0);
if(_current_window_length < _clocks_per_bit - _tolerance) _current_window_length = _clocks_per_bit - _tolerance; if(_current_window_length < _clocks_per_bit - _tolerance) _current_window_length = _clocks_per_bit - _tolerance;
if(_current_window_length > _clocks_per_bit + _tolerance) _current_window_length = _clocks_per_bit + _tolerance; if(_current_window_length > _clocks_per_bit + _tolerance) _current_window_length = _clocks_per_bit + _tolerance;
printf("Total across %d samples is %d; adjusted length to %d\n", _length_of_history, total_offset, _current_window_length); }
// therefore, there was a 1 in this window // therefore, there was a 1 in this window
_window_was_filled = true; _window_was_filled = true;
@ -63,7 +86,7 @@ void DigitalPhaseLockedLoop::add_pulse()
// shift history one to the left, storing new value; act as though the outgoing pulse were exactly halfway through its // shift history one to the left, storing new value; act as though the outgoing pulse were exactly halfway through its
// window for adjustment purposes // window for adjustment purposes
unsigned int outgoing_pulse_time = _pulse_history_array[0] + (_current_window_length >> 1); int outgoing_pulse_time = _pulse_history_array[0];//_pulse_history_array[0] + (_current_window_length >> 1);
for(size_t pulse = 1; pulse < _length_of_history; pulse++) for(size_t pulse = 1; pulse < _length_of_history; pulse++)
{ {

19
Storage/Disk/DigitalPhaseLockedLoop.hpp
View File

@ -22,14 +22,14 @@ class DigitalPhaseLockedLoop {
@param tolerance The maximum tolerance for bit windows — extremes will be clocks_per_bit ± tolerance. @param tolerance The maximum tolerance for bit windows — extremes will be clocks_per_bit ± tolerance.
@param length_of_history The number of historic pulses to consider in locking to phase. @param length_of_history The number of historic pulses to consider in locking to phase.
*/ */
DigitalPhaseLockedLoop(unsigned int clocks_per_bit, unsigned int tolerance, unsigned int length_of_history); DigitalPhaseLockedLoop(int clocks_per_bit, int tolerance, int length_of_history);
/*! /*!
Runs the loop, impliedly posting no pulses during that period. Runs the loop, impliedly posting no pulses during that period.
@c number_of_cycles The time to run the loop for. @c number_of_cycles The time to run the loop for.
*/ */
void run_for_cycles(unsigned int number_of_cycles); void run_for_cycles(int number_of_cycles);
/*! /*!
Announces a pulse at the current time. Announces a pulse at the current time.
@ -51,16 +51,17 @@ class DigitalPhaseLockedLoop {
private: private:
Delegate *_delegate; Delegate *_delegate;
std::unique_ptr<unsigned int> _pulse_history; std::unique_ptr<int> _pulse_history;
unsigned int _current_window_length; int _current_window_length;
unsigned int _length_of_history; int _length_of_history;
int _samples_collected;
unsigned int _next_pulse_time; int _next_pulse_time;
unsigned int _window_offset; int _window_offset;
bool _window_was_filled; bool _window_was_filled;
unsigned int _clocks_per_bit; int _clocks_per_bit;
unsigned int _tolerance; int _tolerance;
}; };
} }