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99 lines
2.5 KiB
C++
99 lines
2.5 KiB
C++
//
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// Stepper.hpp
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// Clock Signal
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//
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// Created by Thomas Harte on 12/01/2016.
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// Copyright © 2016 Thomas Harte. All rights reserved.
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//
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#ifndef Stepper_hpp
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#define Stepper_hpp
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#include <stdint.h>
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namespace SignalProcessing {
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/*!
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Allows a repeating action running at an input rate to determine how many times it should
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trigger an action that runs at an unrelated output rate; therefore it allows something with one
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clock to sample something with another.
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Uses a Bresenham-like error term internally for full-integral storage with no drift.
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Pegs the beginning of both clocks to the time at which the stepper is created. So e.g. a stepper
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that converts from an input clock of 1200 to an output clock of 2 will first fire on cycle 600.
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*/
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class Stepper {
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public:
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/*!
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Establishes a stepper with a one-to-one conversion rate.
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*/
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Stepper() : Stepper(1,1) {}
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/*!
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Establishes a stepper that will receive steps at the @c input_rate and dictate the number
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of steps that should be taken at the @c output_rate.
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*/
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Stepper(uint64_t output_rate, uint64_t input_rate) :
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accumulated_error_(-((int64_t)input_rate << 1)),
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input_rate_(input_rate),
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output_rate_(output_rate),
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whole_step_(output_rate / input_rate),
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adjustment_up_((int64_t)(output_rate % input_rate) << 1),
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adjustment_down_((int64_t)input_rate << 1) {}
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/*!
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Advances one step at the input rate.
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@returns the number of output steps.
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*/
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inline uint64_t step() {
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uint64_t update = whole_step_;
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accumulated_error_ += adjustment_up_;
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if(accumulated_error_ > 0) {
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update++;
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accumulated_error_ -= adjustment_down_;
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}
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return update;
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}
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/*!
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Advances by @c number_of_steps steps at the input rate.
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@returns the number of output steps.
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*/
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inline uint64_t step(uint64_t number_of_steps) {
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uint64_t update = whole_step_ * number_of_steps;
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accumulated_error_ += adjustment_up_ * (int64_t)number_of_steps;
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if(accumulated_error_ > 0) {
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update += 1 + (uint64_t)(accumulated_error_ / adjustment_down_);
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accumulated_error_ = (accumulated_error_ % adjustment_down_) - adjustment_down_;
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}
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return update;
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}
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/*!
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@returns the output rate.
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*/
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inline uint64_t get_output_rate() {
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return output_rate_;
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}
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/*!
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@returns the input rate.
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*/
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inline uint64_t get_input_rate() {
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return input_rate_;
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}
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private:
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uint64_t whole_step_;
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int64_t adjustment_up_, adjustment_down_;
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int64_t accumulated_error_;
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uint64_t input_rate_, output_rate_;
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};
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}
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#endif /* Stepper_hpp */
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