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148 lines
4.7 KiB
C++
148 lines
4.7 KiB
C++
//
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// SerialPort.hpp
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// Clock Signal
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//
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// Created by Thomas Harte on 12/10/2019.
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// Copyright © 2019 Thomas Harte. All rights reserved.
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//
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#ifndef SerialPort_hpp
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#define SerialPort_hpp
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#include <vector>
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#include "../../Storage/Storage.hpp"
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#include "../../ClockReceiver/ClockReceiver.hpp"
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#include "../../ClockReceiver/ForceInline.hpp"
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namespace Serial {
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/*!
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Models one of two connections, either:
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(i) a plain single-line serial; or
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(ii) a two-line data + clock.
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In both cases connects a single reader to a single writer.
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When operating as a single-line serial connection:
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Provides a mechanism for the writer to enqueue levels arbitrarily far
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ahead of the current time, which are played back only as the
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write queue advances. Permits the reader and writer to work at
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different clock rates, and provides a virtual delegate protocol with
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start bit detection.
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Can alternatively be used by reader and/or writer only in immediate
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mode, getting or setting the current level now, without the actor on
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the other end having to have made the same decision.
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When operating as a two-line connection:
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Implies a clock over enqueued data and provides the reader with
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all enqueued bits at appropriate times.
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*/
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template <bool include_clock> class Line {
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public:
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/// Sets the line to @c level instantaneously.
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void write(bool level);
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/// @returns The instantaneous level of this line.
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bool read() const;
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/// Sets the denominator for the between levels for any data enqueued
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/// via an @c write.
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void set_writer_clock_rate(HalfCycles clock_rate);
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/// Enqueues @c count level changes, the first occurring immediately
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/// after the final event currently posted and each subsequent event
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/// occurring @c cycles after the previous. An additional gap of @c cycles
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/// is scheduled after the final output. The levels to output are
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/// taken from @c levels which is read from lsb to msb. @c cycles is
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/// relative to the writer's clock rate.
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void write(HalfCycles cycles, int count, int levels);
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/// Enqueus every bit from @c value as per the rules of write(HalfCycles, int, int),
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/// either in LSB or MSB order as per the @c lsb_first template flag.
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template <bool lsb_first, typename IntT> void write(HalfCycles cycles, IntT value);
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/// @returns the number of cycles until currently enqueued write data is exhausted.
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forceinline HalfCycles write_data_time_remaining() const {
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return HalfCycles(remaining_delays_);
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}
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/// @returns the number of cycles left until it is guaranteed that a passive reader
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/// has received all currently-enqueued bits.
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forceinline HalfCycles transmission_data_time_remaining() const {
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return HalfCycles(remaining_delays_ + transmission_extra_);
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}
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/// Advances the read position by @c cycles relative to the writer's
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/// clock rate.
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void advance_writer(HalfCycles cycles);
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/// Eliminates all future write states, leaving the output at whatever it is now.
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void reset_writing();
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struct ReadDelegate {
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virtual bool serial_line_did_produce_bit(Line *line, int bit) = 0;
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};
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/*!
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Sets a read delegate.
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Single line serial connection:
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The delegate will receive samples of the output level every
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@c bit_lengths of a second apart subject to a state machine:
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* initially no bits will be delivered;
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* when a zero level is first detected, the line will wait half a bit's length, then start
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sampling at single-bit intervals, passing each bit to the delegate while it returns @c true;
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* as soon as the delegate returns @c false, the line will return to the initial state.
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Two-line clock + data connection:
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The delegate will receive every bit that has been enqueued, spaced as nominated
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by the writer. @c bit_length is ignored, as is the return result of
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@c ReadDelegate::serial_line_did_produce_bit.
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*/
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void set_read_delegate(ReadDelegate *delegate, Storage::Time bit_length = Storage::Time());
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private:
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struct Event {
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enum Type {
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Delay, SetHigh, SetLow
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} type;
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int delay;
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};
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std::vector<Event> events_;
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HalfCycles::IntType remaining_delays_ = 0;
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HalfCycles::IntType transmission_extra_ = 0;
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bool level_ = true;
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HalfCycles clock_rate_ = 0;
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ReadDelegate *read_delegate_ = nullptr;
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Storage::Time read_delegate_bit_length_, time_left_in_bit_;
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int write_cycles_since_delegate_call_ = 0;
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enum class ReadDelegatePhase {
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WaitingForZero,
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Serialising
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} read_delegate_phase_ = ReadDelegatePhase::WaitingForZero;
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void update_delegate(bool level);
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HalfCycles::IntType minimum_write_cycles_for_read_delegate_bit();
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template <bool lsb_first, typename IntT> void
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write_internal(HalfCycles, int, IntT);
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};
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/*!
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Defines an RS-232-esque srial port.
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*/
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class Port {
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public:
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};
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}
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#endif /* SerialPort_hpp */
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