MeatPack serial encoding (#20802)
Co-authored-by: Scott Lahteine <thinkyhead@users.noreply.github.com>
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ellensp
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124
Marlin/src/feature/meatpack.h
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124
Marlin/src/feature/meatpack.h
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/**
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* Marlin 3D Printer Firmware
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* Copyright (c) 2020 MarlinFirmware [https://github.com/MarlinFirmware/Marlin]
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*
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* Based on Sprinter and grbl.
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* Copyright (c) 2011 Camiel Gubbels / Erik van der Zalm
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <https://www.gnu.org/licenses/>.
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*
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*/
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/*
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* MeatPack G-code Compression
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*
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* Algorithm & Implementation: Scott Mudge - mail@scottmudge.com
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* Date: Dec. 2020
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*
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* Specifically optimized for 3D printing G-Code, this is a zero-cost data compression method
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* which packs ~180-190% more data into the same amount of bytes going to the CNC controller.
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* As a majority of G-Code can be represented by a restricted alphabet, I performed histogram
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* analysis on a wide variety of 3D printing gcode samples, and found ~93% of all gcode could
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* be represented by the same 15-character alphabet.
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*
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* This allowed me to design a system of packing 2 8-bit characters into a single byte, assuming
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* they fall within this limited 15-character alphabet. Using a 4-bit lookup table, these 8-bit
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* characters can be represented by a 4-bit index.
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*
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* Combined with some logic to allow commingling of full-width characters outside of this 15-
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* character alphabet (at the cost of an extra 8-bits per full-width character), and by stripping
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* out unnecessary comments, the end result is gcode which is roughly half the original size.
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*
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* Why did I do this? I noticed micro-stuttering and other data-bottleneck issues while printing
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* objects with high curvature, especially at high speeds. There is also the issue of the limited
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* baud rate provided by Prusa's Atmega2560-based boards, over the USB serial connection. So soft-
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* ware like OctoPrint would also suffer this same micro-stuttering and poor print quality issue.
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*
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*/
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#pragma once
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#include <stdint.h>
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/**
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* Commands sent to MeatPack to control its behavior.
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* They are sent by first sending 2x MeatPack_CommandByte (0xFF) in sequence,
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* followed by one of the command bytes below.
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* Provided that 0xFF is an exceedingly rare character that is virtually never
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* present in G-code naturally, it is safe to assume 2 in sequence should never
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* happen naturally, and so it is used as a signal here.
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*
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* 0xFF *IS* used in "packed" G-code (used to denote that the next 2 characters are
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* full-width), however 2 in a row will never occur, as the next 2 bytes will always
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* some non-0xFF character.
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*/
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enum MeatPack_Command : uint8_t {
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MPCommand_None = 0,
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MPCommand_TogglePacking = 0xFD,
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MPCommand_EnablePacking = 0xFB,
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MPCommand_DisablePacking = 0xFA,
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MPCommand_ResetAll = 0xF9,
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MPCommand_QueryConfig = 0xF8,
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MPCommand_EnableNoSpaces = 0xF7,
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MPCommand_DisableNoSpaces = 0xF6
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};
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enum MeatPack_ConfigStateBits : uint8_t {
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MPConfig_Bit_Active = 0,
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MPConfig_Bit_NoSpaces = 1
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};
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class MeatPack {
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private:
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friend class GCodeQueue;
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// Utility definitions
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static const uint8_t kCommandByte = 0b11111111,
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kFirstNotPacked = 0b00001111,
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kSecondNotPacked = 0b11110000,
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kFirstCharIsLiteral = 0b00000001,
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kSecondCharIsLiteral = 0b00000010;
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static const uint8_t kSpaceCharIdx = 11;
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static const char kSpaceCharReplace = 'E';
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static bool cmd_is_next; // A command is pending
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static uint8_t state; // Configuration state
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static uint8_t second_char; // Buffers a character if dealing with out-of-sequence pairs
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static uint8_t cmd_count, // Counter of command bytes received (need 2)
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full_char_count, // Counter for full-width characters to be received
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char_out_count; // Stores number of characters to be read out.
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static uint8_t char_out_buf[2]; // Output buffer for caching up to 2 characters
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// Pass in a character rx'd by SD card or serial. Automatically parses command/ctrl sequences,
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// and will control state internally.
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static void handle_rx_char(const uint8_t c);
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/**
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* After passing in rx'd char using above method, call this to get characters out.
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* Can return from 0 to 2 characters at once.
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* @param out [in] Output pointer for unpacked/processed data.
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* @return Number of characters returned. Range from 0 to 2.
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*/
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static uint8_t get_result_char(char* const __restrict out);
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static void reset_state();
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static void report_state();
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static uint8_t unpacked_char(register const uint8_t in);
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static uint8_t unpack_chars(const uint8_t pk, uint8_t* __restrict const chars_out);
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static void handle_command(const MeatPack_Command c);
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static void handle_output_char(const uint8_t c);
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static void handle_rx_char_inner(const uint8_t c);
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};
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extern MeatPack meatpack;
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