TinyGCP

Overview

A simple, extremely barebones G-code parser, implemented in about 100 lines of code!

As is, this library can parse through a sequence of G-code blocks (meaning commands in G-code parlance) and extract:

• M-codes
• G-codes
• X, Y and Z axis position
• Machine feed rate
• Comments (if any)

Adding support for more words, such as additional axes, should be trivial for any C programmer.

TinyGCP may be used as a command prompt interpreter for a serial console link with a CNC machine, or it may be run in a loop, being able to interpret .gcode files. Both CRLF and NL line ending formats are supported.

Installation

Build:

make

Install:

sudo make install

Usage Example

The following example takes G-code blocks from stdin, parses them one by one, and updates the Block structure. Parsed parameters can then be accessed directly through the structure fields (e.g. b.x). For each parsed block, the example dumps the complete structure to stderr.

#include <stdio.h>
#include <tinygcp.h>

int main(void)
{
	Block b = {0};
	char buf[MAX_LINE_SIZE];

    while (fgets(buf, sizeof(buf), stdin) != NULL) {
		parse_line(&b, buf);
		dump_block(stderr, &b);
    }

	return 0;
}

Given a file cam_sw_output.gcode, with contents:

%

G1 X5.5 Y5.5 Z2.0 F1200
G1 X1 Y1 Z1 F1000 ; inline comment

%

Running the example with said file redirected to its input:

./example < cam_sw_output.gcode

Results in the following output (thanks to dump_block(FILE *, Block *)):

block at 0x7ffcea5ec040
{
	block_del = false
	percent = true
	comments = ``
	last_comment = ``
	g_code = -1
	m_code = -1
	{f: 0.000, x: 0.000, y: 0.000, z: 0.000}
}
block at 0x7ffcea5ec040
{
	block_del = false
	percent = false
	comments = ``
	last_comment = ``
	g_code = 1
	m_code = -1
	{f: 1200.000, x: 5.500, y: 5.500, z: 2.000}
}
block at 0x7ffcea5ec040
{
	block_del = false
	percent = false
	comments = `; inline comment`
	last_comment = `; inline comment`
	g_code = 1
	m_code = -1
	{f: 1000.000, x: 1.000, y: 1.000, z: 1.000}
}
block at 0x7ffcea5ec040
{
	block_del = false
	percent = true
	comments = ``
	last_comment = ``
	g_code = -1
	m_code = -1
	{f: 1000.000, x: 0.000, y: 0.000, z: 0.000}
}

G-code Support

Words

Word	Member	Description
G	.g	Active G command
M	.m	Active M command
X	.x	X coordinate
Y	.y	Y coordinate
Z	.z	Z coordinate
F	.f	Feed rate

Comments

Comment blocks (those between parentheses) and in-line comments ; those trailing the block. Both kinds of comments are stored on .comments structure member. Sometimes, comments are used to trigger some action, such as (print, ...) or (debug, ...). If there were several comments on the same block, only the last one would be interpreted. Thus, the last found comment will be pointed to by .last_comment.

Other Symbols

• A leading slash /, which disables the whole block, will set .block_del to true if found.
• A percent symbol % will set .percent to true if found as the first character of a block. Often used to mark the start and end of a G-code program.

Limitations

TinyGCP is a G-code parser, not a complete G-code interpreter.

Features such as variables, expressions, Boolean logic, macros and control flow are intentionally unsupported. The library is designed to parse G-code blocks and expose their contents through a compact C API, leaving execution and motion planning to the application.