Marlin Compatibility

Marlin Compatibility Mode

Why have a Marlin Compatibility mode?

For 3D printing, there is a large number of utilities that are written to speak to Marlin or various other mostly-compatible variants. Even though there are several things that don't translate between Marlin and g2core, we can make an effort to at least accept gcode sliced for Marlin, and to be able to conditionally speak the Marlin protocol.

This gives the authors of those various utilities (assuming that they are still being maintained) some time to support the g2core protocol and gcode flavor.

What it's not

This will support the most-used gcode and protocol of Marlin, and nothing more.

What we don't support as Marlin (you have to use the g2core protocol for these):

• Configuration of the machine and various parameters
• Setup of motors, heaters, etc.
• Tuning PID, limit switch polarity, etc.

Also, this marlin support is a temporary option to ease transition, and will be deprecated once it becomes too difficult to support. This depreciation, once it has been scheduled, will be announced in the g2core changelog and on social media.

Communications protocol and gcode handling

Gcode on Marlin must be all uppercase. g2core accepts both upper- and lower-case mixed.

On Marlin, motion of the extruder is a mixture of E and T words, where on g2core A, B, and C are currently used. (This is planned to change to using spindle-based controls.)

On g2core, G0 does not accept an F word and G1 requires one (but it is 'sticky,' so it only be included once, and from then on when it needs changed).

There are a few other concepts that convert more-or-less from g2core and Marlin:

g2core	Marlin	Notes
{"r":...,"f":[...]}	ok	In response to every sent gcode, g2core will return a response JSON, and Marlin will return ok. <br> (Marlin has an "advanced ok" option as well.)
{"he1st":210}	M104 S201 T1	Set temperature of extruder 1 to 210.
{"he1st":n}	M105	Request the set temperature of extruder 1 (g2core) or current extruder and bed (Marlin).
Nxxx (gcode)	Nxxx (gcode) * (checksum)	Marlin supports a checksum, and has special requirements on line numbers, where g2core accepts arbitrary line numbers and doesn't support a non-standard checksum.
{"out4":0.5}	M106 S128	Set output on the fan (or generic PWM output 4 for g2core) to 50%.

Supported Mxxx codes

• M104, M109, M140, M190, M108 - temperature control

  • On Marlin, you set the extruder temperature (and return immediately) with a M104 Snnn Tnnn
    • Snnn indicates the temperature in celsius
    • Tnnn (optional) indicates the tool, with the first being 0
    • If you wish to wait until the extruder is at temperature, change M104 to M109.
      • Cancel the wait with M108 (with no further words).
      • With Sxxx it will only wait for heating. Change the Sxxx to Rxxx to wait for cooling or heating.
      • Both M104 and M109 (with either S or R) will set the target temperature.
      • During heat-up, the temperature of the extruder and heat-bed will be automatically printed every second.
  • On Marlin, the bed temperature is set with M140 Snnn, and it does NOT wait for the bed to heat up.
    • Snnn indicates the temperature in celsius
    • Wait for the heat bed with M190 Sxxx (for heating only) or M190 Rxxx (for both heating and cooling)
      • Like M109, M190 will also set the target and print the temperature of the extruder and bed every second until while it's waiting.
      • M190 is also cancelled with M108.

• M105 - temperature polling

  • Response is in the format: ok T:18.2 /0.0 B:16.6 /0.0 @:0 B@:0
    • T:nnn contains the temperature of the "current" extruder (in celsius).
    • /nnn contains the set temperature of the given extruder (in celsius).
    • B:nnn contains the bed temperature (in celsius).
    • /nnn after that is the set temperature of the bed (in celsius).
    • @:nnn is the power output level (0-PID_MAX, which appears to generally be 255).
    • B@:nnn is the bed power output level (0-MAX_BED_POWER, which appears to generally be 255).
  • For Ultimaker Marlin, this differs from the response format of M109 and M190 of T:101.9 E:0 W:1
    • T:nnn is the same
    • E:nnn is the extruder number
    • W:nnn is the seconds of wait time left (and may be ?) for the temperature to be considered "stable".
  • For stock Marlin, the output format of M109 and M190 is the same as M105, except it adds the W:nnn wait time.

• G28 homing

  • In marlin, G28 (no decimal) is homing, and the values are possibly provided without numbers, and the number (if provided) are ignored: G28 X Y Z
  • If no axes are provided, then it will home all axes.
  • As a side-effect, it clears the auto bed-levelling rotation, and sets the "ative toolhead" to T0.
  • Will home Z first if Z homes up, then X, then Y. Otherwise it'll home X, then Y, then Z.

• G29 bed tramming

  • This will probe three (internally stored) points, then activate bed levelling

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