klipper-dgus/docs/Command_Templates.md

This document provides information on implementing G-Code command sequences in gcode_macro (and similar) config sections.

Formatting of G-Code in the config

Indentation is important when defining a macro in the config file. To specify a multi-line G-Code sequence it is important for each line to have proper indentation. For example:

[gcode_macro blink_led]
gcode:
  SET_PIN PIN=my_led VALUE=1
  G4 P2000
  SET_PIN PIN=my_led VALUE=0

Note how the gcode: config option always starts at the beginning of the line and subsequent lines in the G-Code macro never start at the beginning.

Save/Restore state for G-Code moves

Unfortunately, the G-Code command language can be challenging to use. The standard mechanism to move the toolhead is via the G1 command (the G0 command is an alias for G1 and it can be used interchangeably with it). However, this command relies on the "G-Code parsing state" setup by M82, M83, G90, G91, G92, and previous G1 commands. When creating a G-Code macro it is a good idea to always explicitly set the G-Code parsing state prior to issuing a G1 command. (Otherwise, there is a risk the G1 command will make an undesirable request.)

A common way to accomplish that is to wrap the G1 moves in SAVE_GCODE_STATE, G91, and RESTORE_GCODE_STATE. For example:

[gcode_macro MOVE_UP]
gcode:
  SAVE_GCODE_STATE NAME=my_move_up_state
  G91
  G1 Z10 F300
  RESTORE_GCODE_STATE NAME=my_move_up_state

The G91 command places the G-Code parsing state into "relative move mode" and the RESTORE_GCODE_STATE command restores the state to what it was prior to entering the macro. Be sure to specify an explicit speed (via the F parameter) on the first G1 command.

Template expansion

The gcode_macro gcode: config section is evaluated using the Jinja2 template language. One can evaluate expressions at run-time by wrapping them in { } characters or use conditional statements wrapped in {% %}. See the Jinja2 documentation for further information on the syntax.

This is most often used to inspect parameters passed to the macro when it is called. These parameters are available via the params pseudo-variable. For example, if the macro:

[gcode_macro SET_PERCENT]
gcode:
  M117 Now at { params.VALUE|float * 100 }%

were invoked as SET_PERCENT VALUE=.2 it would evaluate to M117 Now at 20%. Note that parameter names are always in upper-case when evaluated in the macro and are always passed as strings. If performing math then they must be explicitly converted to integers or floats.

An example of a complex macro:

[gcode_macro clean_nozzle]
gcode:
  SAVE_GCODE_STATE NAME=clean_nozzle_state
  G90
  G0 Z15 F300
  {% for wipe in range(8) %}
    {% for coordinate in [(275,4),(235,4)] %}
      G0 X{coordinate[0]} Y{coordinate[1] + 0.25 * wipe} Z9.7 F12000
    {% endfor %}
  {% endfor %}
  RESTORE_GCODE_STATE NAME=clean_nozzle_state

The "printer" Variable

It is possible to inspect (and alter) the current state of the printer via the printer pseudo-variable. For example:

[gcode_macro slow_fan]
gcode:
  M106 S{ printer.fan.speed * 0.9 * 255}

Important! Macros are first evaluated in entirety and only then are the resulting commands executed. If a macro issues a command that alters the state of the printer, the results of that state change will not be visible during the evaluation of the macro. This can also result in subtle behavior when a macro generates commands that call other macros, as the called macro is evaluated when it is invoked (which is after the entire evaluation of the calling macro).

By convention, the name immediately following printer is the name of a config section. So, for example, printer.fan refers to the fan object created by the [fan] config section. There are some exceptions to this rule - notably the gcode and toolhead objects. If the config section contains spaces in it, then one can access it via the [ ] accessor - for example: printer["generic_heater my_chamber_heater"].temperature.

Some printer objects allow one to alter the state of the printer. By convention, these objects use an action_ prefix. For example, printer.gcode.action_emergency_stop() would cause the printer to go into a shutdown state. These actions are taken at the time that the macro is evaluated, which may be a significant amount of time before the generated commands are executed.

The following are common printer attributes:

• printer.fan.speed: The fan speed as a float between 0.0 and 1.0.
• printer.gcode.action_respond_info(msg): Write the given msg to the /tmp/printer pseudo-terminal. Each line of msg will be sent with a "// " prefix.
• printer.gcode.action_respond_error(msg): Write the given msg to the /tmp/printer pseudo-terminal. The first line of msg will be sent with a "!! " prefix and subsequent lines will have a "// " prefix.
• printer.gcode.action_emergency_stop(msg): Transition the printer to a shutdown state. The msg parameter is optional, it may be useful to describe the reason for the shutdown.
• printer.gcode.gcode_position: The current position of the toolhead relative to the current G-Code origin. It is possible to access the x, y, z, and e components of this position (eg, printer.gcode.gcode_position.x).
• printer["gcode_macro <macro_name>"].<variable>: The current value of a gcode_macro variable.
• printer.<heater>.temperature: The last reported temperature (in Celsius as a float) for the given heater. Available heaters are: heater_bed and heater_generic <config_name>.
• printer.<heater>.target: The current target temperature (in Celsius as a float) for the given heater.
• printer.pause_resume.is_paused: Returns true if a PAUSE command has been executed without a corresponding RESUME.
• printer.toolhead.position: The last commanded position of the toolhead relative to the coordinate system specified in the config file. It is possible to access the x, y, z, and e components of this position (eg, printer.toolhead.position.x).

The above list is subject to change - if using an attribute be sure to review the Config Changes document when upgrading the Klipper software. The above list is not exhaustive. Other attributes may be available (via get_status() methods defined in the software). However, undocumented attributes may change without notice in future Klipper releases.

Variables

The SET_GCODE_VARIABLE command may be useful for saving state between macro calls. For example:

[gcode_macro start_probe]
variable_bed_temp: 0
gcode:
  # Save target temperature to bed_temp variable
  SET_GCODE_VARIABLE MACRO=start_probe VARIABLE=bed_temp VALUE={printer.heater_bed.target}
  # Disable bed heater
  M140
  # Perform probe
  PROBE
  # Call finish_probe macro at completion of probe
  finish_probe

[gcode_macro finish_probe]
gcode:
  # Restore temperature
  M140 S{printer["gcode_macro start_probe"].bed_temp}

Be sure to take the timing of macro evaluation and command execution into account when using SET_GCODE_VARIABLE.