Annotated Bambu Lab P2S Machine Start G-code

Original and annotated versions of the default machine start (pre-print) G-code for the Bambu Lab P2S 3D printer, as shipped with Bambu Studio 2.5.0.66 (G-code version 2026/02/26).

Files

• machine_start.gcode — Original start G-code
• machine_start_annotated.gcode — Annotated copy with documentation comments

Annotation approach

• Every line is documented with a comment explaining what it does
• Only confirmed information is included, unknowns are marked with TODO
• Bambu's own inline comments are preserved as-is
• Slicer template syntax ({if}, {else}, {endif}, [variable]) is explained in context

What's covered

• Standard Marlin G-codes (G0/G1, G28, G90/G91, M104/M109, M140/M190, M106, etc.)
• Bambu-proprietary commands (M1002, M620/M621, M960, M970/M974/M975, G150.x, G380, etc.)
• Slicer conditional logic and template variables
• LCD/app status messages (M1002 gcode_claim_action) with display strings from BambuStudio source
• AMS filament handling, flow dynamics calibration, vibration compensation, build plate detection
• P2S-specific commands not present on older models (G150.x wiper system, G130 purge line, M1010 load cell, G3811 obstacle detection)

Known issues in stock G-code

As of G-code version 2026/02/26 there are two issues present in stock G-code, as documented by community members:

• Redundant homing: An unconditional G28 after the bed leveling block re-homes every print even when ABL already homed (source)
• Noise reduction ordering: M982.2 S1 (cog noise reduction) is called before M975 S1 (input shaping), but depends on it. Therefore it has no effect during the noisiest startup phases (source)

Disclaimer

The G-code itself is authored by Bambu Lab and ships as part of Bambu Studio (AGPL-3.0), in resources/profiles/BBL/machine/. This repository only adds documentation comments and does not modify the original G-code. Bambu Lab is not affiliated with this project.

References

Community G-code documentation

• OpenBambuAPI — G-code reference
• x1plus — Gcode.md
• Bambu Lab X1 Specific G-Code (forum)
• BBL P1S organized start and end gcode (forum)

P2S-specific

• P2S quick start G-code by SylwekK (forum)
• P2S optimized start G-code by scoofz (GitHub)
• P2S quirks and firmware settings (Reddit)
• P2S single filament no-switch startup (GitHub Gist)

Official Bambu Lab sources

• BambuStudio source — get_stage_string() in DeviceManager.cpp — LCD status message strings
• OpenBambuAPI — MQTT reference
• Bambu Lab Wiki — MIDI to A1 mini User Guide — M1006 stepper motor music
• Bambu Lab Wiki — Flow Dynamics Calibration
• Bambu Lab Wiki — Filament Mapping Principles
• Bambu Lab Wiki — P2S Nozzle Purge Position Calibration
• Bambu Lab Wiki — P2S Visual Detection

Other

• ha-bambulab Home Assistant integration — const.py — Stage ID mappings, airduct modes
• NineLizards — Plate Lab: ArUco codes and Bambu Lab plates
• OpenCV — ArUco Marker Detection