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Grbl v1.1 System Commands ($ Commands)

Francis Peet
  • Updated

Grbl system commands are special instructions used to configure and control your CNC controller. They all begin with a $ and are typically sent manually via a serial terminal or through your G-code sender's console.

These commands are not part of standard G-code — they are Grbl-specific and execute immediately.

Configuration and Control Commands

Command Description
$$ View all settings – Displays the current values of all Grbl configuration parameters.
$x=val Set a setting – Sets the value of setting $x to val. For example: $100=250.000.
$# View coordinate offsets – Shows the current G54–G59 work coordinate offsets and any programmed tool or probe offsets.
$G View modal state – Displays the active G-code modes (e.g., G21, G90, G54). Helpful for debugging command behavior.
$I Build info – Returns firmware version and any build metadata (optional).
$N Startup lines – Shows or sets G-code commands that run automatically on startup.
$N0=... / $N1=... Set startup line – Defines custom commands that execute after Grbl initializes. Useful for setting defaults like units or coordinate systems.
$C Check mode – Enables "dry-run" mode where G-code is parsed but not executed. Great for simulation or code validation.
$X Kill alarm lock – Unlocks the machine after an alarm or hard reset. Be sure the machine is safe to move before using this.
$H Run homing cycle – Initiates a homing routine if homing is enabled in settings ($22=1).
~ Cycle start/resume – Starts or resumes G-code execution after a feed hold.
! Feed hold – Pauses motion immediately but safely. Can be resumed with ~.
? Status report – Asks Grbl to send back a real-time status report. Can be sent repeatedly.
Ctrl+X Soft reset – Instantly resets Grbl without cutting power. Stops motion, clears buffer, and reloads settings.

Safety Considerations

  • Always home the machine ($H) after powering on or unlocking to ensure accurate positioning.

  • Use $C to validate new G-code without risking machine motion.

  • The $X unlock command should only be used when you're certain the machine is not in a dangerous or unknown state.

 

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