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Grbl v1.1 Real-Time Commands

  • Updated

Real-time commands are immediate, non-blocking instructions that can be sent to Grbl at any time — even during motion or execution of a G-code program.

These commands are critical for pausing, resuming, checking status, or emergency stopping your CNC system without waiting for the current operation to finish.

Supported Real-Time Commands

Command Symbol Description
Status Report ? Returns current machine state, positions, and settings. Can be used repeatedly to track motion in real-time.
Cycle Start / Resume ~ Resumes motion after a feed hold or a safety door pause.
Feed Hold (Pause) ! Immediately pauses motion. This is a controlled stop that retains machine position and can be resumed with ~.
Soft Reset Ctrl+X Instantly resets Grbl. All operations are stopped, and settings are reloaded. Must unlock with $X afterward.
Safety Door 0x84 Tells Grbl the safety door is open. Motion and spindle pause safely. Resumed via door reopen/resume protocol.
Jog Cancel 0x85 Immediately cancels any jogging operation in progress.
Feed Override +10% 0x90 Increases the feed rate by 10%.
Feed Override -10% 0x91 Decreases the feed rate by 10%.
Feed Override Reset 0x92 Resets the feed rate to 100%.
Rapid Override -100% (disable) 0x93 Disables rapid movement (sets rapid rate to 0%).
Rapid Override -50% 0x94 Reduces rapid movement to 50% speed.
Rapid Override Reset 0x95 Restores rapid movement to full speed.
Spindle Speed Override +10% 0x99 Increases spindle speed by 10%.
Spindle Speed Override -10% 0x9A Decreases spindle speed by 10%.
Spindle Speed Reset 0x9B Resets spindle speed to 100%.
Toggle Spindle Stop 0x9E Stops or restarts the spindle depending on its current state.
Toggle Flood Coolant 0xA0 Turns flood coolant on or off.
Toggle Mist Coolant 0xA1 Turns mist coolant on or off.

Common Use Cases

  • Pause a job: Use ! to pause mid-cut safely.

  • Check position: Send ? during a job to get real-time coordinates.

  • Emergency recovery: Use Ctrl+X for a fast reset in case of failure or crash.

  • Adjust speeds: Use overrides to fine-tune feeds/spindle during a run.

 

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