Feed Hold and Cycle Start

Smoothieware V2, work in progress: The commands described here are implemented in the V2 source checked at commit 2a21c010. The Fall 2026 announcement still describes feed hold as work in progress. An installed firmware build may predate it.

Feed hold pauses queued motion without waiting for the planner queue to empty. Send the real-time character ! to start the hold. Send ~ to resume motion.

Character	Name	Result
!	Feed hold	Smoothie reduces the step-ticker rate until motion stops, then reports the Hold state
~	Cycle start	Smoothie raises the rate again and continues the interrupted motion

These are single real-time characters. Do not add a newline and do not place them inside a G-code file.

How the hold stops motion

The hold starts as soon as the console receives !; it does not wait for buffered moves to finish. Smoothie decelerates by reducing the step-ticker frequency, so the tool still travels some distance before stopping. ~ accelerates the same motion back to its normal rate.

During the held state:

• The GRBL-style ? status query reports Hold.
• The laser module turns the laser output off.
• An SD-card job stops feeding more commands into the planner.
• Smoothie sends // action:feedhold to its consoles so a connected host can pause its own sender. Host support for this message varies.

Limits

• Smoothie ignores ! while the machine is idle.
• Smoothie does not start feed hold during continuous jog mode. Stop a continuous $J -c jog with $J STOP.
• A command that has switched the connection into an input-capture mode, such as ed or le, can consume these characters before the real-time handler sees them. Exit the editor first.
• ~ resumes a feed hold only. It does not clear a halt, recover an emergency stop, or replace M601 after a suspend operation.

Choosing the right stop command

Feed hold preserves the active motion and allows it to resume. Use suspend and resume for a planned SD-card or streamed-job interruption that may include heater handling and jogging. Use a hardware emergency-stop circuit or Smoothie’s kill controls when safety requires power removal or a non-resumable halt.

See Stopping Smoothie for a side-by-side comparison.

Source

• Consoles.cpp receives ! and ~.
• StepTicker.cpp implements deceleration, hold, and acceleration.
• Laser.cpp disables laser output during the hold.

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