Feed Hold and Cycle Start

These real-time feed-hold controls are not available in V1. See Stopping Smoothie for V1 stop and suspend options.

Smoothieware V2 only, merged implementation: The commands described here are implemented in the V2 source checked at commit 2a21c010. PR #8 merged on 2026-08-17, and the upstream wiki moved feed hold out of its WIP list on 2026-10-05. 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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