Stopping Smoothie

There are several different ways to stop Smoothie during operation, each with different behaviors and use cases.

Understanding these methods is important for safe operation and troubleshooting.

Stop Methods Comparison

Command G-code Movement Heaters File playing Recoverable Documentation
Feed hold / cycle start ! / ~ V2 reduces the step rate to a stop without draining the queue Not affected; laser output turns off during the hold Paused while held Yes, with ~ Feed Hold
abort M26 Stops SDCARD print immediately Not affected Aborts Position maintained, file must be restarted Player
suspend M600 Stops once queue is empty Turned off (if option enabled) Paused, can be resumed Yes, with resume or M601 Player
Kill button M112 Stops instantly (if button), waits for buffer (if host) Turned off Aborted No, position lost, home required supported-g-codes
Control-X - Stops instantly, works during streaming Turned off Aborted No, position lost, home required -

Detailed Method Descriptions

Feed Hold and Cycle Start (! / ~, V2)

Send the real-time character ! to start a controlled deceleration without waiting for the planner queue to empty. Send ~ to accelerate and resume the interrupted motion. The Fall 2026 announcement describes this implemented V2 feature as work in progress.

Feed hold preserves the active move. It does not clear a halt, stop continuous jog mode, or replace M600/M601 suspend and resume. See Feed Hold and Cycle Start for console-mode limits and laser behavior.

Abort Command (abort / M26)

Stops the execution of a file being played from SDCARD.

Behavior:

  • Completes the current G-code
  • Stops immediately after that
  • Discards the rest of the queued commands
  • Attempts to maintain the correct position after the abort
  • Heaters remain at their current state

Use Case: Quick stop of a print job while preserving position and keeping heaters on.

Recovery: Position is maintained, but the file must be restarted from the beginning.

Documentation: Player module

Suspend Command (suspend / M600)

Suspends the execution of a file being played from SDCARD or being streamed from a host.

Behavior:

  • Stops once the movement queue is empty
  • All state is saved
  • Heaters turned off by default (configurable)
  • Jogging and extruding are allowed during suspension
  • Can be resumed with resume or M601

Use Case: Mid-print filament change or filament out detection.

Host Support: Requires upstream support. Currently Pronterface and OctoPrint support it. Other hosts need to be manually paused.

Recovery: Yes, fully recoverable with position maintained.

Documentation: Player module

Kill Button / M112

Emergency stop that instantly halts all operations.

Behavior:

  • If kill button pressed: Stops instantly
  • If M112 issued from host: Has to wait for the receive buffer to have room
  • All heaters turned off
  • File playing aborted
  • Position is lost
  • System enters Halt state until M999 is sent

Use Case: Emergency situations requiring immediate stop.

Recovery: No, position is lost. Homing will be required.

Documentation: Supported G-codes, Kill Button

Warning: Using the kill button or M112 will cause position loss. You must home all axes before continuing normal operation.

Control-X

Sends a control character to stop Smoothie instantly.

Behavior:

  • Works at any time, even when streaming
  • Same effect as the kill button
  • All heaters turned off
  • File playing aborted
  • Position is lost
  • System enters Halt state until M999 or $X is sent

Use Case: Emergency stop from terminal/console when streaming G-code.

Recovery: No, position is lost. Homing will be required.

Halt State

When the kill button is pressed (or there is a temperature fault, M112 is issued, a limit switch is hit, or other error), the system enters the Halt state.

Halt State Behavior

Halt State Indicators:
  • Play LED flashes
  • Any command issued from host gets a !! response (with a few exceptions)
  • PSU may be turned off if a PSU Switch is defined

Clearing Halt State

The Halt state can be cleared by:

  1. Issuing M999 from the host
  2. Holding the flashing kill button for 2 seconds
  3. Using the LCD panel (if equipped)

Using Buttons and Sensors

Tip: A Switch module or V2 Button Box can trigger queued stop-related commands such as suspend or kill. The V2 feed-hold characters ! and ~ use a real-time console path and are not ordinary queued G-code commands.

Best Practices

For Normal Operation

  • Use suspend/resume (M600/M601) for planned interruptions like filament changes
  • Use abort when you need to stop quickly but keep heaters on

For Emergencies

  • Use the kill button or Control-X for immediate emergency stops
  • Remember that position will be lost and homing will be required

Recovery After Emergency Stop

  1. Clear the Halt state with M999
  2. Home all axes before attempting further movement
  3. Check that heaters are at safe temperatures before proceeding
  4. Verify machine state before resuming work

Further Reading

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