Emergency Stop

Moonriver provides quick access to emergency stop functionality for immediate printer shutdown.

M112 Command

Type M112 to immediately send an emergency stop signal:

> M112
🚨 EMERGENCY STOP TRIGGERED 🚨

What Happens

When you execute M112:

1. Command buffer is cleared - All queued commands are discarded
2. Emergency stop signal sent - Klipper receives immediate stop command
3. Motors disabled - All stepper motors are immediately disabled
4. Heaters shut off - All heating elements are turned off
5. Printer halted - Printer enters an error state

After Emergency Stop

After triggering M112, the printer must be reset:

Firmware Restart

> FIRMWARE_RESTART

This resets Klipper and clears the emergency stop state.

Full Restart

Alternatively, restart the entire Klipper service:

# On the printer host (via SSH)
sudo systemctl restart klipper

When to Use

Use emergency stop when:

• Collision imminent - Toolhead about to crash
• Fire hazard - Burning smell or visible smoke
• Runaway heating - Temperature rising uncontrollably
• Strange noises - Grinding, clicking, or unusual sounds
• Layer shift - Print visibly misaligned
• Spaghetti detected - Print has failed catastrophically

Alternative Methods

Web Interface

Most web interfaces (Mainsail, Fluidd) have an emergency stop button.

Physical Button

Some printers have a physical emergency stop button wired directly to the control board.

SSH

ssh pi@printer.local
moonriver --host localhost --port 7125 M112

Response Time

Moonriver sends the M112 command immediately:

• No delay - Command sent as soon as you press Enter
• Priority handling - Bypasses command queue
• Direct WebSocket - No HTTP overhead

Typical response time: < 100ms

Prevention

While emergency stop is available, prevention is better:

Before Printing

> G28              # Home all axes
> QUERY_ENDSTOPS   # Verify endstops working
> M105             # Check temperatures normal

During Printing

Monitor:

• Temperature graphs
• Layer time estimates
• First layer adhesion
• Any unusual sounds

Regular Maintenance

> G28, BED_MESH_CALIBRATE, SAVE_CONFIG

Keep printer well-maintained to reduce emergency stop needs.

Safety Tips

1. Don't panic - Take a breath, then execute M112
2. Stay nearby - Especially during first layer
3. Monitor temperatures - Watch for thermal runaway
4. Check belts - Loose belts cause layer shifts
5. Verify paths - Preview G-code before printing

Recovery Procedure

After emergency stop:

1. Assess the situation

   > FIRMWARE_RESTART

2. Check for damage

   • Inspect toolhead, bed, wiring
   • Look for melted plastic
   • Check belt tension

3. Test basic functions

   > M105           # Check temperature reporting
   > QUERY_ENDSTOPS # Verify endstops

4. Re-home if safe

   > G28

5. Resume or restart print (if appropriate)

Scripting Safety

When using Moonriver in scripts, include error handling:

#!/bin/bash

trap 'moonriver --host printer.local --port 7125 M112' ERR

# Your commands here
moonriver --host printer.local --port 7125 G28

This automatically triggers emergency stop if any command fails.

Multiple Printers

Emergency stop a specific printer:

# Stop printer1
moonriver --host printer1.local --port 7125 M112

# Stop all printers
for printer in printer{1..5}.local; do
    moonriver --host $printer --port 7125 M112
done

Non-Emergency Stops

For non-emergency situations:

Pause Print

> PAUSE

Pauses the current print without stopping completely.

Cancel Print

> CANCEL_PRINT

Cancels the print but keeps printer operational.

Stop Heating

> M104 S0    # Turn off extruder
> M140 S0    # Turn off bed

Stops heating without emergency shutdown.

Remember

M112 is for emergencies only. For normal operations, use PAUSE, CANCEL_PRINT, or regular commands.

Next Steps

• Interactive Mode - Normal printer control
• Quick Start - Common commands
• Safety Best Practices - Klipper safety guide