Power Loss Resume Function in Klipper

Overview

The power loss resume function in Klipper refers to the ability to automatically restore the printing state of Klipper after it has been powered off and then powered on again.
This function requires the use of a safety shutdown module.
It is not applicable for machines where the Z-axis will move when the power is cut.

Configuration

plr.cfg Configuration File

In the printer configuration page, click "New Configuration File" to create a plr.cfg file.

The content of the configuration file is as follows:

[mcu host]   
serial: /tmp/klipper_host_mcu

[power_loss_resume]
# power_pin: PA0 # Shutdown pin of the safety shutdown module connected to PA0 of the lower-level MCU
power_pin: host:gpiochip1/gpio21 # Shutdown pin of the safety shutdown module connected to PA21 of the upper-level MCU
is_shutdown: True # Whether to execute the shutdown operation, default is enabled
paused_recover_z: -2.0 # If the machine stops during a pause print, the Z movement distance during recovery, default is no movement
start_gcode:
    # G-code to be executed before resuming printing
    # All parameters saved before power failure can be accessed via {PLR}
    # Use M118 {PLR} to output all available parameters
    M118 Resuming Print: {PLR.print_stats.filename}
    M118 Interrupt Position: X:[{PLR.POS_X}] Y:[{PLR.POS_Y}] Z:[{PLR.POS_Z}] E:[{PLR.POS_E}]
    M140 S{PLR.bed.target}      ; Set bed temperature
    M104 S{PLR.extruder.target-10}  ; Set extruder temperature
    M109 S{PLR.extruder.target-10}  ; Wait for the extruder to heat up to the set temperature
    G91                             ; Relative coordinates
    G1 Z2 F100                      ; Lift Z, prepare for X,Y reset
    G90                             ; Absolute coordinates
    G28 X Y                         ; Reset XY
    M140 S{PLR.bed.target}          ; Set bed temperature
    M104 S{PLR.extruder.target}     ; Set extruder temperature
    M190 S{PLR.bed.target}          ; Wait for the bed to heat up to the set temperature
    M109 S{PLR.extruder.target}     ; Wait for the extruder to heat up to the set temperature
    M83                             ; Relative extrusion
    # G1 E0.5 F400                  ; Extrude a bit
layer_count: 2 # Number of layers to resume before executing layer_change_gcode
layer_change_gcode:                
    # G-code to be executed after resuming {layer_count} layers
    M118 Resuming Print Speed
    M106 S{PLR.fan_speed}             ; Turn on the part cooling fan
    M220 S{PLR.move_speed_percent}    ; Set requested speed percentage
    M221 S{PLR.extrude_speed_percent} ; Set requested extrude speed percentage
shutdown_gcode:
    # G-code to be executed before shutdown
    M118 Low Voltage, Shutting Down
    # M112 ; Emergency stop

Note

The start_gcode macro in the above configuration file may need to be modified based on the actual machine conditions.

After saving the configuration file, open the printer.cfg file and add the following content at the beginning of the file:
```
[include plr.cfg]
```
Click the "Save" button at the top right and restart the system.
The power loss resume function in Klipper has now been configured.

Testing

Start printing any file and click the "Emergency Stop" button during printing to simulate a power failure.
Click "Firmware Restart" again, wait for Klipper to connect normally.
If a pop-up prompt appears on the web interface or KlipperScreen, it indicates that the power loss resume function is working properly.
You can then proceed to test the real power outage scenario.

Overview​

Configuration​

plr.cfg Configuration File​

Testing​

Overview

Configuration

plr.cfg Configuration File

Testing