Introduction

The ALPS pressure module is a pressure sensing solution based on ADS131M02, specifically developed for the automatic Z-axis homing (Home) and mesh bed leveling of 3D printers. With high-sensitivity pressure detection and real-time signal processing, the module can accurately sense the contact state between the print head and the mesh bed, achieving millimeter-level leveling accuracy, eliminating the errors of traditional mechanical limit calibration, and significantly improving the success rate of the first layer printing.

Parameter Comparison

Using the apls Pressure Module

Recommended Nozzle Wiping Function

When using the apls pressure module, it is recommended to use the nozzle wiping function to ensure the cleanliness of the nozzle, thereby improving the accuracy and stability of the leveling.

XH2.54 4Pin Wiring Diagram

The module can be directly inserted into the mainboard UART interface, or connected to the UART interface of the expansion board. If there is no UART interface, find two pin holes on the mainboard, and pay attention to the polarity of the power line.

Installation Notes

1. Ensure the module is securely installed to avoid poor contact due to vibration during printing.
2. Check the wiring to avoid malfunctions caused by incorrect connections.
3. Before first use, it is recommended to perform multiple leveling tests to ensure the module's sensitivity and accuracy meet expectations.

Status Light Display

• Power On State: The green red frame status light is on, indicating the module is working normally.
• Trigger State: The red frame status light flashes, indicating the module is in trigger state.

Status Light Troubleshooting

• If the status light is not lit, check if the power wiring is correct.
• If the status light keeps flashing, it may indicate that the module has detected an abnormal signal. Please check if the probe is stuck or damaged.

Configuration Guide

Replace the 'probe' and 'homing' sections in the original configuration file with the following configuration:

Example Configuration File

The following is the recommended configuration file content. Adjust according to your actual needs:

tip

• If you need to use the ALPS pressure module as a Z-limit, you can refer to the configuration below

[stepper_z]
endstop_pin: probe:z_virtual_endstop
# position_endstop: -0.5  

tip

• ALPS pressure module reference configuration

[homing_override]
axes: xyz
set_position_z: 10
gcode:
    {% set home_all = 'X' not in params and 'Y' not in params and 'Z' not in params %}
    {% set e_target = printer.extruder.target %} # Save current temperature
    {% set fan_speed = printer.fan.speed %}      # Save current fan speed
    
    {% if home_all or 'X' in params %}
        G28 X
    {% endif %}

    {% if home_all or 'Y' in params %}
        G28 Y
    {% endif %}

    {% if home_all or 'Z' in params %}
        G0 X{printer.toolhead.axis_maximum.x / 2} Y{printer.toolhead.axis_maximum.y / 2} F6000
        {% if e_target >= 150 or printer.extruder.temperature >= 150 %}
            M106 S255 # Turn on fan
            M109 S150 # Ensure Z homing at 150 degrees
        {% endif %}
        M106 S0       # Turn off fan

        G91
        G1 Z5 F2000 # Prevent the nozzle from being too close to the hotbed, pull it back in advance
        G90

        # If using eddy plus pressure sensor together, uncomment the following
        #SET_PIN PIN=_probe_ready VALUE=1 
        G28 Z 
        #SET_PIN PIN=_probe_ready VALUE=0
        G1 Z10 F2000
        
        M109 S{e_target}  # Restore temperature
        M106 S{fan_speed} # Restore fan speed
    {% endif %}
        

[output_pin _probe_ready]
pin: PA9 #En #Enable pin
shutdown_value: 0
value:0

[probe]
pin: ^PA10 #out #Probe pin
x_offset: 0                  # X-axis - Offset of sensor relative to nozzle
y_offset: 0               # Y-axis - Offset of sensor relative to nozzle
z_offset:0                # Z-axis - Offset of sensor relative to nozzle
speed: 8                 # Leveling speed
samples: 3                   # Number of samples
samples_result: median       # Sampling method (default median)
sample_retract_dist: 2     # Retract distance during leveling
samples_tolerance: 0.05      # Sample tolerance (note that too small a value may increase the number of samples)
samples_tolerance_retries: 3 # Retry times when tolerance is exceeded
activate_gcode:
        G4 P500
        SET_PIN PIN=_probe_ready VALUE=1
deactivate_gcode:
        SET_PIN PIN=_probe_ready VALUE=0  

• SHT36V3 reference configuration

[output_pin _probe_ready]
pin: SHT36:gpio20
shutdown_value: 0
value:0

[probe]
pin: ^SHT36:gpio16

Reference for Adjusting Z Offset Value

• Use this command to adjust the z-offset:

PROBE_CALIBRATE

• Before adjusting the z-offset value, please refer to the Klipper documentation tutorial: Paper Test

Note

• If you want to use the pressure module as a Z-axis limit, override the original endstop_pin configuration to: endstop_pin: probe:z_virtual_endstop