Introduction

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

Parameter Comparison

Using the APLS Pressure Module

Recommended to Pair with Wiping Functionality

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

XH2.54 4Pin Wiring Diagram

The module can be directly inserted into the mainboard UART interface or connected to the expansion board's UART interface. If there is no UART interface, two pins can be found on the mainboard, paying attention to the polarity of the power line.

Installation Precautions

1. Ensure that the module is installed securely to avoid poor contact due to vibrations during printing.
2. Check the wiring to ensure it is correct to prevent the module from failing to work properly due to incorrect wiring.
3. Before first use, it is recommended to conduct multiple leveling tests to ensure that the sensitivity and precision of the module meet expectations.

Status Light Display

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

Status Light Troubleshooting

• If the status light does not light up, check whether the power connection is correct.
• If the status light keeps flashing, it may indicate that the module detects an abnormal signal; please check if the probe is jammed by foreign objects or damaged.

Configuration Guide

Replace the probe and homing parts in the original configuration file with the following configurations:

Example Configuration File

Below is the recommended content of the configuration file. Please adjust according to actual needs:

tip

• If you need to use the ALPS pressure module as the Z limit, refer to the following configuration:

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

tip

• Reference configuration for the ALPS pressure module:

[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 the fan
            M109 S150 # Ensure homing Z at 150 degrees
        {% endif %}
        M106 S0       # Turn off the fan

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

        # If using eddy and pressure sensor simultaneously, uncomment below
        #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 the sensor relative to the nozzle
y_offset: 0               # Y-axis offset of the sensor relative to the nozzle
z_offset:0                # Z-axis offset of the sensor relative to the nozzle
speed: 8                 # Leveling speed
samples: 3                   # Number of samples
samples_result: median       # Value selection method (default median-median value)
sample_retract_dist: 2     # Retract distance during leveling
samples_tolerance: 0.05      # Sampling tolerance (note that smaller values may increase the number of samples)
samples_tolerance_retries: 3 # Retry times when exceeding tolerance
activate_gcode:
           G4 P500
           SET_PIN PIN=_probe_ready VALUE=1
deactivate_gcode:
           SET_PIN PIN=_probe_ready VALUE=0  

Reference for Adjusting Z Offset Value

Use this command to adjust 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 the Z-axis limit, overwrite the original endstop_pin configuration to: endstop_pin: probe:z_virtual_endstop