Introduction

ALPS Pressure Module is a pressure sensing solution based on ADS131M02, specifically developed for 3D printers' automatic Z-axis homing (Home) and Mesh Bed Leveling. Through high-sensitivity pressure detection and real-time signal processing, the module can accurately sense the contact status 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

apls Pressure Module Usage

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 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 connections to avoid module failure caused by incorrect wiring.
3. It is recommended to perform multiple leveling tests before first use to ensure the module's sensitivity and accuracy meet expectations.

Status Light Display

• Power On State: The green red frame status light remains 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 continues to flash, the module may detect an abnormal signal, please check if the probe is blocked or damaged by foreign objects.

Configuration Guide

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

Example Configuration File

The following is the recommended configuration file content, please adjust according to 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 nozzle from being too close to the hot bed, pull back distance in advance
        G90

        # if using eddy plus pressure sensor, 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 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       # sampling method (default median - median)
sample_retract_dist: 2     # leveling retraction distance
samples_tolerance: 0.05      # sampling tolerance (note that too small a value may increase the number of samples)
samples_tolerance_retries: 3 # retry times for out-of-tolerance samples
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

Adjust Z Offset Value Reference

• Use this command to adjust z-offset:

PROBE_CALIBRATE

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

Note

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