!!! This project is in a BETA state, use at your own risk !!!

The ADXL345 has an interesting feature called tap detection. With the appropriate tuning, this can be used to implement a nozzle probe on 3D printers. This project aims to support nozzle probing through tap detection for printers using Klipper.

You can watch this thing in action here: https://www.youtube.com/shorts/_qd0kMkrVZw

Results you can expect for a properly tuned system (This was on a Voron Trident):

probe accuracy results: maximum 0.007500, minimum 0.000937, range 0.006563, average 0.004031, median 0.004219, standard deviation 0.001841

I also measured the force on the bed using a standard kitchen scale, this was approximately 200g. A CAN bus board was used, so a direct connection might result in a quicker stop (See Multi MCU homing in the Klipper docs for more information on this).

cd $HOME
git clone https://github.com/jniebuhr/adxl345-probe
cd adxl345-probe
./scripts/install.sh

This code requires the ADXL int1 or int2 pins to be wired to one of your boards (preferrably the one that controls Z motion). For a ADXL345 breakout board, simply run a wire. If you're using a CAN toolboard, the following boards are supported as they have wired the pins:

• Mellow Fly SB2040
• Mellow Fly SHT36 v2
• Huvud

[adxl345_probe]
probe_pin: <pin for either int1 or int2>
int_pin: int1 # select either int1 or int2, depending on your choice of wiring
tap_thresh: 12000 # this needs to be tuned
tap_dur: 0.01 # this needs to be tuned
speed: 20 # this needs to be tuned
# Adjust this to your liking
samples: 3
sample_retract_dist: 3.0
samples_result: median
samples_tolerance: 0.01
samples_tolerance_retries: 20

In progress...

This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.