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klipper-dgus/docs/BLTouch.md

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Connecting BL-Touch

A warning before you start: Avoid touching the BL-Touch pin with your bare fingers, since it is quite sensitive to finger grease. And if you do touch it, be very gentle, in order to not bend or push anything.

Hook up the BL-Touch "servo" connector to a control_pin according to the BL-Touch documentation or your MCU documentation. Using the original wiring, the yellow wire from the triple is the control_pin and the white wire from the pair is the sensor_pin. You need to configure these pins according to your wiring. For example:

[bltouch]
sensor_pin: P1.24
control_pin: P1.26

If the BL-Touch will be used to home the Z axis then set endstop_pin: probe:z_virtual_endstop in the [stepper_z] config section and add a [safe_z_home] config section to raise the z axis, home the xy axes, move to the center of the bed, and home the z axis. For example:

[safe_z_home]
home_xy_position: 100,100 # Change coordinates to the center of your print bed
speed: 50
z_hop: 10                 # Move up 10mm
z_hop_speed: 5

It's important that the z_hop movement in safe_z_home is high enough that the probe doesn't hit anything even if the probe pin happens to be in its lowest state.

Initial tests

Before moving on, verify that the BL-Touch is mounted at the correct height, the pin should be roughly 2 mm above the nozzle when retracted

When you turn on the printer, the BL-Touch probe should perform a self-test and move the pin up and down a couple of times. Once the self-test is completed, the pin should be retracted and the red LED on the probe should be lit. If there are any errors, for example the probe is flashing red or the pin is down instead of up, please turn off the printer and check the wiring and configuration.

If the above is looking good, it's time to test that the probe responds to commands from the firmware. First run BLTOUCH_DEBUG COMMAND=pin_down in your printer terminal. Verify that the pin moves down and that the red LED on the probe turns off. If not, check your wiring and configuration again. Next issue a BLTOUCH_DEBUG COMMAND=pin_up, verify that the pin moves up, and that the red light turns on again. If it's flashing then there's some problem.

The next step is to confirm that the sensor pin is working correctly. Run BLTOUCH_DEBUG COMMAND=pin_down, verify that the pin moves down, run BLTOUCH_DEBUG COMMAND=touch_mode, run QUERY_PROBE, and verify that command reports "probe: open". Then while gently pushing the pin up slightly with the nail of your finger run QUERY_PROBE again. Verify the command reports "probe: TRIGGERED". If either query does not report the correct message then check your wiring and configuration again. At the completion of this test run BLTOUCH_DEBUG COMMAND=pin_up and verify that the pin moves up.

After completing the BL-Touch command and sensor tests, it is now time to test probing, but with a twist. Instead of letting the probe pin touch the print bed, let it touch the nail on your finger. Position the toolhead far from the bed, issue a G28 (or PROBE if not using probe:z_virtual_endstop), wait until the toolhead starts to move down, and stop the movement by very gently touching the pin with your nail. You may have to do it twice, since the default homing configuration probes twice. Be prepared to turn off the printer, to avoid damage, if it doesn't stop when you touch the pin.

If that was successful, do another G28 (or PROBE) but this time let it touch the bed as it should.

BL-Touch gone bad

Once the BL-Touch is in inconsistent state, it starts blinking red. You can force it to leave that state by issuing:

BLTOUCH_DEBUG COMMAND=reset

This may happen if its calibration is interrupted by the probe being blocked from being extracted.

However, the BL-Touch may also not be able to calibrate itself anymore. This happens if the screw on its top is in the wrong position or the magnetic core inside the probe pin has moved. If it has moved up so that it sticks to the screw, it may not be able to lower its pin anymore. With this behavior you need to open the screw and use a ball-point pen to push it gently back into place. Re-Insert the pin into the BL-Touch so that it falls into the extracted position. Carefully readjust the headless screw into place. You need to find the right position so it is able to lower and raise the pin and the red light turns on and of. Use the reset, pin_up and pin_down commands to achieve this.

BL-Touch "clones"

Many BL-Touch "clone" devices work correctly with Klipper using the default configuration. However, some "clone" devices may require configuration of pin_up_reports_not_triggered or pin_up_touch_mode_reports_triggered.

Important! Do not configure pin_up_reports_not_triggered or pin_up_touch_mode_reports_triggered to False without first following these directions. Do not configure either of these to False on a genuine BL-Touch. Incorrectly setting these to False can increase probing time and can increase the risk of damaging the printer.

Some "clone" devices are unable to perform Klipper's internal sensor verification test. On these devices, attempts to home or probe can result in Klipper reporting a "BLTouch failed to verify sensor state" error. If this occurs, then manually run the steps to confirm the sensor pin is working as described in the initial tests section. If the QUERY_PROBE commands in that test always produce the expected results and "BLTouch failed to verify sensor state" errors still occur, then it may be necessary to set pin_up_touch_mode_reports_triggered to False in the Klipper config file.

A rare number of old "clone" devices are unable to report when they have successfully raised their probe. On these devices Klipper will report a "BLTouch failed to raise probe" error after every home or probe attempt. One can test for these devices - move the head far from the bed, run BLTOUCH_DEBUG COMMAND=pin_down, verify the pin has moved down, run QUERY_PROBE, verify that command reports "probe: open", run BLTOUCH_DEBUG COMMAND=pin_up, verify the pin has moved up, and run QUERY_PROBE. If the pin remains up, the device does not enter an error state, and the first query reports "probe: open" while the second query reports "probe: TRIGGERED" then it indicates that pin_up_reports_not_triggered should be set to False in the Klipper config file.

Calibrating the BL-Touch offsets

Follow the directions in the Probe Calibrate guide to set the x_offset, y_offset, and z_offset config parameters.

It's a good idea to verify that the Z offset is close to 1mm. If not, then you probably want to move the probe up or down to fix this. You want it to trigger well before the nozzle hits the bed, so that possible stuck filament or a warped bed doesn't affect any probing action. But at the same time, you want the retracted position to be as far above the nozzle as possible to avoid it touching printed parts. If an adjustment is made to the probe position, then rerun the probe calibration steps.

BL-Touch output mode

  • A BL-Touch V3.0 supports setting a 5V or OPEN-DRAIN output mode, a BL-Touch V3.1 supports this too, but can also store this in its internal EEPROM. If your controller board needs the fixed 5V high logic level of the 5V mode you may set the 'set_output_mode' parameter in the [bltouch] section of the printer config file to "5V".

    *** Only use the 5V mode if your controller boards input line is 5V tolerant. This is why the default configuration of these BL-Touch versions is OPEN-DRAIN mode. You could potentially damage your controller boards CPU ***

    So therefore: If a controller board NEEDs 5V mode AND it is 5V tolerant on its input signal line AND if

    • you have a BL-Touch Smart V3.0, you need the use 'set_output_mode: 5V' parameter to ensure this setting at each startup, since the probe cannot remember the needed setting.
    • you have a BL-Touch Smart V3.1, you have the choice of using 'set_output_mode: 5V' or storing the mode once by use of a 'BLTOUCH_STORE MODE=5V' command manually and NOT using the parameter 'set_output_mode:'.
    • you have some other probe: Some probes have a trace on the circuit board to cut or a jumper to set in order to (permanently) set the output mode. In that case, omit the 'set_output_mode' parameter completely.

    If you have a V3.1, do not automate or repeat storing the output mode to avoid wearing out the EEPROM of the probe.The BLTouch EEPROM is good for about 100.000 updates. 100 stores per day would add up to about 3 years of operation prior to wearing it out. Thus, storing the output mode in a V3.1 is designed by the vendor to be a complicated operation (the factory default being a safe OPEN DRAIN mode) and is not suited to be repeatedly issued by any slicer, macro or anything else, it is preferably only to be used when first integrating the probe into a printers electronics.

Troubleshooting

  • A BL-Touch v3 may not work correctly when its signal wire is connected to the Z end-stop pin on some printer boards. The symptoms of this problem are: the BL-Touch probe deploys, the printer descends, the probe contacts a surface, the BL-Touch raises the probe, the BL-Touch does not successfully notify the micro-controller, and the printer continues to descend. The Z end-stop pin on some printer boards have a capacitor to filter the signal which the BL-Touch v3 may not support. The simplest solution is to connect the BL-Touch v3 sensor wire to an available pin on the printer board that is not associated with an end-stop (and thus is unlikely to have a capacitor). An alternative solution is to physically alter the printer board to disable the given end-stop capacitor or to add a hardware "pull up resistor" to the BL-Touch v3 sensor wire.