Z homing issue

Hi.

I'm building a custom 3D printer controlled by a SKR 1.4 turbo running Marlin 2.0.

I am having a problem getting homing to work correctly; X and Y will home just fine, the carriage moves to the centre of the bed as expected but Z will go in the wrong direction until the Z axis crashes.

The direction of Z appears correct; a negative Z move command will move the bed closer to the nozzle and vice versa. The Z endstop is an inductive probe wired to the Z_min conector; the inductive sensor seems to work correctly when tested with M119. When the problem occurs and the Z axis is moving down (away from the nozzle), manually triggering the probe with a metallic object causes the LED to turn on but does not halt the homing process as expected.

I've tried Googling the problem and have checked common things such as ensuring Z_MIN_PROBE_USES_Z_MIN_ENDSTOP_PIN is enabled and that Z_HOME_DIR is set to -1 tp no avail.

I've run out of ideas of what to try or what to Google so if anyone has any idea as to what is going on it would be much appreciated. Config files are attached.

Thanks.

.

Edited 1 time(s). Last edit at 01/25/2021 12:06PM by NeueKlasse.

Do you have TMC drivers installed? If so, make sure you cut the DIAG pin from the driver - otherwise the TMC driver's stallguard signal will interfere with your sensor. The SKR 1.3 board had jumpers to disable this, but the SKR 1.4 requires the pin to be cut.

Have you tried setting Z_HOME_DIR 1 and using both
#define USE_XMAX_PLUG
and
#define ENDSTOPPULLUP_ZMAX