mirror of https://github.com/Desuuuu/klipper.git
43 lines
2.0 KiB
Markdown
43 lines
2.0 KiB
Markdown
# Multiple Micro-controller Homing and Probing
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Klipper supports a mechanism for homing with an endstop attached to
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one micro-controller while its stepper motors are on a different
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micro-controller. This support is referred to as "multi-mcu
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homing". This feature is also used when a Z probe is on a different
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micro-controller than the Z stepper motors.
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This feature can be useful to simplify wiring, as it may be more
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convenient to attach an endstop or probe to a closer micro-controller.
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However, using this feature may result in "overshoot" of the stepper
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motors during homing and probing operations.
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The overshoot occurs due to possible message transmission delays
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between the micro-controller monitoring the endstop and the
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micro-controllers moving the stepper motors. The Klipper code is
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designed to limit this delay to no more than 25ms. (When multi-mcu
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homing is activated, the micro-controllers send periodic status
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messages and check that corresponding status messages are received
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within 25ms.)
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So, for example, if homing at 10mm/s then it is possible for an
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overshoot of up to 0.250mm (10mm/s * .025s == 0.250mm). Care should be
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taken when configuring multi-mcu homing to account for this type of
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overshoot. Using slower homing or probing speeds can reduce the
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overshoot.
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Stepper motor overshoot should not adversely impact the precision of
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the homing and probing procedure. The Klipper code will detect the
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overshoot and account for it in its calculations. However, it is
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important that the hardware design is capable of handling overshoot
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without causing damage to the machine.
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Should Klipper detect a communication issue between micro-controllers
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during multi-mcu homing then it will raise a "Communication timeout
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during homing" error.
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Note that an axis with multiple steppers (eg, `stepper_z` and
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`stepper_z1`) need to be on the same micro-controller in order to use
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multi-mcu homing. For example, if an endstop is on a separate
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micro-controller from `stepper_z` then `stepper_z1` must be on the
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same micro-controller as `stepper_z`.
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