Homing and Microsteps  

Re: Homing and Microsteps

From everything I've read Prusa uses microstepping on all axis, and 16 microsteps per step is a common theme; but I've not personally confirmed the numbers.

Re: Homing and Microsteps

Based on the question, let's first adjust the concept of what homing does. It does not store an absolute micro step or step value as the current position. It merely syncrhonizes the physical axis positions with the internal, numerical representation of current position.

The firmware works with and stores position data as floats storing position in millimeters. All motion is done via micro stepping, but again it does not store the micro-step during homing. It merely performs motions far enough that the axis should hit an end stop (be it physical switch or Stealthguard senseless). When finds a stop, it sets its current mm position for that axis to be home

Subsequent motions are specified as moves to a mm position. For example a move on x might be requested to 10.358 mm. Marlin knows how many steps are needed to move that distance. That many steps are performed to move the requested motion. Current position in mm is updated as each motion is performed.

So, now you know why asking whether homing is in micro for full steps doesn't quite match what actually is happening. It isn't stored that way.

Re: Homing and Microsteps

To add to Guy's comment: HOME simply bangs the extruder against the left X-Axis bracket; the bed bearings against the rear rod holder, and the Z-Axis (when you do a cal) against the top rod brackets. This is a physical home: and the firmware calls it zero then subtracts a small fixed offset so the nozzle is close to where the corner of the sheet is.

When it does an xyz cal, it uses the PINDA to "zoom in" on metal targets in the fiberglass bed heater. The concept is these targets are positionally accurate enough to be a known distance apart. The FW then saves a cal factor to set 100 steps per mm (or something like that)..