3.0.12-RC2 firmware for Prusa i3 MK2

3.0.12-RC2 firmware for Prusa i3 MK2

Description of changes with respect to 3.0.12-RC1:

Selftest fixed:

Selftest Heater/thermistor test was failing on some printers which worked correctly (issue #116). This was caused by combination of short selftest heating period and strict selftest limits. Heating period in selftest has been prolonged in current firmware version to ensure that there is enough margin to safely distinguish between workable and faulty printers.
Selftest has been furthermore improved to avoid "Static memory has been overwriten" error message in case of endstop selftest fail.

Multi material stop print:

In 3.0.12-RC1 all filaments were unloaded in the end of multi material stop print sequence. If the print was stopped, cutting filament ends and loading filaments back is the safest way how to ensure that new print will be successfull. However it is not always necessary to unload all filaments, especially if user decides to stop print right at the beginninig or if user uses just one or two extruders during the print.
In this firmware version, in the end of stop print user is asked if he wants to unload all four filaments, all filaments which has been used during current print or just filament in currently active extruder.

Multi material - choosing extruder:

There is new gcode "T?" which (if used in gcode start sequence) envokes menu for choosing which extruder will be used for print. This is useful when printing single material prints with multi material printer.

XYZ calibration:

In 3.0.11 first part of xyz calibration was slightly modified to avoid aborting calibration process with "consult the manual" message as much as possible. However there was bug which caused that in some cases (new printer or erased EEPROM) improvement was very little. This has been fixed in current firmware version.
In current firmware version if XYZ calibration process fails during first part (searching for first four points) and front point is not reachable by PINDA probe, calibration process is terminated. User is then informed by message on LCD, that front points are out of reach instead of showing just less informative "consult the manual" message as in previous firmware versions.
For debugging purposes, there is also possible to show details from xyz calibration in menu Support -> XYZ cal. details. XYZ cal. details menu should help to determin if the printer is very close to some boundary.
On the first screen, there are distances between measured calibration points and minimum allowed calibration points positions for all three points which are in front row. Positive number means that PINDA probe can reach calibration points in front row. Negative number is means that point couldn't be reached by PINDA probe and calibration may be compromised.
On the first row of second screen there is measured parameter which determines how much are axis skewed. Below that there are values which determine boundary between perpendicular and mild skew and between mild and severe skew.

MK1 support:

New configuration files and precompiled hex files were added to make current firmware version compatible with MK1 printers.

Unload filament:

In previous firmware version, there was little extrusion added to the beginning of single material unload filament sequence, which should ease filament unloading. However it turned out problamatic with some filaments. That is why in 3.0.12 there is just fast unload with no extrusion or ramming.