- Initially restore the last E position from the eeprom in any case, not
just when using absolute mode (although unnecessary: since it will be
reset later), fixing a possible unitialized position and crash during
recovery (thanks to @leptun)
- Remove useless extra calls to put the extruder in relative mode:
the extruder already starts in relative mode and is later switched to
absolute.
- Replace incorrect calls to STRINGIFY with sprintf_P
- Retract after pressure has been restored in uvlo_tiny, to be
consistent with a regular uvlo (remove the bogus double unretract
as a result).
- Set the real E position prior to the panic *after* the retraction,
using the now-fixed G92.
Do not process serial commands when re-enabling the global isr.
While printing via USB and a power panic is triggered, *any* extra
command should be ignored.
Abuse the "saved_printing" variable to inhibit serial processing.
To maintain an accurate step count (which is required for correct
position recovery), any call to plan_set_position&co needs to be done
synchronously and from a halted state.
However, G92 E* is currently special-cased to skip the sync (likely to
avoid the associated performance cost), causing an incorrect E step
count and position to be set. This breaks absolute position recovery,
miscalculation of the LA factor and possibly other weird issues.
We rewrite the handling of G92 to always sync but still special-case the
frequent "G92 E0" for performance by using a free bit in the block flags.
To avoid a sync, we relay the request for reset first to the planner
which clears its internal state and then relays the request to the final
stepper isr.
When check_z_endstop is set, Z_MIN_PIN is checkend regardless of the
moving direction to support Z calibration. This prevents the ability
to use _just_ SG when moving upwards.
But since we know the extruder is at Z_MIN, it's always safe to raise
irregardless, so we can dodge the issue.
Do not unconditionally enqueue a Z move if no move has been requested.
Since Z is calculated using the absolute current (saved) position and
scheduled for later execution, the queue order becomes relevant.
