There is frequently plenty of power left during a PP. Take advantage of
it by moving the extruder to either side of the axis to detach
completely the nozzle from the print.
Re-enable Z during this move to avoid losing the current step.
When the printer is connected to a USB host during a PP (and the host
does not lose power), the rambo can linger for longer, sometimes for
long enough to recover the print state. Drain some more power.
If the motors are off-phase, this is more likely to "bump" them to an
incorrect/reverse full-step, doing worse.
We need to ensure the motors are already positioned on a fullstep
during power panic instead.
Remove the PSU_DELTA exception: Z _always_ needs to be powered here.
Also clear the UVLO flag when using lcd_print_stop. This prevents an
aborted print which has been cancelled while unparking (just prior to
recover) to come back again at the next startup.
- 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.
