It was certainly a good idea, but also always a suspect of
malfunctions and as such, almost never used. Newer code
organisation moves most of the code behind it to dda_clock()
anyways, so it also became mostly obsolete.
Rest In Peace, STEP_INTERRUPT_INTERRUPTIBLE, you were matter
of quite a number of interesting discussions and investigations.
Changes for Configtool by jbernardis <jeff.bernardis@gmail.com>
Eventual debugging LEDs aren't part of the CPU, but part of the
electronics. Accordingly, define it in config.*.h, not in
arduino_*.h (which would be better named something like
"atmega_*.h).
This meant to be a firmware-provided retract feature but was
never really supported by G-code generators. Without their support
(by issueing M101/M103), it's pretty hard to detect extrusion
pauses, so this feature simply has no future.
As this was on by default, it saves over 200 bytes binary size
in a default configuration.
Markus Hitter
David Forrest