Previously, when backing off of X_MIN, X_MAX was also checked,
which of course was already open, so it signals endstop release
even while X_MIN is still closed. The issue exposed only when
endstops on both ends of an axis were defined, a more rare situation.
Essentially the fix simply makes a distinct endstop check case
for each side of each axis.
This even makes binary size 40 bytes smaller for the standard case.
This can be counterproductive if the actual zero point is
outside the available build room. For example, if an additional
bed probing is going to happen. It also costs quite some
time on the Z axis. If you actually want this behaviour,
send a simple G0 XYZ after homing.
In preparation for more efficient and scalable code using axis-loops
for common operations, add two new array-types for signed and unsigned
32-bit values per axis. Make the TARGET type use this array instead of
its current X, Y, Z, and E variables.
Traumflug notes:
- Did the usual conversion to spaces for changed lines.
- Added X = 0 to the enum. Just for peace of mind.
- Excellent patch!
Initially I wanted to make the new array an anonymous union with the
old variables to allow accessing values both ways. This way it would
have been possible to do the transition in smaller pieces. But as
the patch worked so flawlessly and binary size is precisely the
same, I abandoned this idea. Maybe it's a good idea in other areas.
For now for X min only, but it works excellently already.
Tested quite a few combinations and raising acceleration
or endstop clearance raises homing feedrate just as expected.
Quite a chunk of the code is for testing the given configuration,
only. A thing which would ideally be done for every macro
used in each code file.
These were commits 9dbfa7217e0de8b140846ab480d6b4a7fc9b6791 and
2b596cb05e621ed822071486f812eb334328267a.
There are several reasons why this new approach didn't work out well:
- The machine coordinate system is lost on relative movements.
OK, we could keep tracking it, but this would mean even more
code, so even more chances for bugs.
- With the lost coordinate system, no software endstops are possible.
- Neither of X, Y, Z will ever overflow.
- If a movement planner would appear one day, he'd have to handle
relative movements as well. Even more code duplication.
Instead of converting them to absolute first, then back to
relative and having all the fuzz with working on the queue's
start vs. working at the queue's end, mark a movement as relative
and use this directly.
This is a intrusive patch and for now, it's done for the X axis only.
To make comparison with the former approach easier ...
The advantages of this change:
- Converting from mm to steps in gcode_parse.c and back in dda.c
wastes cycles and accuracy.
- In dda.c, UM_PER_STEP simply goes away, so distance calculations
work now with STEPS_PER_MM > 500 just fine. 1/16 microstepping
on threaded rods (Z axis) becomes possible.
- Distance calculations (feedrate, acceleration, ...) become much
simpler.
- A wide range of STEPS_PER_M can now be handled at reasonable
(4 decimal digit) accuracy with a simple macro. Formerly,
we were limited to 500 steps/mm, now we can do 4'096 steps/mm
and could easily raise this another digit.
Disadvantages:
- STEPS_PER_MM is gone in config.h, using STEPS_PER_M is required,
because the preprocessor refuses to compare numbers with decimal
points in them.
- The DDA has to store the position in steps anyways to avoid
rounding errors.
Markus Hitter
Phil Hord
Ben Gamari
Bas Laarhoven
Michael Moon
Markus Amsler