Merge pull request #34 from beardicus/pulse_error_msg

Step Pulse Error Message thanks to beardicus. 
reordered a couple of functions for consistency
Moved comment and block delete handling to be done in protocol.c rather than gcode.c. Prevents these from being held in memory. Also, fixes bug when comments and block delete character are mixed with g-code.
Removed comment and block delete handling from gcode.c. Parser expects clean gcode.
Revert fdc90f1821f1f5edb7756fcddce75b4b4fbf6bbf^..HEAD
Revert "Moved comment and block delete handling to be done in protocol.c rather than gcode.c. Prevents these from being held in memory. Also, fixes bug when comments and block delete character are mixed with g-code."

This reverts commit ea5b8942db2616e93fc0478922010c3bab7c0481.
Revert 517a0f659a06182c89cafe27ee371edccad777a4^..HEAD
Moved comment and block delete handling into protocol.c from gcode.c. Fixes bug when comment and block delete are not isolated. Blank lines ignored.

Comments, block delete characters, and blank lines are no longer passed
to the gcode parser and should free up some memory by ignoring these
characters. Gcode parser now expects clean gcode only. There was a bug
if there were block deletes or comments not in the first character (i.e.
spindle on/off for proofing geode without turning it on, or a NXX
followed by a comment). This should fix it by bypassing the problem.
Left a commented line for easily turning on and off block deletes for a
later feature, if desired.
Revert ea5b8942db2616e93fc0478922010c3bab7c0481^..HEAD
Moved comment and block delete handling into protocol.c from gcode.c. Fixes bug when comment and block delete are not isolated. Blank lines ignored.

Comments, block delete characters, and blank lines are no longer passed
to the gcode parser and should free up some memory by ignoring these
characters. Gcode parser now expects clean gcode only. There was a bug
if there were block deletes or comments not in the first character (i.e.
spindle on/off for proofing geode without turning it on, or a NXX
followed by a comment). This should fix it by bypassing the problem.
Left a commented line for easily turning on and off block deletes for a
later feature, if desired.
Significantly improved junction control and fixed computation bugs in planner

- Junction jerk now re-defined as junction_deviation. The distance from
the junction to the edge of a circle tangent to both previous and
current path lines. The circle radii is used to compute the maximum
junction velocity by centripetal acceleration. More robust and
simplified way to compute jerk.   - Fixed bugs related to entry and exit
factors. They were computed based on the current nominal speeds but not
when computing exit factors for neighboring blocks. Removed factors and
replaced with entry speeds only. Factors now only computed for stepper
trapezoid rate conversions.  - Misc: Added min(), next_block_index,
prev_block_index functions for clarity.
Add G02/03 arc conversion/pre-processor script and example streaming script

Beta pre-processor script used to clean and streamline g-code for
streaming and converts G02/03 arcs into linear segments. Allows for full
acceleration support if the pre-processed g-code is then streamed to
grill, sans G02/03 arcs. Added a simple example streaming script for
Python users.
Minor bug fixes in planner.
More minor bug fixes in planner.

Reverse planner was over-writing the initial/buffer tail entry speed,
which reset the forward planner and caused it to lose track of its
speed. Should now accelerate into short linear segments much nicer now.
Minor update for memory savings in ring buffer and fleshed out commenting.

No changes in functionality. Path vectors moved from ring buffer to
local planner static variables to save 3*(BUFFER_SIZE - 1) doubles in
memory. Detailed comments. Really need to stop micro-updating. Should be
the last until a planner optimization (ala Jens Geisler) has been
completed.
Optimized planner re-write. Significantly faster. Full arc support enabled by rotation matrix approach.

- Significant improvements in the planner. Removed or reordered
repetitive and expensive calculations by order of importance:
recalculating unchanged blocks, trig functions [sin(), cos(), tan()],
sqrt(), divides, and multiplications. Blocks long enough for nominal
speed to be guaranteed to be reached ignored by planner. Done by
introducing two uint8_t flags per block. Reduced computational overhead
by an order of magnitude.   - Arc motion generation completely
re-written and optimized. Now runs with acceleration planner. Removed
all but one trig function (atan2) from initialization. Streamlined
computations. Segment target locations generated by vector
transformation and small angle approximation. Arc path correction
implemented for accumulated error of approximation and single precision
calculation of Arduino. Bug fix in message passing.
Further planner improvements and misc minor bug fixes. Memory savings and increased buffer size.

- Update grbl version and settings version to automatically reset
eeprom. FYI, this will reset your grbl settings. - Saved
3*BLOCK_BUFFER_SIZE doubles in static memory by removing obsolete
variables: speed_x, speed_y, and speed_z. - Increased buffer size
conservatively to 18 from 16. (Probably can do 20). - Removed expensive!
modulo operator from block indexing function. Reduces significant
computational overhead. - Re-organized some sqrt() calls to be more
efficient during time critical planning cases, rather than non-time
critical. - Minor bug fix in planner max junction velocity logic. -
Simplified arc logic and removed need to multiply for CW or CCW
direction.
More '%' modulo opertor removals and some housecleaning.

- Serial functions contained quite a few modulo operations that would
be executed with high frequency when streaming. AVR processors are very
slow when operating these. In one test on the Arduino forums, it showed
about a 15x slow down compared to a simple if-then statement. -
Clarified some variable names and types and comments.
Fixed minor bugs in planner. Increased max dwell time. Long slope bug stop-gap solution note.

- Fixed the planner TODO regarding minimum nominal speeds. Re-arranged
calculations to be both more efficient and guaranteed to be greater
than zero. - Missed a parenthesis location on the rate_delta
calculation. Should fix a nearly in-perceptible issue with incorrect
acceleration ramping in diagonal directions. - Increased maximum dwell
time from 6.5sec to an 18hour max. A crazy amount more, but that's how
the math works out. - Converted the internal feedrate values to mm/min
only, as it was switching between mm/min to mm/sec and back to mm/min.
Also added a feedrate > 0 check in gcode.c. - Identified the long slope
at the end of rapid de/ac-celerations noted by stephanix. Problem with
the numerical integration truncation error between the exact solution
of estimate_acceleration_distance and how grbl actually performs the
acceleration ramps discretely. Increasing the
ACCELERATION_TICKS_PER_SECOND in config.h helps fix this problem.
Investigating further.
Fixed long slope at deceleration issue. Moved things into config.h. New MINIMUM_PLANNER_SPEED parameter.

- The long standing issue of a long slope at deceleration is likely
fixed. The stepper program was not tracking and timing the end of
acceleration and start of deceleration exactly and now is fixed to
start and stop on time. Also, to ensure a better acceleration curve fit
used by the planner, the stepper program delays the start of the
accelerations by a half trapezoid tick to employ the midpoint rule. -
Settings version 3 migration (not fully tested, but should work) -
Added a MINIMUM_PLANNER_SPEED user-defined parameter to planner to let
a user change this if problems arise for some reason. - Moved all
user-definable #define parameters into config.h with clear comments on
what they do and recommendations of how to change them. - Minor
housekeeping.